Abstract
Abstract Human cytochrome P450 1B1 (CYP1B1) belongs to the CYP1 family and is known as a major enzyme for estradiol 4-hydroxylation. It has been reported that CYP1B1 expression is higher in the tumor tissues than the normal ones, especially in hormone-related cancers such as breast, ovarian and prostate. Previously, we identified that CYP1B1 induces cell proliferation by activation of Wnt/β-catenin signal pathway. To explore the role of CYP1B1 on cancer cell proliferation further, we investigated whether CYP1B1 blocks apoptotic pathways. Using Western blot and RT-PCR, the expression of TRAIL was examined in MCF-7 cells, and we found that CYP1B1 overexpression or treatment with a CYP1B1 inducer, 7, 12-dimethylbenz[α]anthracene (DMBA) caused suppression of TRAIL and its receptors (DR4 and DR5) expression. However, when cells were treated with CYP1B1 siRNA or a selective CYP1B1 inhibitor, tetramethoxystilbene (TMS), expression of TRAIL and its receptors were significantly increased. Sp1, a zinc finger-containing transcription factor, has been reported to suppress TRAIL gene expression by binding TRAIL promoter. Interestingly, CYP1B1 overexpression and DMBA induced Sp1 expression and TMS was able to prevent DMBA-induced Sp1 expression. Sp1 knockdown with siRNA suppressed c-FLIP, an inhibitor protein of TRAIL-mediated apoptosis while it enhanced TRAIL and DR4 expression. These results were reversed by Sp1 overexpession. Moreover, attenuation of Sp1 DNA binding activity using mithramycin A, a Sp1 binding inhibitor, resulted in recovery of TRAIL expression suppressed by DMBA. Taken together, these data suggest that CYP1B1 prevents apoptosis via TRAIL suppression and this is mediated by Sp1 induction. Citation Format: Yeo-Jung Kwon, Nahee Park, Sangyun Shin, Dong-Jin Ye, Mihye Hong, Young-Jin Chun. Induction of Sp1 factor by CYP1B1 inhibits TRAIL-mediated apoptotic pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2754. doi:10.1158/1538-7445.AM2014-2754
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