Abstract 2975: Vitamin D receptor signaling limits DNA damage at early stage of prostate tumorigenesis and prevents tumor aggressiveness

Abstract Prostate cancer (PCa) is the most common visceral neoplasm and the second leading cause of cancer-related deaths in male of western societies. Low circulating vitamin D levels and reduced expression of its receptor (VDR) correlate with PCa risk and severity, but the clinical use of vitamin D is limited by its pro-calcemic activities. To characterize the role of VDR in PCa, PTEN (i) pe-/− mice, that recapitulate the human disease and in which the tumor suppressor gene PTEN is selectively inactivated in prostatic epithelial cells (PECs) at adulthood, were compared to PTEN/VDR (i) pe-/− mice in which PECs are PTEN and VDR-deficient. Histological analysis showed that prostatic intraepithelial neoplasia (PIN) are formed between 1-3 months after gene inactivation (AGI). Importantly, VDR-deficiency increased by 2-fold the PECs proliferation rate as early as 1-month AGI. At this stage, RNA-seq and immunohistochemistry analysis revealed the presence of oxidative DNA damage selectively in VDR-deficient PINs. Moreover, a 4-week supplementation with the antioxidant N-acetyl cysteine reduced oxidative DNA damage in PTEN/VDR (i) pe-/- prostates, and normalized the number of Ki-67+ cells to the levels of PTEN (i) pe-/- ones. After 3 months AGI, both PTEN (i) pe-/- and PTEN/VDR (i) pe-/- tumors entered in a latency phase characterized by cellular senescence. However, the prostate weight in PTEN/VDR (i) pe-/− mice was 2-fold higher than in PTEN (i) pe-/− mice 12 months AGI. In addition, tumors of PTEN (i) pe-/− were mostly composed of non-invasive PIN-like adenocarcinoma, whereas invasive adenocarcinoma, sarcomatoid and squamous-cell carcinoma were observed in those of PTEN/VDR (i) pe-/- mice. Using single cell and spatial transcriptomics, we unraveled the presence of epithelial cells with epithelial-mesenchymal transition (EMT) hallmarks in PTEN/VDR (i) pe-/− prostate 10 months AGI. In addition, immunophenotyping revealed a higher infiltration of neutrophils, also termed as myeloid-derived suppressive cells and implicated in EMT and metastasis dissemination, in PTEN/VDR (i) pe-/− prostates compared to PTEN (i) pe-/− ones. Moreover, pan-cytokeratin-positive micro-metastasis were detected in lymph nodes and livers of PTEN/VDR (i) pe-/− mice, but not in those of PTEN (i) pe-/- mice, demonstrating that VDR-deficiency in PECs promotes aggressive PCa. Thus, VDR signaling exerts a protective role on PTEN-deficient PECs by limiting the oxidative-stress and proliferation during PINs initiation, and prevents PCa progression. Citation Format: Kateryna Len, Justine Gantzer, Nicolas Le May, Christelle Thibault-Carpentier, Daniel Metzger, Gilles Laverny. Vitamin D receptor signaling limits DNA damage at early stage of prostate tumorigenesis and prevents tumor aggressiveness abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2975.