sta-9090 and Sarcoma--Ewing

Withanolides constitute a valuable class of bioactive natural products because some members of the class are known to exhibit cytotoxic activity and also induce a cytoprotective heat-shock response. In order to understand the relationship between their structures and these dual bioactivities of the withanolide scaffold, we obtained 25 analogues of withaferin A (WA) and withanolide D (WD) including 17 new compounds by semisynthesis involving chemical and microbial transformations. Hitherto unknown 16β-hydroxy analogues of WA and WD were prepared by their reaction with triphenylphosphine/iodine, providing unexpected 5β-hydroxy-6α-iodo analogues (iodohydrins) followed by microbial biotransformation with Cunninghamella echinulata and base-catalyzed cyclization of the resulting 16β-hydroxy iodohydrins. Evaluation of these 25 withanolide analogues for their cytotoxicity and heat-shock-inducing activity (HSA) confirmed the known structure-activity relationships for WA-type withanolides and revealed that WD analogues were less active in both assays compared to their corresponding WA analogues. The 5β,6β-epoxide moiety of withanolides contributed to their cytotoxicity but not HSA. Introduction of a 16β-OAc group to 4,27-di- O-acetyl-WA enhanced cytotoxicity and decreased HSA, whereas introduction of the same group to 4- O-acetyl-WD decreased both activities.

Topics: Biological Products; Cell Line; Cell Line, Tumor; Cytotoxins; Heat-Shock Response; HEK293 Cells; Humans; Iodine; Organophosphorus Compounds; Sarcoma, Ewing; Structure-Activity Relationship; Withanolides

The long-term overall survival of Ewing sarcoma (EWS) patients remains poor; less than 30% of patients with metastatic or recurrent disease survive despite aggressive combinations of chemotherapy, radiation and surgery. To identify new therapeutic options, we employed a multi-pronged approach using in silico predictions of drug activity via an integrated bioinformatics approach in parallel with an in vitro screen of FDA-approved drugs. Twenty-seven drugs and forty-six drugs were identified, respectively, to have anti-proliferative effects for EWS, including several classes of drugs in both screening approaches. Among these drugs, 30 were extensively validated as mono-therapeutic agents and 9 in 14 various combinations in vitro. Two drugs, auranofin, a thioredoxin reductase inhibitor, and ganetespib, an HSP90 inhibitor, were predicted to have anti-cancer activities in silico and were confirmed active across a panel of genetically diverse EWS cells. When given in combination, the survival rate in vivo was superior compared to auranofin or ganetespib alone. Importantly, extensive formulations, dose tolerance, and pharmacokinetics studies demonstrated that auranofin requires alternative delivery routes to achieve therapeutically effective levels of the gold compound. These combined screening approaches provide a rapid means to identify new treatment options for patients with a rare and often-fatal disease.

Topics: Antineoplastic Combined Chemotherapy Protocols; Auranofin; Cell Line, Tumor; Cell Proliferation; Cell Survival; Computer Simulation; Drug Screening Assays, Antitumor; Gene Expression Regulation, Neoplastic; Humans; In Vitro Techniques; Oncogene Proteins, Fusion; Proto-Oncogene Protein c-fli-1; RNA-Binding Protein EWS; Sarcoma, Ewing; Transcription Factors; Triazoles