Abstract SY24-01: Changes in adaptive landscapes and somatic evolution as we age

Abstract

Abstract Why do we get cancer? Why is cancer highly associated with old age, and why are insults like smoking, obesity, and sunlight associated with increased risk of cancers? Of course, these contexts all cause mutations, and some of these mutations can contribute to malignant phenotypes. But we now understand that carcinogenesis is much more complex than originally appreciated. In particular, there are microenvironmental forces that both impede and promote cancer evolution. Just as organismal evolution is known to be driven by environmental changes, somatic evolution in our bodies is similarly driven by changes in tissue environments, whether caused by the normal process of aging, by lifestyle choices or by extrinsic exposures. Environmental change promotes selection for new phenotypes that are adaptive to the new context. In our tissues, aging or insult-driven alterations in tissues drives selection for adaptive mutations, and some of these mutations can confer malignant phenotypes. We will discuss the evidence from many labs for microenvironmental change driven selection in the evolution of cancer, additional support from epidemiological and clinical studies, as well as the limitations, inconsistencies and unknowns that require the attention of cancer researchers. My own lab has been using mouse models of cancer initiation, mathematical models of clonal evolution, and analyses of human tissue samples to better understand the evolutionary forces that control somatic cell evolution and thus cancer risk. Using Monte Carlo modeling, we have explored the impact of key somatic evolutionary parameters on multi-stage carcinogenesis, revealing that two additional major mechanisms, aging-dependent somatic selection and life history-dependent evolution of species-specific tumor suppressor mechanisms, need to be incorporated into the multi-stage model of carcinogenesis to make it capable of generalizing cancer incidence across tissues and species. Using mouse models, we have shown that aging and inflammation dependent changes in tissue microenvironments dramatically impact the fitness impact of oncogenic mutations, leading to aging and inflammation driven clonal expansions in the hematopoietic compartment. These studies have also uncovered molecular mechanisms underlying oncogene-driven adaptation to aged and inflammatory tissue environments. In all, these studies indicate that strategies to prevent or treat cancers will need to incorporate interventions that alter tissue microenvironments. While we largely cannot prevent mutation accumulation through our lives, we do have the ability to manipulate tissue microenvironments so as to change the evolutionary trajectories of oncogenically-mutated cells. Citation Format: James V. DeGregori. Changes in adaptive landscapes and somatic evolution as we age [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr SY24-01.