Effects of hypoxia-inducible factor-1α on radiation-induced autophagic cell death in breast cancer cells / 中华放射医学与防护杂志

ABSTRACT

Objective To study the effects of hypoxia-inducible factor-1α (HIF-1α) on radiationinduced autophagic cell death in breast cancer cells.Methods MCF-7 cells were divided into four groupscontrol (normoxia,21％ Oxygen),irradiation (8 Gy X-rays),hypoxia (Cobalt chloride,CoCl2)and irradiation with hypoxia (CoCl2).150 μmol/L CoCl2 was utilized to induce hypoxic conditions.Western blot was applied to detect the expression of HIF-1α and MAPLC3.MDC and Hoechst staining were used to detect autophagy and apoptosis.Radiosensitivity was detected by cloning formation.The short hairpin interfering RNA (shRNA) retroviral transduction particles targeting HIF-1α was transfected into MCF-7 cells to establish HIF-1 α knockdown cells,then the radiosensibility,autophagy and apoptosis were detected.Results Compared with control group and irradiation group,the protein level of HIF-1 increased obviously in the normaxia,irradiation,hypoxia and irradiation with hypoxia groups,and the values were 0,0,1.00,1.89,respectively.The expression levels of MAPLC3 were markedly up-regulated in irradiation,hypoxia and irradiation with hypoxia groups as compared with control,and the ratios of LC3Ⅱ/LC3Ⅰ were 1.15,1.73,2.38 and 3.60,respectively.The radiosensitivity of MCF-7 cells decreased in the following ordernormoxia with 3MA ＞ normoxia ＞ hypoxia with 3MA ＞ hypoxia.HIF-1α knockdown cell (pSUPER-HIF-1α Ri) and vector control were constructed.After treatment with CoCl2,survival fraction of MCF-7-pSUPER was significantly higher than that of control (t =3.080,6.946,6.658,6.380,P ＜0.05),and radiosensitivity was down-regulated after irradiation,but there was no significant difference between normoxia and hypoxia in survival fraction of MCF-7-pSUPER-HIF-1α Ri.After treatment of irradiation or hypoxia,the autophagic fractions in MCF-7-pSUPER-HIF-1α Ri significantly decreased,reduced by 21.1％,25.5％,15.5％,respectively(t =4.635,4.738,6.354,P ＜0.05) as compared with MCF-7-pSUPER,but there was no change in apoptosis.Conclusions HIF-1α may increase radiationinduced autophagy and decrease radiosensitivity,but have no influence on apoptosis.