Experimental Modeling of Multiple Primary Malignant Processes with One Tumor Suppressed by Another under Conditions of Primary Immunodeficiency.

The phenomenon of multiple primary malignant tumors (MPMT) is characterized by the presence of several primary neoplasms in the same patient. An experimental model of MPMT with one dominating tumor was developed. Female BALB/c nude mice received simultaneous subcutaneous inoculation of Guerin's carcinoma (5×105 tumor cells in 0.5 ml saline) and B16/F10 melanoma (0.5 ml suspension diluted 1:20 with saline). Control females received transplantation of either melanoma or carcinoma alone in the same doses and volumes. In animals with MPMT model, tumors appeared 3-fold faster than after isolated transplantation of melanoma or Guerin's carcinoma and were larger by 7.5 and 2.2 times, respectively; the survival of mice with MPMT was lower. Guerin's carcinoma in the MPMT model metastasized to melanoma and almost completely suppressed its growth. Thus, a MPMT model was created with carcinoma suppressing the malignant growth of melanoma.