Study Of Hmof On The Global Histone H4K16Acetylation In Gastric Carcinoma

Histone post-translational modifications are a critical epigenetic regulatory mechanismthat include methylation, acetylation, ubiquitination, sumoylation, phosphorylation andglycosylation. Histone acetylation as one of the earlier and most studied epigenetic regulatorymechinisms is controlled by histone acetyltransferases (HATs) and histone deacetyltases(HDACs). Thus, any reason to make this imbalance can lead to abnormal cell processes, evencancer. Recently, increasing evidence has suggested that the alteration of global histoneH4K16acetylation (H4K16ac) may be involved in several types of cancer. It has been knownthat the global histone H4K16ac level in cells is controlled by several enzymes includinghistone acetyltransferases (HATs) and histone deacetylases (HDACs). Histone acetyltrans-ferase hMOF participates in a variety of cellular biological functions through acetylation ofhistone H4K16. It has been reported that abnormal expression of hMOF may be involved inoccurrence of certain cancer, such as renal cell carcinoma, ovarient cancer and colorectalcancer. We previously found the low-expression tendency of hMOF in limited number ofgastric cancer tissues. In order to further investigate and clarify the relationship between theexpression of hMOF and its responding histone H4K16ac in gastric cancer, and to confirmwhich particular enzyme is mainly responsible for global reduction of H4K16ac in gastriccancer, in this study, the gastric cancer tissues and gastric cancer cell line as researchmaterials, combined RT-qPCR, western blot, immunofluorescience staining, overexpressionand siRNA knockdown approaches, we studied in detail the correlation between the hMOFexpression/status of H4K16ac and clinical characteristics of gastric cancer.(1)156frozen tissue samples including primary diagnosed gastric cancer tissues andmatched adjacent or normal tissues were collected. Statistical analysis of performedRT-qPCR data revealed that a significant reduction (>2-fold decreased) of hMOF expressionin gastric cancer tissues in81%(42/52) of patients. In patients with gastric cancer, down-regulation of hMOF was connected to gastric cancer and tissues with pT2-T4tumorstatus, lymph node metastasis and distant metastasis. Overall survival rates revealed asignificant difference between the low-and high-hMOF expression groups. However, therewas no significant difference by age, gender and cell differentiation.(2)96tissue samples including primary diagnosed gastric cancer tissues and matchedadjacent or normal tissues were used to measure the expression of HDAC4by RT-qPCR.Although the high-expression tendency of HDAC4was found in gastric cancer tissues, nosignificant difference was found between high-expression of HDAC4and clinicalcharacteristics.(3) Low expression of hMOF and high expression of HDAC4in both SGC-7901andMGC-803gastric cancer cell line were confirmed by RT-qPCR, WB and immunofl-uorescience staining approaches. Compared to gastric mucosal cells, remarkable reduction ofH4K16ac in both cancer cell lines was detected. To verify the regulatory mechanism ofH4K16ac in cells, overexpression and siRNA knockdown technichs were used in MGC-803cells. The results indicate that over-expression of hMOF increased global H4K16ac in cells,however, no obvious increase of global H4K16ac in HDAC4knockdown MGC-803cells wasobserved.(4) Histone acetyltransferase hMOF and global histone H4K16ac status might beinvolved in gastric cancer tumorigenic pathways. hMOF, but not HDAC4, is mainlyresponsible for global histone H4K16ac in gastric cancer cells.