Purpose of the study. Creation and study of models of primary multiple malignant tumors (MMPT model) under experimental conditions.Materials and methods. The study was carried out involving male and female BALB/c Nude mice (n = 42). Experimental groups of mice: with melanoma B16/F10 (B16/F10), males (control 1) and females (control 3) by n = 7; control 2 – with sarcoma 45 (C45), males n = 7; control 4 – with Guerin carcinoma (KG), females n = 7; basic: MMPT model No. 1 – B16/F10 and S45, males n = 7, and MMPT model No. 2 – B16/F10 and GC, females n = 7. 0.5 ml suspension of murine B16/F10 melanoma tumor cells diluted in the saline proportions 1:20 was injected under the skin of the left dorsal side to all animals with MMPT model, as well as 0.5 ml of a suspension containing 0.50 × 106 S45 or GC tumor cells in the saline under the skin on the right dorsum. Control groups received the same amount of tumors as the MMPT model.Results. Tumors in male mice in MMPT model No. 1 appeared simultaneously and significantly earlier than in controls: В16/ F10 melanoma by 3 times, S45 by 2 times. Tumor zises in MMPT model No. 1 were larger than in the corresponding controls: by 8.5 times at the area of В16/F10 melanoma inoculation and by 2.2 times at the area of S45 inoculation. Melanoma metastasized under the S45 capsule. Tumor at the area of GC transplantation in MMPT model No. 2 grew 5 times faster than at the area of В16/F10 melanoma injection; both tumors appeared on average 3 times earlier than in control groups 3 and 4. Tumor volumes in MMPT model No. 2 were larger than in the corresponding controls: by 7.5 times at the area of В16/F10 melanoma inoculation and by 2.2 times at the area of GC inoculation. However, almost the entire volume of the tumor node in the area of B16/F10 melanoma transplantation was represented by GC tumor tissue due to metastasis from the primary GC tumor. Melanoma remained as a small black spot with a diameter of 5–6 mm at the area of its inoculation under the skin. The average survival of mice in MMPT models No. 1 and No. 2 was 1.5–2 times (p < 0.05) lower than in the corresponding controls.Conclusions. Sequential subcutaneous transplantation of mouse B16/F10 melanoma and rat sarcoma 45 to BALB/c Nude mice increased the malignant potential of each tumor: the time of their onset was shorter, and the growth rate of tumors increased which decreased the survival of animals. Sequential subcutaneous transplantation of mouse B16/F10 melanoma and Guerin's rat carcinoma to female BALB/c Nude mice suppressed tumor growth of B16/F10 melanoma and increased the malignant potential of rat GC.
