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BackgroundBreast cancer is a heterogeneous disease. Genomic studies have revealed five different intrinsic subtypes - Luminal A, Luminal B, HER2-enriched, Claudin-low, and Basal-like. Patients diagnosed with Basal-like or Claudin-low breast cancer (BL-CL) suffer from poor prognosis and limited treatment options. Hence, there is an urgent need to identify a new therapeutic lead that can benefit patients with BL-CL breast cancer.MethodsWe used a step-wise screening approach to screen 2778 HP20 fractions from our Marine Invertebrate Compound Library (MICL) to identify compounds that specifically target BL-CL breast cancer. We also performed biochemical investigations to study the effect of the compound in the signaling pathway. Finally, we generated a drug response gene-expression signature and projected it against a human tumor panel of 12 different cancer types to identify other cancer types sensitive to the compound.ResultsWe identified a previously unreported trisulfated sterol, topsentinol L trisulfate (TLT) that exhibits increased efficacy against BL-CL relative to Luminal/HER2+ breast cancer. Biochemical investigation of the effects of TLT on BL-CL revealed its ability to inhibit activation of AMPK and CHK1 and promote activation of p38. The importance of targeting AMPK and CHK1 in BL-CL was validated by treating a panel of breast cancer cell lines with known small molecule inhibitors of AMPK (Dorsomorphin) and CHK1 (Ly2603618) and recording the increased effectiveness against BL-CL compared to Luminal/HER2+ breast cancer. The TLT sensitivity gene-expression signature identified breast and bladder cancer as the most sensitive to TLT while glioblastoma multiforme as least sensitive.ConclusionsOur study identified TLT, a previously uncharacterized trisulfated sterol, as a potential therapeutic selective against BL-CL. Our results also showed that inhibition of AMPK and/or CHK1 might be an effective therapy in BL-CL.