Study The Significance Of LETM1 In Esophageal Squamous Cell Carcinoma And Its Relationship With Cancer Stem Cells

Background:Leucine zipper-EF-hand containing transmembrane protein 1(LETM1)is a mitochondrial protein closely related to the various organs of the tumors.It’s overexpression in the tumors(such as gastric cancer,lung cancer,ovarian cancer,kidney cancer,colorectal cancer,liver cancer,etc.),indicated that it’s closely related to the occurrence and development of malignant tumors.However,the expression of LETM1 in esophageal squamous carcinoma(ESCC)has not been reported yet,and its relationship with cancer stem cells(CSC)is unclear.Objectives:Aimed to investigate the significance of LETM1 and its role in evaluating the prognosis of ESCC.Furthermore,discussed the association of LETM1 with CSC that provides a new target for targeted therapy of ESCC.Methods:The expression of LETM1 was detected from the level of histological and cytology.Firstly,we used immunohistochemistry(IHC)method to detect LETM1 expression in 166 cases of ESCC and 16 cases of adjacent non-tumor esophageal mucosa samples,thus further statistical analysis the correlation of LETM1 expression and clinicopathological parameters,the CSC markers,tumor microenvironment related factors,and the cell cycle related factors.In addition,Kaplan-meier survival analysis was used to demonstrate the effective value of LETM1 in evaluating the prognosis of patients with ESCC.Secondly,the expression of LETM1 in different ESCC cell lines(TE1,TE8,TE10,TE11,ECG10,HCE7),and CSC markers were detected by western blot and immunofluorescent(IF).Results:LETM1 expression was mainly observed in the cytoplasm of ESCC cells by IHC and IF methods.The expression of LETM1 in ESCC was significantly higher compared to the normal esophageal epithelium(P<0.05).In ESCC,the expression of LETM1 was closely related to the primary tumor(pT)stage and clinical stage(all P<0.05).Kaplan-Meier survival analysis revealed that LETM1 was significantly associated with lower disease-free survival(DFS)(P=0.04)and overall survival(OS)(P<0.001).Multivariate cox suggested that LETM1 was an independent prognostic factor for the OS and DFS of ESCC patients.In addition,LETM1 was significantly correlated as well as co-located with CSC markers LSD1(P = 0.03),CD44(P<0.001)and OCT4(P = 0.04).Western blot revealed that LETM1 was expressed in various cell lines of ESCC and the highest expression was observed in TE11 and ECG10.IF analysis revealed that LETM1 co-stained with CD44 and OCT4 in ECG10.The expression of LETM1 was associated with not only the expression of HIF-1α,but also higher microvessel density(MVD)and tumor associated macrophage(TAM)(all P<0.05).Furthermore,the expression of LETM1 in ESCC was significantly correlated with cell cycle related factors Cyclin D1(P = 0.017),pAkt-Thr308(P =0.001)and pAkt-Ser473(P = 0.022).Conclusion:1.LETM1 may be a potential CSC marker and indicated poor prognosis in ESCC.2.LETM1 regulates the tumor cell proliferation by enhancing cell cycle progression probably via the PI3K/Akt signaling in ESCC.3.LETM1 provide a promising target for the development of novel therapy in the treatment of ESCC.