Chaga mushroom triterpenoids as adjuncts to minimally invasive cancer therapies: A review

Cancer has become the second leading cause of death in the world. Integrative cancer therapy management is continuously evolving to enhance treatment outcomes. Chaga mushroom (Inonotus obliquus) is a parasitic fungus acclaimed to contain pharmaceutical and nutraceutical value in the fight against cancer. In particular, triterpenoid constituents derived from Chaga mushrooms have been recognized for their anti-cancer activity after distinguished cytotoxicity was repeatedly observed in cancer cells treated in vitro with lipophilic fractions of extract compared to aqueous ones. Studies that investigate the anti-cancer activity of Chaga mushroom triterpenoids are reviewed in this article to determine which cancer cell lines demonstrate the greatest susceptibility to them while highlighting the structure-activity relationships that are involved. Triterpenoid supplementation as an adjunct to cancer treatment may be a viable option as inotodiol and 3-β-22 α-dihydroxylanosta-8, 25-diene-24-one have been shown to exhibit anti-cancer activity similar to that of conventional drugs. Advances in addressing bioavailability challenges are also included in this review as studies include in vivo components.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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.

AIM OF THE STUDY

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Inotodiol From Inonotus obliquus Chaga Mushroom Induces Atypical Maturation in Dendritic Cells

Dendritic cells (DCs) have the ability to stimulate naïve T cells that coordinate subsequent adaptive response toward an inflammatory response or tolerance depending on the DC differentiation level. Inotodiol, a lanostane triterpenoid found in Inonotus obliquus (wild Chaga mushroom), is a natural compound with a wide range of biological activities. In this study, we investigated whether inotodiol promotes the maturation of bone marrow-derived DCs (BMDCs) and inotodiol-treated BMDCs induce T cell activation. Inotodiol increased the expression of surface maturation markers, including MHC-I, MHC-II, CD86, and CD40, on BMDCs without affecting the production of various cytokines, including TNF-α and IL-12p40 in these cells. T cells primed with inotodiol-treated BMDCs proliferated and produced IL-2, without producing other cytokines, including IL-12p40 and IFN-γ. Injection of inotodiol into mice induced maturation of splenic DCs and IL-2 production, and the administration of inotodiol and inotodiol-treated BMDCs induced the proliferation of adoptively transferred CD8⁺ T cells in vivo. The phosphatidylinositol-3-kinase inhibitor wortmannin abrogated the upregulation of Akt phosphorylation and CD86 and MHC-II expression induced by inotodiol. However, inotodiol failed to induce phosphorylation of the IκB kinase and degradation of IκB-α, and increased expression of CD86 induced by inotodiol was not blocked by an IκB kinase inhibitor. These results suggest that inotodiol induces a characteristic type of maturation in DCs through phosphatidylinositol-3-kinase activation independent of NF-κB, and inotodiol-treated DCs enhance T cell proliferation and IL-2 secretion.

Extracts of Phellinus linteus, Bamboo (Sasa senanensis) Leaf and Chaga Mushroom (Inonotus obliquus) Exhibit Antitumor Activity through Activating Innate Immunity

Natural products have attracted great interest for some time as alternative methods against cancers by fulfilling immunomodulating properties. In this study, we investigated the activity of hot water extracts (120 °C, >30 min) of Phellinus linteus, fresh leaves of Kumaizasa bamboo and Chaga mushroom which we called MeshimaMax, for cancer prevention and treatment by using different solid tumor models. In the implanted mouse sarcoma S180 tumor, MeshimaMax treatment significantly inhibited tumor growth when it was applied at the early stage of tumor inoculation. The effect was further confirmed by using carcinogen induced tumors, i.e., azoxymethane (AOM)/dextran sulfate sodium (DSS) induced mouse colon cancer and 7,12-dimethylbenz anthracene (DMBA) induced rat breast cancer. In both cases the occurrences of tumors were remarkably suppressed by administration of MeshimaMax which consists of three components above. More importantly, when MeshimaMax was combined with an anticancer chemotherapeutic drug, the therapeutic effect was remarkably improved. In vitro studies showed that when MeshimaMax was applied to mouse macrophage RAW264.7 cells the phagocytosis of macrophages was significantly activated, which was evaluated by using living yeast cells as well as synthetic nanoparticles. A cytotoxicity assay showed the 50% inhibitory concentration (IC₅₀) was higher than 1 mg/mL and normal cells were 2–3 times more tolerant to MeshimaMax than cancer cells. These findings suggest the potential application of MeshimaMax for cancer prevention and as supplement regimen for anticancer chemotherapy, probably functioning through activation of innate immunity, which may benefit cancer patients as an alternative supplement.

Bioactivity-based analysis and chemical characterization of cytotoxic constituents from Chaga mushroom (Inonotus obliquus) that induce apoptosis in human lung adenocarcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Inonotus obliquus, also known as Chaga mushroom, is one of the most widely appreciated wild edible mushrooms in Russia and northern European countries and is renowned for its use in cancer treatment. Indeed, recently published in vitro and in vivo studies have demonstrated its anticancer activity in various types of cancer and support its potential application for therapeutic intervention in cancer. However, its activity against lung cancer, the most commonly diagnosed cancer and the leading cause of cancer death worldwide, and the underlying molecular basis of its action remain to be fully elucidated.

OBJECTIVE

This study aimed to evaluate the cytotoxic activity of I. obliquus in four human lung adenocarcinoma cell lines with different p53 status (A549, H1264, H1299, and Calu-6) and identify its active constituents by bioactivity-based analysis and the underlying molecular basis of their cytotoxicity on lung cancer cells.

MATERIALS AND METHODS

Bioactivity-guided fractionation and preparative/semi-preparative HPLC purification were used with LC/MS analysis to separate the bioactive constituents. Cell viability and apoptosis in human lung cancer cell lines (A549, H1264, H1299, and Calu-6) were assessed using the WST-1 assay and TUNEL staining, respectively. Caspase activation was assessed by detecting its surrogate markers, cleaved poly (ADP-ribose) polymerase (PARP) and caspase-3, using an immunoblot assay.

RESULTS

The MeOH extract of I. obliquus reduced cell viability in all lung cancer cell lines tested through induction of apoptosis accompanied by caspase-3 cleavage. Bioactivity-guided fractionation of the MeOH extract and chemical investigation of its cytotoxic hexane-soluble and CH₂Cl₂-soluble fractions led to the isolation of eight triterpenoids (1-8), including a new lanostane-type triterpenoid named chagabusone A (7). The structures of the isolates were elucidated based on spectroscopic analysis, including 1D and 2D NMR and high-resolution ESIMS. Among isolated compounds, compounds 1, 6, and 7 showed the most potent cytotoxic activity in all human lung cancer cell lines examined, with IC₅₀ values ranging from 75.1 to 227.4 μM. Cytotoxicity of these compounds was mediated by apoptosis with caspase-3 activation.

CONCLUSION

These findings provide experimental evidence supporting the potential application of I. obliquus in lung cancer treatment and reveal the molecular basis underlying its cytotoxic activity against human lung cancer cells.

The mast cell stabilizing activity of Chaga mushroom critical for its therapeutic effect on food allergy is derived from inotodiol

While an anti-allergic effect of Chaga mushroom (Inonotus obliquus) has been indicated, its therapeutic effect on allergy and immunoregulatory mechanisms and chemical constituents directly responsible for that are hardly known. We examined the effect of 70% ethanol extract of Chaga mushroom (EE) and its dichloromethane (DF) and aqueous (AF) fractions using a mouse model of chicken ovalbumin (cOVA)-induced food allergy, and found that only EE and DF ameliorated allergy symptoms to a significant extent. The in vivo mast cell-stabilizing activity was also found only in EE and DF whereas the activities to suppress Th2 and Th17 immune responses and cOVA-specific IgE production in the small intestine were observed in all three treatment regimens, implying that inhibition of the mast cell function by lipophilic compounds was vital for the therapeutic effect. Results also indicated that inotodiol, a triterpenoid predominantly present in DF, played an active role as a mast cell stabilizer.

Terpenoids with alpha-glucosidase inhibitory activity from the submerged culture of Inonotus obliquus

Lanostane-type triterpenoids, inotolactones A and B, a drimane-type sesquiterpenoid, inotolactone C, and five known terpenoids 6β-hydroxy-trans-dihydroconfertifolin, inotodiol, 3β,22-dihydroxyanosta-7,9(11),24-triene, 3β-hydroxycinnamolide, and 17-hydroxy-ent-atisan-19-oic acid, were isolated from the submerged culture of chaga mushroom, Inonotus obliquus. Their structures were characterized by spectroscopic methods, including MS and NMR (1D and 2D) spectroscopic techniques. Inotolactones A and B, examples of lanostane-type triterpenoids bearing α,β-dimethyl, α,β-unsaturated δ-lactone side chains, exhibited more potent alpha-glucosidase inhibitory activities than the positive control acarbose. This finding might be related to the anti-hyperglycemic properties of the fungus and to its popular role as a diabetes treatment. In addition, a drimane-type sesquiterpenoid and an atisane-type diterpenoid were isolated from I. obliquus.