Kundu Aishwarya, Quirit Jeanne G, Khouri Michelle G, Firestone Gary L
Department of Molecular and Cell Biology and The Cancer Research Laboratory, University of California at Berkeley, Berkeley, California.
Mol Carcinog. 2017 Jan;56(1):49-61. doi: 10.1002/mc.22472. Epub 2016 Feb 15.
Indole-3-carbinol (I3C), an anti-cancer phytochemical derived from cruciferous vegetables, strongly inhibited proliferation and down-regulated protein levels of the melanocyte master regulator micropthalmia-associated transcription factor (MITF-M) in oncogenic BRAF-V600E expressing melanoma cells in culture as well as in vivo in tumor xenografted athymic nude mice. In contrast, wild type BRAF-expressing melanoma cells remained relatively insensitive to I3C anti-proliferative signaling. In BRAF-V600E-expressing melanoma cells, I3C treatment inhibited phosphorylation of MEK and ERK/MAPK, the down stream effectors of BRAF. The I3C anti-proliferative arrest was concomitant with the down-regulation of MITF-M transcripts and promoter activity, loss of endogenous BRN-2 binding to the MITF-M promoter, and was strongly attenuated by expression of exogenous MITF-M. Importantly, in vitro kinase assays using immunoprecipitated BRAF-V600E and wild type BRAF demonstrated that I3C selectively inhibited the enzymatic activity of the oncogenic BRAF-V600E but not of the wild type protein. In silico modeling predicted an I3C interaction site in the BRAF-V600E protomer distinct from where the clinically used BRAF-V600E inhibitor Vemurafenib binds to BRAF-V600E. Consistent with this prediction, combinations of I3C and Vemurafenib more potently inhibited melanoma cell proliferation and reduced MITF-M levels in BRAF-V600E expressing melanoma cells compared to the effects of each compound alone. Thus, our results demonstrate that oncogenic BRAF-V600E is a new cellular target of I3C that implicate this indolecarbinol compound as a potential candidate for novel single or combination therapies for melanoma. © 2016 Wiley Periodicals, Inc.
吲哚 - 3 - 甲醇(I3C)是一种源自十字花科蔬菜的抗癌植物化学物质,在体外培养的表达致癌性BRAF - V600E的黑色素瘤细胞以及体内肿瘤异种移植的无胸腺裸鼠中,它能强烈抑制增殖并下调黑素细胞主调节因子小眼相关转录因子(MITF - M)的蛋白质水平。相比之下,表达野生型BRAF的黑色素瘤细胞对I3C的抗增殖信号相对不敏感。在表达BRAF - V600E的黑色素瘤细胞中,I3C处理抑制了BRAF的下游效应分子MEK和ERK/MAPK的磷酸化。I3C的抗增殖阻滞伴随着MITF - M转录本和启动子活性的下调、内源性BRN - 2与MITF - M启动子结合的丧失,并且通过外源性MITF - M的表达而强烈减弱。重要的是,使用免疫沉淀的BRAF - V600E和野生型BRAF进行的体外激酶分析表明,I3C选择性地抑制致癌性BRAF - V600E的酶活性,而不抑制野生型蛋白的酶活性。计算机模拟预测I3C在BRAF - V600E原体中的相互作用位点与临床使用的BRAF - V600E抑制剂维莫非尼与BRAF - V600E结合的位点不同。与该预测一致,与单独使用每种化合物的效果相比,I3C和维莫非尼的组合更有效地抑制了表达BRAF - V600E的黑色素瘤细胞的增殖并降低了MITF - M水平。因此,我们的结果表明致癌性BRAF - V600E是I3C的一个新的细胞靶点,这表明这种吲哚甲醇化合物是黑色素瘤新型单药或联合疗法的潜在候选药物。©2016威利期刊公司