Hif-1α Up-regulates Expression Of Abcg2 And Contributes To The Abcg2-induced Chemoresistance In A549 Cell Lines Under Hypoxia Condition

AimsLung cancer is currently the leading cause of cancer-related morbidity and mortality worldwide. MDR is the main obstacle associated with poor survival rate. Recent studies indicate that Hypoxia inducible factor-1αincreased expresses in many tumors. It is believed that this can contribute to the development of MDR. But the role of HIF-1αin MDR of lung cancer remains unclear. The aim of this study was to explore the role of HIF-1αin MDR of NSCLC and interaction with ABCG2. It may provide a new way for treatment of NSCLC.Methods1. The expression of HIF-1αin 60 cases NSCLC tissues was detected by Immunohistochemical staining. The relationship between HIF-1αexperssion in NSCLC and pathologic types, TNM stages and lymph node metastasis was analyzed.2. SiRNA targeting HIF-1αand control siRNA were commercially synthesized. Transfections of A549 were performed using the cationic lipid Lipofectamine 2000. The sensitivity of the cells to cisplatin and the cell survival percentage were determined by MTT assay.3. Western blot was used to analyze the expression of HIF-1αand ABCG2 in all groups. The sensitivity of the cells to cisplatin and the cell survival percentage were determined by MTT assay.Results1. Immunohistochemical staining analysis showed that HIF-1αprotein located in the nucleus and/or cytoplasm of positive cells with a positive rate of 60% (36 of 60) in NSCLC. But no positive staining was observed in the normal lung cells taken from non-cancerous regions and adjacent to lung cancer tissue. Comparing the expression of HIF-1αprotein between squamous carcinoma (50%) and adenocarcinoma (68.75%) but there was no significant statistical difference. The rates of HIF-1αexpression in stageⅠ, stageⅡ, stageⅢ, negative lymph node metastasis and positive lymph node metastasis were 25%(4/16),58.82%(10/17),81.48%(22/27) , 25%(5/20), 77.50%(31/40)respectively. The expresssion of HIF-1αwas significantly correlated with TNM staging and lymph node metastasis (P< 0.05). The rate of expression of ABCG2 in NSCLC was 63.33%(38/60). There was a significant positive correlation between expression of HIF-1αand ABCG2 in NSCLC.2. Expression of HIF-1αprotein in A549-siRNA-HIF-1αcells was increased than that in A549 cells treated with hypoxia. MTT assay showed that the survival percentage of A549 cells to cisplatin under hypoxia was higher than A549 cells under normoxia. Also, the survival percentage to cisplatin of control A549 cells was higher than A549-siRNA-HIF-1αcells under hypoxia.3. Down-regulation of expression of ABCG2 was performed by RNAi. Expression of ABCG2 protein in A549-siRNA-ABCG2 cells was increased than that in A549 cells. Expression of HIF-1αand ABCG2 was increased under hypoxia than normoxia. Expression of HIF-1αand ABCG2 dereased correspondingly in A549-siRNA- HIF-1αcells with different time of hypoxia. MTT assasy showed that the suivival percentage of A549-siRNA-ABCG2 cells was lower than normal hypoxia-treated A549 cells, but still higher than normal A549 under normoxia.Conclusions1. HIF-1αand ABCG2 protein highly co-expressed in NSCLC. Expresssion of HIF-1αwas significantly correlated with TNM staging and lymph node metastasis in NSCLC. This may correlate with poor suivival. There was a significant positive correlation between expression of HIF-1αand ABCG2 in NSCLC.2. Increasd drug resistance in NSCLC can be induced by hypoxia. This process mainly completed by HIF-1α3. HIF-1αcontributed to the chemoresistance induced by ABCG2 through up-regulating ABCG2.