Integrin alpha6beta4 regulation of cancer epigenetics

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How DNA demethylation machinery can be targeted to specific genomic loci is still poorly understood, yet has important implications for tumor biology. Mounting evidence suggests that the microenvironment influences epigenetics; however, the mechanisms guiding these events have not been elucidated. We have demonstrated that integrin α6β4 dramatically alters the transcriptome toward an invasive phenotype. The integrin regulates this process, in part, by substantially changing the epigenome through the regulation of DNA demethylation of select CpG rich regions and loci. Thus, we expect that understanding how integrin α6β4 regulates the cancer epigenome holds the key to how site-specific and mechanotransduced epigenetics are regulated. Investigations into how integrin α6β4 regulates DNA demethylation (funded by an NCI R21) led to our discovery that integrin α6β4 utilizes and stimulates the base excision repair (BER) pathway to mediate these epigenetic events, but not in cells in which the link between integrin α6β4 and the nucleus is compromised. We have also identified specific mutations in integrin β4 subunit that preventing the integrin from binding to intermediate filaments and anchoring under the nucleus, thus indicating a pathway for integrin- mediated alterations in nuclear function. Based on our preliminary data and supporting literature, we hypothesize that integrin α6β4 coordinates signal and mechano-transduction to the nucleus that drives BER and results in DNA demethylation of select loci, which in turn enhances tumor invasion and metastasis. We will test our central hypothesis through completion of the following three aims: 1) Determine how integrin α6β4 cytoskeletal linkages impacts invasion, metastasis and epigenetics, 2) Elucidate how integrin α6β4 regulates BER-mediated DNA demethylation, and 3) Define changes in the epigenome mediated by integrin α6β4 signaling. We expect that by elucidating the genes and pathways used by integrin α6β4 to modulate the demethylation of select genes, we will provide critical insight into how specific sites within the genome are demethylated to foster an invasive and metastatic transcriptome.