Vaccination with polyclonal non-tumor-specific IgG has no therapeutic effects on tumorigenic activity of hepatoma cells grafted to rats: Experimental and biochemical studies

Background: We studied whether non-tumor-specific polyclonal IgG possesses antitumor effects on hepatoma tumor cells grafted to rats. Methods: Hepatoma cells (5 x 10⁵-10⁶) were injected subcutaneously into 6-week-old rats. Some of the rats were vaccinated 2 months later with non-tumor-specific anti-R sheep IgG. Experimental results were checked after additional 2 months. Results: The tumorigenic effect of grafted hepatoma cells was very high, manifesting itself in the rapid development of subcutaneous tumors in injected rats. Vaccination did not significantly change the number of tumors, their size or spleen weight. A biochemical study showed the main expression of two soluble proteins in high amounts in response to tumorigenesis, with molecular masses of 64 and 53 kDa. HPLC determination revealed that only the blood level of the soluble 53 kDa protein increased significantly with vaccination. Conclusions: Vaccination of rats with non-tumor-specific IgG had no tumor-therapeutic effects, despite the concomitant increase in the blood level of the soluble tumor-associated 53 kDa protein. Reaction of this protein should be considered non specific, reflecting the host's reaction to stress.