Bi-allelic loss of CDKN2A initiates melanoma invasion and metastasis via E2F1-BRN2 axis

CDKN2A acts as a critical tumor suppressor in melanoma, as evidenced by frequent loss of function mutations and deletion. Loss of CDKN2A is believed to permit escape from senescent pre-neoplastic cell populations through relieve of a cell cycle block mediated by its two gene products. We performed a comprehensive analysis of CDKN2A gene status, mRNA and protein expression levels of p16 and p14 in a cohort of melanomas and their adjacent pre-neoplastic lesions and observed that bi-allelic CDKN2A loss coincides with the progression stage when primary melanomas become invasive. In melanoma lines, p16 INK4A , one of the protein products of the CDKN2A locus, is a potent barrier to metastasis, independent of its known role inhibiting cell proliferation. We genetically engineered primary human melanocytes to harbor CDKN2A deletions and/or BRAF V600E mutation at their endogenous BRAF locus. Using this physiologic model for the early phases of neoplastic transformation, we found no evidence for BRAF-induced senescence, rather observing that p16INK4A loss activates a master regulator of melanoma invasion, BRN2, through Rb-E2F1 pathway. These results demonstrate that one of the most frequently altered genes across human cancers, CDKN2A, has an unexpected novel role in inhibiting cellular invasion through lineage specific transcription factors and acts as an essential gatekeeper of early metastatic dissemination. Citation Format: Hanlin Zeng, Aparna Jorapur, A. Hunter Shain, Ursula E. Lang, Rodrigo Torres, Yuntian Zhang, Thomas Botton, Jue Lin, Andrew S. Mcneal, Matthew Donne, Ingmar N. Bastian, Jeffrey North, Laura Pincus, Richard Yu, Beth S. Ruben, Nancy Joseph, Iwei Ye, Boris C. Bastian, Robert L. Judson. Bi-allelic loss of CDKN2A initiates melanoma invasion and metastasis via E2F1-BRN2 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5518.