Selective Covalent Targeting of Pyruvate Kinase M2 Using Arsenous Warheads.

There is growing interest in covalent targeted inhibitors in drug discovery against previously "undruggable" sites and targets. These molecules typically feature an electrophilic warhead that reacts with nucleophilic groups of protein residues, most notably the thiol group of cysteines. One main challenge in the field is to develop versatile utilizable warheads. Here, we characterize the unique features of novel arsenous warheads for reaction with thiol species in a reversible manner and further demonstrate that organoarsenic probes can be chemically tuned toward specific molecular targets by developing selective and potent inhibitors of pyruvate kinase M2 (PKM2). We show that compound 24 is a covalent and allosteric inhibitor of PKM2 and its orally bioavailable prodrug 25 exerts efficacious inhibition of PKM2-dependent tumor growth in vitro and in vivo. Our results introduce 25 and its derivatives as useful pharmacological tools and provide a general road map for targeting the protein cysteinome using arsenous warheads.

SLC1A1-mediated cellular and mitochondrial influx of R-2-hydroxyglutarate in vascular endothelial cells promotes tumor angiogenesis in IDH1-mutant solid tumors.

Mutant isocitrate dehydrogenase 1 (mIDH1) drives tumorigenesis via producing oncometabolite R-2-hydroxyglutarate (R-2-HG) across various tumor types. However, mIDH1 inhibitors appear only effective in hematological tumors. The therapeutic benefit in solid tumors remains elusive, likely due to the complex tumor microenvironment. In this study, we discover that R-2-HG produced by IDH1-mutant tumor cells is preferentially imported into vascular endothelial cells and remodels mitochondrial respiration to promote tumor angiogenesis, conferring a therapeutic vulnerability in IDH1-mutant solid tumors. Mechanistically, SLC1A1, a Na+-dependent glutamate transporter that is preferentially expressed in endothelial cells, facilitates the influx of R-2-HG from the tumor microenvironment into the endothelial cells as well as the intracellular trafficking of R-2-HG from cytoplasm to mitochondria. R-2-HG hijacks SLC1A1 to promote mitochondrial Na+/Ca2+ exchange, which activates the mitochondrial respiratory chain and fuels vascular endothelial cell migration in tumor angiogenesis. SLC1A1 deficiency in mice abolishes mIDH1-promoted tumor angiogenesis as well as the therapeutic benefit of mIDH1 inhibitor in solid tumors. Moreover, we report that HH2301, a newly discovered mIDH1 inhibitor, shows promising efficacy in treating IDH1-mutant cholangiocarcinoma in preclinical models. Together, we identify a new role of SLC1A1 as a gatekeeper of R-2-HG-mediated crosstalk between IDH1-mutant tumor cells and vascular endothelial cells, and demonstrate the therapeutic potential of mIDH1 inhibitors in treating IDH1-mutant solid tumors via disrupting R-2-HG-promoted tumor angiogenesis.

Bufalin exerts antitumor effects in neuroblastoma via the induction of reactive oxygen species­mediated apoptosis by targeting the electron transport chain.

The prognosis of high­risk neuroblastoma remains poor. Clinical first­line drugs for treating neuroblastoma have been developed over the previous half­century; however, progress in the identification of new drugs with high efficiency is required. Bufalin, one of the major components of extracts obtained from the venom of the Chinese toad Bufo gargarizans, which is used to treat heart failure in Asian Pacific countries, has been reported to be a potential drug against multiple types of tumor; however, the detailed mechanisms underlying its antitumor activities remain unclear, largely due to lack of knowledge regarding its targets. In the present study, bufalin was revealed to exhibit potent antitumor effects against neuroblastoma, both in vitro and in vivo, using cell proliferation, colony formation, Transwell migration and flow cytometry assays, as well as a nude mouse subcutaneous xenograft model. Moreover, a chemically modified bufalin probe was designed to identify the potential targets of bufalin in neuroblastoma via chemical proteomics. With this strategy, it was revealed that the electron transport chain (ETC) on the inner membrane of mitochondria may contain potential targets for bufalin, and that bufalin­induced mitochondrial­dependent apoptosis may be caused by disruption of the ETC. Collectively, the present study suggests that bufalin may a promising drug for chemotherapy against neuroblastoma, and provides a foundation for further studies into the antitumor mechanisms of bufalin.

Identification of metabolic vulnerabilities of receptor tyrosine kinases-driven cancer.

One of the biggest hurdles for the development of metabolism-targeted therapies is to identify the responsive tumor subsets. However, the metabolic vulnerabilities for most human cancers remain unclear. Establishing the link between metabolic signatures and the oncogenic alterations of receptor tyrosine kinases (RTK), the most well-defined cancer genotypes, may precisely direct metabolic intervention to a broad patient population. By integrating metabolomics and transcriptomics, we herein show that oncogenic RTK activation causes distinct metabolic preference. Specifically, EGFR activation branches glycolysis to the serine synthesis for nucleotide biosynthesis and redox homeostasis, whereas FGFR activation recycles lactate to fuel oxidative phosphorylation for energy generation. Genetic alterations of EGFR and FGFR stratify the responsive tumors to pharmacological inhibitors that target serine synthesis and lactate fluxes, respectively. Together, this study provides the molecular link between cancer genotypes and metabolic dependency, providing basis for patient stratification in metabolism-targeted therapies.

Chemotherapy-induced intestinal inflammatory responses are mediated by exosome secretion of double-strand DNA via AIM2 inflammasome activation.

Chemotherapies are known often to induce severe gastrointestinal tract toxicity but the underlying mechanism remains unclear. This study considers the widely applied cytotoxic agent irinotecan (CPT-11) as a representative agent and demonstrates that treatment induces massive release of double-strand DNA from the intestine that accounts for the dose-limiting intestinal toxicity of the compound. Specifically, "self-DNA" released through exosome secretion enters the cytosol of innate immune cells and activates the AIM2 (absent in melanoma 2) inflammasome. This leads to mature IL-1ß and IL-18 secretion and induces intestinal mucositis and late-onset diarrhoea. Interestingly, abrogation of AIM2 signalling, either in AIM2-deficient mice or by a pharmacological inhibitor such as thalidomide, significantly reduces the incidence of drug-induced diarrhoea without affecting the anticancer efficacy of CPT-11. These findings provide mechanistic insights into how chemotherapy triggers innate immune responses causing intestinal toxicity, and reveal new chemotherapy regimens that maintain anti-tumour effects but circumvent the associated adverse inflammatory response.