The Aging Cutaneous Microenvironment and Cancer Initiation

ABSTRACT Cancer is clearly a disease of aging. This connection between aging and cancer incidence is especially true in the case of skin cancer, which is the most common form of human cancer, accounting for more than all other cancers combined in USA. The major objective of this application is to gain understanding of cellular and molecular mechanisms that link age-related skin changes to the initiation of skin cancer. This application is based on our findings that fibroblasts in aged human skin express elevated levels of a matricellular protein named CCN1, and that elevated CCN1 acts to deleteriously alter the dermal compartment of skin to create a microenvironment that enhances cancer initiation. Based on these observations, we have created genetically modified mice that express elevated levels of CCN1 selectively in dermal fibroblasts (source of elevated CCN1 in aged human skin). These mice exhibit strikingly accelerated dermal aging and display multiple hallmarks of aging that are seen in human skin. Importantly, mice that express elevated levels of CCN1 in the dermis also have a high propensity for skin tumor initiation. These results provide direct support for the overarching hypothesis of this application; that age- related changes in the dermal microenvironment, driven by fibroblast expression of CCN1, create a dermal microenvironment that enhances initiation of keratinocyte cancer. We propose to test this hypothesis with the following specific aims. Aim 1: define the impact of CCN1-induced accelerated dermal aging on keratinocyte cancer initiation. Aim 2: test the hypothesis that activation of the hepatocyte growth factor pathway by the CCN1-induced dermal aging microenvironment drives keratinocyte cancer initiation. Aim 3: using targeted gene deletion, test the requirement for CCN1 expression in dermal fibroblasts for the development of an aging-related dermal microenvironment and initiation of keratinocyte cancer. The aims of this proposal directly address the objectives of the National Cancer Institute/National Aging Institute Funding Opportunity Announcement to understand mechanisms by which age-related alterations in the cellular niche/microenvironment contribute to cancer initiation.