Cryptococcus neoformans capsular polysaccharides modulate the tumor microenvironment in murine breast cancer cells.

Cryptococcus neoformans is an opportunistic pathogenic fungus of the Cryptococcus genus that causes invasive infections in immunosuppressed individuals. An example of an immunosuppressive condition is cancer, since chemotherapy and radiotherapy make cancer patients more susceptible to this type of infection. The most important virulence factor of this fungus species is the polysaccharides they produce, namely Glucuronoxylomannan (GXM) and Glucuronoxylomannogalactan (GXMGal), which have the potential to modulate the host's immune response. In light of this, the capsular polysaccharides of the fungus can modulate the tumor microenvironment, so we decided to evaluate the impact of GXM and GXMGal during the progression of breast cancer. To this end, we treated murine breast cancer 4T1 cells with purified capsular polysaccharides in vitro experiments and observed that the treatment induced cell death characterized as apoptosis and also a reduction in TGF-β production. Furthermore, in vivo experiments, we investigated the effect of treatment with the polysaccharides in animals during the progression of breast cancer over 28 days. From this, we observed that the polysaccharides have the potential to reduce the progression of the primary breast tumor and delay the advancement of the clinical pathological score of the animals. Therefore, the polysaccharides have the potential to regulate tumor progression and possibly the aggressiveness of murine breast cancer tumors.