Experimental study of the inhibition of human hepatocarcinoma Bel7402 cells by the tripeptide tyroserleutide(YSL).

PURPOSE: To investigate the antitumor effects of tyroserleutide (tyrosyl-seryl-leucine, YSL) on human Bel7402 hepatocarcinoma in vitro and in vivo, with preliminary exploration of its antitumor mechanism. METHODS: MTT was used to observe the anticarcinogenic effects of YSL on human hepatocarcinoma Bel7402 cells in vitro. The ultrastructure of tumor cells was observed by electron microscopy. Nude mice bearing xenografts of human hepatocarcinoma Bel7402 were given daily i.p. injections of YSL or saline and an admixture of amino acids as controls, after tumor implantation. The inhibition of xenografts was determined by calculating the tumor volume and measuring tumor weight. The effects of YSL on the cell cycle and apoptosis of Bel7402 cells were determined by flow cytometry, and the effects on the ultrastructure of the cells by electron microscopy. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and proliferating-cell nuclear antigen (PCNA) immunohistochemical staining were used to investigate apoptosis in tumor tissue in nude mice. RESULTS: In vitro YSL inhibited the proliferation of human Bel7402 tumor cells and changed their ultrastructure, resulting in the necrosis and apoptosis of the tumor cells. YSL at 80, 160, or 320 microg/kg/d inhibited tumor growth in nude mice by 40.26, 64.17, and 59.19%, respectively, which are significantly lower than the inhibition exerted by saline and an admixture of YSL amino acids (P<0.05). The ultrastructure and cell cycle of human hepatocarcinoma Bel7402 cells were changed by treatment with YSL, with a rate of apoptosis higher than that of the control group. TUNEL and PCNA analysis showed that YSL inhibited the proliferation of tumor cells and induced apoptosis at the level of the cell. CONCLUSIONS: YSL significantly inhibited human hepatocarcinoma Bel7402 growth in vitro and in vivo. The growth inhibition of the tumor may involve necrosis and apoptosis of the tumor induced by YSL.

The effect of tripeptide tyroserleutide (YSL) on animal models of hepatocarcinoma.

This study aimed to observe the effects of tyroserleutide (tyrosyl-seryl-leucine, YSL) on the survival time of mice transplanted with the ascitic fluid-type hepatocarcinoma H22, as well as the inhibitory effect of tyroserleutide on the human hepatocarcinoma Bel-7402 that was transplanted into nude mice. At doses of 80, 20 and 5 microg/kg/d, tyroserleutide significantly prolonged the survival of mice transplanted with H22 tumor cells, producing survival rates of 89%, 39% and 49%, respectively, which were statistically significantly different from the saline group (P < 0.05). YSL, at doses of 80, 160 and 320 microg/kg/d significantly inhibited the growth of the human hepatocarcinoma Bel-7402 tumor in nude mice, producing inhibition of 40%, 64% and 59%, respectively; this inhibition was significantly greater than that by saline (P < 0.05). HE staining and electron microscopy of the pathological changes of the tumor in nude mice showed that YSL changed the structure Bel-7402 tumor cells that were transplanted into nude mice, and also induced tumor cell apoptosis and necrosis, which could be a mechanism by which YSL inhibits the tumor growth in animal models.

Expression of PTEN, p27, p21 and AKT mRNA and protein in human BEL-7402 hepatocarcinoma cells in transplanted tumors of nude mice treated with the tripeptide tyroservatide (YSV).

The tripeptide, tyroservatide (YSV), has been previously shown to have antitumor effects through unknown mechanism. In the current study, we examined whether YSV modulates the protumorigenic PI3K pathway in human BEL-7402 hepatocarcinoma cells. BEL-7402 hepatocarcinoma was transplanted into the subcutaneous tissues of nude mice, and YSV, at varying doses, was administered. RT-PCR and Western blot were used to analyze the expression of PTEN, AKT, p21 and p27. YSV at doses of 80 microg/kg/day, 160 microg/kg/day and 320 microg/kg/day markedly inhibited the growth of human BEL-7402 hepatocarcinoma (p < 0.05). YSV increased mRNA and protein expression of the tumor-suppressor genes, PTEN, p21 and p27, and inhibited the mRNA and protein expression of the oncogene AKT. Furthermore, YSV administration was associated with dephosphorylation of both PTEN (which activates PTEN) and AKT (which inhibits AKT). These results are consistent with the possibility that YSV mediates inhibition of tumor growth through inhibition of the PI3K pathway and suggests that YSV should be explored for use as an antitumor agent for hepatocarcinoma.

Preliminary investigation of the inhibitory effects of the tyroservaltide (YSV) tripeptide on human hepatocarcinoma BEL-7402.

This study aimed to investigate the inhibitory effect of tyroservaltide (YSV) on the human hepatocarcinoma BEL-7402 transplanted into nude mice and to explore its possible anti-tumor mechanism. Nude mice bearing xenografts of the human BEL-7402 hepatoma were given daily i.p. injections of YSV or saline (as a control) after the tumor were transplanted. Calculating tumor volume and measuring tumor weight determined the extent of inhibition of xenografts. The ultrastructure of tumor cells was observed by electron microscopy. Proliferating cell nuclear antigen (PCNA) expression in tissues of the YSV-treated group was observed by immunohistochemistry. Apoptosis of tumor tissue cells was assayed by the terminal transferase uridyl nick end labeling (TUNEL) method. At doses of 80 microg/kg/d and 160 microg/kg/d, YSV could significantly inhibit growth of tumors transplanted into nude mice, with inhibition rates of 60% and 64%, respectively, compared with that of the controls (P < 0.05). Moreover, YSV changed the ultrastructure of tumor cells, resulting in necrosis and apoptosis of the tumor cells. Compared with the saline group, the expression of PCNA in tumor tissue decreased and the count of apoptotic cell increased. Therefore, YSV can significantly inhibit the growth of human hepatocarcinoma BEL-7402 in nude mice, decrease the expression of PCNA in tumor tissue, and induce tumor cell apoptosis.