MOLECULAR & CELLULAR ONCOLOGY 2016, VOL. 3, NO. 3, e1128515 (3 pages) http://dx.doi.org/10.1080/23723556.2015.1128515
COMMENTARY
Taking out the JNK: A window of opportunity to improve cancer therapy Petranel T. Ferraoa,b a Cancer Research Division, Peter MacCallum Cancer Center, St. Andrew’s Place, East Melbourne, VIC, Australia; bDepartment of Pathology and The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, VIC, Australia
ABSTRACT
ARTICLE HISTORY
c-JUN-N-terminal kinase (JNK) signaling is a stress-induced response that enables survival of normal cells and is also utilized by cancer cells to evade therapy. Combining JNK inhibitors with standard therapies provides a potential strategy for overcoming drug resistance. Use of the optimal combination dosing and scheduling may substantially improve outcomes for cancer patients.
Received 23 November 2015 Revised 30 November 2015 Accepted 30 November 2015 KEYWORDS
Combination therapies; dosing; drug resistance; early adaptation; EMT; JNK signaling; phenotypeswitching; scheduling; stress response
Despite initial dramatic responses of cancer to conventional cytotoxic therapies or new targeted therapies, resistance invariably develops. The highly adaptive nature of cancer cells presents a challenge for eradicating residual cells able to survive effective therapy, providing an avenue for re-establishment of disease at a later time. Cancer cells that survive treatment have commonly undergone a transition to a more mesenchymal-like or stem cell-like state that is accompanied by the ability to evade drug-induced apoptosis and is associated with increased metastatic potential. This provides a selective pressure for the acquisition of drug resistance mechanisms through altered gene expression or mutation that enables tumor re-establishment. Hence, identifying targets to overcome cancer cell resistance to therapyinduced apoptosis, in addition to inhibiting phenotypic plasticity1 to control metastatic spread, offers a potentially efficacious therapeutic strategy for the eradication of residual cancer cells during early treatment with the hope of increased progression-free survival rates for patients. We recently identified the transcription co-factor c-JUN as a key mediator of survival, drug resistance, and phenotypic switching to a mesenchymal-like state resembling epithelialmesenchymal-transition (EMT) in BRAFV600-mutant metastatic melanomas that have been subjected to drug therapy with BRAF and/or MEK inhibitors.2 The ability to target c-JUN through upstream inhibition of its activator enzyme c-JUN-N-terminal kinase (JNK) offers a significant opportunity to target both therapy resistance and phenotype-switching associated with enhanced metastatic potential.2 The JNK-JUN pathway has been verified as a key pathway in mediating survival following BRAF and MEK inhibitor treatment in parallel studies by other research groups.3,4 The JNK signaling pathway has also been reported to confer therapy resistance in multiple
CONTACT Petranel T. Ferrao © 2016 Taylor & Francis Group, LLC
[email protected]
tumor types,5 including chemoresistance in ovarian,6 colorectal,7 and pancreatic8 cancers, and has been linked to the stem cell-like properties of cancer cells. The potential for JNK inhibitors to overcome EMT-mediated tumor cell survival following chemotherapy has also been proposed in breast cancer.9 Our study reports a mechanism by which JNK pathway activation can be a direct consequence of target inhibition and unites these concepts to demonstrate the “multi-targeting” potential of JNK inhibitors for overcoming therapy resistance and phenotype-switching,2 as schematically represented in Fig. 1. Efforts toward the development of clinical candidate JNK inhibitors by pharmaceutical companies have focused on treatments for inflammatory and neurodegenerative conditions. The role of JNK in cancer may depend on the type of tumor and the stress-inducing factor(s), as JNK activation has also previously been associated with promotion of cell death.10 This may explain why there has been a degree of restraint in pursuing JNK as a target in the oncology field. However, a number of recent studies have implicated JNK signaling in early therapy resistance and/or EMT in multiple cancer types. Our study demonstrates the potential of JNK inhibitors to overcome both phenomena, suggesting that JNK should be considered a bona fide target for these aspects of therapy in these cancers. Ultimately, the usefulness of a target in the oncology field is influenced by its relative activity in cancer versus normal cells. JNK inhibitors have been clinically evaluated for inflammatory conditions without any unexpected adverse effects in patients. The JNK signaling pathway, also known as the stress-activated protein kinase (SAPK) pathway, is activated upon cellular stress in normal cells.10 As such, JNK signaling is not activated in the majority of normal cells, making it an “Achilles’ heel” and an ideal target in tumors reliant on the JNK-JUN pathway for survival in the face of therapy. However, as the main benefit of
e1128515-2
P. T. FERRAO
Figure 1. Taking out the JNK to achieve more effective drug-induced tumor cell killing. A schematic representation of the activation of c-JUN-N-terminal kinase (JNK) signaling as a consequence of drug target inhibition and/or through a stress-induced response. The potential intervention points that enable a combination of JNK inhibitors to enhance drug treatment efficacy by overcoming JNK-mediated tumor cell survival mechanisms are indicated.
targeting JNK is envisaged to be overcoming cancer cell survival and phenotype-switching during early treatment, it is necessary to consider whether drug treatment may induce stress in some normal cells. In particular, cytotoxic drugs are known to cause adverse effects in the proliferating cell compartments of normal tissues. The role of JNK in these normal cells is not clear. If JNK performs a survival function its inhibition may cause increased toxicity, but if its role is to induce cell death, it may be a serendipitous target for reducing toxicity to normal cells while enhancing treatment efficacy in the cancer cells. Indeed, the potential benefit from combining JNK inhibitors with existing cancer treatments warrants proper clinical evaluation. One other important aspect of combination treatment that requires further investigation in preclinical models is the dosing and scheduling of combination drugs for the optimal responses. Our findings using cell line models revealed that a greater extent of cell killing could be attained with the same concentrations of the BRAF and JNK inhibitors if the cells were initially treated with the BRAF inhibitor that induced activation of the JNK pathway.2 In essence this offers a way to ‘prime’ the surviving cancer cells and select for characteristics that confer enhanced responsiveness to the combination treatment. Our findings also revealed that the highest doses are not necessarily the best, as the greatest drug synergy was obtained at combinations within the mid-range of doses assessed.2 Animal models could be utilized to predict the best dosing and scheduling of single agents with combination therapies to guide strategies for achieving the best responses in patients. Real-time monitoring of biomarkers predictive for response or resistance to drug(s) may guide the timing of treatment based on responses from preclinical studies. In the case of BRAFV600mutant metastatic melanoma, we predict that phosphorylated cJUN would be an ideal biomarker for monitoring the tumors following initial treatment with BRAF/MEK inhibitors to reveal the
window of opportunity for combination treatment with JNK and BRAF/MEK inhibitors.2 Matched samples from patients at progression of disease showed a reversion to reduced c-JUN levels and activation,2 suggesting that this window is early during drug treatment. Our data also demonstrated that JNK inhibitor doses that did not result in cancer cell death were able to reduce drug-induced cell migration,2 suggesting that therapeutic benefit may be obtained even in protected niches or compartments with reduced drug concentrations. It is well established that acquired resistance mechanisms to targeted therapies vary greatly, both within each patient and across patient groups, and are due to clonal heterogeneity, especially at progression of disease. Targeting an early adaptive mechanism such as the JNK-JUN pathway, which appears to be a more common mechanism of early survival across multiple patients, offers the potential to develop a widely applicable strategy for improving treatment efficacy and outcomes. As we enter an era of varied choices for cancer treatment, it becomes increasingly important to advance our scientific understanding of not only the options for therapy, but also the underlying molecular and cellular features contributing to therapy resistance at various stages of treatment. Although our knowledge and understanding of the processes that confer resistance and the pathways that can be targeted has expanded, defining the best treatment options, drug(s), dosing, and scheduling are all important factors for consideration to obtain the best outcomes for patients. These factors may be more efficiently explored in the preclinical setting. Our hope is to utilize our understanding of early drug adaptation to overcome tumor cells survival and evasion of treatment in order to eradicate residual disease. Ultimately, being prepared to inhibit the evolving targets during cancer cell adaptation to maximize therapeutic response early during treatment rather than at the point of disease progression may provide the best chance of long-term benefit, and possibly even a greater cure rate in cancer patients.
MOLECULAR & CELLULAR ONCOLOGY
Disclosure of potential conflicts of interest No potential conflicts of interest were disclosed.
Acknowledgments
5.
I thank Dr Robert N. Jorissen from The Walter and Eliza Hall Institute of Medical Research Australia and Prof. Richard B. Pearson from The Peter MacCallum Cancer Center Australia for providing helpful comments on this Author View.
6.
Funding PTF is supported by the NHMRC (GNT1042980).
7.
References 1. Ferrao PT, Behren A, Anderson RL, Thompson EW. Cellullar and phenotypic plasticity in cancer. Frontiers Oncol 2015; 5:171; PMID:26301202; http://dx.doi.org/10.3389/fonc.2015.00171 2. Ramsdale R, Jorissen RN, Li FZ, Al-Obaidi S, Ward T, Sheppard KE, Bukczynska PE, Young RJ, Boyle SE, Shackleton M, et al. The transcription cofactor c-JUN mediates phenotype switching and BRAF inhibitor resistance in melanoma. Science Signal 2015; 8:ra82; PMID:26286024; http://dx.doi.org/10.1126/scisignal.aab1111 3. Fallahi-Sichani M, Moerke NJ, Niepel M, Zhang T, Gray NS, Sorger PK. Systematic analysis of BRAFV600E melanomas reveals a role for JNK/c-Jun pathway in adaptive resistance to drug-induced apoptosis. Mol Syst Biol 2015; 11:797; PMID:25814555; http://dx.doi.org/ 10.15252/msb.20145877 4. Delmas A, Cherier J, Pohorecka M, Medale-Giamarchi C, Meyer N, Casanova A, Sordet O, Lamant L, Savina A, Pradines A, et al.
8.
9.
10.
e1128515-3
The c-Jun/RHOB/AKT pathway confers resistance of BRAFmutant melanoma cells to MAPK inhibitors. Oncotarget 2015; 6:15250-64; PMID:26098773; http://dx.doi.org/10.18632/ oncotarget.3888 Vasilevskaya I, O’Dwyer PJ. Role of Jun and Jun kinase in resistance of cancer cells to therapy. Drug Resistance Updates 2003; 6:147-56; PMID:12860462; http://dx.doi.org/10.1016/S1368-7646 (03)00043-8 Li F, Meng L, Zhou J, Xing H, Wang S, Xu G, Zhu H, Wang B, Chen G, Lu YP, Ma D. Reversing chemoresistance in cisplatin-resistant human ovarian cancer cells: a role of c-Jun NH2-terminal kinase 1. Biochem Biophys Res Commun 2005; 335:1070-7; PMID:16105650; http://dx.doi.org/10.1016/j.bbrc.2005.07.169 Sui X, Kong N, Wang X, Fang Y, Hu X, Xu Y, Chen W, Wang K, Li D, Jin W. JNK confers 5-fluorouracil resistance in p53-deficient and mutant p53-expressing colon cancer cells by inducing survival autophagy. Scientific Reports 2014; 4:4694; PMID:24733045; http:// dx.doi.org/10.1038/srep04694 Suzuki S, Okada M, Shibuya K, Seino M, Sato A, Takeda H, Seino S, Yoshioka T, Kitanaka C. JNK suppression of chemotherapeutic agents-induced ROS confers chemoresistance on pancreatic cancer stem cells. Oncotarget 2015; 6:458-70; PMID:25473894; http://dx.doi. org/10.18632/oncotarget.2693 Wang J, Kuiatse I, Lee AV, Pan J, Giuliano A, Cui X. Sustained cJun-NH2-kinase activity promotes epithelial-mesenchymal transition, invasion, and survival of breast cancer cells by regulating extracellular signal-regulated kinase activation. Mol Cancer Res 2010; 8:266-77; PMID:20145041; http://dx.doi.org/10.1158/15417786.MCR-09-0221 Johnson GL, Nakamura K. The c-jun kinase/stress-activated pathway: regulation, function and role in human disease. Biochimica Et Biophysica Acta 2007; 1773:1341-8; PMID:17306896; http://dx.doi.org/ 10.1016/j.bbamcr.2006.12.009
COMMENTARY
Taking out the JNK: A window of opportunity to improve cancer therapy Petranel T. Ferraoa,b a Cancer Research Division, Peter MacCallum Cancer Center, St. Andrew’s Place, East Melbourne, VIC, Australia; bDepartment of Pathology and The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, VIC, Australia
ABSTRACT
ARTICLE HISTORY
c-JUN-N-terminal kinase (JNK) signaling is a stress-induced response that enables survival of normal cells and is also utilized by cancer cells to evade therapy. Combining JNK inhibitors with standard therapies provides a potential strategy for overcoming drug resistance. Use of the optimal combination dosing and scheduling may substantially improve outcomes for cancer patients.
Received 23 November 2015 Revised 30 November 2015 Accepted 30 November 2015 KEYWORDS
Combination therapies; dosing; drug resistance; early adaptation; EMT; JNK signaling; phenotypeswitching; scheduling; stress response
Despite initial dramatic responses of cancer to conventional cytotoxic therapies or new targeted therapies, resistance invariably develops. The highly adaptive nature of cancer cells presents a challenge for eradicating residual cells able to survive effective therapy, providing an avenue for re-establishment of disease at a later time. Cancer cells that survive treatment have commonly undergone a transition to a more mesenchymal-like or stem cell-like state that is accompanied by the ability to evade drug-induced apoptosis and is associated with increased metastatic potential. This provides a selective pressure for the acquisition of drug resistance mechanisms through altered gene expression or mutation that enables tumor re-establishment. Hence, identifying targets to overcome cancer cell resistance to therapyinduced apoptosis, in addition to inhibiting phenotypic plasticity1 to control metastatic spread, offers a potentially efficacious therapeutic strategy for the eradication of residual cancer cells during early treatment with the hope of increased progression-free survival rates for patients. We recently identified the transcription co-factor c-JUN as a key mediator of survival, drug resistance, and phenotypic switching to a mesenchymal-like state resembling epithelialmesenchymal-transition (EMT) in BRAFV600-mutant metastatic melanomas that have been subjected to drug therapy with BRAF and/or MEK inhibitors.2 The ability to target c-JUN through upstream inhibition of its activator enzyme c-JUN-N-terminal kinase (JNK) offers a significant opportunity to target both therapy resistance and phenotype-switching associated with enhanced metastatic potential.2 The JNK-JUN pathway has been verified as a key pathway in mediating survival following BRAF and MEK inhibitor treatment in parallel studies by other research groups.3,4 The JNK signaling pathway has also been reported to confer therapy resistance in multiple
CONTACT Petranel T. Ferrao © 2016 Taylor & Francis Group, LLC
[email protected]
tumor types,5 including chemoresistance in ovarian,6 colorectal,7 and pancreatic8 cancers, and has been linked to the stem cell-like properties of cancer cells. The potential for JNK inhibitors to overcome EMT-mediated tumor cell survival following chemotherapy has also been proposed in breast cancer.9 Our study reports a mechanism by which JNK pathway activation can be a direct consequence of target inhibition and unites these concepts to demonstrate the “multi-targeting” potential of JNK inhibitors for overcoming therapy resistance and phenotype-switching,2 as schematically represented in Fig. 1. Efforts toward the development of clinical candidate JNK inhibitors by pharmaceutical companies have focused on treatments for inflammatory and neurodegenerative conditions. The role of JNK in cancer may depend on the type of tumor and the stress-inducing factor(s), as JNK activation has also previously been associated with promotion of cell death.10 This may explain why there has been a degree of restraint in pursuing JNK as a target in the oncology field. However, a number of recent studies have implicated JNK signaling in early therapy resistance and/or EMT in multiple cancer types. Our study demonstrates the potential of JNK inhibitors to overcome both phenomena, suggesting that JNK should be considered a bona fide target for these aspects of therapy in these cancers. Ultimately, the usefulness of a target in the oncology field is influenced by its relative activity in cancer versus normal cells. JNK inhibitors have been clinically evaluated for inflammatory conditions without any unexpected adverse effects in patients. The JNK signaling pathway, also known as the stress-activated protein kinase (SAPK) pathway, is activated upon cellular stress in normal cells.10 As such, JNK signaling is not activated in the majority of normal cells, making it an “Achilles’ heel” and an ideal target in tumors reliant on the JNK-JUN pathway for survival in the face of therapy. However, as the main benefit of
e1128515-2
P. T. FERRAO
Figure 1. Taking out the JNK to achieve more effective drug-induced tumor cell killing. A schematic representation of the activation of c-JUN-N-terminal kinase (JNK) signaling as a consequence of drug target inhibition and/or through a stress-induced response. The potential intervention points that enable a combination of JNK inhibitors to enhance drug treatment efficacy by overcoming JNK-mediated tumor cell survival mechanisms are indicated.
targeting JNK is envisaged to be overcoming cancer cell survival and phenotype-switching during early treatment, it is necessary to consider whether drug treatment may induce stress in some normal cells. In particular, cytotoxic drugs are known to cause adverse effects in the proliferating cell compartments of normal tissues. The role of JNK in these normal cells is not clear. If JNK performs a survival function its inhibition may cause increased toxicity, but if its role is to induce cell death, it may be a serendipitous target for reducing toxicity to normal cells while enhancing treatment efficacy in the cancer cells. Indeed, the potential benefit from combining JNK inhibitors with existing cancer treatments warrants proper clinical evaluation. One other important aspect of combination treatment that requires further investigation in preclinical models is the dosing and scheduling of combination drugs for the optimal responses. Our findings using cell line models revealed that a greater extent of cell killing could be attained with the same concentrations of the BRAF and JNK inhibitors if the cells were initially treated with the BRAF inhibitor that induced activation of the JNK pathway.2 In essence this offers a way to ‘prime’ the surviving cancer cells and select for characteristics that confer enhanced responsiveness to the combination treatment. Our findings also revealed that the highest doses are not necessarily the best, as the greatest drug synergy was obtained at combinations within the mid-range of doses assessed.2 Animal models could be utilized to predict the best dosing and scheduling of single agents with combination therapies to guide strategies for achieving the best responses in patients. Real-time monitoring of biomarkers predictive for response or resistance to drug(s) may guide the timing of treatment based on responses from preclinical studies. In the case of BRAFV600mutant metastatic melanoma, we predict that phosphorylated cJUN would be an ideal biomarker for monitoring the tumors following initial treatment with BRAF/MEK inhibitors to reveal the
window of opportunity for combination treatment with JNK and BRAF/MEK inhibitors.2 Matched samples from patients at progression of disease showed a reversion to reduced c-JUN levels and activation,2 suggesting that this window is early during drug treatment. Our data also demonstrated that JNK inhibitor doses that did not result in cancer cell death were able to reduce drug-induced cell migration,2 suggesting that therapeutic benefit may be obtained even in protected niches or compartments with reduced drug concentrations. It is well established that acquired resistance mechanisms to targeted therapies vary greatly, both within each patient and across patient groups, and are due to clonal heterogeneity, especially at progression of disease. Targeting an early adaptive mechanism such as the JNK-JUN pathway, which appears to be a more common mechanism of early survival across multiple patients, offers the potential to develop a widely applicable strategy for improving treatment efficacy and outcomes. As we enter an era of varied choices for cancer treatment, it becomes increasingly important to advance our scientific understanding of not only the options for therapy, but also the underlying molecular and cellular features contributing to therapy resistance at various stages of treatment. Although our knowledge and understanding of the processes that confer resistance and the pathways that can be targeted has expanded, defining the best treatment options, drug(s), dosing, and scheduling are all important factors for consideration to obtain the best outcomes for patients. These factors may be more efficiently explored in the preclinical setting. Our hope is to utilize our understanding of early drug adaptation to overcome tumor cells survival and evasion of treatment in order to eradicate residual disease. Ultimately, being prepared to inhibit the evolving targets during cancer cell adaptation to maximize therapeutic response early during treatment rather than at the point of disease progression may provide the best chance of long-term benefit, and possibly even a greater cure rate in cancer patients.
MOLECULAR & CELLULAR ONCOLOGY
Disclosure of potential conflicts of interest No potential conflicts of interest were disclosed.
Acknowledgments
5.
I thank Dr Robert N. Jorissen from The Walter and Eliza Hall Institute of Medical Research Australia and Prof. Richard B. Pearson from The Peter MacCallum Cancer Center Australia for providing helpful comments on this Author View.
6.
Funding PTF is supported by the NHMRC (GNT1042980).
7.
References 1. Ferrao PT, Behren A, Anderson RL, Thompson EW. Cellullar and phenotypic plasticity in cancer. Frontiers Oncol 2015; 5:171; PMID:26301202; http://dx.doi.org/10.3389/fonc.2015.00171 2. Ramsdale R, Jorissen RN, Li FZ, Al-Obaidi S, Ward T, Sheppard KE, Bukczynska PE, Young RJ, Boyle SE, Shackleton M, et al. The transcription cofactor c-JUN mediates phenotype switching and BRAF inhibitor resistance in melanoma. Science Signal 2015; 8:ra82; PMID:26286024; http://dx.doi.org/10.1126/scisignal.aab1111 3. Fallahi-Sichani M, Moerke NJ, Niepel M, Zhang T, Gray NS, Sorger PK. Systematic analysis of BRAFV600E melanomas reveals a role for JNK/c-Jun pathway in adaptive resistance to drug-induced apoptosis. Mol Syst Biol 2015; 11:797; PMID:25814555; http://dx.doi.org/ 10.15252/msb.20145877 4. Delmas A, Cherier J, Pohorecka M, Medale-Giamarchi C, Meyer N, Casanova A, Sordet O, Lamant L, Savina A, Pradines A, et al.
8.
9.
10.
e1128515-3
The c-Jun/RHOB/AKT pathway confers resistance of BRAFmutant melanoma cells to MAPK inhibitors. Oncotarget 2015; 6:15250-64; PMID:26098773; http://dx.doi.org/10.18632/ oncotarget.3888 Vasilevskaya I, O’Dwyer PJ. Role of Jun and Jun kinase in resistance of cancer cells to therapy. Drug Resistance Updates 2003; 6:147-56; PMID:12860462; http://dx.doi.org/10.1016/S1368-7646 (03)00043-8 Li F, Meng L, Zhou J, Xing H, Wang S, Xu G, Zhu H, Wang B, Chen G, Lu YP, Ma D. Reversing chemoresistance in cisplatin-resistant human ovarian cancer cells: a role of c-Jun NH2-terminal kinase 1. Biochem Biophys Res Commun 2005; 335:1070-7; PMID:16105650; http://dx.doi.org/10.1016/j.bbrc.2005.07.169 Sui X, Kong N, Wang X, Fang Y, Hu X, Xu Y, Chen W, Wang K, Li D, Jin W. JNK confers 5-fluorouracil resistance in p53-deficient and mutant p53-expressing colon cancer cells by inducing survival autophagy. Scientific Reports 2014; 4:4694; PMID:24733045; http:// dx.doi.org/10.1038/srep04694 Suzuki S, Okada M, Shibuya K, Seino M, Sato A, Takeda H, Seino S, Yoshioka T, Kitanaka C. JNK suppression of chemotherapeutic agents-induced ROS confers chemoresistance on pancreatic cancer stem cells. Oncotarget 2015; 6:458-70; PMID:25473894; http://dx.doi. org/10.18632/oncotarget.2693 Wang J, Kuiatse I, Lee AV, Pan J, Giuliano A, Cui X. Sustained cJun-NH2-kinase activity promotes epithelial-mesenchymal transition, invasion, and survival of breast cancer cells by regulating extracellular signal-regulated kinase activation. Mol Cancer Res 2010; 8:266-77; PMID:20145041; http://dx.doi.org/10.1158/15417786.MCR-09-0221 Johnson GL, Nakamura K. The c-jun kinase/stress-activated pathway: regulation, function and role in human disease. Biochimica Et Biophysica Acta 2007; 1773:1341-8; PMID:17306896; http://dx.doi.org/ 10.1016/j.bbamcr.2006.12.009
