Objective:To explore HtrA1 gene expression aud its regulation in human gastric cancers.Methods:The HtrA1 mRNA levels were examined by QPCR analysis and coufirmed its expression with Northern blot analysis.The HtrA1 protein levels in all six gastric epithelial cell lines were investigated by Western blot analysis.Gene copy number was accessed and then sequenced the coding region from each mRNA in all six cell lines.The HtrA1 promoter region DNA methylation status was detected by using bisulfite sequeucing analysis.Effect of decitabine and TSA on HTRA1 expression in gastric cancer cell line was determined by RTPCR.Results:HIC analysis indicated that HtrA1 was highly expressed in normal epithelium,but dramatically down-regulated in gastric carcinoma tissues and variably expressed in tumor-adjacent tissues.HtrA1 gene expression was dramatically decreased in gastric carcinoma cells compared to nontumorigenic counterparts.The HtrA1 gene loss in any of the 4 breast cancer cell lines was not detected.Total 14 CpGs in this region were all methylated in gastric cancer cells,whereas two normal cells.GES-1 and HFI-145,were having several unmethylated cytosines in this region.HtrA1 showed as~Mr 44,000,Expression of HtrA1 protein was not observed in any of the four gastric caucer cell lines.BGC-823.MKN-45.SGC-7901and MKN-28.HtrA1 expression was observed in the HF1-145and GES-1 cell lines.Conclusions:The epigenetic silencing for HtrA1gene expression could provide a possible strategy for re-activating Htrt1 gene expression in gastric cancer cells.thus facilitating further investigation of HtrA1’s role in chemotherapy. Objective: To explore HtrA1 gene expression aud its regulation in human gastric cancers. Methods: The HtrA1 mRNA levels were examined by QPCR analysis and coufirmed its expression with Northern blot analysis. HtrA1 protein levels in all six gastric epithelial cell lines were investigated by Western blot analysis. Gene copy number was accessed and then sequenced the coding region from each mRNA in all six cell lines. The HtrA1 promoter region DNA methylation status was detected by using bisulfite sequeucing analysis. Effect of decitabine and TSA on HTRA1 expression in gastric cancer cell line was determined by RTPCR. Results: HIC analysis showed that HtrA1 was highly expressed in normal epithelium, but dramatically down-regulated in gastric carcinoma tissues and variably expressed in tumor-adjacent tissues. HtrA1 gene expression was dramatically decreased in gastric carcinoma cells compared to nontumorigenic counterparts. The HtrA1 gene loss in any of the 4 breast cancer cell lines was not d etected.Total 14 CpGs in this region were all methylated in gastric cancer cells, while two normal cells. GES-1 and HFI-145, were having several unmethylated cytosines in this region. HtrA1 showed as ~ Mr 44,000, Expression of HtrA1 protein was not observed in any of the four gastric caucer cell lines. BGC-823.MKN-45. SGC-7901 and MKN-28. HtrA1 expression was observed in the HF1-145 and GES-1 cell lines. Conclusions: The epigenetic silencing for HtrA1 gene expression could provide a possible strategy for re-activating Htrt1 gene expression in gastric cancer cells. thus further further investigation of HtrA1’s role in chemotherapy.