Gene Expression Profile And Chemoresistance Of Ovarian Clear Cell Carcinoma

Objectives1.To explore the gene expression profile of ovarian clear cell carcinoma(OCCC)and to investigate the genes and molecular pathways associated with OCCC pathogenesis.2.To probe the correlation between HELLS expression and clinicopathological characteristics of patients with OCCC,and to investigate the potential mechanisms of HELLS in OCCC.3.To identify genes associated with chemoresistance in OCCC and to explore their mechanisms on cisplatin sensitivity in OCCC cells.Methods1.OCCC and paired normal ovarian epithelial tissues from 28 patients who were treated with initial surgery were collected for NanoString nCounter gene expression profiling.2.HELLS expression in OCCC and normal ovarian tissues was analyzed by immunohistochemistry.Based on the histochemical score of HELLS expression,the patients were divided into two groups.The correlation between HELLS expression and clinicopathological features was analyzed.OCCC cell lines with stable knockdown of HELLS were constructed and the roles of HELLS on cell proliferation,migration,invasion,and cell cycle were examined.RNA-seq,qRT-PCR,Western blot,and chromatin immunoprecipitation assays were used to investigate the potential mechanism.3.Primary tumor tissues from 12 patients with platinum-sensitive and 12 patients with platinum-resistant at stage Ⅱ-Ⅳ OCCC were collected.The gene expression profile was analyzed using NanoString nCounter to screen for genes associated with platinum resistance.Results1.In the comparison of OCCC and paired normal ovarian tissues,a total of 198 differentially expressed genes(DEGs)were selected,of which 100(50.5%)were upregulated and 98(49.5%)were down-regulated.The cell cycle-apoptosis,chromatin remodeling and DNA damage-repair pathways were significantly altered.In the chromatin remodeling pathway,three genes were significantly up-regulated(HMGA1,HELLS,BNIP3)and one gene was significantly down-regulated(HDAC4).2.High HELLS expression was positively associated with tumor diameter>8cm(P=0.014),lymph node metastasis(P=0.000),later FIGO stage(P=0.001),and worse OS(HR=1.76,P=0.033).Downregulation of HELLS significantly inhibited OCCC cell proliferation,migration,invasion and tumorigenic capacity in vivo,and hindered the G1/S transition of the cell cycle.The transcription factor E2F1 can bind to the promoter region of HELLS,upregulating CDC6 and enhancing cancer cell proliferation.3.In the comparison of platinum-resistant and platinum-sensitive tumor tissues,32 DEGs were screened,including 17(53.1%)genes up-regulated and 15(46.9%)genes downregulated.DEGs were mainly enriched in PI3K-AKT,MAPK and Ras signaling pathways,with FGF11 being the most upregulated.Mechanically,FGF11 was regulated by HIF-1α to modulate resistance to cisplatin.Conclusions1.Cell cycle-Apoptosis,DNA damage-Repair,and Chromatin remodeling pathways were significantly upregulated in OCCC and may be closely associated with the pathogenesis of OCCC.2.The chromatin remodeling factor HELLS was highly expressed in OCCC and was significantly associated with a poor prognosis.HELLS was regulated by the upstream transcription factor E2F1 and could activate downstream CDC6 to promote cell cycle G1/S transition.3.FGF11 was highly expressed in platinum-resistant OCCC tissues,and the HIF1α/FGF11 axis induced resistance to cisplatin by regulating cell apoptosis.