Antitumor potential of Pleurotus ostreatus i-fraction in carcinomas with few therapeutic options

Abstract

Pleurotus ostreatus is an edible mushroom recognized by the Ar- gentine Food Code. The antitumor activity of its polysaccharides, free or bound to proteins, has been demonstrated on different types of cancer. However, this potential in Triple-Negative Breast Cancer (TNBC) and Head and Neck Squamous Cell Carcinoma (HNSCC) is unknown. Therefore, our objective is to determine the direct an- titumor activity of I-Fraction: a polysaccharide-enriched extract obtained from P. ostreatus in TNBC and HNSCC. Previously, we reported that I-Fraction decreases the viability of 4T1 cells (TN- BC-murine) starting at 2.5 mg/mL and 24 h of treatment. In the pres- ent work, by crystal violet assay, we demonstrated that this effect is also displayed on MDA-MB-231 cells (TNBC-human) starting at 2 mg/mL and 48 h of treatment (p<0.01). HN13 cells (HNSCC-human) were less sensitive respect to TNBC cells, decreasing its viability after 5 mg/mL and 48 h of I-Fraction treatment (p<0.01). Through cell cycle analysis with PI staining, we demonstrated that treatment with I-Fraction (2.5 mg/mL, 48 h) increases the number of MDA- MB-231 cells in S phase (p<0.001). This increase was accompanied by a decrease of the cell population in G0/G1 (p<0.001) and G2/M (p<0.05) phase. The staining with Annexin V/PI of 4T1 cells treated with I-Fraction (2.5 mg/mL, 48 h) or vehicle, showed that the extract induces cell death by apoptosis (p<0.001) added to a lower induc- tion of death by necrosis (p<0.05). Through wound healing assay, we demonstrated that I-Fraction (2 mg/mL) decreases the migratory capability of MDA-MB-231 cells (p<0.01). Furthermore, started with the characterization of I-Fraction, by phenol-sulfuric acid and Brad- ford method we determined that 68.72 % +/- 6.60 % of the extract are glucans and that 9.02 % +/- 3.32 % are proteins. In conclusion, these results demonstrate a direct antitumor activity in vitro of P. ostreatus I-Fraction and endorse the continuation of in vivo assays in TNBC murine models.