Suppression of tumor development by another tumor in primary immunodeficiency in experiment.

Abstract

e21583 Background: Multiple primary malignant tumors (MPMTs) are characterized by the presence of several primary neoplasms in one patient. The purpose of the study was to create an experimental model of MPMTs with one dominating tumor. Methods: The study included 21 female BALB/c Nude mice. The main group included mice with simultaneous subcutaneous inoculation of tumors: Guerin's carcinoma (0.5 million tumor cells in 0.5 ml of saline solution) under the right scapula and B16/F10 melanoma (0.5 ml of suspension diluted 1:20 in saline solution) under the left scapula. Control groups included females with melanoma or carcinoma inoculated at the same dosage and volume as in the main group. Results: In a MPMT model, tumors appeared 3 times faster than in controls and demonstrated larger volumes: melanoma – by 7.5 times, carcinoma – by 2.2 times; the survival of mice with MPMTs decreased. Carcinoma in a MPMT model metastasized to melanoma and almost completely suppressed its growth. Melanoma was represented by a small “island” of tumor tissue 3-4 mm in diameter and was located just under the skin at the site of injection of melanoma cells. The light part of the same loose pasty consistency as the dark part, with a diameter of 6-7 mm, was located around the dark “center” of melanoma. The rest part of the tumor located under the left scapula looked like an elongated grayish-pink node of a dense elastic consistency - just like the tumor located under the right scapula, which was much larger in volume. The right and left tumors did not merge with each other; there was a small distance of about 2-3 mm between them. A small lesion of caseous necrosis, 6–7 mm in diameter, was recorded in the center of the right tumor node of Guerin's carcinoma; there was no necrosis in the left tumor. Smaller size, the absence of necrosis and visually more “young” carcinoma tissue on the left indicated its later appearance than that on the right, which, in combination with the remnants of melanoma fused to the left tumor and the absence of “contact” between the left tumor and the right one, indicated the metastatic nature of Guerin’s carcinoma on the left. B16/F10 melanoma did not metastasize. Conclusions: In simultaneous subcutaneous inoculation of murine B16/F10 melanoma and rat Guerin’s carcinoma to female BALB/c Nude mice, carcinoma cells metastasized to melanoma and suppressed its growth.