Division of Genetics, Department of Medicine , Brigham and Women's Hospital , Boston , Massachusetts 02115 , United States.
Department of Biological Chemistry and Molecular Pharmacology , Harvard Medical School , Boston , Massachusetts 02115 , United States.
Biochemistry. 2019 Apr 23;58(16):2133-2143. doi: 10.1021/acs.biochem.9b00160. Epub 2019 Apr 11.
p300 and CBP are highly related histone acetyltransferase (HAT) enzymes that regulate gene expression, and their dysregulation has been linked to cancer and other diseases. p300/CBP is composed of a number of domains including a HAT domain, which is inhibited by the small molecule A-485, and an acetyl-lysine binding bromodomain, which was recently found to be selectively antagonized by the small molecule I-CBP112. Here we show that the combination of I-CBP112 and A-485 can synergize to inhibit prostate cancer cell proliferation. We find that the combination confers a dramatic reduction in p300 chromatin occupancy compared to the individual effects of blocking either domain alone. Accompanying this loss of p300 on chromatin, combination treatment leads to the reduction of specific mRNAs including androgen-dependent and pro-oncogenic prostate genes such as KLK3 (PSA) and c-Myc. Consistent with p300 directly affecting gene expression, mRNAs that are significantly reduced by combination treatment also exhibit a strong reduction in p300 chromatin occupancy at their gene promoters. The relatively few mRNAs that are up-regulated upon combination treatment show no correlation with p300 occupancy. These studies provide support for the pharmacologic advantage of concurrent targeting of two domains within one key epigenetic modification enzyme.
p300 和 CBP 是高度相关的组蛋白乙酰转移酶（HAT）酶，它们可以调节基因表达，其功能失调与癌症和其他疾病有关。p300/CBP 由多个结构域组成，包括一个 HAT 结构域，该结构域受小分子 A-485 的抑制，以及一个乙酰-赖氨酸结合溴结构域，最近发现该结构域可被小分子 I-CBP112 选择性拮抗。在这里，我们表明 I-CBP112 和 A-485 的组合可以协同抑制前列腺癌细胞的增殖。我们发现，与单独阻断任一结构域的效果相比，该组合导致 p300 染色质占有率显著降低。伴随着染色质上 p300 的丢失，联合治疗导致特定 mRNA 的减少，包括雄激素依赖性和致癌性前列腺基因，如 KLK3（PSA）和 c-Myc。与 p300 直接影响基因表达一致，组合治疗显著减少的 mRNA 在其基因启动子处也表现出 p300 染色质占有率的强烈减少。在联合治疗时上调的相对较少的 mRNA 与 p300 占有率没有相关性。这些研究为同时靶向一个关键表观遗传修饰酶中的两个结构域的药理学优势提供了支持。
