The Function And Mechanism Study Of PDPN Positive Cancer Associated Fibroblasts In Lymphangiogenesis Of Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma is a highly malignant hepatic neoplasm,the incidence of which ranks second only after hepatocellular carcinoma in liver malignant tumors.In the past three decades,intrahepatic cholangiocarcinoma has rapidly increased in China.Surgical resection is currently considered the only curative way to treat intrahepatic cholangiocarcinoma.However,the prognosis of patients is not quite satisfactory due to high invasiveness of tumors and early metastasis of lymph nodes.Therefore,it is necessary to explore suitable prognostic markers and tumor microenvironment,to seek new approaches to inhibit lymphangiogenesis and block nodal metastasis for improving long-term prognosis.By analyzing a cohort of 106 patients who underwent tumor resection for intrahepatic cholangiocarcinoma,we found that PDPN positive cancer associated fibroblasts(CAFs)were independent risk factor for poor prognosis;also,the overall and recurrence-free survival rates were much worse in these patients.In addition,PDPN positive CAFs were correlated with tumor associated lymphangiogenesis,which indicated that nodal metastasis may be promoted by PDPN positive CAFs through lymphangiogenesis.All the results above suggest that PDPN positive CAFs can be regarded as one of the prognostic markers for prognosis of intrahepatic cholangiocarcinoma,which is of great clinical value.Next,we isolated and purified CAFs from human intrahepatic cholangiocarcinoma for the first time and further divided them into PDPN positive CAFs subgroup.This group of cells can significantly promote the proliferation,migration,and invasion of cholangiocarcinoma cells,which is consistent with previous clinical analysis.Meanwhile,we discovered the existence of“mesenchymal lymphatic endothelial”cells in tumor specimens of patients and mouse models.Finally,we found that PDPN positive CAFs can develop into structures of vessels through culture with no serum.The vessels can be stained with lymphatic specific markers,which confirmed that PDPN positive CAFs can develop into neo-lymphatic vessels through“mesenchymal lymphatic endothelial transition”,facilitating lymph node metastasis and unfavorable outcomes.In summary,we first illustrated the crucial prognostic role of PDPN positive CAFs in intrahepatic cholangiocarcinoma,and innovatively discovered that PDPN positive CAFs could transform into neo-lymphatic vessels through “mesenchymal lymphatic endothelial transition”,facilitating lymph node metastasis and poor prognosis.This provides important basis for developing new target therapy for tumor associated fibroblasts and lymphangiogenesis.