TMCO3 Promotes Malignant Progression Of Hepatocellular Carcinoma Through Controlling Autophagy

Background Hepatocellular carcinoma(HCC)is one of the most malignant tumors with high morbidity and it has the third highest tumor-related lethality which means poor prognosis in patients.In China,HCC threatens many people’s health for the reason of prevalence of HBV in last century.HCC ranked the fourth highest morbidity and second lethality in all kinds of tumors in our country.Considering that this tendency hasn’t been control,it’s meaningful to deeply study molecular and biological mechanism underlying occurrence of HCC.Autophagy,an evolutionally conserved mechanism in eukaryotic cell,degrades substrate and releases amino acids and ATP for further recycle and metabolism.Ion channels are broadly distributed on membrane organelles,including mitochondria,endoplasmic reticulum,Golgi apparatus,endosomes,and lysosomes and take part in diverse pathways.More and more researches in cancer have demonstrated that interfering ion channels can change biological features of cancer cells.Some researches have found that ion channels affect progression of tumor through controlling autophagy activity,which has a great impact on understanding the metabolism mode in tumor.Transmembrane and coiled-coil domain-containing protein 3(TMCO3)is probably a Na+/H+ antiporter according to its sequence.Little was known about its role in hepatocellular carcinoma.It was reported to be associated with Cornea Guttata and Anterior Polar Cataract.Its homologous protein,TMCO1,was found to impair the AKT signaling pathway in urinary bladder urothelial carcinoma.Our research aimed to explore its function and involved pathway in HCC.PurposeThis research focused on TMCO3’s potential role in HCC and relationship between TMCO3 and autophagy flux.We tried to explore whether TMCO3 promoted tumor growth via upregulation of autophagy activity.This research would shed light on new direction in studying signals of autophagy and new target in comprehensive treatment of HCC.MethodsSeveral kinds of immunology experiments were conducted according to research’s need,including immunoblot assay,immunohistochemistry,and immunofluorescence.To explain how TMCO3 affected tumor features,we combined experiments in vitro and vivo and constructed knockdown and overexpression of TMCO3 cell lines.Based on results in vitro and clinical specimens immunostaining,we could further validate the axis.Results(1)High level of TMCO3 expression in HCC indicated poor prognosis.(2)Knock down of TMCO3 in HCC cells inhibited tumor growth.(3)TMCO3 was mainly located on membrane of Golgi apparatus and possibly involved in autophagy flux through phosphorylation of AMPK(T172).This pathway sustained tumor growth.(4)In clinical tumor specimens,TMCO3’s level was found to be positively associated with LC3 and ULK1(AMPK’s target),which proved the signal pathway to some extent.ConclusionsHCC has a relatively high expression of TMCO3,which could enhance phosphorylation of AMPK(T172)and activate its target,ULK1.Autophagy flux is further upgraded to supply the metabolic need of tumor cells.