LAUSR

Vitamin D plays a critical role in the maintenance of tissue homeostasis by regulating the expression of genes affecting cell proliferation, differentiation, and apoptosis. The vitamin D 24-hydroxylase CYP24A1 functions in vitamin D target tissues to degrade the hormonal form of vitamin D. Existing knowledge regarding dysregulated CYP24A1 expression supports its candidacy as a putative oncogene. In our presentation, we demonstrate that the suppression of constitutive CYP24A1 expression by CYP24A1-specidic shRNA conferred target cells with increased susceptibility to apoptosis and consequently inhibited anchorage-independent growth in breast carcinoma cells. In addition, suppression of vitamin D metabolism following knockdown of CYP24A1 significantly reduced tumor growth in vivo. Since these data provide substantial evidence for a pro-survival and stimulatory oncogenic effect of CYP24A1 in breast carcinoma cells, we will discuss the potential feasibility of CYP24A1-inhibitory cancer therapies. Citation Format: Makoto Osanai, Yusuke Ono, Akira Takasawa, Kumi Takasawa, Masaki Murata, Norimasa Sawada. CYP24A1-induced vitamin D insufficiency promotes breast cancer growth [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 2485.