Dar Altaf A, Nosrati Mehdi, Bezrookove Vladimir, de Semir David, Majid Shahana, Thummala Suresh, Sun Vera, Tong Schuyler, Leong Stanley P L, Minor David, Billings Paul R, Soroceanu Liliana, Debs Robert, Miller James R, Sagebiel Richard W, Kashani-Sabet Mohammed
Center for Melanoma Research and Treatment (AAD, MN, VB, DdS, ST, VS, ST, SPLL, DM, JRMIII, RWS, MKS), California Pacific Medical Center Research Institute, San Francisco, CA (AAD, MN, VB, DdS, ST, VS, ST, SPLL, DM, LS, RD, JRMIII, RWS, MKS); Department of Urology, Veterans Affairs Medical Center and University of California San Francisco, San Francisco, CA (SM); Life Technologies, Inc. Carlsbad, CA (PRB).
J Natl Cancer Inst. 2015 Feb 23;107(5):djv034. doi: 10.1093/jnci/djv034.
Bromodomain PHD finger transcription factor (BPTF) plays an important role in chromatin remodeling, but its functional role in tumor progression is incompletely understood. Here we explore the oncogenic effects of BPTF in melanoma.
The consequences of differential expression of BPTF were explored using shRNA-mediated knockdown in several melanoma cell lines. Immunoblotting was used to assess the expression of various proteins regulated by BPTF. The functional role of BPTF in melanoma progression was investigated using assays of colony formation, invasion, cell cycle, sensitivity to selective BRAF inhibitors, and in xenograft models of melanoma progression (n = 12 mice per group). The biomarker role of BPTF in melanoma progression was assessed using fluorescence in situ hybridization and immunohistochemical analyses. All statistical tests were two-sided.
shRNA-mediated BPTF silencing suppressed the proliferative capacity (by 65.5%) and metastatic potential (by 66.4%) of melanoma cells. Elevated BPTF copy number (mean ≥ 3) was observed in 28 of 77 (36.4%) melanomas. BPTF overexpression predicted poor survival in a cohort of 311 melanoma patients (distant metastasis-free survival P = .03, and disease-specific survival P = .008), and promoted resistance to BRAF inhibitors in melanoma cell lines. Metastatic melanoma tumors progressing on BRAF inhibitors contained low BPTF-expressing, apoptotic tumor cell subclones, indicating the continued presence of drug-responsive subclones within tumors demonstrating overall resistance to anti-BRAF agents.
These studies demonstrate multiple protumorigenic functions for BPTF and identify it as a novel target for anticancer therapy. They also suggest the combination of BPTF targeting with BRAF inhibitors as a novel therapeutic strategy for melanomas with mutant BRAF.
溴结构域PHD指转录因子（BPTF）在染色质重塑中起重要作用，但其在肿瘤进展中的功能作用尚未完全明确。在此，我们探究BPTF在黑色素瘤中的致癌作用。
利用短发夹RNA（shRNA）介导的敲低技术，在多种黑色素瘤细胞系中研究BPTF差异表达的后果。采用免疫印迹法评估受BPTF调控的多种蛋白质的表达。通过集落形成、侵袭、细胞周期、对选择性BRAF抑制剂的敏感性检测以及黑色素瘤进展的异种移植模型（每组12只小鼠），研究BPTF在黑色素瘤进展中的功能作用。使用荧光原位杂交和免疫组化分析评估BPTF在黑色素瘤进展中的生物标志物作用。所有统计检验均为双侧检验。
shRNA介导的BPTF沉默抑制了黑色素瘤细胞的增殖能力（降低65.5%）和转移潜能（降低66.4%）。在77例黑色素瘤中的28例（36.4%）中观察到BPTF拷贝数升高（平均≥3）。BPTF过表达预示着311例黑色素瘤患者队列的预后不良（无远处转移生存期P = 0.03，疾病特异性生存期P = 0.008），并促进黑色素瘤细胞系对BRAF抑制剂产生耐药性。在BRAF抑制剂作用下进展的转移性黑色素瘤肿瘤含有低表达BPTF的凋亡肿瘤细胞亚克隆，表明在对抗BRAF药物产生总体耐药性的肿瘤中持续存在药物反应性亚克隆。
这些研究证明了BPTF具有多种促肿瘤功能，并将其确定为抗癌治疗的新靶点。它们还提示将靶向BPTF与BRAF抑制剂联合使用，作为BRAF突变型黑色素瘤的一种新型治疗策略。
