Effects of immunization against human choriogonadotropin on the growth of transplanted Lewis lung carcinoma and spontaneous mammary adenocarcinoma in mice.

We studied the effects of preimmunization with a synthetic carboxy-terminal peptide of the beta-subunit of human choriogonadotropin (hCG) conjugated to diphtheria toxoid on the growth of two tumor models, the transplantable Lewis lung carcinoma in C57BL/6J mice and the spontaneous mammary carcinoma in C3H/OuJ mice. Immunization with the conjugate prior to Lewis lung tumor implantation significantly (P less than 0.05) retarded the growth of tumors as measured by tumor weight 18 days following transplantation. The weights of Lewis lung tumors in animals preimmunized with the hCG immunogen were inversely correlated (r = 0.61) with the levels of circulating antibodies against human chorionic gonadotropin, whereas no statistical correlation was found between tumor weights and the levels of antibodies reactive to diphtheria toxoid. The number of conjugate-treated C3H/OuJ mice that developed mammary tumors was significantly (P less than 0.05) reduced compared to their vehicle-treated cohorts. Pretreatment with the synthetic muramyl dipeptide analog utilized as an adjuvant with both immunogens did not show any effect on the tumor growth in either tumor system.