Microsporidia are opportunistic, obligate intracellular pathogens that modulate host cell metabolic mechanisms to ensure their survival. Cancer cells exhibit alterations in energy metabolism, favoring increased ATP production from glucose. As microsporidia modify glycolytic pathways of host cells for their survival, we hypothesized that metabolic changes found in tumor cells could contribute to rapid pathogen development within these cells. To analyze the proliferation of the microsporidia Encephalitozoon cuniculi and E. hellem in tumor cell cultures derived from hepatic, pulmonary, and breast carcinomas. Spores of E. cuniculi and E. hellem were cultured in RK13 cells, purified using a Percoll gradient, and stored. Hepatocellular carcinoma cells (HEPG2), pulmonary carcinoma cells (H292), and breast carcinoma cells (MCF-7) were cultured in 24-well plates in RPMI medium supplemented with 10% fetal bovine serum and 1% penicillin/streptomycin, at a concentration of 2 × 10⁵ cells per well. Subsequently, H292 and MCF-7 cells were challenged with E. cuniculi spores at multiplicities of infection (MOI) of 2:1, 4:1, and 6:1 spores per cell to determine the optimal spore concentration at incubation times of 48 and 72 hours, while HEPG2 cells were challenged with the same MOIs of E. hellem spores. At the end of incubation, cells were lysed and spores were counted using a Neubauer chamber. Statistical analysis was performed using one-way ANOVA and t-test, adopting a significance level of p < 0.05. Encephalitozoon cuniculi spores successfully developed in MCF-7 and H292 cells. E. hellem infected and multiplied in HEPG2 hepatocytes, with greater spore proliferation observed at higher concentrations, particularly 6:1, and at the longer incubation time of 72 hours. For the H292 cell line, MOIs of 4:1 and 6:1 resulted in greater E. cuniculi spore proliferation at 48 hours. Regarding incubation time, 72 hours was clearly superior for spore production. In the MCF-7 cell line, after 72 hours, the 4:1 ratio resulted in the highest spore production, standing out as the most effective. Tumor cell lines supported the proliferation of both microsporidia, with higher concentrations and longer incubation times resulting in greater spore production.
Gomes et al. (Sun,) studied this question.