Abstract: Objective To explore the expression of protein arginine deiminases (PADs) and protein arginine methyltransferases (PRMTs) in hepatocellular carcinoma, and to analyze whether the level of protein citrullination catalyzed by PADs is related to the expression of PRMTs. Methods The mRNA transcription of PADs and PRMTs in hepatoma cells was detected by quantitative PCR and the protein expression of PADs, citrullinated proteins and PRMTs was detected by Western blot. The mRNA correlation between PADs and PRMTs in liver cancer tissues in TCGA database was analyzed by bioinformatics, and the expressions of PADs, citrullinated proteins and PRMTs in liver cancer tissues was detected by immunohistochemistry. Results Compared with normal liver cell LX-2, the mRNA transcription of PAD2 and PRMT1 in Huh7 cells was higher (P＜0.001), and that of PAD4, PRMT1, PRMT5 and PRMT7 in HepG2 cells was higher (P＜0.01). The protein level of PAD2 and PAD4 in HepG2 and Huh7 was significantly higher than those in LX-2 (P＜0.01). The expression level of citrullinated protein in HepG2 and Huh7 was lower than that in LX-2. The expression of PADs and PRMTs in hepatocellular carcinoma was stronger than that in adjacent tissues, and the expression of citrullinated proteins was almost negative. There were positive correlation between PAD2 and all PRMTs in clinical sample database (P＜0.05). Conclusions The expression of PADs is high in hepatocellular carcinoma, whereas the expression of citrullinated proteins is low, which may be affected by the competition of PRMTs enzyme highly expressed in cells.

Key words: hepatocellular carcinoma, protein arginine deiminases, citrullination, protein arginine methyltransferases