AUTHOR'S VIEW OncoImmunology 4:10, e1027474; October 2015; © 2015 Taylor & Francis Group, LLC
Old enemies meet new friends for colon cancer prevention Theofilos Poutahidis1,*, Katerina Angelopoulou2, and Suzan E Erdman3 1
Laboratory of Pathology; Faculty of Health Sciences; School of Veterinary Medicine; Aristotle University of Thessaloniki; Thessaloniki, Greece; 2Laboratory of Biochemistry and Toxicology; Faculty of Health Sciences; School of Veterinary Medicine; Aristotle University of Thessaloniki; Thessaloniki, Greece; 3Division of Comparative Medicine; Massachusetts Institute of Technology; Cambridge, MA USA
Keywords: colon cancer, cholera-toxin, colitis, mice, tumor microenvironment
Our studies in mice have suggested that the immunological microenvironment of preneoplastic lesions could determine their fate toward neoplasia or regression. A role for gastrointestinal tract bacteria antigens in modulating cancer-related immune responses in the tumor micro- and macro-environment is emerging, thus opening new possibilities for colon cancer prevention.
The Immunological Microenvironment of Initially Transformed Cells
Evidence from Mouse Models of Inflammation-Associated Carcinogenesis
The over-interpretation of recently published data suggesting that the lifetime risk of cancer in a tissue correlates with how often its constituent cells replicate1 elicited an interesting debate. Cells surviving the wrong kind of random genetic damage are “bad luck” as they initiate the majority of cancers1. The natural history of such cancers is indeed replete with coincidental mishappenings. But how much of this misfortune is due to the nature of the initially transformed cells themselves and how much depends on their being in the wrong place at the wrong time? Autopsy studies have shown that focal lesions with neoplastic potential are commonplace in the human body.2 This is consistent with the high expectancy of the accumulation of random gene mutations during one’s life. Fortunately, these lesions rarely develop into cancer. The local environment of such lesions, including the presence of immune system cells and factors, is not always conducive to their thriving.2
Studying the initial steps of carcinogenesis in human tissues is not always possible. Instead mouse models of cancer provide an excellent tool for such analyses. We have recently used one such murine model to examine the extent to which the evolution of preneoplastic lesions in the colon depends on their immunological environment.3 Toward that goal, mice were given a single dose of the genotoxic agent azoxymethane (AOM), which by itself did not lead to the formation of colonic polyps. Following AOM-treatment, mice underwent 3 repeated episodes of colitis induced by dextran sodium sulfate (DSS). In that case, 3.5 months after DSS treatment, several wellformed polyps were found residing in an otherwise normal colon. However, when a single, non-pathogenic dose of cholera-toxin (CT) was given orally at the beginning of each DSS treatment cycle, colonic polypoidogenesis was significantly suppressed (Fig. 1). Probing the mucosal immune environment of colonic preneoplastic lesions at 3 d after DSS treatment led us to characterize, at least in part, the CT-induced disruption of the tumor-promoting character of colitis.
At this early time-point, both CT-treated and untreated mice had colitis and epithelial dysplasia of comparable extent and severity. However, CT downregulated neutrophils and upregulated regulatory T-cells, interleukin (IL)-10 and tumor necrosis factor a (TNFa) in the colonic mucosa3 (Fig. 1). This result shows that the inflammatory milieu in the colonic mucosa, rather than the severity of inflammation per se, can determine the fate of epithelial preneoplastic lesions toward evolving into adenomatous polyps. The AOM/DSS model, similarly to other mouse models of inflammation-associated carcinogenesis we used before, showed that the survival and growth of dysplastic or even established neoplastic lesions arising on the grounds of colitis are much more vitally dependent on certain inflammatory stimuli than previously thought.4,5 Could the same be true, however, for other types of sporadic, non-inflammation-associated cancers?
Expanding the Paradigm with Mouse Models of NonInflammation-Associated Cancer Over the last years we have examined the effects of gastrointestinal (GI) bacteria in different mouse models of
*Correspondence to: Theofilos Poutahidis; Email: [email protected] Submitted: 03/03/2015; Accepted: 03/03/2015 http://dx.doi.org/10.1080/2162402X.2015.1027474
www.tandfonline.com
OncoImmunology
e1027474-1
Figure 1. Bacterial antigens impact cancer prevention. Orally introduced cholera-toxin was used to alter the character of cancer-promoting inflammation in a mouse model of colon cancer. Cholera-toxin decreased the risk of dysplastic lesion progression to polyps by downregulating mucosal neutrophils and upregulating regulatory T cells and the levels of interleukin 10 (IL-10).
neoplasia.6,7 We found that bacteriainduced effects on local GI-tract immunity expand to impart subclinical alterations of the inflammatory tone at the whole-organism level. These alterations, involving regulatory T cells, neutrophils, mast cells, IL-10, IL-6, IL-17 and TNFa, are significant but silent in terms of inflammatory disease clinical manifestations. Nonetheless, they have been proven critical in either fueling or blocking cancer development in epithelia located distally from the gut, such as those of the prostate and the mammary glands.6,7 Our 2 most recent reports complement previous observations. The former shows that the intestinal colonization of C3–1-TAg mice with Helicobacter hepaticus accelerates their typical mammary carcinogenesis. Also, the depletion of neutrophils negates this distant, immune-mediated, pro-tumorigenic effect and rescues mice from
e1027474-2
mammary tumors.8 The latter observation demonstrates that gut microbiota effects transcend not only the local boundaries of the GI tract, but generations as well. Indeed, mice with a westernized-diet type, obesity-related gut microbiota have children and grandchildren, which although fed with normal diets, develop lung and liver cancers and lymphoma in particularly high rates. This high cancer risk in F1 and F2 mice, which coexists with an increased systematic inflammatory tone, is lost when the descended mice consume the probiotic bacterium Lactobacillus reuteri daily.9
Emerging roles of Gut Bacteria in Cancer Prevention Our studies in mice suggest that the immunological microenvironment of
OncoImmunology
initially transformed cells —a critical factor promoting carcinogenesis— is not completely autonomous. Instead, it is influenced by the status of the immune system at the whole-organism level.6-9 In our paradigm, the systematic immunological tone may affect co-existing dysplastic lesions in the body. The immune system, the hormonal profile and the psychological condition of human beings are interrelated. Interestingly, all elements of this integral triad are influenced by gut microbiota.9 This parallels the “hygiene” or “old friend” hypothesis, according to which inhabitants of developed countries have immune systems of reduced regulatory competence due to insufficient microbial antigen exposure.6,7,10 Therefore, the use of selected antigens from bacteria that have been banned from the industrialized world (the so-called “old friends”)10 as health-promoting products analogous to probiotics is worth exploring. Ideally, these products would be a safe and
Volume 4 Issue 10
effective approach reinforcing the regulatory arm of the human immune system and decreasing the modern living-associated cancer risk at the population level. Since many of the bacteria that humans rarely encounter nowadays are pathogens, the search for beneficial antigens may not be restricted to our
probiotic “new friends,”7-10 but involve some of our “old enemies” as well.3
References
4. Poutahidis T, Haigis KM, Rao VP, Nambiar PR, Taylor CL, Ge Z, Watanabe K, Davidson A, Horwitz BH, Fox JG, et al. Rapid reversal of interleukin-6-dependent epithelial invasion in a mouse model of microbially induced colon carcinoma. Carcinogenesis 2007; 28:2614-23; PMID:17724375; http://dx.doi.org/ 10.1093/carcin/bgm180 5. Erdman SE, Poutahidis T. Roles for inflammation and regulatory T cells in colon cancer. Toxicol Pathol 2010; 38:76-87; PMID:20019355; http://dx.doi.org/ 10.1177/0192623309354110 6. Erdman SE, Poutahidis T. Cancer inflammation and regulatory T cells. Int J Cancer 2010; 127:768-79; PMID:20518013 7. Poutahidis T, Kleinewietfeld M, Erdman SE. Gut microbiota and the paradox of cancer immunotherapy.
1. Tomasetti C, Vogelstein B. Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science 2015; 347:78-81; PMID:25554788; http://dx.doi.org/10.1126/science. 1260825 2. Bissell MJ, Hines WC. Why don’t we get more cancer? A proposed role of the microenvironment in restraining cancer progression. Nat Med 2011; 17:320-9; PMID:21383745; http://dx.doi.org/10.1038/nm.2328 3. Doulberis M, Angelopoulou K, Kaldrymidou E, Tsingotjidou A, Abas Z, Erdman SE, Poutahidis T. Cholera-toxin suppresses carcinogenesis in a mouse model of inflammation-driven sporadic colon cancer. Carcinogenesis 2015; 36:280-90; PMID:25550315; http:// dx.doi.org/10.1093/carcin/bgu325
www.tandfonline.com
Disclosure of Potential Conflicts of Interest
Funding
This work was supported in part by National Institutes of Health Grant RO1CA108854 (to SEE).
No potential conflicts of interest were disclosed.
OncoImmunology
Front Immunol 2014; 5:157; PMID:24778636; http:// dx.doi.org/10.3389/fimmu.2014.00157 8. Lakritz JR, Poutahidis T, Mirabal S, Varian BJ, Levkovich T, Ibrahim YM, Ward JM, Teng EC, Fisher B, Parry N, et al. Gut bacteria require neutrophils to promote mammary tumorigenesis. Oncotarget 2015; 6 (11):9387-96; PMID:25831236. 9. Poutahidis T, Varian BJ, Levkovich T, Lakritz JR, Mirabal S, Kwok C, Ibrahim YM, Kearney SM, Chatzigiagkos A, Alm EJ, et al. Dietary microbes modulate transgenerational cancer risk. Cancer Res 2015; 75 (7):1197-204; PMID:25716681 10. Rook GA, Dalgleish A. Infection, immunoregulation, and cancer. Immunol Rev 2011; 240:141-59; PMID:21349092; http://dx.doi.org/10.1111/j.1600065X.2010.00987.x
e1027474-3
Old enemies meet new friends for colon cancer prevention Theofilos Poutahidis1,*, Katerina Angelopoulou2, and Suzan E Erdman3 1
Laboratory of Pathology; Faculty of Health Sciences; School of Veterinary Medicine; Aristotle University of Thessaloniki; Thessaloniki, Greece; 2Laboratory of Biochemistry and Toxicology; Faculty of Health Sciences; School of Veterinary Medicine; Aristotle University of Thessaloniki; Thessaloniki, Greece; 3Division of Comparative Medicine; Massachusetts Institute of Technology; Cambridge, MA USA
Keywords: colon cancer, cholera-toxin, colitis, mice, tumor microenvironment
Our studies in mice have suggested that the immunological microenvironment of preneoplastic lesions could determine their fate toward neoplasia or regression. A role for gastrointestinal tract bacteria antigens in modulating cancer-related immune responses in the tumor micro- and macro-environment is emerging, thus opening new possibilities for colon cancer prevention.
The Immunological Microenvironment of Initially Transformed Cells
Evidence from Mouse Models of Inflammation-Associated Carcinogenesis
The over-interpretation of recently published data suggesting that the lifetime risk of cancer in a tissue correlates with how often its constituent cells replicate1 elicited an interesting debate. Cells surviving the wrong kind of random genetic damage are “bad luck” as they initiate the majority of cancers1. The natural history of such cancers is indeed replete with coincidental mishappenings. But how much of this misfortune is due to the nature of the initially transformed cells themselves and how much depends on their being in the wrong place at the wrong time? Autopsy studies have shown that focal lesions with neoplastic potential are commonplace in the human body.2 This is consistent with the high expectancy of the accumulation of random gene mutations during one’s life. Fortunately, these lesions rarely develop into cancer. The local environment of such lesions, including the presence of immune system cells and factors, is not always conducive to their thriving.2
Studying the initial steps of carcinogenesis in human tissues is not always possible. Instead mouse models of cancer provide an excellent tool for such analyses. We have recently used one such murine model to examine the extent to which the evolution of preneoplastic lesions in the colon depends on their immunological environment.3 Toward that goal, mice were given a single dose of the genotoxic agent azoxymethane (AOM), which by itself did not lead to the formation of colonic polyps. Following AOM-treatment, mice underwent 3 repeated episodes of colitis induced by dextran sodium sulfate (DSS). In that case, 3.5 months after DSS treatment, several wellformed polyps were found residing in an otherwise normal colon. However, when a single, non-pathogenic dose of cholera-toxin (CT) was given orally at the beginning of each DSS treatment cycle, colonic polypoidogenesis was significantly suppressed (Fig. 1). Probing the mucosal immune environment of colonic preneoplastic lesions at 3 d after DSS treatment led us to characterize, at least in part, the CT-induced disruption of the tumor-promoting character of colitis.
At this early time-point, both CT-treated and untreated mice had colitis and epithelial dysplasia of comparable extent and severity. However, CT downregulated neutrophils and upregulated regulatory T-cells, interleukin (IL)-10 and tumor necrosis factor a (TNFa) in the colonic mucosa3 (Fig. 1). This result shows that the inflammatory milieu in the colonic mucosa, rather than the severity of inflammation per se, can determine the fate of epithelial preneoplastic lesions toward evolving into adenomatous polyps. The AOM/DSS model, similarly to other mouse models of inflammation-associated carcinogenesis we used before, showed that the survival and growth of dysplastic or even established neoplastic lesions arising on the grounds of colitis are much more vitally dependent on certain inflammatory stimuli than previously thought.4,5 Could the same be true, however, for other types of sporadic, non-inflammation-associated cancers?
Expanding the Paradigm with Mouse Models of NonInflammation-Associated Cancer Over the last years we have examined the effects of gastrointestinal (GI) bacteria in different mouse models of
*Correspondence to: Theofilos Poutahidis; Email: [email protected] Submitted: 03/03/2015; Accepted: 03/03/2015 http://dx.doi.org/10.1080/2162402X.2015.1027474
www.tandfonline.com
OncoImmunology
e1027474-1
Figure 1. Bacterial antigens impact cancer prevention. Orally introduced cholera-toxin was used to alter the character of cancer-promoting inflammation in a mouse model of colon cancer. Cholera-toxin decreased the risk of dysplastic lesion progression to polyps by downregulating mucosal neutrophils and upregulating regulatory T cells and the levels of interleukin 10 (IL-10).
neoplasia.6,7 We found that bacteriainduced effects on local GI-tract immunity expand to impart subclinical alterations of the inflammatory tone at the whole-organism level. These alterations, involving regulatory T cells, neutrophils, mast cells, IL-10, IL-6, IL-17 and TNFa, are significant but silent in terms of inflammatory disease clinical manifestations. Nonetheless, they have been proven critical in either fueling or blocking cancer development in epithelia located distally from the gut, such as those of the prostate and the mammary glands.6,7 Our 2 most recent reports complement previous observations. The former shows that the intestinal colonization of C3–1-TAg mice with Helicobacter hepaticus accelerates their typical mammary carcinogenesis. Also, the depletion of neutrophils negates this distant, immune-mediated, pro-tumorigenic effect and rescues mice from
e1027474-2
mammary tumors.8 The latter observation demonstrates that gut microbiota effects transcend not only the local boundaries of the GI tract, but generations as well. Indeed, mice with a westernized-diet type, obesity-related gut microbiota have children and grandchildren, which although fed with normal diets, develop lung and liver cancers and lymphoma in particularly high rates. This high cancer risk in F1 and F2 mice, which coexists with an increased systematic inflammatory tone, is lost when the descended mice consume the probiotic bacterium Lactobacillus reuteri daily.9
Emerging roles of Gut Bacteria in Cancer Prevention Our studies in mice suggest that the immunological microenvironment of
OncoImmunology
initially transformed cells —a critical factor promoting carcinogenesis— is not completely autonomous. Instead, it is influenced by the status of the immune system at the whole-organism level.6-9 In our paradigm, the systematic immunological tone may affect co-existing dysplastic lesions in the body. The immune system, the hormonal profile and the psychological condition of human beings are interrelated. Interestingly, all elements of this integral triad are influenced by gut microbiota.9 This parallels the “hygiene” or “old friend” hypothesis, according to which inhabitants of developed countries have immune systems of reduced regulatory competence due to insufficient microbial antigen exposure.6,7,10 Therefore, the use of selected antigens from bacteria that have been banned from the industrialized world (the so-called “old friends”)10 as health-promoting products analogous to probiotics is worth exploring. Ideally, these products would be a safe and
Volume 4 Issue 10
effective approach reinforcing the regulatory arm of the human immune system and decreasing the modern living-associated cancer risk at the population level. Since many of the bacteria that humans rarely encounter nowadays are pathogens, the search for beneficial antigens may not be restricted to our
probiotic “new friends,”7-10 but involve some of our “old enemies” as well.3
References
4. Poutahidis T, Haigis KM, Rao VP, Nambiar PR, Taylor CL, Ge Z, Watanabe K, Davidson A, Horwitz BH, Fox JG, et al. Rapid reversal of interleukin-6-dependent epithelial invasion in a mouse model of microbially induced colon carcinoma. Carcinogenesis 2007; 28:2614-23; PMID:17724375; http://dx.doi.org/ 10.1093/carcin/bgm180 5. Erdman SE, Poutahidis T. Roles for inflammation and regulatory T cells in colon cancer. Toxicol Pathol 2010; 38:76-87; PMID:20019355; http://dx.doi.org/ 10.1177/0192623309354110 6. Erdman SE, Poutahidis T. Cancer inflammation and regulatory T cells. Int J Cancer 2010; 127:768-79; PMID:20518013 7. Poutahidis T, Kleinewietfeld M, Erdman SE. Gut microbiota and the paradox of cancer immunotherapy.
1. Tomasetti C, Vogelstein B. Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science 2015; 347:78-81; PMID:25554788; http://dx.doi.org/10.1126/science. 1260825 2. Bissell MJ, Hines WC. Why don’t we get more cancer? A proposed role of the microenvironment in restraining cancer progression. Nat Med 2011; 17:320-9; PMID:21383745; http://dx.doi.org/10.1038/nm.2328 3. Doulberis M, Angelopoulou K, Kaldrymidou E, Tsingotjidou A, Abas Z, Erdman SE, Poutahidis T. Cholera-toxin suppresses carcinogenesis in a mouse model of inflammation-driven sporadic colon cancer. Carcinogenesis 2015; 36:280-90; PMID:25550315; http:// dx.doi.org/10.1093/carcin/bgu325
www.tandfonline.com
Disclosure of Potential Conflicts of Interest
Funding
This work was supported in part by National Institutes of Health Grant RO1CA108854 (to SEE).
No potential conflicts of interest were disclosed.
OncoImmunology
Front Immunol 2014; 5:157; PMID:24778636; http:// dx.doi.org/10.3389/fimmu.2014.00157 8. Lakritz JR, Poutahidis T, Mirabal S, Varian BJ, Levkovich T, Ibrahim YM, Ward JM, Teng EC, Fisher B, Parry N, et al. Gut bacteria require neutrophils to promote mammary tumorigenesis. Oncotarget 2015; 6 (11):9387-96; PMID:25831236. 9. Poutahidis T, Varian BJ, Levkovich T, Lakritz JR, Mirabal S, Kwok C, Ibrahim YM, Kearney SM, Chatzigiagkos A, Alm EJ, et al. Dietary microbes modulate transgenerational cancer risk. Cancer Res 2015; 75 (7):1197-204; PMID:25716681 10. Rook GA, Dalgleish A. Infection, immunoregulation, and cancer. Immunol Rev 2011; 240:141-59; PMID:21349092; http://dx.doi.org/10.1111/j.1600065X.2010.00987.x
e1027474-3
