Identification Of Biomarkers And Characterization Of Its Mechanisms Involved In Chemoresistance In Small-Cell Lung Cancer

First part:Decline in serum progastrin-releasing peptide predicts the response of patients with small cell lung cancer to chemotherapyWe evaluated the utility of serum progastrin-releasing peptide(ProGRP)and neuron-specific enolase(NSE)as biomarkers for treatment monitoring and as prognostic factors in small cell lung cancer(SCLC)patients.Patients were first diagnosed pathologically at the First Affiliated Hospital of the University of Science and Technology of China had their serum ProGRP and NSE levels measured using an electrochemiluminescence immunoassay.A total of 120 SCLC patients were enrolled.For responsive patients,ProGRP levels decreased significantly following two cycles of chemotherapy and continued to decline throughout treatment.However,this decrease in ProGRP levels was not observed in nonresponsive patients.Changes in ProGRP levels were more accurate than changes in NSE levels for monitoring the effects of chemotherapy in SCLC patients.We found that after two treatment cycles or after the occurrence of drug resistance,changes in ProGRP levels in patients with low ProGRP levels at the time of diagnosis were not obvious,whether or not patients were responders.The receiver operating characteristic curve area of the decline in ProGRP levels as a therapeutic biomarker of SCLC was 0.9643,and the cutoff value was 55.02%.Decline in ProGRP levels could be a good predictor of objective response to chemotherapy in SCLC patients with higher ProGRP levels at diagnosis.This model is expected to replace or be combined with imaging to predict chemotherapeutic treatment effects in SCLC patients.Second part:Circulating miR-92b and miR-375 for monitoring the chemoresistance and prognosis of small cell lung cancermiRNAs have been reported to be stably detectable in plasma and to function as potent biomarkers in multiple cancers.The study aimed to evaluate the expression of candidate circulating miRNAs in patients with SCLC to identify potential noninvasive biomarkers.The expression of five miRNAs(miR-92b,miR-146a,miR-375,miR-1224,and miR-1246)was significantly upregulated in plasma after chemoresistance induction.Receiver operating characteristic curve(ROC)analysis showed that the area under the curve(AUC)values of miR-92b and miR-375 were 0.766 and 0.791,respectively.The data demonstrated that among the five miRNAs assessed,these two miRNAs had better diagnostic accuracy for monitoring drug resistance.In addition,miR-92b and miR-375 levels were decreased after effective chemotherapy.Furthermore,Kaplan-Meier survival analysis confirmed that high expression of miR-92b and miR-375 was closely related to shorter progression-free survival(PFS)in SCLC patients.In conclusion,these findings indicate that circulating miR-92b and miR-375 might be ideal noninvasive biomarkers for monitoring drug resistance during chemotherapy and evaluating the prognosis of patients with SCLC.Third part:Exosome-delivered miR-92b-3p promotes chemoresistance in small cell lung cancerThe five-year survival rate of small cell lung cancer is less than 10%.Multidrug resistance is the main reason for the failure of SCLC chemotherapy.In this study,high-throughput microRNA(miRNA)sequencing technology was used to screen and identify the biomarkers of SCLC chemotherapy resistance,and we found that the expression of miR-92b-3p in plasma exosomes was significantly upregulated after chemotherapy resistance.The molecular mechanism of exosomal miR-92b-3p promoting SCLC resistance was explored by in vitro and in vivo experiments.The SCLC cell lines were transfected by lentivial vectors with different miR-92b-3p expression,and changes in expression profiles of apoptosis,invasion and metastasis in SCLC cells before and after miR-92b-3p transfection were observed.The molecular mechanism of miR-92b-3p promoted SCLC chemoresistance has been verified in animal experiments.Through the co-culture of exosomes,it was explored that miR-92b-3p might promote the resistance of SCLC through the delivery of exosomes.Finally,circulating plasma miR-92b-3p served as biomarkers to evaluate the efficacy of therapy and the prognosis of SCLC.Overexpression of miR-92b-3p promoted drug resistance,invasion and metastasis of SCLC cells.Exosomal miR-92b-3p may promote SCLC resistance through PTEN/p-AKT signaling pathway,miR-92b-3p can be used as a biomarker for chemoresistance in SCLC.