Elevating H3K27me3 level sensitizes colorectal cancer to oxaliplatin

USP38 regulates the stemness and chemoresistance of human colorectal cancer via regulation of HDAC3

Histone modification represents a crucial level of gene expression regulation and is actively involved in the carcinogenesis of human colorectal cancer. Histone acetyltransferases and deacetylases modulate the landscape of histone acetylation, which controls key genes of colorectal cancer pathology. However, the fine tune of histone deacetylases, especially the modification of histone deacetylases that facilitate colorectal cancer, remains elusive. Here, we identified that an ubiquitin-specific protease (USP), USP38, was downregulated in clinical colorectal cancer samples and colorectal cancer cell lines. Importantly, our results showed that USP38 was a specific deubiquitinase of histone deacetylase 3 (HDAC3), which cleaved the lysine 63 ubiquitin chain. Ubiquitination of HDAC3 resulted in a decreased level of histone acetylation and finally led to upregulation of cancer stem cell-related genes. In addition, our results demonstrated a tumor suppressor role of USP38 in colorectal cancer via inhibiting cancer stem cell populations. Most importantly, the ubiquitination level of HDAC3 was responsible for USP38 mediated regulation of cancer stem cell-related transcripts. Our data provided functional insights of USP38 and HDAC3 in colorectal cancer and revealed novel mechanisms of ubiquitination mediated epigenetic regulation.

SETDB1 promotes the progression of colorectal cancer via epigenetically silencing p21 expression

SETDB1, a histone H3K9 methyltransferase, has been reported to be upregulated in a variety of tumors and promotes cancer development. However, the exact pathogenesis of SETDB1 in human colorectal cancer (CRC) is hitherto unknown. Here, we showed that SETDB1 expression was highly amplified in CRC. Functionally, SETDB1 downregulation in SW480 and HCT116 cells reduced cell proliferation, migration, invasion, and increased CRC cells apoptosis. In contrast, SETDB1 overexpression promoted CRC cells proliferation, migration, and invasion. High expression of SETDB1 was associated with a more aggressive phenotype in vitro. Flow cytometry showed that cell cycle was arrested in G1 phase after SETDB1 silencing. Furthermore, depletion of SETDB1 in vivo suppressed CRC cells proliferation. Mechanistically, p21 was identified as the target of SETDB1. After transfected with siSETDB1, expression of p21 was distinctly increased. In contrast, expression of p21 was significantly decreased after overexpression SETDB1. We also showed that SETDB1 could be involved in the regulation of epithelial–mesenchymal transition (EMT) in HCT116 cells. Moreover, we confirmed that SETDB1 could regulate the activity of p21 promoter by dual-luciferase repoter assay, and proved that SETDB1 could bind to the promoter of p21 and regulate its H3K9me3 enrichment level by ChIP-PCR experiment. Finally, we verified that silencing of SETDB1 inhibited CRC tumorigenesis in vivo. In conclusion, our results indicate that SETDB1 is a major driver of CRC development and might provide a new therapeutic target for the clinical treatment of CRC.