TMEM165, a Golgi transmembrane protein, is a novel marker for hepatocellular carcinoma and its depletion impairs invasion activity

Transmembrane protein 165 (TMEM165), a Golgi protein, functions in ion homeostasis and vesicular trafficking in the Golgi apparatus. While mutations in TMEM165 are known to cause human ‘congenital disorders of glycosylation’, a recessive autosomal metabolic disease, the potential association of this protein with human cancer development has not been explored to date. In the present study, we revealed that TMEM165 is overexpressed in HCC and its depletion weakens the invasive activity of cancer cells through suppression of matrix metalloproteinase-2 (MMP-2) expression. Levels of TMEM165 mRNA and protein were clearly increased in HCC patient tissues and cell cultures. Quantitative real-time RT-PCR analysis of fresh HCC tissues (n=88) revealed association of TMEM165 overexpression with more frequent macroscopic vascular invasion, microscopic serosal invasion and higher α-fetoprotein levels. Notably, depletion of TMEM165 led to a marked decrease in the invasive activity of two different HCC cell types, Huh7 and SNU475, accompanied by downregulation of MMP-2. Our collective findings clearly indicated that TMEM165 contributed to the progression of HCC by promoting invasive activity, supporting its utility as a novel biomarker and therapeutic target for cancer.