Inhibition effects on liver tumors of BALB/c mice bearing H22 cells by immunization with a recombinant immunogen of GnRH linked to heat shock protein 65

In the following study, we prepared a double-chain miniprotein with each chain containing three linear repeats of the self-peptide gonadotropin-releasing hormone (GnRH₃), the hinge region of human IgG1 (hinge), and a T-helper epitope from the measles virus protein (MVP). The di-GnRH₃-hinge-MVP miniprotein was conjugated to purified recombinant heat shock protein 65 (Hsp65) of Mycobacterium bovis and used to immunize BALB/c mice primed with subcutaneous injection of Bacillus Calmette-Gurerin (BCG) in the absence of adjuvants. After anti-GnRH antibodies were successfully produced, mice were inoculated with H22 cells as a solid tumor. The results showed that after GnRH was inhibited by anti-GnRH antibodies the testosterone levels in sera markedly decreased (P < 0.01) and the testicle weights reduced as well (P < 0.05) in GnRH₃-hinge-MVP-Hsp65-immunized mice. The average weight of tumors in mice treated with GnRH₃-hinge-MVP-Hsp65 was significantly lower than in mice treated with saline only (neutral control, P < 0.001), or less than in mice treated with Hsp65 (negative control, P < 0.005). The data reported here demonstrated that GnRH₃-hinge-MVP-Hsp65 could significantly attenuate the progression of liver tumor in mice transplanted with H22 cells, and might develop to be palliative treatment of hepatocellular carcinoma (HCC) patients in the future.