Successes and limitations of targeted cancer therapy in lung cancer.

Peters S, Stahel RA (eds): Successes and Limitations of Targeted Cancer Therapy. Prog Tumor Res. Basel, Karger, 2014, vol 41, pp 62–77 (DOI: 10.1159/000355902)

Successes and Limitations of Targeted Cancer Therapy in Lung Cancer Kenichi Suda a, b · Tetsuya Mitsudomi a

a

Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, Osaka-Sayama, and of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

b Department

Abstract

Lung cancer is the leading cause of cancer-related mortality in many developed countries, including the United States and Japan. Platinum-based systemic chemotherapies have been the standard of care for patients with unresectable or recurrent lung cancers; however, their efficacies are limited, with a median survival time of 7.4–8.1 months typically shown in the ECOG 1594 study. This situation, however, has been changing

Downloaded by: UCSF Library & CKM 169.230.243.252 - 1/10/2015 12:46:31 AM

Human cancers usually evolve through multistep processes. These processes are driven by the accumulation of abundant genetic and epigenetic abnormalities. However, some lung cancers depend on a single activated oncogene by somatic mutation, termed ‘driver oncogenic mutations’, for their proliferation and survival. EGFR (epidermal growth factor receptor) mutations and ALK (anaplastic lymphoma kinase) rearrangement are typical examples of such driver oncogenic mutations found in lung adenocarcinomas. EGFR-tyrosine kinase inhibitors (TKIs) or ALK-TKIs significantly improved treatment outcomes compared with conventional cytotoxic chemotherapy in patients with lung cancers harboring EGFR mutations or ALK rearrangement, respectively. Therefore, treatment strategies for lung cancers have dramatically changed from a ‘general and empiric’ to a ‘personalized and evidence-based’ approach according to the driver oncogenic mutation. Several novel driver oncogenic mutations, which are candidates as novel targets, such as ERBB2, BRAF, ROS1, and RET, have been discovered. Despite these successes, several limitations have arisen. One example is that some lung cancers do not respond to treatments targeting driver oncogenic mutations, as exemplified in KRASmutated lung cancers. Another is resistance to molecular-targeted drugs. Such resistance includes de novo resistance and acquired resistance. A number of molecular mechanisms underlying such resistance have been reported. These mechanisms can be roughly divided into three categories: alteration of the targeted oncogenes themselves by secondary mutations or amplification, activation of an alternative oncogenic signaling track, and conversion of cellular characteristics. Overcoming © 2014 S. Karger AG, Basel resistance is a current area of urgent clinical research.

a

Gefitinib 4 months

b

Gefitinib 3 months

c

from 2004, the year of the discovery of somatic activating mutations in the epidermal growth factor receptor (EGFR) gene in lung cancers. One of the most important features of EGFR-mutated lung cancers is that these cancers depend on aberrantly activated EGFR signaling (oncogene addiction phenomenon [1]) for their proliferation and survival. Therefore EGFR-mutated lung cancers often dramatically respond to EGFR-tyrosine kinase inhibitors (TKIs), such as gefitinib or erlotinib (fig. 1a, b).

Lung Cancer – Targeting Drivers Peters S, Stahel RA (eds): Successes and Limitations of Targeted Cancer Therapy. Prog Tumor Res. Basel, Karger, 2014, vol 41, pp 62–77 (DOI: 10.1159/000355902)

63


Fig. 1. Clinical efficacy of EGFR-TKI and acquired resistance. A typical clinical course of EGFR-TKI therapy in patients with EGFR- mutated lung cancer is shown. a A 54-year-old Japanese female received gefitinib monotherapy for her stage IV lung adenocarcinoma with EGFR exon 19 deletion mutation. b Four months later, she experienced remarkable tumor shrinkage. c However, the tumor acquired resistance to gefitinib and re-grew after 3 months despite continuous treatment with gefitinib.

Another important feature of EGFR-mutated lung cancers is that they seldom harbor the concomitant KRAS gene mutations, which were discovered in 1982. This mutually exclusionary relationship between EGFR mutations and KRAS mutations is explained by the presumption that both mutations are ‘driver oncogenic mutations’. A driver oncogenic mutation is one (or a few) genetic change(s) that are essential for development, growth or survival of cancer cells; in contrast with passenger mutations that occur by chance because of the genetic instability of cancer cells during accelerated mitoses. Anaplastic lymphoma kinase (ALK) gene rearrangement was discovered in 2007 as an alternative mechanism of driver oncogene activation. These tumors respond to ALK-TKI such as crizotinib, as in the case of EGFR-TKI. Currently, identification of patients with EGFR or ALK activation by clinical testing and administration of the relevant drugs form the standard of care. The concept of driver oncogenic mutationbased personalized therapies was established in treatment strategies for lung cancers. Several novel driver oncogenic mutations have been discovered as candidates for future molecular targets (fig. 2). However, there are limitations to molecular-targeted therapies. For example, there is difficulty in targeting lung cancers with KRAS mutations, and there is resistance to molecular-targeted therapies. In this chapter, we summarize the current knowledge of the successes and limitations of molecular-targeted therapies in lung cancers.

Successes in Clinical Application of Molecular-Targeted Therapies

EGFR-mutated lung cancers account for ∼40% of adenocarcinomas in East-Asians and ∼15% in Caucasians. EGFR-mutated lung cancers are more common in patients who have never smoked, a fact that has attracted the interest of lung cancer researchers to investigate biology of lung cancers unrelated to smoking [2]. EGFR mutations usually occur in the first four exons of the tyrosine kinase domain (exons 18–21) and induce ligand-independent activation of EGFR, followed by signaling through downstream proliferative and antiapoptotic pathways. The types of EGFR mutation are important in EGFR-TKI therapy; lung cancers with either of the two most common mutations, exon 19 deletions and L858R point mutation (exon 21) respond very well to first generation EGFR-TKIs, gefitinib and erlotinib, followed by G719X point mutation (exon 18) and L861Q point mutation (exon 21); exon 20 insertion mutation usually indicates intrinsic resistance. EGFR mutation as a strong predictive biomarker in the treatment of EGFR-TKIs has been reported in several retrospective analyses, and finally confirmed in biomarker analyses of IPASS (Iressa Pan-Asian Study) [3]. For chemotherapy-naïve patients with EGFR-mutated lung cancers, 6 phase III trials were all able to show that progression-free survival (PFS) of patients treated by EGFR-TKIs (gefitinib, erlotinib, or afa-

64

Suda · Mitsudomi Peters S, Stahel RA (eds): Successes and Limitations of Targeted Cancer Therapy. Prog Tumor Res. Basel, Karger, 2014, vol 41, pp 62–77 (DOI: 10.1159/000355902)


EGFR-Mutated Lung Cancers and EGFR-TKIs

KRAS

BRAF

1982

2000

EGFR Mutation MET Amplification MET Rearrangement ERBB2 PDGFRA EGFR vIII FGFR ROS1 DDR2 ALK RET AKT1 FGFR MEK1 2005

2010

2013

a

SCLC

Other squamous PDGFRA FGFRs

EGFR

DDR2 EGFR vIII Large

Other adeno.

ALK KRAS

RET

b

ROS1

MET

HER2

BRAF MEK1

tinib) was superior to that of patients under platinum-doublet chemotherapy (table 1) [4–9]. However, in these trials, overall survival did not differ between treatment arms, probably because of allowed and frequently encountered patient crossover between treatment arms. Retrospective analyses that compared patient survival before gefitinib approval with patient survival after gefitinib approval in Japan clearly indicated that introduction of EGFR-TKI to clinical practice actually doubled the overall survival of patients with EGFR-mutated lung cancers from ∼1 year to ∼2 years [10]. Lung Cancer – Targeting Drivers Peters S, Stahel RA (eds): Successes and Limitations of Targeted Cancer Therapy. Prog Tumor Res. Basel, Karger, 2014, vol 41, pp 62–77 (DOI: 10.1159/000355902)

65


Fig. 2. Identified and potential driver oncogenic mutations in lung cancers. a Time course (reported year) of discovery of driver oncogenic mutations is shown. Underlined driver oncogenic mutations indicate a higher prevalence in squamous cell carcinomas, while others do so in adenocarcinomas. b Prevalence of identified and potential driver oncogenic mutations in lung cancers. Data are combined from some reviews and original researches reporting each driver oncogenic mutation.

Table 1. Summary of PFS and overall survival (OS) in prospective studies that compared EGFR-TKIs with platinum doublet chemotherapies Study

Patient group

EGFR-TKI

n

PFS, months TKI

chemotherapy

OS, months TKI

chemotherapy

0.48 (0.36–0.64) 0.61 (0.31–1.22)

21.6 30.6

21.9 26.5

5.4 6.6 4.6 5.2 6.9

0.32 (0.24–0.44) 0.52 (0.38–0.72) 0.16 (0.10–0.26) 0.37 (0.25–0.54) 0.58 (0.43–0.78)

27.7 35.5 22.7 19.3 N/A

26.6 38.8 28.9 19.5 N/A

5.6

0.28 (0.20–0.39)

N/A

N/A

Subset analyses of patients selected by clinical background IPASS Asian gefitinib 261 9.5 6.3 First SIGNAL Korean gefitinib 42 8.4 6.7 Phase III trials for patients selected by EGFR mutation NEJ002 Japanese gefitinib 228 10.8 WJTOG3405 Japanese gefitinib 172 9.6 OPTIMAL Chinese erlotinib 154 13.7 EURTAC Caucasian erlotinib 173 9.7 Lux Lung 3 Caucasian 26% afatinib* 345 11.1 Asian 72% Lux Lung 6 Asian afatinib 364 13.7

HR for PFS (95% CI)

Afatinib is one of second-generation EGFR-TKIs that irreversibly binds to EGFR.

Activation of the ALK gene by forming the EML4-ALK fusion gene through a small inversion within chromosome 2p was discovered in 2007 in lung adenocarcinoma [11, 12]. Because EML4 has a coiled-coil dimerization domain, EML4-ALK is assumed to dimerize without ligand binding and undergo autophosphorylation leading to oncogenic activation. In addition to variants of EML4 segments, other molecules that have a coiled-coil domain are reported to fuse with ALK, including kinesin family member 5B (KIF5B), kinesin light chain 1 (KLC1), or TRK-fused gene (TFG). ALK-positive lung cancers have distinguishable clinicopathological characteristics. These include a younger age (difference in median age is almost 10 years compared with other types of lung cancers, and some very young patients suffer ALK-positive lung cancers), never smoker or a light smoker status, and acinar, cribriform or signet ring morphology. However, it should be noted that a failure to present with the abovementioned clinical characteristics does not rule out the possibility of ALK-rearranged lung cancer; i.e. lung cancer in an 80-year-old smoker patient may harbor ALK fusion. ALK fusion has also been identified in lung squamous cell carcinoma at haphazard [13]; however, ALK testing in this histology is not routinely recommended in the National Comprehensive Cancer Network guideline (version 3, 2012) due to its scarcity. Lung cancers with ALK rearrangement account for 5–7% of adenocarcinomas. Despite such scarcity, development of the ALK inhibitor crizotinib went very smoothly. A high objective response rate (60.8%, 95% CI: 52.3–68.9) and long median PFS (9.7 months, 95% CI: 7.7–12.8) were obtained in phase I study [14]. This resulted in rapid

66



Lung Cancers with ALK Rearrangement and Crizotinib

approval by the Food and Drug Administration in 2011, only 4 years after the discovery of ALK rearrangement. A phase III trial of crizotinib with 347 patients with stage IIIB/IV ALK-positive lung cancers who were previously treated with one prior platinum-based regimen (PROFILE 1007) also yielded a hazard ratio of 0.49 compared with chemotherapy (docetaxel or pemetrexed) [15]. A phase III trial of crizotinib in comparison with cisplatin or carboplatin plus pemetrexed (PROFILE 1014) for the first-line setting is now ongoing. Retrospective matched analysis suggests that crizotinib prolongs overall survival in ALK-positive lung cancer patients [16]. In addition to crizotinib, other ALK inhibitors, e.g. a highly selective ALK inhibitor CH5424802 [17], are now under clinical development.

Successes in Identification of Novel Driver Oncogenic Mutations

The successes of EGFR-TKI therapy in lung cancers encouraged researchers to explore novel targetable driver oncogenic mutations in lung cancers. Notably, they are usually in mutually exclusive relationships (fig. 2b). Therapies targeting lung cancers harboring these minor driver oncogenic mutations are now extremely limited because of unaccomplished detection systems. Future development of high-throughput analyses may enable clinical application of these driver oncogenic mutations [18]. ERBB2 Mutations ERBB2 mutations usually occur as small insertions in exon 20 of the tyrosine kinase domain, especially a 4-amino acid insertion at codon 776 (YVMA776–779 ins). ERBB2-mutated lung cancers account for 3% of adenocarcinomas, and are generally sensitive to ERBB2-targeted drugs. The disease control rate for trastuzumab-based therapies was 93% (n = 15) and that for afatinib was 100% (n = 4) in a large retrospective analysis (PFS of all ERBB2-targeting therapy was 5.1 months) [19], while only 3 of 18 patients responded to dacomitinib in a first-line setting [20].

The RAF-MEK-ERK pathway is one of the important downstream signaling pathways for many receptor tyrosine kinases including EGFR. A small fraction of lung adenocarcinomas harbor somatic activating mutations in this pathway. For example, BRAF mutations (3–4.9% [21, 22]) and MEK1 mutations (∼1% [23]). Although ∼90% of BRAF mutations in melanoma is due to a V600E mutation, mutation in this position only accounts for half of the BRAF mutations in lung cancers. BRAF mutations preferentially occur in former or current smokers, as with KRAS mutations [21, 22]. In a


67


BRAF Mutations and MEK1 Mutations

phase II study of lung cancer patients with BRAF V600E mutations, the response rate of a BRAF-TKI, dabrafenib, was reported to be 54% [24]. Lung cancers with MEK mutations are supposed to be sensitive to MEK inhibitors from in vitro analysis [23]. MET Alterations MET is a receptor tyrosine kinase for hepatocyte growth factor (HGF). A small fraction of lung cancer patients harbor MET gene amplification. One patient with lung cancer harboring MET amplification was reported to respond dramatically to crizotinib (an ALK inhibitor also inhibiting MET and ROS1) [25]. On the other hand, somatic mutations of MET that result in deletion of exon 14 are reported in about 3% of lung adenocarcinomas; however, their clinical implication as molecular potential targets is unclear. ROS1 and RET Fusion Genes Fusion genes involving other receptor tyrosine kinases, ROS1 and RET, are also oncogenic drivers in lung adenocarcinoma. In a similar way to ALK, several partner genes have been reported to fuse with ROS1 and RET [26]. ROS1 rearrangement was identified in 18 patients from 694 lung adenocarcinomas (2.6%), and patients with lung cancers with ROS1 rearrangement were significantly younger and more likely to have never smoked [27]. In a phase II study of crizotinib on lung cancer patients with ROS1 rearrangement, the response rate was 60% [28]. RET rearrangement is present in 1.7% of lung adenocarcinomas and common in young nonsmokers [29]. A lung cancer cell line (LC-2/ad) with RET rearrangement is sensitive to a RET inhibitor, vandetanib, and a lung adenocarcinoma patient with RET rearrangement reportedly responded to vandetanib [30]. Recently, preliminary data for the first 3 patients with RET-positive lung cancers from a prospective phase II trial of another RET inhibitor, cabozantinib (XL-184), were reported. Confirmed partial responses were observed in 2 patients, and a third patient showed prolonged stable disease approaching 8 months [31].

The above driver oncogenic mutations usually occur in lung adenocarcinomas. There has not been a targeted therapy against driver oncogenic mutations developed for the second most common types of lung cancer, squamous cell carcinomas. However, several recent studies have revealed that a part of squamous cell carcinomas also have potentially ‘targetable’ driver oncogenic mutations (fig. 2).

68



Oncogenic Mutations in Lung Squamous Cell Carcinomas

The EGFR variant III (vIII) mutation that lacks exon 2–7 of its extracellular domain was detected in 5% of squamous cell carcinomas. EGFR vIII-driven murine tumors were sensitive to HKI-272, an irreversible EGFR-TKI. Amplification of platelet-derived growth factor receptor-α (PDGFRA) gene was also identified in lung squamous cell carcinomas. A squamous cell carcinoma cell line (H1703) exhibits focal amplification of PDGFRA and was sensitive to PDGFRA inhibition. A gain-of-function E17K mutation in the AKT1 gene, an important component of the PI3K-AKT pathway, has also been reported in a minor subset of lung squamous cell carcinomas. In addition, focal amplification of fibroblast growth factor receptor 1 (FGFR1) gene and DDR2 somatic mutations have been reported in squamous cell carcinomas. Lung cancer cell lines harboring FGFR1 amplification (e.g. H1581 and H520) or DDR2 mutations (H2286 and HCC366) were sensitive to a nonisoform-specific FGFR inhibitor, PD173074, or a multi-targeted kinase inhibitor dasatinib, respectively [32, 33]. A squamous cell lung cancer patient who responded to dasatinib + erlotinib therapy was reported to harbor the DDR2 mutation but not the EGFR mutation. Most recently, fusion genes involving FGFR1, FGFR2, and FGFR3 were also identified in squamous cell carcinoma [34].

The KRAS mutation in lung cancer was discovered in 1982, and accounts for ∼30% of lung adenocarcinomas in Caucasians and ∼15% in East-Asians. Despite such a high incidence and long history, no specific treatment for KRAS-mutated cancers has succeeded, probably for two major reasons: (1) difficulties in targeting KRAS itself, and (2) the fact that several KRAS-mutated lung cancers do not depend on mutant KRAS for their survival and proliferation [35]. The fact that survival in some KRAS-mutated lung cancers is not dependent on KRAS gene function seems to conflict with the definition of ‘driver oncogenic mutations’. There is evidence to suggest that KRAS tumors may be dependent on KRAS function at first, and that KRAS independency is ‘acquired’ during tumor development. Singh et al. [36] observed that acquisition of the epithelial to mesenchymal transition phenotype correlated with KRAS independency. Sotillo et al. [37] suggested chromosomal instability in the early phase of tumor development may cause KRAS independency. They observed that Mad2 overexpression, which causes chromosomal instability, increased the likelihood of tumor recurrence in doxycycline-inducible mutant Kras transgenic mice after withdrawal of doxycycline (11/24 and 0/25 in mice with and without Mad2 overexpression, respectively). The recurrent tumors did not depend on mutant Kras signaling. Since targeting mutant KRAS is not sufficient to treat KRAS-mutated lung cancers, several alternative strategies have been tried. One strategy is targeting the major downstream signaling pathways of KRAS simultaneously; the RAF-MEK-ERK and


69


Limitations of Molecular-Targeted Therapies – Untargetable KRAS Mutations

PI3K-AKT pathways. This includes combination treatment of PI3K/AKT pathway inhibitor + RAF/MEK inhibitor or insulin-like growth factor-1 receptor (IGF-1R) inhibitor + RAF/MEK inhibitor. The latter combination therapy is based on results that suggest that activation of the PI3K/AKT pathway was dependent on IGF-1R in KRASmutated lung cancer cells but not in KRAS wild-type lung cancer cells [38]. Another approach is targeting the molecules that are identified with synthetic lethal RNA interference (RNAi) screens. Synthetic lethality describes the relationship between two genes, whereby alteration of either gene is compatible with cell viability, but simultaneous alteration of both genes results in cell death. Synthetic lethal RNAi screens attempt to identify genes of which inhibition is in synthetic lethal interaction with KRAS mutation. This approach enables the identification of factors or pathways that are not directly regulated by KRAS but are selectively necessary for survival and proliferation of KRAS-mutated lung cancer cells. The list of candidates obtained thus far includes the serine threonine kinase 33, the polo-like kinase 1, the TANK-binding kinase 1, the transforming growth factor β-activated kinase 1, the transcription factor GATA2, the G1-S regulator cyclin-dependent kinase 4, mitotic regulators and proteasome components [35]. The presence of many synthetically lethal partners for KRAS mutations may suggest the difficulty of targeting RAS for cancer treatment. Compound screening using a large cohort of cell lines with various driver oncogenic mutations is another approach. A pilot study screening 12 inhibitors in 84 genomically validated cell lines identified KRAS-mutant cells as being sensitive to heat shock protein 90 inhibitors, a finding that was confirmed by in vivo analysis. A fourth approach is the recently reported in silico screen for compounds that may inhibit activated RAS proteins. From a screen for small molecules that can target a pocket found in the crystal structure of GTP-bound RAS, several small molecules named Kobe0065 family compounds were identified and proved to show in vivo and in vitro activities in RAS-mutated cancer models including KRAS [39]. Clinical trials selectively enrolling patients with KRAS mutant lung cancers have also been performed. A prospective study demonstrated a small clinical benefit of adding a MEK inhibitor, selumetinib, to docetaxel in previously treated patients [40].

Not all patients with ‘sensitive’ driver oncogenic mutations respond to the relevant molecular-targeted drugs (de novo or inherent resistance). In addition, even in patients with good initial responses, almost all tumors become refractory to drugs within a few years (acquired resistance). Identification of the molecular mechanisms underlying these resistances and establishment of treatment strategies to overcome them are a current area of research interest.

70



Limitations of Molecular-Targeted Therapies – De novo Resistance and Acquired Resistance

De novo Resistance Even in patients with sensitive EGFR mutations who were enrolled in clinical trials, about 3–7% of patients were inherently resistant to EGFR-TKI and experienced progressive disease [4, 6, 7]. Coexistence of pretreatment T790M gatekeeper mutation (a resistant mutation described later), which is present in ∼0.5% of lung cancer patients with activating EGFR mutations by direct sequencing, is reported to cause inherent resistance. On the other hand, 38–79% of lung cancers with EGFR mutations are reported to have small populations of cancer cells with T790M mutations prior to EGFR-TKI treatment, if high sensitivity methods are used. Although these patients usually respond to first-generation EGFR-TKIs, several groups reported that the presence of the T790M mutation, in a small fraction, is correlated with shorter PFS after EGFR-TKI therapy [41–43]. However, this observation remains controversial [44, 45]. Another molecule that confers de novo resistance to EGFR-TKI therapy in lung cancers with the EGFR mutation is PTEN. As PTEN negatively regulates the PI3KAKT antiapoptotic and proliferation pathway, PTEN inactivation is considered to allow sufficient phosphatidyl-inositol 3,4,5-triphosphate accumulation and AKT activation through growth factor receptors other than inhibited EGFR. PTEN is also reported to promote ubiquitylation and degradation of activated EGFR. Therefore, PTEN inactivation may also increase EGFR activity and cause EGFR-TKI resistance [46]. High-level expression of HGF, a ligand of MET proto-oncogene, and MET gene amplification are other candidates identified in 29 and 4% of inherent resistance clinical specimens, respectively [47]. The HGF-MET oncogenic pathway is considered to bypass inhibited EGFR signaling and confer resistance to EGFRTKIs. A recent analysis found not only somatic aberration of tumors but also the genetic characteristics of the patient may affect sensitivity to EGFR-TKIs [48]. BCL2interacting mediator of cell death (BCL2-like 11, BIM) is one of the proapoptotic BCL-2 family proteins and for which upregulation is required for TKI-induced apoptosis. Previous reports have observed low BIM expression correlated with shorter PFS after EGFR-TKI treatment in lung cancer patients with EGFR mutations. Ng et al. [48] discovered an intronic deletion polymorphism of BIM provides decreased expression of BIM-EL (extra-long), the most abundant isoform of BIM. The presence of BIM deletion polymorphism was well correlated with shorter PFS for EGFRTKI in lung cancer patients with EGFR mutations. Two EGFR-mutated lung cancer cell lines with BIM deletion polymorphisms (PC3 and HCC2279) also showed low susceptibility to gefitinib-induced apoptosis. However, another research group was not able to confirm BIM deletion polymorphism as a negative predictive biomarker of PFS for EGFR-TKI treatment in 193 lung cancer patients with EGFR mutations [49].


71


Resistance to First-Generation EGFR-TKI Therapy in EGFR-Mutated Lung Cancers

72



Acquired Resistance Despite initial dramatic responses, almost all EGFR-mutated lung cancer patients eventually develop acquired resistance to gefitinib or erlotinib (fig. 1c). Molecular mechanisms underlying acquired resistance have been extensively studied. Acquisition of T790M, a gatekeeper mutation of EGFR, which substitutes methionine for threonine at amino acid position 790, is reportedly the most frequently acquired resistance mechanism, with an incidence of up to 68–83% if high sensitivity methods are used [43, 50]. Initially, the larger methionine residue was thought to sterically block bind gefitinib or erlotinib; however, a later study revealed that increased affinity of EGFRT790M to ATP (adenosine triphosphate) relative to EGFRT790M to first generation EGFR-TKI is the mechanism of resistance [51]. Several other secondary EGFR mutations, D761Y, L747S, or T854A, may cause acquired resistance to first generation EGFR-TKIs; however, these mutations are very rare. In addition, many kinds of acquired resistance molecular mechanisms have been reported, such as MET gene amplification, high expression of ligand HGF, PTEN inactivation, CRKL amplification, NFκB signaling activation, AXL activation, ERBB2 amplification, reactivation of ERK signaling by either an amplification of MAPK1 or by downregulation of negative regulators of ERK signaling, BRAF mutation, loss of EGFR mutant allele, epithelial to mesenchymal transition including stem cell-like features, or conversion to small-cell lung cancer (fig. 3) [52–59]. A critical issue in the analyses of acquired resistance is that cancer cells may have the ability to develop several resistance mechanisms depending on the environment and/or the drug(s) used [53]. Among these mechanisms, the T790M secondary mutation is most commonly detected in tumor specimens obtained from patients after acquisition of resistance. Therefore, to overcome T790M-mediated resistance, irreversible EGFR-TKIs (socalled second generation EGFR-TKIs), such as afatinib and dacomitinib, which form a covalent bond to cysteine 797 of EGFR, have been developed. These compounds are expected to overcome acquired resistance to gefitinib or erlotinib because they show in vitro activity in cancer cells with the T790M mutation. However, the IC50 value of these compounds for wild-type EGFR is less than that for EGFRT790M. Therefore, dose limitations due to inhibition of wild-type EGFR would result in inadequate clinical activity. Indeed, there was no overall survival advantage for afatinib over a placebo in the LUX-Lung 1 study that enrolled patients who had received at least 12 weeks of gefitinib or erlotinib and experienced treatment failure [60]. To overcome this drawback, so-called ‘third generation EGFR-TKIs’ that selectively inhibit mutant EGFR including T790M while sparing wild-type EGFR are being developed [61–63]. Another approach, a combination therapy of anti-EGFR antibody, cetuximab, and an irreversible EGFR-TKI, afatinib, was evaluated in an in vivo mouse model with EGFRT790M lung cancer. Anti-EGFR antibodies bind to EGFR and induce endocytosis of EGFR, therefore depleting total EGFR from cell surfaces. Clinical validity of this treatment strategy was evaluated in a phase I/II study, and high efficacy was obtained (disease control rate and response rate were 94 and 40%, respectively) [64].

a

b

c

Survival

Apoptosis

d

Survival

EGFR mutation EGFR mutation T790M MET/HGF ALK fusion AXL L1196M and others ERBB2, etc. ALK amplification ALK fusion ROS1 fusion EGFR G2032R KIT

Oncogenic driver products

Secondary mutation

Specific kinase inhibitor

Other receptors

Survival signaling

Intracellular molecule

e

Survival

Survival

EGFR mutation CRKL BRAF MAPK1 PTEN, etc. ALK fusion KRAS BRAF mutation KRAS/CDKN2A

EGFR mutation EMT Stem-like change Small-like change Loss of EGFR

Fig. 3. Classification of resistance mechanisms to molecular-targeted drugs. a Lung cancer cells with driver oncogenic mutations are sensitive to their respective molecular-targeted drugs. Resistance mechanisms can be classified into three categories: alteration of molecular targets themselves (b), activation of another oncogenic signaling pathway (c, d), and unidentified molecular mechanisms (e).

Similar to tumors with EGFR mutations, some tumors with ALK rearrangement show de novo resistance to crizotinib. In addition, acquired resistance also emerges after a good initial response to crizotinib. For acquired resistance mechanisms, about half occur in ALK itself and the other half are due to activation of other oncogenic pathways. The secondary alterations of ALK include secondary mutations, ALK amplification, and concurrent ALK mutations and amplification. Secondary ALK mutations include gatekeeper L1196M mutation, which is compatible with the T790M mutation of the EGFR gene. In contrast to lung cancers with EGFR mutations, in which T790M mutation is almost always the sole secondary mutation, many secondary ALK mutations, such as 1151Tins, L1152R, C1156Y, F1174C/L, G1202R, D1203N, S1206Y, and G1269A, have been reported [65]. As for other resistance mechanisms, activation of other oncogenic pathways, activation of EGFR or KRAS, and increased phosphorylation of KIT have been reported (fig. 3) [66, 67].


73


Resistance to ALK-TKI Therapy in Lung Cancers with ALK Rearrangement

Resistance to Molecular-Targeted Therapies in Lung Cancers with Minor Driver Oncogenic Mutations Several patients with minor driver oncogenic mutations have had the opportunity to be treated with molecular-targeted drugs for respective drivers; however, acquired resistance is also inevitable. A lung cancer patient with BRAF mutation who was treated with dabrafenib experienced disease progression after 8 months, and the recurrent tumor had three acquired mutations in KRAS, CDKN2A, and TP53 genes in addition to the original BRAF V600E mutation [68]. A patient with CD74-ROS1 fusion-positive lung cancer also acquired resistance to crizotinib. A biopsy of a resistant tumor revealed a secondary mutation of the ROS1 kinase domain (fig. 3) [69].

Conclusions

In the past decade, the standard care for patients with lung cancer has shifted from ‘general and empiric’ to ‘personalized and evidence-based’ treatment according to driver oncogenic mutations as molecular biomarkers. Suitable molecular-targeted therapies for selected patients dramatically improve treatment outcomes. However, lung cancer genomes are too heterogenic and too unstable; therefore, it may be difficult to eradicate all cancer cells in a patient by molecular-targeted drugs. We suppose that the ultimate end of treatment strategies for unresectable or recurrent lung cancers is to change this fatal disease to a chronic disorder using the ‘utile’ cat-and-mouse chase [70] between cancer cells and molecular-targeted drugs.

1 Weinstein IB: Cancer. Addiction to oncogenes – the Achilles heel of cancer. Science 2002;297:63–64. 2 Suda K, Tomizawa K, Yatabe Y, Mitsudomi T: Lung cancers unrelated to smoking: characterized by single oncogene addiction? Int J Clin Oncol 2011; 16: 294–305. 3 Fukuoka M, Wu YL, Thongprasert S, Sunpaweravong P, Leong SS, Sriuranpong V, et al: Biomarker analyses and final overall survival results from a phase III, randomized, open-label, first-line study of gefitinib versus carboplatin/paclitaxel in clinically selected patients with advanced non-small-cell lung cancer in Asia (IPASS). J Clin Oncol 2011;29:2866–2874. 4 Mitsudomi T, Morita S, Yatabe Y, Negoro S, Okamoto I, Tsurutani J, et al: Gefitinib versus cisplatin plus docetaxel in patients with non-small-cell lung cancer harbouring mutations of the epidermal growth factor receptor (WJTOG3405): an open label, randomised phase 3 trial. Lancet Oncol 2010;11:121–128.

74

5 Maemondo M, Inoue A, Kobayashi K, Sugawara S, Oizumi S, Isobe H, et al: Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR. N Engl J Med 2010;362:2380–2388. 6 Rosell R, Carcereny E, Gervais R, Vergnenegre A, Massuti B, Felip E, et al: Erlotinib versus standard chemotherapy as first-line treatment for European patients with advanced EGFR mutation-positive non-small-cell lung cancer (EURTAC): a multicentre, open-label, randomised phase 3 trial. Lancet Oncol 2012;13:239–246. 7 Zhou C, Wu YL, Chen G, Feng J, Liu XQ, Wang C, et al: Erlotinib versus chemotherapy as first-line treatment for patients with advanced EGFR mutation-positive non-small-cell lung cancer (OPTIMAL, CTONG-0802): a multicentre, open-label, randomised, phase 3 study. Lancet Oncol 2011;12: 735– 742.



References

19 Mazieres J, Peters S, Lepage B, Cortot AB, Barlesi F, Beau-Faller M, et al: Lung cancer that harbors an HER2 mutation: epidemiologic characteristics and therapeutic perspectives. J Clin Oncol 2013;31:1997– 2003. 20 Kris M, Goldberg A, Janne P, Kim D, Martins R, Mok T, et al: Dacomitinib (PF-00299804), an irreversible pan-HER tyrosine kinase inhibitor, for firstline treatment of EGFR-mutant or HER2-mutant or -amplified lung cancers (abstract 1228O). Ann Oncol 2012;23(suppl 9):ix401. 21 Marchetti A, Felicioni L, Malatesta S, Grazia Sciarrotta M, Guetti L, Chella A, et al: Clinical features and outcome of patients with non-small-cell lung cancer harboring BRAF mutations. J Clin Oncol 2011;29:3574–3579. 22 Paik PK, Arcila ME, Fara M, Sima CS, Miller VA, Kris MG, et al: Clinical characteristics of patients with lung adenocarcinomas harboring BRAF mutations. J Clin Oncol 2011;29:2046–2051. 23 Marks JL, Gong Y, Chitale D, Golas B, McLellan MD, Kasai Y, et al: Novel MEK1 mutation identified by mutational analysis of epidermal growth factor receptor signaling pathway genes in lung adenocarcinoma. Cancer Res 2008;68:5524–5528. 24 Planchard D, Mazieres J, Riely G, Rudin CM, Barlesi F, Quoix E, et al: Interim results of phase II study BRAF113928 of dabrafenib in BRAF V600E mutation-positive non-small cell lung cancer (NSCLC) patients (abstract). J Clin Oncol 2013; 31(suppl): 8009. 25 Ou SH, Kwak EL, Siwak-Tapp C, Dy J, Bergethon K, Clark JW, et al: Activity of crizotinib (PF02341066), a dual mesenchymal-epithelial transition (MET) and anaplastic lymphoma kinase (ALK) inhibitor, in a non-small cell lung cancer patient with de novo MET amplification. J Thorac Oncol 2011;6:942–946. 26 Takeuchi K, Soda M, Togashi Y, Suzuki R, Sakata S, Hatano S, et al: RET, ROS1 and ALK fusions in lung cancer. Nat Med 2012;18:378–381. 27 Bergethon K, Shaw AT, Ou SH, Katayama R, Lovly CM, McDonald NT, et al: ROS1 rearrangements define a unique molecular class of lung cancers. J Clin Oncol 2012;30:863–870. 28 Ou SH, Bang YJ, Camidge DR, Riely G, Salgia R, Shapiro CL, et al: Efficacy and safety of crizotinib in patients with advanced ROS1-rearranged non-small cell lung cancer (MSCLC) (abstract). J Clin Oncol 2013;31(suppl):8032. 29 Wang R, Hu H, Pan Y, Li Y, Ye T, Li C, et al: RET fusions define a unique molecular and clinicopathologic subtype of non-small-cell lung cancer. J Clin Oncol 2013;30:4352–4359. 30 Gautschi O, Zander T, Keller FA, Strobel K, Hirschmann A, Aebi S, et al: A patient with lung adenocarcinoma and RET fusion treated with vandetanib. J Thorac Oncol 2013;8:e43–e44.


75


8 Yang JC-H, Schuler MH, Yamamoto N, O’Byrne KJ, Hirsch V, Mok T, et al: LUX-Lung 3: a randomized, open-label, phase III study of afatinib versus pemetrexed and cisplatin as first-line treatment for patients with advanced adenocarcinoma of the lung harboring EGFR-activating mutations (abstract). J Clin Oncol 2012;30(suppl):LBA7500. 9 Wu YL, Zhou C, Hu C, Feng J, Lu S, Huang Y, et al: LUX-Lung 6: a randomized, open-label, phase III study of afatinib (A) versus gemcitabine/cisplatin (GC) as first-line treatment for Asian patients (pts) with EGFR mutation-positive (EGFR M+) advanced adenocarcinoma of the lung (abstract). J Clin Oncol 2013;31(suppl):8016. 10 Takano T, Fukui T, Ohe Y, Tsuta K, Yamamoto S, Nokihara H, et al: EGFR mutations predict survival benefit from gefitinib in patients with advanced lung adenocarcinoma: a historical comparison of patients treated before and after gefitinib approval in Japan. J Clin Oncol 2008;26:5589–5595. 11 Soda M, Choi YL, Enomoto M, Takada S, Yamashita Y, Ishikawa S, et al: Identification of the transforming EML4-ALK fusion gene in non-small-cell lung cancer. Nature 2007;448:561–566. 12 Rikova K, Guo A, Zeng Q, Possemato A, Yu J, Haack H, et al: Global survey of phosphotyrosine signaling identifies oncogenic kinases in lung cancer. Cell 2007;131:1190–1203. 13 Ochi N, Yamane H, Yamagishi T, Takigawa N, Monobe Y: Can we eliminate squamous cell carcinoma of the lung from testing of EML4-ALK fusion gene? Lung Cancer 2013;79:94–95. 14 Camidge DR, Bang YJ, Kwak EL, Iafrate AJ, VarellaGarcia M, Fox SB, et al: Activity and safety of crizotinib in patients with ALK-positive non-small-cell lung cancer: updated results from a phase 1 study. Lancet Oncol 2012;13:1011–1019. 15 Shaw AT, Kim DW, Nakagawa K, Seto T, Crinò L, Ahn M, et al: Phase III study of crizotinib versus pemetrexed or docetaxel chemotherapy in patients with advanced ALK-positive non-small cell lung cancer (NSCLC) (PROFILE 1007). Ann Oncol 2012; 23(suppl 9):ixe21. 16 Shaw AT, Yeap BY, Solomon BJ, Riely GJ, Gainor J, Engelman JA, et al: Effect of crizotinib on overall survival in patients with advanced non-small-cell lung cancer harbouring ALK gene rearrangement: a retrospective analysis. Lancet Oncol 2011;12:1004–1012. 17 Seto T, Kiura K, Nishio M, Nakagawa K, Maemondo M, Inoue A, et al: CH5424802 (RO5424802) for patients with ALK-rearranged advanced non-small-cell lung cancer (AF-001JP study): a single-arm, open-label, phase 1–2 study. Lancet Oncol 2013;14:590–598. 18 Li T, Kung HJ, Mack PC, Gandara DR: Genotyping and genomic profiling of non-small-cell lung cancer: implications for current and future therapies. J Clin Oncol 2013;31:1039–1049.

76

43 Su KY, Chen HY, Li KC, Kuo ML, Yang JC, Chan WK, et al: Pretreatment epidermal growth factor receptor (EGFR) T790M mutation predicts shorter EGFR tyrosine kinase inhibitor response duration in patients with non-small-cell lung cancer. J Clin Oncol 2012;30:433–440. 44 Fujita Y, Suda K, Kimura H, Matsumoto K, Arao T, Nagai T, et al: Highly sensitive detection of EGFR T790M mutation using colony hybridization predicts favorable prognosis of patients with lung cancer harboring activating EGFR mutation. J Thorac Oncol 2012;7:1640–1644. 45 Rosell R, Molina MA, Taron M, Bertran-Alamillo J, Mayo C, Vergnenegre A, et al: EGFR compound mutants discriminate survival to erlotinib in non-smallcell lung cancer (NSCLC) patients (p) in the EURTAC study (abstract). J Clin Oncol 2012; 30(suppl):7522. 46 Vivanco I, Rohle D, Versele M, Iwanami A, Kuga D, Oldrini B, et al: The phosphatase and tensin homolog regulates epidermal growth factor receptor (EGFR) inhibitor response by targeting EGFR for degradation. Proc Natl Acad Sci USA 2010; 107: 6459–6464. 47 Yano S, Yamada T, Takeuchi S, Tachibana K, Minami Y, Yatabe Y, et al: Hepatocyte growth factor expression in EGFR mutant lung cancer with intrinsic and acquired resistance to tyrosine kinase inhibitors in a Japanese cohort. J Thorac Oncol 2011; 6: 2011– 2017. 48 Ng KP, Hillmer AM, Chuah CT, Juan WC, Ko TK, Teo AS, et al: A common BIM deletion polymorphism mediates intrinsic resistance and inferior responses to tyrosine kinase inhibitors in cancer. Nat Med 2012;18:521–528. 49 Lee JK, Shin JY, Kim S, Lee S, Park C, Kim JY, et al: Primary resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in patients with non-small-cell lung cancer harboring TKI-sensitive EGFR mutations: an exploratory study. Ann Oncol 2013;24:2080–2087. 50 Arcila ME, Oxnard GR, Nafa K, Riely GJ, Solomon SB, Zakowski MF, et al: Rebiopsy of lung cancer patients with acquired resistance to EGFR inhibitors and enhanced detection of the T790M mutation using a locked nucleic acid-based assay. Clin Cancer Res 2011;17:1169–1180. 51 Suda K, Onozato R, Yatabe Y, Mitsudomi T: EGFR T790M mutation: a double role in lung cancer cell survival? J Thorac Oncol 2009;4:1–4. 52 Sequist LV, Waltman BA, Dias-Santagata D, Digumarthy S, Turke AB, Fidias P, et al: Genotypic and histological evolution of lung cancers acquiring resistance to EGFR inhibitors. Sci Transl Med 2011; 3: 75ra26.



31 Drilon A, Wang L, Hasanovic A, Suehara Y, Lipson D, Stephens P, et al: Response to cabozantinib in patients with RET fusion-positive lung adenocarcinomas. Cancer Discov 2013;3:630–635. 32 Weiss J, Sos ML, Seidel D, Peifer M, Zander T, Heuckmann JM, et al: Frequent and focal FGFR1 amplification associates with therapeutically tractable FGFR1 dependency in squamous cell lung cancer. Sci Transl Med 2010;2:62ra93. 33 Hammerman PS, Sos ML, Ramos AH, Xu C, Dutt A, Zhou W, et al: Mutations in the DDR2 kinase gene identify a novel therapeutic target in squamous cell lung cancer. Cancer Discov 2011;1:78–89. 34 Wu YM, Su F, Kalyana-Sundaram S, Khazanov N, Ateeq B, Cao X, et al: Identification of targetable FGFR gene fusions in diverse cancers. Cancer Discov 2013;3:636–647. 35 Suda K, Tomizawa K, Mitsudomi T: Biological and clinical significance of KRAS mutations in lung cancer: an oncogenic driver that contrasts with EGFR mutation. Cancer Metastasis Rev 2010; 29: 49–60. 36 Singh A, Greninger P, Rhodes D, Koopman L, Violette S, Bardeesy N, et al: A gene expression signature associated with ‘K-Ras addiction’ reveals regulators of EMT and tumor cell survival. Cancer Cell 2009;15: 489–500. 37 Sotillo R, Schvartzman JM, Socci ND, Benezra R: Mad2-induced chromosome instability leads to lung tumour relapse after oncogene withdrawal. Nature 2010;464:436–440. 38 Molina-Arcas M, Hancock DC, Sheridan C, Kumar MS, Downward J: Coordinate direct input of both KRAS and IGF1 receptor to activation of PI3 kinase in KRAS-mutant lung cancer. Cancer Discov 2013;3: 548–563. 39 Shima F, Yoshikawa Y, Ye M, Araki M, Matsumoto S, Liao J, et al: In silico discovery of small-molecule Ras inhibitors that display antitumor activity by blocking the Ras-effector interaction. Proc Natl Acad Sci USA 2013;110:8182–8187. 40 Janne PA, Shaw AT, Pereira JR, Jeannin G, Vansteenkiste J, Barrios C, et al: Selumetinib plus docetaxel for KRAS-mutant advanced non-smallcell lung cancer: a randomised, multicentre, placebo-controlled, phase 2 study. Lancet Oncol 2013;14: 38–47. 41 Maheswaran S, Sequist LV, Nagrath S, Ulkus L, Brannigan B, Collura CV, et al: Detection of mutations in EGFR in circulating lung-cancer cells. N Engl J Med 2008;359:366–377. 42 Rosell R, Molina MA, Costa C, Simonetti S, GimenezCapitan A, Bertran-Alamillo J, et al: Pretreatment EGFR T790M mutation and BRCA1 mRNA expression in erlotinib-treated advanced non-small-cell lung cancer patients with EGFR mutations. Clin Cancer Res 2011;17:1160–1168.

61 Zhou W, Ercan D, Chen L, Yun C-H, Li D, Capelletti M, et al: Novel mutant-selective EGFR kinase inhibitors against EGFR T790M. Nature 2009; 462: 1070–1074. 62 Sequist LV, Soria JC, Gadgeel SM, Wakelee HA, Camidge DR, Varga A, et al: First-in-human evaluation of CO-1686, an irreversible, selective, and potent tyrosine kinase inhibitor of EGFR T790M (abstract). J Clin Oncol 2013;31:2524. 63 Lee HJ, Schaefer G, Heffron TP, Shao L, Ye X, Sideris S, et al: Noncovalent wild-type-sparing inhibitors of EGFR T790M. Cancer Discov 2013; 3: 168– 181. 64 Janjigian YY, Smit E, Horn L, et al: Activity of afatinib/cetuximab in patients with EGFR mutant nonsmall cell lung cancer (NSCLC) and acquired resistance to EGFR inhibitors (abstract). Ann Oncol 2012;23:12270. 65 Camidge DR, Doebele RC: Treating ALK-positive lung cancer – early successes and future challenges. Nat Rev Clin Oncol 2012;9:268–277. 66 Doebele RC, Pilling AB, Aisner DL, Kutateladze TG, Le AT, Weickhardt AJ, et al: Mechanisms of resistance to crizotinib in patients with ALK gene rearranged non-small cell lung cancer. Clin Cancer Res 2012;18:1472–1482. 67 Katayama R, Shaw AT, Khan TM, Mino-Kenudson M, Solomon BJ, Halmos B, et al: Mechanisms of acquired crizotinib resistance in ALK-rearranged lung cancers. Sci Transl Med 2012;4:120ra17. 68 Rudin CM, Hong K, Streit M: Molecular characterization of acquired resistance to the BRAF Inhibitor dabrafenib in a patient with BRAF-mutant nonsmall-cell lung cancer. J Thorac Oncol 2013; 8:e41– e42. 69 Awad MM, Katayama R, McTigue M, Liu W, Deng YL, Brooun A, et al: Acquired resistance to crizotinib from a mutation in CD74-ROS1. New Engl J Med 2013;369:1173. 70 Suda K, Tomizawa K, Osada H, Maehara Y, Yatabe Y, Sekido Y, et al: Conversion from the ‘oncogene addiction’ to ‘drug addiction’ by intensive inhibition of the EGFR and MET in lung cancer with activating EGFR mutation. Lung Cancer 2012;76:292–299.

Kenichi Suda, MD 377-2 Ohno-higashi Osaka-Sayama, Osaka 589-8511 (Japan) E-Mail ascaris @ surg2.med.kyushu-u.ac.jp


77


53 Suda K, Mizuuchi H, Maehara Y, Mitsudomi T: Acquired resistance mechanisms to tyrosine kinase inhibitors in lung cancer with activating epidermal growth factor receptor mutation-diversity, ductility, and destiny. Cancer Metastasis Rev 2012; 31: 807– 814. 54 Takezawa K, Pirazzoli V, Arcila ME, Nebhan CA, Song X, de Stanchina E, et al: HER2 amplification: a potential mechanism of acquired resistance to EGFR inhibition in EGFR-mutant lung cancers that lack the second-site EGFRT790M mutation. Cancer Discov 2012;2:922–933. 55 Zhang Z, Lee JC, Lin L, Olivas V, Au V, LaFramboise T, et al: Activation of the AXL kinase causes resistance to EGFR-targeted therapy in lung cancer. Nat Genet 2012;44:852–860. 56 Ercan D, Xu C, Yanagita M, Monast CS, Pratilas CA, Montero J, et al: Reactivation of ERK signaling causes resistance to EGFR kinase inhibitors. Cancer Discov 2012;2:934–947. 57 Ohashi K, Sequist LV, Arcila ME, Moran T, Chmielecki J, Lin YL, et al: Lung cancers with acquired resistance to EGFR inhibitors occasionally harbor BRAF gene mutations but lack mutations in KRAS, NRAS, or MEK1. Proc Natl Acad Sci USA 2012;109:E2127–E2133. 58 Tabara K, Kanda R, Sonoda K, Kubo T, Murakami Y, Kawahara A, et al: Loss of activating EGFR mutant gene contributes to acquired resistance to EGFR tyrosine kinase inhibitors in lung cancer cells. PLoS One 2012;7:e41017. 59 Shien K, Toyooka S, Yamamoto H, Soh J, Jida M, Thu KL, et al: Acquired resistance to EGFR inhibitors is associated with a manifestation of stem celllike properties in cancer cells. Cancer Res 2013; 73: 3051–3061. 60 Miller VA, Hirsh V, Cadranel J, Chen YM, Park K, Kim SW, et al: Afatinib versus placebo for patients with advanced, metastatic non-small-cell lung cancer after failure of erlotinib, gefitinib, or both, and one or two lines of chemotherapy (LUX-Lung 1): a phase 2b/3 randomised trial. Lancet Oncol 2012; 13: 528–538.

Successes and limitations of targeted cancer therapy in ovarian cancer.

Successes and limitations of targeted cancer therapy in breast cancer.

Successes and limitations of targeted cancer therapy in colon cancer.

Successes and limitations of targeted cancer therapy in melanoma.

Successes and limitations of targeted cancer therapy in gastrointestinal stromal tumors.

Successes and limitations of targeted therapies in renal cell carcinoma.

Targeted therapy in lung cancer: IPASS and beyond, keeping abreast of the explosion of targeted therapies for lung cancer.

Indications and limitations of chemotherapy and targeted agents in non-small cell lung cancer brain metastases.

[Advances of molecular targeted therapy in squamous cell lung cancer].

Surviving with lung cancer: medication-taking and oral targeted therapy.

EGFR targeted therapy in lung cancer; an evolving story.

Osimertinib making a breakthrough in lung cancer targeted therapy.

[Lung cancer therapy in transition: targeted therapies are coming].

Targeted therapy in cancer.

Non-small cell lung cancer: the era of targeted therapy.

Folate-conjugated polyspermine for lung cancer-targeted gene therapy.

Nanoparticle-based targeted gene therapy for lung cancer.

SapC-DOPS nanovesicles as targeted therapy for lung cancer.

Overcoming resistance to targeted therapy for lung cancer.

Targeted therapy in gastric cancer.

Targeted therapy in ovarian cancer.

Beyond chemotherapy and targeted therapy: adoptive cellular therapy in non-small cell lung cancer.

Biomarkers and Targeted Therapy in Pancreatic Cancer.

Targeted Lung Cancer Treatments and Eye Metastasis.