Effects of the C-terminal of endostatin on the tumorigenic potential of H22 cells.

Endostatin is an endogenous angiogenesis inhibitor whose specific functional site has not yet been determined. In the present experiment, 13 amino acids (LCIENSFMTSFSK) were selectively deleted from the C-terminal of endostatin and the resulting mutant endostatin was named EM13. To determine the effect of the C-terminal deletion on the biological activity of endostatin, EM13, wild-type endostatin and empty plasmid were transfected into H22 cells. After 48 h, the three types of transfected cells were harvested and injected into nude mice. The results demonstrated that there was no significant difference in tumor size, as determined by hematoxylin and eosin staining, between the EM13-transfected group and the endostatin and empty plasmid groups, although the nude mice that were injected with EM13-transfected H22 cells exhibited smaller tumors and lower density of blood vessels compared to those injected with endostatin- and empty plasmid-transfected H22 cells. The results suggested that the 13 amino acids of the C-terminal of endostatin do not play an important role in the tumorigenic potential of H22 cells. This experiment was unsuccessful in reproducing the results of several investigators. Therefore, the mechanism underlying the tumorigenesis of H22 cells remains to be elucidated.