Macrocybin, A Mushroom Natural Triglyceride, Reduces Tumor Growth In Vitro And In Vivo Through Interference With The Actin Cytoskeleton

Mushrooms have been used for millennia in Eastern traditional medicine as cancer remedies and recent scientific studies have corroborated the presence of anticancer molecules in mushroom extracts. Our goal in this study was to screen a number of scarcely known mushroom species collected in the rain forest of Costa Rica looking for new antitumor molecules. Mushroom pieces were subjected to diverse extraction procedures involving water or ethanol at different temperatures. Extracts were screened using two human cell lines: A549 (lung adenocarcinoma) and NL20 (immortalized normal lung epithelium). Extracts able to kill tumor cells while preserving the integrity of non-tumor cells were considered “anticancer”. Positive extracts were fractionated with different techniques and the purification of the active compound was guided by its biological activity on the cell lines. When the compound was pure enough, its chemical structure was elucidated through nuclear magnetic resonance, mass spectrometry, and other ancillary techniques. The new molecule was synthesized and tested for biological activity both in vitro and in vivo with a xenograft assay. The mechanism of action was investigated through confocal microscopy, qRT-PCR, and Western blotting. The mushroom species with a better therapeutic window was Macrocybe titans, a local edible mushroom of very large proportions. The active ingredient was found in the precipitated phase of a 95% ethanol extraction with ultrasounds for 30 min, kept at -20°C for 24 h. To purify the active compound this extract was subjected to alkaloidal separation followed by column chromatography with polymeric resin (HP20-SS). The fraction obtained at pH 12 contained the active substance. Chemical analysis of the active molecule showed that it was a triglyceride containing oleic acid, palmitic acid, and a more complex fatty acid with 2 double bonds. Synthesis of all possible triglycerides with those characteristics and biological testing identified the natural compound as the R enantiomer of the triglyceride, which was named Macrocybin. A xenograft study showed that Macrocybin significantly reduces A549 tumor growth. In addition, Macrocybin treatment resulted in the dismantlement of the actin cytoskeleton in tumor cells (but not in normal cells). In conclusion, we have shown that the mushroom Macrocybe titans has anticancer properties and that the active principle is the new triglyceride, Macrocybin. This molecule constitutes a first-in-class new drug that works through the dismantlement of the actin cytoskeleton. Future experiments will establish the usefulness of Macrocybin for different types of cancer, either alone or in combination with other therapies. Citation Format: Marcos Vilarino, Josune Garcia-Sanmartin, Laura Ochoa-Callejero, Rafael Pelaez, Alfredo Martinez. Macrocybin, a mushroom natural triglyceride, reduces tumor growth in vitro and in vivo through interference with the actin cytoskeleton [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6544.