PROJECT ABSTRACT. Antiretroviral therapy (ART) has led to better control of HIV infection and therefore improved survival for people with HIV (PWH). This increasing longevity has translated into a growing chronic disease burden, resulting in cancer now being a leading cause of death among PWH. Biomarkers that identify PWH at highest risk of cancer are therefore needed to tailor early detection programs to ameliorate this growing cancer burden. Methylation naturally accumulates on human DNA over time with aging. Using methylation information, epigenetic clocks create metrics of biological age that are distinct from chronological age (i.e., birth year). Previous studies in the non-cancer setting have demonstrated that PWH have an estimated biological age that is accelerated an average of 5 years beyond an individual’s chronological age. Our preliminary data indicate that this epigenetic aging biomarker also differs among PWH compared to HIV negative patients at the time of cancer diagnosis. What remains unknown is (1) whether the degree of HIV control is associated with accelerated aging as assessed using the full spectrum of modern epigenetic clocks and (2) whether this aging biomarker is uniquely present among PWH presenting with a NADC diagnosis vs cancer free PWH. We hypothesize that PWH experience accelerated aging that is related to the level of HIV control, and perhaps more importantly, that accelerated aging is associated with cancer risk. To test this hypothesis, we will leverage 400 archived specimens from PWH from the NCI-sponsored AIDS Cancer Specimen Resource (ACSR) to accomplish study aims that evaluate the association between level of HIV control and accelerated biological aging (Aim 1) and evaluate the association between accelerated biological aging and NADC risk among PWH (Aim 2). DNA will be extracted from whole blood, buffy coat, or PBMC specimens, and DNA methylation will be assayed using the Illumina MethylationEPIC BeadChip. Methylome data will be translated into a metric of biological aging using six epigenetic clocks (e.g., epiTOC2, which has not been evaluated in prior studies). For Aim 1, we will cross-sectionally compare biological age between 100 PWH with poor viral control (HIV viral load >10,000 or CD4 count <200) and 100 PWH with controlled infection (HIV viral load <100 or CD4 count >350), matched on chronological age and biological sex. For Aim 2, we will compare biological age between 100 PWH on ART who were followed without a cancer diagnosis (controls) and 100 PWH with a NADC diagnosis (cases), matched on chronological age and biological sex. In an exploratory manner, we will characterize the biological age of 50 PWH at Moffitt Cancer Center diagnosed with anal high-grade squamous intraepithelial lesions (anal HSIL), the precursor to anal cancer, and 50 PWH diagnosed with invasive anal cancer. We anticipate that this study will shed light on the degree to which HIV control impacts accelerated biological aging in...