The Role Of MiR-137in Multidrug Resistance Of Small Cell Lung Cancer

Lung cancer is one of the leading cancers with high incidence rate worldwide. Smallcell lung cancer (SCLC) accounts for approximately15-20%among lung canercharacterized for its dismal prognosis and carcinoid syndrome. Chemotherpy is theprimary therapeutic approach for SCLC. However, the multidrug resistance (MDR)emerges after the treatment of chemotherapy and increases the rate of relapse andmortality. The median survival time is only6-8mouths and5-year-survival rate is3-8%.The emergency of new chemotherapeutics and adjusting the chemotherapy program couldnot improve the survival rates. Therefore, the MDR has become the major clinical obstaclein the treatment of SCLC.Many previous studies have indicated that the MDR mechanism is complex andinclude intrinsic and acquired drug resistance. Being important regulating factor, miRNAhas become the hot topic in the area of life science. Recently, increasing studies haverevealed that miRNAs are not only related to the initation, progression and metastasis oflung cancer, but also play importment roles in sensitivity of tumor cells tochemotherapeutic drugs, which give us clue that target potential miRNAs might help us reverse SCLC MDR.To investigate the MDR mechanism of SCLC, the microRNAs of human MDR SCLCcells H446/CDDP were compared with its parental cells H446by HiSeq sequencing in thestudy. The comparison revealed that miR-137was significantly higher in H446cellscompared with H446/CDDP, verified by following real-time PCR. The decrease ofmiR-137of H446cells transfected with miR-137inhibitor caused the decreased apoptosisof H446cells induced by cis-platin. Additionally, the increased miR-137of H446/CDDPcells transfected with miR-137mimics caused the increased apoptosis of H446/CDDPcells induced by cis-platin and the decreased expression of KIT. The findings indicatedthat miR-137may provide a promising therapeutic approach in sensitizing SCLC cells tochemotherapeutic drugs.AimsTo investigate the role of miR-137in MDR of SCLC to provide experimental andtheoretical basis for MDR reversal.Methods1. The differentially expressed miRNAs between MDR cells H446/CDDP and itsparents cells H446were identified using miRNAs deep sequencing.The potentialcandidates of miRNAs were validated by real-time PCR.2. After the miR-137mimics was transfected into H446/CDDP cells, cell cycle, cellapoptosis and drug toxicity experiment were carried out to discover the roles ofinvolvement of miR-137in MDR of SCLC.3. The potential targeted genes regulated by miR-137was predicted using the sofewareof Targetscan, miRanda and miRDB.4. Western-blot was carried out to investigate the expression of potential candidate geneof KIT regulated by miR-137.Results1. The expression of miR-137in H446/CDDP cells was significantly lower than that ofits parent H446cells detected by Hiseq deep sequencing, which was validated byreal-time PCR (P<0.01). 2. Overexpression of miR-137in H446/CDDP cells was found to promote cellsensitivity to cisplatin by increased apoptosis(P<0.01).3. Down-regulated expression of miR-137in H446cells was found to decrease cellsensitivity to cisplatin by reduced apoptosis (P<0.01).4. Western-blot assay indicated that KIT was the candidate gene regulated by miR-137.ConclusionsmiR-137has been found to play important role in the development of SCLC MDRby regulating apoptosis.