Objective To observe the methylation status of the promoter region of the tumor suppressor gene PDCD4 in gastric cancer tissues and its effect on the expression level of PDCD4, and to explore its clinical significance.

Methods The protein expression of PDCD4 in gastric cancer tissues was detected by immunohistochemistry (IHC) and Western blot; the mRNA expression of PDCD4 was detected by RT-PCR; the methylation level of PDCD4 promoter region was detected by MSP. The correlation between PDCD4 expression, promoter methylation level and clinicopathological characteristics of gastric cancer patients was analyzed.

Results The expression levels of PDCD4 protein and mRNA in gastric cancer tissues were significantly decreased (P < 0.05), and the methylation of PDCD4 was significantly enhanced (P < 0.05). Deficiency of PDCD4 protein expression is closely correlated with the differentiation, clinical stage and lymph node metastasis of gastric cancer (P < 0.05); hypermethylation of PDCD4 is closely correlated with lymph node metastasis and clinical stage of gastric cancer (P < 0.05). The methylation level of PDCD4 was negatively correlated with the protein and mRNA expression levels of PDCD4 (P < 0.05).

Conclusion The expression of PDCD4 in gastric cancer tissues is significantly decreased and correlated with the development of gastric cancer. Hypermethylation of CpG island in promoter region may be the reason for the deficiency of PDCD4 expression.