Peculiarities of the course of Lewis lung epidermoid carcinoma in mice infected with mycobacter tuberculosis

Material and methods . The study was carried out on 88 C57BL/6 mice aged two months. In accordance with the purpose of the study, the following groups of animals were composed: group 1 – "intact mice" (n=12), group 2 - "the reference H37R infection" (animals infected with the M.tuberculosis H37RV strain) (n=24), group 3 - "the reference tumors” (animals transplanted with Lewis epidermoid lung carcinoma) (n=23), group 4 – “the main test group 1” (animals infected with M.tuberculosis H37RV strain, which were simultaneously transplanted with Lewis epidermoid lung carcinoma) (n=24). Animals were infected by inoculating a suspension of Mycobacteria (1x106 CFU/0.2 ml) into the lateral tail vein. Transplantation of a 10% suspension of the pulverized tumor in a 0.9% solution of sodium chloride was performed intramuscularly into the femur within 2 hours after their infection with the suspension of Mycobacteria. Weekly, starting with day 14, 6 animals 23 Cardiometry, Issue 24, November 2022

Conference Proceedings were removed from groups 2, 3 and 4 by euthanasia, for periodic intermediate evaluation of the course of the experiment. The obtained samples of organs and tissues were subjected to morphological and bacteriological examinations. Individual and group-related parameters were assessed using the SPSS Statistica v23 software package.

Results . On the 7th day of the experiment, the tumor developed at the site of the primary tumor cell transplantation in all mice from groups 3 and 4 (3rd group V=161.3±14.80 mm³; 4th group V=99.50±8.72 mm³). The tumor size in group 4, the main test group, was smaller than it was in group 3, the tumor reference group (on the 14th day in the 3rd group V=343.9±77.05 mm³; in the 4th group V=366, 3±36.96 mm³; on the 21st day in the 3rd group V=1297.00±180.1 mm³, in the 4th group V=864.5±92.33 mm³). The significance level p according to the Mann-Whitney test, when comparing the tumor volume in groups 3 and 4, was as given below: 0.001 on the 7th day, 0.319 on the 14th day, 0.046 on the 21st day, and 0.044 on the 28th day of the experiment.

In the femur, in the area of the transplantation of the tumor suspension, in a morphological examination in all animals we revealed a tumor nodule, which was characterized by extensive areas of tumor necrosis, destruction of the muscle tissue, and bone plate invasion areas. Tumor metastases in the lungs were represented by foci of various sizes, predominantly of subpleural locations. Starting from the 14th day of the experiment, all infected animals developed pulmonary tuberculosis, which was confirmed by the bacteriological examination of their lung samples and the PCR-RT test. In the morphological examination in the infected mice, the pattern of pulmonary tuberculosis was represented by areas of productive pneumonia. When comparing survival rates in groups using the Log Rank test (Mantel-Cox), it was found that the survival of the animals was determined by the presence of a tumor rather than by infection with tuberculosis (p = 0.001). At the same time, the survival rates in groups 3 and 4 did not differ significantly.

Conclusions . When studying the course of Lewis epidermoid lung carcinoma in mice infected with Mycobacterium tuberculosis, an inhibition in the tumor growth was found in comparison with the uninfected animals.

The study was supported by the Russian Science Foundation grant No. 22-15-00470, The study was approved by the Local Ethics Committee of the SPbNIIF at the Russian Ministry of Health.

Cardiometry, Issue 24, November 2022