Histone Deacetylase-3/CAGE Axis Targets EGFR Signaling and Regulates the Response to Anti-Cancer Drugs

We have previously reported the role of miR-326-HDAC3 loop in anti-cancer drug-resistance. CAGE, a cancer/testis antigen, regulates the response to anti-cancer drug-resistance by forming a negative feedback loop with miR-200b. Studies investigating the relationship between CAGE and HDAC3 revealed that HDAC3 negatively regulated the expression of CAGE. ChIP assays demonstrated the binding of HDAC3 to the promoter sequences of CAGE. However, CAGE did not affect the expression of HDAC3. We also found that EGFR signaling regulated the expressions of HDAC3 and CAGE. Anti-cancer drug-resistant cancer cell lines show an increased expression of pEGFR^Y845. HDAC3 was found to negatively regulate the expression of pEGFR^Y845. CAGE showed an interaction and co-localization with EGFR. It was seen that miR-326, a negative regulator of HDAC3, regulated the expression of CAGE, pEGFR^Y845, and the interaction between CAGE and EGFR. miR-326 inhibitor induced the binding of HDAC3 to the promoter sequences in anti-cancer drug-resistant Malme3M^R cells, decreasing the tumorigenic potential of Malme3M^R cells in a manner associated with its effect on the expression of HDAC3, CAGE and pEGFR^Y845. The down-regulation of HDAC3 enhanced the tumorigenic, angiogenic and invasion potential of the anti-cancer drug-sensitive Malme3M cells in CAGE-dependent manner. Studies revealed that PKCδ was responsible for the increased expression of pEGFR^Y845 and CAGE in Malme3M^R cells. CAGE showed an interaction with PKCδ in Malme3M^R cells. Our results show that HDAC3-CAGE axis can be employed as a target for overcoming resistance to EGFR inhibitors.     

Histone deacetylase inhibition regulates miR-449a levels in skeletal muscle cells

microRNAs (miRNAs) are small non-coding RNAs that regulate cellular processes by fine-tuning the levels of their target mRNAs. However, the regulatory elements determining cellular miRNA levels are not well studied. Previously, we had described an altered miRNA signature in the skeletal muscle of db/db mice. Here, we sought to explore the role of epigenetic mechanisms in altering these miRNAs. We show that histone deacetylase (HDAC) protein levels and activity are upregulated in the skeletal muscle of diabetic mice. In C2C12 cells, HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) altered the levels of 24 miRNAs: 15 were downregulated and 9 were upregulated. miR-449a, an intronic miRNA localized within the Cdc20b gene, while being downregulated in the skeletal muscle of diabetic mice, was the most highly upregulated during HDAC inhibition. The host gene, Cdc20b, was also significantly upregulated during HDAC inhibition. Bioinformatics analyses identified a common promoter for both Cdc20b and miR-449a that harbors significant histone acetylation marks, suggesting the possibility of regulation by histone acetylation-deacetylation. These observations suggest an inverse correlation between miR-449a levels and HDAC activity, in both SAHA-treated skeletal muscle cells and db/db mice skeletal muscle. Further, in SAHA-treated C2C12 cells, we observed augmented occupancy of acetylated histones on the Cdc20b/miR-449a promoter, which possibly promotes their upregulation. In vivo injection of SAHA to db/db mice significantly restored skeletal muscle miR-449a levels. Our results provide insights into the potential regulatory role of epigenetic histone acetylation of the miR-449a promoter that may regulate its expression in the diabetic skeletal muscle.     

miR-335 Targets SIAH2 and Confers Sensitivity to Anti-Cancer Drugs by Increasing the Expression of HDAC3

We previously reported the role of histone deacetylase 3 (HDAC3) in response to anti-cancer drugs. The decreased expression of HDAC3 in anti-cancer drug-resistant cancer cell line is responsible for the resistance to anti-cancer drugs. In this study, we investigated molecular mechanisms associated with regulation of HDAC3 expression. MG132, an inhibitor of proteasomal degradation, induced the expression of HDAC3 in various anti-cancer drug-resistant cancer cell lines. Ubiquitination of HDAC3 was observed in various anti-cancer drug-resistant cancer cell lines. HDAC3 showed an interaction with SIAH2, an ubiquitin E3 ligase, that has increased expression in various anti-cancer drug-resistant cancer cell lines. miRNA array analysis showed the decreased expression of miR-335 in these cells. Targetscan analysis predicted the binding of miR-335 to the 3′-UTR of SIAH2. miR-335-mediated increased sensitivity to anti-cancer drugs was associated with its effect on HDAC3 and SIAH2 expression. miR-335 exerted apoptotic effects and inhibited ubiquitination of HDAC3 in anti-cancer drug-resistant cancer cell lines. miR-335 negatively regulated the invasion, migration, and growth rate of cancer cells. The mouse xenograft model showed that miR-335 negatively regulated the tumorigenic potential of cancer cells. The down-regulation of SIAH2 conferred sensitivity to anti-cancer drugs. The results of the study indicated that the miR-335/SIAH2/HDAC3 axis regulates the response to anti-cancer drugs.     

LncRNA C9orf139 can regulate the progression of esophageal squamous carcinoma by mediating the miR-661/HDAC11 axis

Increasing evidence has indicated that long non-coding RNAs (LncRNAs) play multiple functions in the development of cancer and function as indicators of diagnosis and prognosis. This aim of this study was to investigate the roles LncRNA C9orF139 had in the progression of esophageal squamous carcinoma (ESCC). We found C9orf139 was highly expressed in ESCC and knock down the expression of C9orf139 significantly suppressed cell proliferation, promoted apoptosis, and inhibited migration and invasion. C9orf139 was able to negatively regulate miR-661 expression. At the same time, HDAC11 expression was negatively regulated by miR-661. The C9orf139/miR-661/HDAC11 axis was further involved in regulating the expression of the NF-κB signaling pathway. The association between the C9orf139 knockdown and the reduced tumor growth and size was observed during in vivo study. C9orf139 is highly expressed in ESCC, and is thus qualified to be used as a potential diagnostic and prognostic marker for ESCC. Its promotion of ESCC progression is achieved by mediating the miR-661/HDAC11 axis.