The Biological Characteristics Of SYK Aberrant Expression In Cholangiocarcinoma,and Its Potential As A Therapeutic Target By Tyrosine Kinase Inhibitor

BACKGROUND:Cholangiocarcinoma(CCA)is an epithelial cell malignancy originating from the bile ducts,and the incidence and mortality rates of CCA are increasing worldwide in recent years.Highly malignant and invasive characteristic make CCA have poor prognosis,with the 5-year survival less than 5%.Surgical resection is the only effective but not satisfactory treatment,accompanied by a high risk of recurrence.Besides,the effectiveness of chemotherapy and radiation therapy needs further investigation till now.Therefore,it is an important research direction to explore the tumorigenic and developmental mechanisms and find effective molecular targets for precision treatment of CCA.Spleen tyrosine kinase(SYK)is a member of the family of non-receptor tyrosine kinases that plays an important role in autoimmune diseases and malignancies.As a modulator of tumorigenesis,SYK has a bit of a schizophrenic reputation,acting in some cells as a tumor promoter and in others as a tumor suppressor.In previous studies,we found that the intrahepatic bile duct hyperplasia with significantly increased expression of S YK in bile duct ligation liver fibrosis models,and bile duct hyperplasia is the initial stage of CCA.In this study,the expression,biological characteristics,and targeted therapy of SYK in CCA were explored to provide new theoretical basis and preclinical evidence for the precision treatment of clinical Cholangiocarcinoma patients.METHODS(1)The rat and mouse progressive models of cholangiocarcinoma were established to assess the expression of SYK during the evolution of CCA by immunohistochemistry.The expression of SYK protein was detected in 241 CCA tissues using immunohistochemical staining,correlations between SYK expression and clinical pathological characters were analyzed.(2)The cytological experiment and subcutaneous xenograft in nude mice were used to study the pro-tumor functions,such as cell proliferation,invasion,tumor growth,and the underlying molecular mechanisms in CCA before and after SYK targeted knockdown or overexpression lentivirus transducted into CCA cell lines.(3)The small-molecule inhibitor GS-9973 of SYK was used to treat CCA cells,the subcutaneously transplanted tumors and rat progressive models of CCA,respectively,to investigate the antitumor efficacy of SYK inhibitors on CCA in vitro and in vivo.RESULTS(1)We successfully generated two progressive murine models of CCA,including a thioacetamide rat model and diethylnitrosamine-left median bile duct ligation mouse model.SYK began to aberrant expression during the stage of bile duct hyperplasia,and gradually increased with the evolution of CCA.(2)SYK was significantly increased in CCA tissues compared with paratumor tissues(P<0.001),and was positively related with tumor size(P<0.05).On the basis of the Kaplan-Meier survival estimates,the overall survival in CCA patients with high SYK expression is lower in our cohort(P=0.0313).(3)SYK can promote the proliferation,migration and invasion of human CCA cells in vitro,and accelerate the formation and growth of subcutaneous tumors in nude mice in vivo.The pro-tumor functions of SYK in CCA by interaction with M2 macrophages and promoting the polarization of macrophages to M2 type,and M2 macrophages facilitate tumor growth and invasiveness in CCA.(4)The small-molecule inhibitor GS-9973 of SYK can effectively inhibit the proliferation and invasion ability of SYK overexpression/high expression CCA cells,the tumor growth of subcutaneous xenografts in nude mice and rat progressive models of CCA.CONCLUSIONSSYK was aberrantly expressed during the evolution of CCA,and high expression of SYK in human CCA patients have poor postoperative prognosis.SYK plays the biological characteristics of oncogenes in CCA,targeted SYK therapy displays effective antitumor activity.Therefore,SYK might be a potential target for the treatment of CCA.