Study On The Role And Function Of RNFT2 In The Onset And Development Of Liver Cancer

Liver cancer is the sixth most common cancers in the world.In recent years,the prevalence and mortality of liver cancer are still rising.In 2018,about 782,000 people died of liver cancer in the world,accounting for 8.2% of cancer-related deaths.Epidermal Growth Factor Receptor(EGFR),a transmembrane protein of receptor tyrosine kinase,can be activated by different ligands,triggering various signaling pathways that regulates growth,proliferation,differentiation and survival.EGFR signaling pathway plays important roles in liver regeneration after acute and chronic liver injury,liver cirrhosis and hepatocellular carcinoma(HCC).RING finger protein,transmembrane 2(RNFT2)is a transmembrane protein containing the RING domain,a typical E3 ubiquitin ligase-associated domain,making it potential E3 ubiquitin ligase activity.However,the function of this protein has rarely been reported.Through database search,we found that RNFT2's levels showed more expression in HCC's patients than normal persons.Moreover,HCC patients with high RNFT2 levels had poor prognosis.We speculate that RNFT2 may have a role in the tumorigenesis of liver cancer.By MTT,soft agar colony formation and transwell migration experiments,we found that overexpression of RNFT2 promoted the growth,proliferation and migration of liver cancer cells HepG2 or Hep3 B,while knockdown or knockout of RNFT2 had the opposite effects.In previous yeast two-hybrid experiment,we identified phospholipid scramblase 1(PLSCR1)as one of the binding partners of RNFT2.PLSCR1 not only interacts with activated EGFR receptor,but also rapidly shuttles through plasma membrane and endosome.This suggests a potential link between RNFT2 and EGFR.HCC,a malignant tumor,which is characterized by abnormal cell proliferation and EGFR signaling pathway's activation.We also explored possible mechanisms underlying RNFT2-induced cell proliferation and migration.We found that overexpression of RNFT2 activated EGFstimulated EGFR pathway,whereas knockdown or knockout of RNFT2 significantly attenuated EGF-trigged signaling.Ubiquitination experiments revealed that RNFT2 enhanced the ubiquitination of EGFR,and,C387 in the RING domain of RNFT2 may be an important site for such modification.Finally,we found that RNFT2 also regulated EGFR transport by affecting endocytosis of EGFR suggested by the confocal experiments.In summary,RNFT2 could enhance EGF-trigged EGFR activation,possibly based on the regulation of EGFR ubiquitination,thus potentiating growth,proliferation and migration of liver cancer cells.Abnormal RING domain E3 ubiquitin ligase expression promotes the development of a variety of malignant diseases,such as HCC.To a certain extent,the research on the function and mechanism of RNFT2,a new molecule containing RING domain,can provide new ideas and dimensions for the exploration of HCC's new target.