Targeting the E2F1/Rb/HDAC1 axis with the small molecule HR488B effectively inhibits colorectal cancer growth.

Colorectal cancer (CRC), the third most common cancer worldwide, remains highly lethal as the disease only becomes symptomatic at an advanced stage. Growing evidence suggests that histone deacetylases (HDACs), a group of epigenetic enzymes overexpressed in precancerous lesions of CRC, may represent promising molecular targets for CRC treatment. Histone deacetylase inhibitors (HDACis) have gradually become powerful anti-cancer agents targeting epigenetic modulation and have been widely used in the clinical treatment of hematologic malignancies, while only few studies on the benefit of HDACis in the treatment of CRC. In the present study, we designed a series of small-molecule Thiazole-based HDACis, among which HR488B bound to HDAC1 with a high affinity and exerted effective anti-CRC activity both in vitro and in vivo. Moreover, we revealed that HR488B specifically suppressed the growth of CRC cells by inducing cell cycle G0/G1 arrest and apoptosis via causing mitochondrial dysfunction, reactive oxygen species (ROS) generation, and DNA damage accumulation. Importantly, we noticed that HR488B significantly decreased the expression of the E2F transcription factor 1 (E2F1), which was crucial for the inhibitory effect of HR488B on CRC. Mechanistically, HR488B obviously decreased the phosphorylation level of the retinoblastoma protein (Rb), and subsequently prevented the release of E2F1 from the E2F1/Rb/HDAC1 complex, which ultimately suppressed the growth of CRC cells. Overall, our study suggests that HR488B, a novel and efficient HDAC1 inhibitor, may be a potential candidate for CRC therapy in the future. Furthermore, targeting the E2F1/Rb/HDAC1 axis with HR488B provides a promising therapeutic avenue for CRC.

YF343, A Novel Histone Deacetylase Inhibitor, Combined with CQ to Inhibit- Autophagy, Contributes to Increased Apoptosis in Triple- Negative Breast Cancer.

BACKGROUND: Compounds that target tumor epigenetic events are likely to constitute a prominent strategy for anticancer treatment. Histone deacetylase inhibitors (HDACis) have been developed as prospective candidates in anticancer drug development, and currently, many of them are under clinical investigation. We assessed the anticancer efficacy of a now hydroxamate-based HDACi, YF-343, in triple-negative breast cancer development and studied its potential mechanisms. METHODS: YF-343 was estimated as a novel HDACi by the HDACi drug screening kit. The biological effects of YF-343 in a panel of breast cancer cell lines were analyzed by Western blot and flow cytometry. YF-343 exhibited notable cytotoxicity, promoted apoptosis, and induced cell cycle arrest. Furthermore, it also induced autophagy, which plays a pro-survival role in breast cancer cells. RESULTS: The combination of YF-343 with an autophagy inhibitor chloroquine (CQ) significantly suppressed breast tumor progression as compared to the YF-343 treatment alone both in vitro and in vivo. Mechanistically, the molecular mechanism of YF-343 on autophagy was elucidated by gene chip expression profiles, qPCR analysis, luciferase reporter gene assay, chromatin immunoprecipitation assays, immunohistochemical analysis, and other methods. E2F7, a transcription factor, promoted the expression of ATG2A via binding to the ATG2A promoter region and then induced autophagy in triple-negative breast cancer cells treated with YF-343. CONCLUSION: Our studies have illustrated the mechanisms for potential action of YF-343 on tumor growth in breast cancer models with pro-survival autophagy. The combination therapy of YF-343 and CQ maybe a promising strategy for breast cancer therapy.