ANGPTL4 Enhances Angiogenesis In Metastatic Progression Of Ovarian Cancer Via CDH5

Background&Aims Ovarian cancer is the most lethal gynecological malignancy and the 5th leading cause of cancer death in women.It is a global problem,typically diagnosed at a late stage and has no effective treatment or screening strategy so far.Similar to other cancers,metastasis is the main cause of ovarian cancer recurrence and chemotherapy resistance.However,High-grade serous ovarian cancer has a more complex molecular pathological phenotype.This suggests that we need to further study the molecular mechanism of metastasis and provide new clinical ideas for the analysis of chemotherapy resistance and individualized treatment of ovarian cancer.ANGPTL4(angiopoietin-like 4)belongs to a superfamily of proteins that share structural similarities to the angiopoietins.It has been described to play a key role in the regulation of a myriad of physiologic processes,including serving as essential modulators of lipid and glucose metabolism.Recently,many studies revealed an important role of ANGPTL4 in angiogenesis and malignant progression of many caners.In 2011,The Cancer Genome Atlas and the Australian Ovarian Cancer Study identified four subtypes of HGSC based on gene expression: differentiated,immunoreactive,mesenchymal and proliferative subtypes,among which the mesenchymal has a worst prognosis,ANGPTL4 was one of the increased stromal components characterized the Mesenchymal subtype.But the role of ANGPTL4 in the development of ovarian cancer is not completely understood.In the present study,we evaluated the clinical significance and biological role of ANGPTL4 in ovarian cancer.Methods We analyzed the expression of ANGPTL4 by high-throughout sequencing technology,immunohistochemical and quantitative real-time polymerase chain reaction(RTPCR).Immunoblotting was conducted to investigate it's clinical significance using tissue microarray(TMAs)analysis of samples from 97 patients with ovarian cancer and 18 samples with normal ovarian tissues.Commercial lentivirus expressing sh RNAs was used for silencing ANGPTL4 in order to evaluate the molecular effects of high expression levels of ANGPTL4 in ovarian cacner cells.The EDU assay was employed for evaluating the cell proliferation ability,wound healing and transwell assay with or without matrigel were used for cell migration and invasion assay.To further confirm the metastasis-promoting effects and angiogenesis of ANGPTL4,we performed an in vivo xenograft tumor experiment in nude mice.Results ANGPTL4 was over-expressed in ovarian cancer tissues compared with benign ovarian tissues Also,there is a positive correlation between ANGPTL4 and CD31,suggesting that ANGPTL4 is positively correlated with angiogenesis in human ovarian cancer.Overexpression of ANGPTL4 correlated with poor prognosis of patients with ovarian cancer.Silencing ANGPTL4 expression strongly inhibited the migration and invasion of SKOV3 and HO8910 cells.Compared with SKOV3 sh ANGPTL4 cells,conditioned medium collected form SKOV3 normal control cells has stronger ability to promote HUVEC cells proliferation,migration,adhesion and tube formation capacity.The same phenomenon was also found in HO8910 cell lines.The tumor volumes,tumor weights,number of metastatic nodules of tumors in the abdominal cavities and microvessel density were significantly increased in the tumors derived from the control group compare with the ANGPTL4 KD group.After silencing ANGPTL4 expression by sh RNA in SKOV3 and HO8910 cells,the levels of CDH5,p-AKT,MMP9 and MMP2 significantly down-regulated.Conclusion In the present study,we demonstrated that overexpression of ANGPTL4 was significantly correlated with poor clinical outcome of ovarian cancer.Moreover,for the first time,we demonstated that ANGPTL4 promote ovarian cancer invasion and metastasis.Our results suggested that ANGPTL4 may be an important regulator of ovarian cancer as well as a biomarker for progression and diagnosis.In particular,ANGPTL4 stimulates angiogenesis by regulating CDH5/AKT/MMP9/MMP2 signaling pathway and might be a valuable marker for antiangiogenic therapy selection.