1.LHX2 Enhances The Malignant Phenotype Of Esophageal Squamous Cell Carcinoma By Upregulating The Expression Of SERPINE2 2.RAD21 Enhances The Radiotherapy Resistance Of Esophageal Squamous Cell Carcinoma By Inhibiting DNA Damage Repair

LIM-homeodomain gene 2(LHX2),known to be an important transcription factor.belongs to the subfamily of homeobox genes.Numerous studies have reported that LHX2 is fundamental to embryonic development.In addition,LHX2 is closely related to tumorigenesis and tumor progression.The Kaplan-Meier survival analysis of Pan-cancer showed that patients with high LHX2 expression had a shorter overall survival and diseasefree survival when compared with patients with low LHX2 expression according to the TCGA data.Then we analyzed the available TCGA and GEO esophageal squamous cell carcinoma(ESCC)datasets,and we found that the mRNA levels of LHX2 were remarkably upregulated in ESCC tissues compared with the levels in normal tissues or matched adjacent normal tissues.Meanwhile,our unpublished RNA-seq data of 155 paired ESCC tissues and adjacent normal tissues also indicated that ESCC tissues displayed much higher LHX2 mRNA expression than matched adjacent normal tissues.To verify whether LHX2 executes the oncogenic functions in ESCC progression.we conducted a series of functional assays through gain or loss-of-function of LHX2 in ESCC cell lines.Our results support the concept that LHX2 silencing dramatically suppressed the cell proliferation,tumor growth,migration,invasion and metastasis of ESCC Cells.In contrast,overexpression of LHX2 exhibited the opposite effects.Next.we performed transcriptome profiling using LHX2-knockdown cells and their corresponding control cells,to explain how LHX2 enhances the malignant phenotype of ESCC.Functional annotation illustrated that differential expressed genes regulated by LHX2 mainly located in the GO terms of cell development,cell proliferation and cell motility were chosen for the following research.Then.the RT-qPCR analysis and Western blotting preformed the change of SERPINE2 expression after the reduction in LHX2.Meanwhile,we found that SERPINE2 was significantly increased in ESCC tissues compared with adjacent normal tissues by analyzing the GEO datasets,and Pearson correlation analysis showed that SERPINE2 expression was positively correlated with LHX2 expression in ESCC tissues.To further assess whether SERPINE2 exerts an essential effect on LHX2-induced cell proliferation and motility,we performed a series of functional recovery experiments.And results showed that the exogenous overexpression of SERPINE2 appreciably restored cell proliferation and motility weakened by LHX2 knockdown.In conclusion,LHX2 is significantly upregulated in ESCC tissues,which is an important molecule that promotes the proliferation and metastasis of ESCC in vitro and in vivo.LHX2 promotes the malignant phenotype of ESCC by increasing the expression of SERPINE2.Thereby,our study may provide a theoretical basis for potential therapeutic targets of esophageal cancer.Esophageal cancer is one of the most common malignant tumors of the digestive tract.Most patients are diagnosed at the advanced stage,the 5-year survival rate is less than 30%,and appropriately 90%of esophageal cancers patients in China are esophageal squamous cell carcinoma(ESCC).Despite radiotherapy has achieved significant survival benefits for patients with ESCC,only 15.6-16%of esophageal cancer patients can achieve the expected therapeutic effect,and the occurrence of local recurrence and distant metastasis also means treatment failure.RAD21 is an important component of the Cohesin complex,which involved in the cohesion of sister chromatids in mitosis and the repair of DNA double-strand breaks.The genomic and transcriptome data of RAD21 in the TCGA database showed that its percentage of copy number amplification was about 9%in the esophageal cancer dataset,and there was a positive relationship between copy number amplification of RAD21 and its mRNA.We also detected RAD21experssion in ESCC tissues and matched normal tissues through immunohistochemistry(IHC)analysis and the results showed that the protein level of RAD21 was upregulated in ESCC.To confirm the function of RAD21 in ESCC,we conducted a series of in vitro and in vivo functional experiments.The results showed that RAD21 silencing significantly inhibited the proliferation,invasion and migration of ESCC cells.Besides,RAD21 knockdown caused accumulation of DNA damage and inhibition of DNA damage response(DDR)in ESCC cells.Moreover,we demonstrated that RAD21 knockdown enhanced the radiotherapy sensitivity of ESCC cells by colony-formation assay and in vivo radiotherapy sensitivity tests.In conclusion,RAD21 is significantly upregulated in ESCC tissues,and RAD21 silencing induces the accumulation of DNA damage,inhibits the malignant phenotype of ESCC cells and enhances their radiotherapy resistance.