Chaga mushroom extract induces autophagy via the AMPK-mTOR signaling pathway in breast cancer cells

• Published in: Journal of ethnopharmacology Vol. 274; p. 114081
• Main Authors: Lee, Min-Gu, Kwon, Yun-Suk, Nam, Kyung-Soo, Kim, Seo Yeon, Hwang, In Hyun, Kim, Soyoung, Jang, Hyunsoo
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 28.06.2021
• Subjects: Agaricales; AMP-Activated Protein Kinases - metabolism; AMPK; Animals; Antineoplastic Agents - chemistry; Antineoplastic Agents - pharmacology; Antineoplastic Agents - therapeutic use; Autophagy; Autophagy - drug effects; Breast cancer; Breast Neoplasms - drug therapy; Breast Neoplasms - metabolism; Cell Line, Tumor; Cell Survival - drug effects; Chaga mushroom; Complex Mixtures - chemistry; Complex Mixtures - pharmacology; Complex Mixtures - therapeutic use; Female; Humans; Inonotus obliquus; Inotodiol; Lanosterol - analogs & derivatives; Lanosterol - analysis; Lanosterol - pharmacology; Mice; Mice, Inbred BALB C; mTOR; Signal Transduction - drug effects; TOR Serine-Threonine Kinases - metabolism; Trametenolic acid; Triterpenes - analysis; Triterpenes - pharmacology; PR; Chaga mushroom; S6; Breast cancer; IEF; Autophagy; ER; S6K1; Inonotus obliquus; Inotodiol; Bcl-xL; Trametenolic acid; TEF; mTOR; AMPK; CME; LC3; GAPDH; AIF
• ISSN: 0378-8741; 1872-7573
• DOI: 10.1016/j.jep.2021.114081

Chaga mushrooms (Inonotus obliquus) are commonly used in traditional treatments in Eastern Europe and Asia due to their diverse pharmacological effects, including anti-tumor and immunologic effects. Thus, many cancer patients take Chaga mushrooms as a complementary medicine, even during chemotherapy or radiotherapy. However, few studies have investigated the effects or molecular targets of Chaga mushrooms in breast cancer. Herein, we examined the anticancer effects of Chaga mushrooms in different types of breast cancer cell lines, and explored the underlying molecular mechanism to better understand their effects and benefits. Chaga mushroom extract (CME) was prepared by extracting Chaga mushrooms with 70% ethanol. The cytotoxic effects of CME were assessed by MTT assay and protein expressions were evaluated by western blotting. To evaluate in vivo anti-tumor effects of CME, CME (2 g/kg) was orally administered to 4T1 tumor-bearing BALB/c mice every other day over 30 days (15 administrations), and tumor sizes were measured. Silica gel column chromatography was used to fractionate CME, and major constituents responsible for cytotoxic effects of CME were identified by 1H/13C-NMR and LC-MS. CME inhibited the proliferation of 4T1 mouse breast cancer cells in a dose and time-dependent manner. The expression of LC3 and phosphorylation of AMPK were increased by CME, while the phosphorylation of mTOR, S6, and S6K1 were suppressed, suggesting that CME induced autophagy by activating AMPK and inhibiting mTOR signaling pathways. Consistent with its observed cytotoxic effect in vitro, CME effectively suppressed tumor growth in 4T1 tumor-bearing BALB/c mice. In addition, inotodiol and trametenolic acid were identified as the major constituents responsible for the cytotoxic effects of CME on breast cancer cells. Moreover, inotodiol and trametenolic acid-enriched fractions both exhibited cytotoxic effects regardless of breast cancer cell subtypes and did not interfere with the cytotoxic effects of conventional drugs. Taken together, Chaga mushroom extract induced autophagy by activating AMPK and inhibiting the mTOR signaling pathway. Our data suggest Chaga mushrooms may be a beneficial complementary medicine for breast cancer patients. [Display omitted] •Chaga mushrooms extract (CME) induced autophagy in breast cancer cell lines.•CME activated AMPK but inhibited the mTOR signaling pathway.•Inotodiol and trametenolic acid were responsible for the cytotoxic effects of CME.•Inotodiol and trametenolic acid did not interfere with effects of cytotoxic drugs.