SIRT6 overexpression inhibits HIF1α expression and its impact on tumor angiogenesis in lung cancer

摘要

Objective: To investigate the effect of silencing information regulator 6 (SIRT6) on HIF1α expression of cell line A549 in non-small cell lung cancer and on tumor angiogenesis in lung cancer. Methods: Cell line A549 in the logarithmic growth phase was transfected with Ad-SIRT6 and Ad-null respectively. According to the study design, the cells were divided into control group, Ad-null group and Ad-SIRT6 group. The HIF1α and HIF2α mRNA expression in each group were detected by real-time quantitative PCR (qPCR). The level of prolyl hydroxylase (PHD) 1-3 after 48 h of Ad-SIRT6-transfected cell line A549 and the levels of VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in the supernatants were determined by ELISA. The nude mice were injected subcutaneously with Ad-null or Ad-SIRT6 transfected cell line A549. The tumor volume was observed at 6, 12, 18, 24 and 30 d after inoculation, and the tumor mass was weighed at 30 d. Also, microvessel density (MVD) and the number of positive HIF1α and VEGF cells were detected by immunohistochemistry. The VEGF and HIF1α levels in tumor tissue were detected by ELISA and qPCR respectively. Results: qPCR showed that the levels of HIF-1α mRNA, VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in the supernatant were decreased, the level of PHD2 was increased (P<0.05), and the levels of HIF-2α mRNA, PHD1 and PHD3 did not change much (P>0.05) in the Ad-SIRT6 group as compared with those in the control group and Ad-null group. The tumor growth rate was decreased, and the tumor volume at 12-30 d after inoculation was less in the Ad-SIRT6 group than in the control group and Ad-null group (P<0.05); the tumor mass was also lower than that of control and Ad-null groups (P<0.05). Immunohistochemistry showed that MVD and the number of HIF-1α and VEGF positive cells were less in the Ad-SIRT6 group than in control and Ad-null groups (P<0.05); and HIF-1α and VEGF levels in tumor tissue were decreased in the Ad-SIRT6 group compared to the control and Ad-null groups (P<0.05). There were no significant differences in the above measurements between the control group and Ad-null group (P>0.05). Conclusion: SIRT6 overexpression can inhibit HIF1α and VEGF expression, promoting PHD2 expression, which can inhibit angiogenesis and xenograft growth and may play a role in reducing HIF1α and VEGF expression.