The natural compound GL22, isolated from Ganoderma mushrooms, suppresses tumor growth by altering lipid metabolism and triggering cell death.

Cancer cells rewire their metabolism to satisfy the demands of uncontrolled proliferation and survival. The reprogramming of lipid metabolism supports tumor growth, metastasis, and therapy-resistance. Therefore, targeting lipid metabolic reprogramming is a potential cancer treatment strategy. We recently isolated the novel natural triterpene GL22 from Ganoderma leucocontextum, a traditional Chinese medicine. Here, we show that GL22 significantly inhibits the growth of the liver cancer cell line Huh7.5 in vitro and of Huh7.5-derived tumor xenografts in vivo. We further find that GL22 induces mitochondrial dysfunction and cell death in Huh7.5 cells, in part due to fatty acid immobilization and loss of the mitochondrial lipid cardiolipin, which has vital structural and metabolic functions. Importantly, we demonstrate that GL22 treatment decreases the expression of fatty acid-binding proteins (FABPs), which likely underlies the loss of cardiolipin, mitochondrial dysfunction, and cell death. The over-expressions of FABPs prevented the GL22-induced cell death, loss of cardiolipin, decrease of ATP production, and reduction of oxygen consumption rate in Huh7.5 cells. Our results support targeting lipid metabolism via manipulating FABPs as a cancer treatment strategy, and promote Chinese medicine as an important source of novel anticancer drugs.

2-Methoxystypandrone inhibits signal transducer and activator of transcription 3 and nuclear factor-κB signaling by inhibiting Janus kinase 2 and IκB kinase.

Constitutive activation of the signal transducer and activator of transcription 3 (STAT3) or the nuclear factor-κB (NF-κB) pathway occurs frequently in cancer cells and contributes to oncogenesis. The activation of Janus kinase 2 (JAK2) and IκB kinase (IKK) are key events in STAT3 and NF-κB signaling, respectively. We have identified 2-methoxystypandrone (2-MS) from a traditional Chinese medicinal herb Polygonum cuspidatum as a novel dual inhibitor of JAK2 and IKK. 2-MS inhibits both interleukin-6-induced and constitutively-activated STAT3, as well as tumor necrosis factor-α-induced NF-κB activation. 2-MS specifically inhibits JAK and IKKß kinase activities but has little effect on activities of other kinases tested. The inhibitory effects of 2-MS on STAT3 and NF-κB signaling can be eliminated by DTT or glutathione and can last for 4 h after a pulse treatment. Furthermore, 2-MS inhibits growth and induces death of tumor cells, particularly those with constitutively-activated STAT3 or NF-κB signaling. We propose that the natural compound 2-MS, as a potent dual inhibitor of STAT3 and NF-κB pathways, is a promising anticancer drug candidate.

Wedelolactone, a naturally occurring coumestan, enhances interferon-γ signaling through inhibiting STAT1 protein dephosphorylation.

Signal transducers and activators of transcription 1 (STAT1) transduces signals from cytokines and growth factors, particularly IFN-γ, and regulates expression of genes involved in cell survival/death, proliferation, and migration. STAT1 is activated through phosphorylation on its tyrosine 701 by JAKs and is inactivated through dephosphorylation by tyrosine phosphatases. We discovered a natural compound, wedelolactone, that increased IFN-γ signaling by inhibiting STAT1 dephosphorylation and prolonging STAT1 activation through specific inhibition of T-cell protein tyrosine phosphatase (TCPTP), an important tyrosine phosphatase for STAT1 dephosphorylation. More interestingly, wedelolactone inhibited TCPTP through interaction with the C-terminal autoinhibition domain of TCPTP. We also found that wedelolactone synergized with IFN-γ to induce apoptosis of tumor cells. Our data suggest a new target for anticancer or antiproliferation drugs, a new mechanism to regulate PTPs specifically, and a new drug candidate for treating cancer or other proliferation disorders.

Small-molecule STAT3 signaling pathway modulators from Polygonum cuspidatum.

Constitutively activated STAT3 plays a pivotal role in oncogenesis and metastasis in many human cancers, and STAT3 has been validated as a novel anticancer drug target. Thus, the identification of small molecules that modulate STAT3 activity could be of great therapeutic importance. The aim of this study was to isolate novel modulators of the STAT3 signaling pathway from the roots of Polygonum cuspidatum by bioassay-guided fractionation using a STAT3 reporter gene assay. 2-Methoxystypandrone (1), as well as three anthraquinones (2-4), were identified as major active components of P. cuspidatum. Compound 1 demonstrated a potent inhibitory effect on STAT3 activation and significantly inhibited cell proliferation of human breast cancer cells, especially those with constitutively activated STAT3 (IC50 = 2.7-3.1 µM). The SAR analysis of quinone analogues suggested that the phenolic and carbonyl groups are the key structures contributing to their inhibitory activities against the STAT3 signaling.