Effect of DR4 promoter methylation on the TRAIL-induced apoptosis in lung squamous carcinoma cell

The aim of the present study was to examine the relationship between DR4 methylation status and gene expression and to determine whether DR4 methylation status affects TRAIL-induced apoptosis in lung squamous carcinoma cells. MSP, RT-PCR and western blot analysis were applied to detect the methylation status and gene expression. An MTT assay was used to detect the cell proliferation inhibition rate and flow cytometry was utilized to detect the apoptotic rate. The results showed that there was no association of the apoptotic rate with the clinicopathological characteristics for 80.6% of 36 lung squamous carcinoma patients in the methylation status (P>0.05). In the lung squamous carcinoma patients, the probability of DR4 low expression was approximately 58.3%, which may be associated with DR4 promoter methylation. The results also showed that a low expression of DR4 was correlated with the prognosis of patients. The in vitro experiments suggested DR4 genes of H226 and SK-MES-1 cells were in the methylation status and their mRNA and proteins had a low expression. Following intervention with 5-Aza-CdR, the DR4 genes of H226 and SK-MES-1 cells were in the unmethylation status and their mRNA and protein expression was significantly upregulated compared with the pre-interference ones, with differences being statistically significant (P<0.05). In addition, following interference with 5-Aza-CdR, H226 and SK-MES-1 cells became significantly sensitive to TRAIL (P<0.05). The results revealed 5-Aza-CdR was able to reverse DR4 methylation status to upregulate its expression, thereby increasing the TRAIL-induced apoptosis in lung squamous carcinoma cells. Therefore, combining 5-Aza-CdR and TRAIL is a new strategy for treating lung squamous carcinoma.