The anti-cancer potential of sRNAs isolated from different mushroom species

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Jan 31 2024

In a recent study published in the journal the anti-cancer potential of sRNAs isolated from different mushroom species, researchers in Portugal expanded upon previous studies that demonstrated the anti-cancer activity of a small RNA (sRNA) fraction obtained from Cantharellus cibarius (CCI), a golden chanterelle mushroom. The present study investigates the anti-cancer potential of sRNA from Boletus edulis (Porcini) and Agaricus bisporus (Portobello). It additionally evaluated if the microRNAs from these mushrooms may have anti-cancer properties.

Study: MUSHROOMS4LIFE: Decoding the Molecular Basis of a Cancer-Fighting Small RNA Extracted from Edible Mushrooms. Image Credit: JeannieR / Shutterstock

Experiments on normal and cancer cell lines revealed that while all mushroom sRNAs displayed anti-cancer properties, their relative activities varied widely, suggesting that anti-cancer sRNAs are enriched in specific sequences. These findings highlight the potential of mushrooms as sources of biomolecules with anti-cancer potential and illustrate the need for further research into commonly available fruits, vegetables, and (in this case) fungi with the potential of discovering remarkable bioactives with substantial medical application.

A brief history of mushrooms’ application in cancer research

Mushrooms are the common name for the conspicuous umbrella-shaped fruiting body (sporophore) of certain fungi. Despite over 14,000 of these fungi being described thus far, only a fraction are safe for human consumption. These few species, however, have been staples in diets across almost every culture and civilization. Some (mainly Asian) cultures have used ‘medicinal mushrooms’ to treat infections for hundreds of years, yet global interest in mushrooms’ clinical properties has, until recently, been largely ignored.

With increasing interest in bioprospecting (the scientific search for natural biochemical or genetic products with beneficial applications), medical research has begun screening mushroom biomolecules for potential pharmaceutical applications. In recent decades, a plethora of nutraceuticals with anti-oxidant, anti-cancer, anti-inflammatory, and neurologically beneficial potencies have been described. Mushroom anti-cancer research has recently received special attention due to the description of water-soluble small RNA (sRNA) fractions isolated from Cantharellus cibarius (CCI) and Boletus edulis (BED) depicting potent apoptosis-inducing and cell proliferation-inhibiting effects.

Unfortunately, the mechanisms of action of these sRNAs remain unknown. Identifying these mechanisms and expanding the mushroom species samples would benefit both medical and nutritional industries – the former as it will form the basis for future research into optimizing these anti-cancer benefits (dosages, potential in vivo toxicity) and the latter by furthering the case 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 hitherto untested mushroom species harvested from Trás-os-Montes and Alto Douro (Portugal), were compared against sRNA fractions from CCI to investigate the potential anti-cancer efficacy of their sRNAs. Since previous work has hypothesized that microRNAs (miRNAs) may also serve anti-cancer functions, miRNAs from all three species were also evaluated. All samples were freeze-dried (lyophilized) following harvesting to prevent RNA degradation and maintain sample freshness.

sRNAs were extracted using anion-exchange chromatography using 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 HDFn normal cell line were used. Drug sensitivity metrics were evaluated using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay in tandem with spectrophotometric quantification. Finally, RNA Fluorescence in situ hybridization (RNA-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.

Study findings

Purification of BED resulted in two unique sRNA fractions, named BEDA and BEDB. Surprisingly, ABI purification produced only one fraction (ABIA), hinting that not all mushrooms (or their sRNAs) are chemically and functionally similar.

Cell line evaluations of sRNA efficacy revealed that ABIA was capable of suppressing cancer cell viability at 50 µg/mL concentration. While higher concentrations suppressed the cancer more effectively, they proved cytotoxic to normal cells and thus need to be further researched to elucidate their ideal dosages. In contrast, BEDA did not show any anti-cancer properties.

BEDB and CCI3 proved to be the best anti-cancer agents, depicting high anti-cancer efficacy at low dosages and normal cell cytotoxicity only at much higher concentrations (250 µg/mL). miRNA BED and ABI results differed from previously reported CCI3 results by showing no statistically significant differences between cancer and normal cells, discounting their effectiveness as anti-cancer therapeutics.

“Despite the similar purity and molecular weight when compared with the CCI3 and BEDB fractions, the BEDS and BEDH samples did not show the same biological effect. These data suggest a different primary structure of sRNA and a sequence-dependent effect. In order to understand whether 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 that were untreated and treated with CCI3 and BEDB for 96 h, using a clone isolated from CCI3 as a probe.”

RNA-FISH results revealed that BEDB and CCI3 fractions were more than 80% similar in their genetic sequence, suggesting that both fractions are enriched in the same sRNA sequence.

“However, further functional studies will be needed in order to understand their target in tumor cells and the mechanism behind their anti-tumor capacity.”