Identification Of The Expression And Function Of IGFBP5 In Cancer Stem-like Cells In Non-small Cell Lung Cancer

Background:Lung cancer is the leading cause of cancer-related death in the world. Traditional treatment for lung cancer is surgery combined with radiation and chemotherapy, with a 5-year survival rate less than 15%. Recently, studies show that there are a rare population of CSCs in lung cancer. They are closely related to the occurrence, metastasis, recurrence and drug resistance of lung cancer. Insulin-like growth factor binding protein 5 (IGFBP5) plays an important role in biological processes such as proliferation, differentiation, apoptosis, adhesion and motility, and are also closely related to oncogenesis. However, IGFBP5 has tissue specific and cell specific effects. Till now, the role of IGFBP5 in lung cancer is not yet clear. There is little report about its impact and regulating mechanism of CSCs in these events.Objective:In this study, we identify the expression and function of IGFBP5 in NSCLC. Then we explore the role of IGFBP5 in regulating CSC properties and the probable mechanism. This study may provide a novel promising therapeutic target for NSCLC stem cells.Methods:1. We collected the gathered CSCs of both NSCLC cell lines and primary lung cancer cell lines by serum-free ultra-low attachment culture, whose cDNA and protein were tested by qRT-PCR and Western Blotting to assess IGFBP5 expression; 2. We isolated CD133+ NSCLC cells using magnetic cell sorting, whose protein expression were tested by Western Blotting to assess IGFBP5; 3. We silenced IGFBP5 expression using lentiviral delivery of IGFBP5-specific shRNA, and detect its tumorigenesis ability; 4. We detected sphere forming ability using IGFBP5 silenced cells in vitro compared with control, and examined the effect of IGFBP5 on iPS factors; 5. IGFBP5-pCMV-myc plasmid was constructed and transfected into NSCLC cell lines to explore the probable regulating pathway of IGFBP5.Results:1. cDNA and protein expression level of IGFBP5 in oncospheres were higher compared with control group; 2. IGFBP5 expressed higher in CD133+cells; 3.IGFBP5 knockdown showed weakened tumorigenesis ability; 4. IGFBP5 knockdown led to significant decrease in the number and size of oncospheres formed, and a group of critical transcript factors associated with iPSC including Sox2 and c-Myc decreased compared to the control cells; 5. IGFBP5 promoted NSCLC to exhibite a reprogrammed phenotype by activation of Wnt signaling pathway.Conclusions:Our findings demonstrate an important role of IGFBP5 in CSCs. IGFBP5 can activate Wnt pathway and regulate critical reprogramming factors in NSCLC, thus providing a novel promising therapeutic target for NSCLC stem cells.