The Clinical Significance Of Epithelial Mesenchymal Transformation In Small Cell Lung Cancer

Background and Objective Small cell lung cancer(SCLC)is a common type of neuroendocrine carcinoma with high malignancy degree.Despite high sensitivity of treatment response,the majority of SCLC patients have no opportunity to receive surgical resection at the time of diagnosis,and the 5-year survival rate is low.It has been proved that HGF/c-Met signaling axis plays a critical role in the onset,progression and metastasis of carcinoma.Serum HGF can promote tumorigenicity,induce epithelial mesenchymal transition(EMT)and drug resistance,and participate in the process of EMT through the activation of Met genes.Tumor cells acquire the ability to metastasize to lymph nodes,blood vessels as well as bone marrow by undergoing EMT and its reverse mesenchymal-to-epithelial transition(MET)may help facilitate the formation of metastases at distant organs.Our previous study has found that Vimentin positive Circulating Tumor Cells(CTCs)may serve as an indicator in the prognosis of lung cancer.CTCs at the EMT status may escape from immune surveillance and are likely to be the source of tumor recurrence.The purpose of our study is to investigate the expression of EMT markers vimentin、cMET and HGF in the tumor tissues as well as in serum and explore the clinical significance of Vim+CTCs thus to seek the potential prognostic surrogate marker.Methods Immunohistochemistry(IHC)staining and scoring of the EMT marker Vimentin,cMET and HGF in tumor tissues of SCLC was conducted and ELISA was used to detect the concentration of Vimentin and HGF in the serum of pre-treatment SCLC patients.SE-iFISH was applied to analyze the heterogeneity of CTCs and the relationship between CTCs,Vim+CTCs with clinical characteristics,treatment efficacy and prognosis was as well investigated.Results 1.A total of 47 SCLC patients was recruited in the first part of the study,IHC staining and scoring was applied to detect the EMT markers in tumor tissue.The positive rates of Vimentin and cMET were 8.51%and 12.77%,respectively,and the HGF expression wasn’t detected.There was no significant correlation between Vimentin and cMET expression and clinical characteristics of patients(P>0.05).Vimentin positive patients were all in extensive stage.The SCLC patients with Vimentin positive expression compared with Vimentin negative expression in tumor had shorter PFS(3.07m vs 8.53m p=0.086)and OS(5.53m vs 13.07m p=0.209),although the difference did not reach statistical significance,there was an obvious trend of shortening.2.The expression of Vimentin and HGF in serum of SCLC patients was detected by ELISA method.Serum HGF of patients was associated with distant organs metastasis such as liver,bone and brain metastasis and was an independent predictor of liver metastasis(P<0.05).Before treatment,the PFS of the high-concentration Vimentin group was significantly shorter than the low-concentration Vimentin group(6.23m vs 9.47m,P=0.033),and the difference was statistically significant.The combined detection of Vimentin and HGF was an independent prognostic factor for OS of SCLC patients.3.SE-iFISH can isolate and identify the heterogeneity of CTCs according to the cell morphology and karyotype of Chr8 in SCLC patients.The positive rate of vimentin expression in the CTCs is 1.44%.Vim+CTCs were of significant difference both in cell morphology and Chr8 karyotype compared with Vim-CTCs.Patients with CTCs≥21/6ml at baseline had shorter PFS(3.77m vs 8.67m,P=0.018)and OS(8.30m vs 14.90m,P=0.001)than those patients with CTCS<21/6ml.The positive detection of aneuploid Vim+CTCs at baseline predict shorter PFS(3.07m vs 7.97m,P=0.013)and OS(5.73m vs 13.5m,P=0.005)compared with patients not haboring aneuploid Vim+CTCs.Conclusion 1.The expression rate of EMT related markers Vimentin and cMET in tumor tissues of SCLC patients is low and no HGF expression was detected.The positive expression of vimentin in tumor tissues indicates a trend of shorter PFS and OS in SCLC patients.Vimentin may be a better marker than cMET for the study of EMT in patients with SCLC.2.Serum HGF is associated with distant organ metastasis in patients and is an independent predictor of liver metastasis.Both baseline Vimentin and HGF concentrations have certain clinical value in the prognosis of SCLC patients,and combined detection of Vimentin and HGF is an independent prognostic factor for OS of SCLC patients.3.SE-iFISH can identify the heterogeneity of peripheral blood CTCs of SCLC patients;Vimentin,the EMT marker,has a low expression rate in CTCs,and there are significant differences between Vim+CTCs and Vim-CTCs in cell morphology and distribution of CHR8 aneuploidy.Baseline aneuploidy Vim+CTCs has important clinical value in the prognosis of SCLC patients,which needs further study.