In a recent study published in the Forum of Medical Sciences, researchers in Portugal extended earlier studies that showed the anticancer activity of a small RNA fraction (sRNA) found in Cantharellus cibarius (CCI), a golden chanterelle. This study investigated the anticancer potential of sRNA from Boletus edulis (porcini) and Agaricus bisporus (portobello) mushrooms. Additionally, the study examined whether the microRNAs of these mushrooms might have anticancer properties.
Studie: MUSHROOMS4LIFE: Entschlüsselung der molekularen Basis einer krebsbekämpfenden kleinen RNA, die aus Speisepilzen gewonnen wird. Bildnachweis: JeannieR / Shutterstock
Experiments on normal and cancer cell lines showed that all mushroom-sRNAs exhibited anticancer properties, but their relative activities varied significantly. This suggests that anticancer sRNAs are enriched with specific sequences. These results highlight the potential of mushrooms as sources of biomolecules with anticancer properties and underscore the need for further research on widely available fruits, vegetables, and, in this case, mushrooms, with the potential to discover notable bioactive compounds with significant medical applications.
A Brief History of Mushroom Use in Cancer Research
Mushrooms are the common name for the conspicuous umbrella-shaped fruiting bodies (sporophores) of certain fungi. Although over 14,000 species of these mushrooms have been described, only a fraction of them are safe for human consumption. However, these few species have been staple food sources in almost all cultures and civilizations. Some cultures, particularly in Asia, have been using „medicinal mushrooms“ for hundreds of years to treat infections. However, until recently, global interest in the clinical properties of mushrooms was largely overlooked.
With the increasing interest in bioprospecting, the scientific search for natural biochemical or genetic products with useful applications, medical research has begun to explore mushroom biomolecules for potential pharmaceutical applications. Over the last few decades, a variety of nutraceuticals with antioxidant, anticancer, anti-inflammatory, and neurologically beneficial effects have been described. Due to the identification of water-soluble small RNA fractions isolated from mushrooms, mushroom cancer research has received special attention lately. Cantharellus cibarius (CCI) and Boletus edulis (BED) have shown strong apoptosis-inducing and cell-proliferation-inhibiting effects.
Unfortunately, the mechanisms of action of these sRNAs are still unknown. Identifying these mechanisms and expanding the variety of mushroom samples would benefit both the medical and nutrition industries. It would provide the basis for future research to optimize the anticancer benefits of these mushrooms (dosages, potential in vivo toxicity) and promote the arguments for the nutritional benefits of these treasure troves of nutraceuticals.
About the Study
In the present study, BED and Agaricus bisporus (ABI), commonly known as portobello, two previously untested types of mushrooms harvested in Trás-os-Montes and Alto Douro, Portugal, were compared with sRNA fractions of CCI to investigate the potential efficacy of their sRNAs against cancer. Since previous work hypothesized that microRNAs (miRNAs) could also fulfill anticancer functions, miRNAs from all three species were also examined. All samples were freeze-dried (lyophilized) after harvesting to prevent RNA degradation and preserve the freshness of the samples.
sRNAs were extracted using anion exchange chromatography, following the protocols described by Lemieszek et al. miRNAs were extracted using the MirVana miRNA Isolation Kit. For in vivo efficacy evaluations, the Caco-2 tumor cell line and the normal HDFn cell line were used. Drug sensitivity metrics were assessed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in combination with spectrophotometric quantification. Finally, RNA fluorescence in situ hybridization (FISH) experiments were used to visualize target messenger RNA transcripts in cultured cells. The statistical significance of the results was verified using one-way analysis of variance (ANOVA) tests.
The purification of BED led to two unique sRNA fractions named BEDA and BEDB. Surprisingly, ABI purification yielded only one fraction (ABIA), suggesting that not all mushrooms (or their sRNAs) are chemically and functionally similar.
Cell line evaluations of sRNA efficacy revealed that ABIA was able to suppress the viability of cancer cells at a concentration of 50 µg/ml. While higher concentrations were more effective at suppressing cancer, they proved to be cytotoxic to normal cells and therefore need further research to determine their ideal dosage. In contrast, BEDA showed no anticancer properties.
BEDB and CCI3 proved to be the best anticancer agents, showing high anticancer efficacy at low dosages and normal cell cytotoxicity only at much higher concentrations (250 µg/ml). The miRNA results of BED and ABI differed from previously reported CCI3 results, as they did not show statistically significant differences between cancer and normal cells, disregarding their efficacy as cancer therapeutics.
„Despite the similar purity and molecular weight compared to the CCI3 and BEDB fractions, the BEDS and BEDH samples did not exhibit the same biological effect. These data suggest a different primary structure of the sRNA and a sequence-dependent effect. To understand if the effect of CCI3 and BEDB was sequence-dependent and if the sequence isolated in these fractions was similar, we carried out an RNA-FISH in Caco-2 cells untreated and treated with CCI3 and BEDB for 96 hours, using a clone isolated from CCI3 as a probe.“
The RNA-FISH results showed that BEDB and CCI3 fractions were over 80% similar in their genetic sequence, indicating that both fractions are enriched with the same sRNA sequence.
„However, further functional studies are necessary to understand their target in tumor cells and the mechanism behind their antitumor capacity.“
- Sá, I., Ribeiro, M., Nunes, FM, Marques, G., Chaves, R. & Ferreira, D. (2024). MUSHROOMS4LIFE: Deciphering the molecular basis of an anticancer small RNA derived from edible mushrooms. Forum der medizinischen Wissenschaften, 23(1), 9, DOI – 10.3390/msf2023023009, https://www.mdpi.com/2673-9992/23/1/9