Metabolically stable diphenylamine derivatives suppress androgen receptor and BET protein in prostate cancer

Androgen receptor (AR) is a crucial driver of prostate cancer (PC). AR-relevant resistance remains a major challenge in castration-resistant prostate cancer (CRPC). Bromodomain and extra-terminal domain (BET) family are critical AR coregulators. Here, we developed several diphenylamine derivatives and identified compound 7d that disrupted the functions of AR and BET family in prostate cancer and exhibited favorable metabolic stability in vitro and high drug exposure in vivo. We showed 7d not only bound to AR, suppressed transactivation of wild-type AR (wt-AR) and the mutant that mediates Enzalutamide resistance, but also reduced c-Myc protein expression through BET inhibition. In addition, 7d inhibited the proliferation of AR-positive PC cells with favorable selectivity and suppressed AR-V7-expressing VCaP and 22Rv1 xenografts growth in vivo. Collectively, these results indicate the potential of lead compound 7d as an orally available AR and BET inhibitor to treat CRPC and overcome antiandrogen resistance.

Bromodomain and extra-terminal domain (BET) proteins regulate melanocyte differentiation

BACKGROUND

Pharmacologic inhibition of bromodomain and extra-terminal (BET) proteins is currently being explored as a new therapeutic approach in cancer. Some studies have also implicated BET proteins as regulators of cell identity and differentiation through their interactions with lineage-specific factors. However, the role of BET proteins has not yet been investigated in melanocyte differentiation. Melanocyte inducing transcription factor (MITF) is the master regulator of melanocyte differentiation, essential for pigmentation and melanocyte survival. In this study, we tested the hypothesis that BET proteins regulate melanocyte differentiation through interactions with MITF.

RESULTS

Here we show that chemical inhibition of BET proteins prevents differentiation of unpigmented melanoblasts into pigmented melanocytes and results in de-pigmentation of differentiated melanocytes. BET inhibition also slowed cell growth, without causing cell death, increasing the number of cells in G1. Transcriptional profiling revealed that BET inhibition resulted in decreased expression of pigment-specific genes, including many MITF targets. The expression of pigment-specific genes was also down-regulated in melanoma cells, but to a lesser extent. We found that RNAi depletion of the BET family members, bromodomain-containing protein 4 (BRD4) and bromodomain-containing protein 2 (BRD2) inhibited expression of two melanin synthesis enzymes, TYR and TYRP1. Both BRD4 and BRD2 were detected on melanocyte promoters surrounding MITF-binding sites, were associated with open chromatin structure, and promoted MITF binding to these sites. Furthermore, BRD4 and BRD2 physically interacted with MITF.

CONCLUSION

These findings indicate a requirement for BET proteins in the regulation of pigmentation and melanocyte differentiation. We identified changes in pigmentation specific gene expression that occur upon BET inhibition in melanoblasts, melanocytes, and melanoma cells.

Design, synthesis and biological evaluation of benzo[cd]indol-2(1H)-ones derivatives as BRD4 inhibitors

Compound 1 bearing with benzo [cd]indol-2(1H)-one scaffold was identified as an effective BRD4 inhibitor through the AlphaScreen-based high-throughput screening and its high-resolution crystal structure with BRD4_BD1 protein. A series of 48 compounds were designed and synthesized by structural optimization on compound 1. All the compounds have been evaluated for their BRD4 inhibitory activities. The results showed that compounds 23, 24, 28 and 44 are the most potential ones with the IC₅₀ values of 1.02 μM, 1.43 μM, 1.55 μM and 3.02 μM, respectively. According to their co-crystal structures in complex with BRD4_BD1 and the protein thermal shift assays, the binding modes were revealed that the additional indirect hydrogen bonds and hydrophobic interactions make such four compounds more active than 1 against BRD4. Furthermore, compounds 1, 23 and 44 were chosen to evaluate for their antiproliferative activities on the MLL-AF4-expression acute leukemia cell line (MV4-11), other cancer cell lines (MDA-MB-231, A549, 22Rv1) and the non-cancer cell lines (HUV-EC-C, MRC5, RPTEC). The results showed that these compounds exhibited good and selective inhibitory activities against MV4-11 cells with the IC₅₀ values of 11.67 μM, 5.55 μM, and 11.54 μM, respectively, and could act on the cell proliferation by blocking cell cycle at G1 phase. They could markedly down-regulate the expressions of the c-Myc, Bcl-2 and CDK6 oncogenes in MV4-11 in the qRT-PCR and western blot studies, which further demonstrated that compound 1 and its derivatives could serve as a promising therapeutic strategy for MLL leukemia by targeting BRD4_BD1 protein.