Gene expression data from WM983B melanoma cells treated with vehicle or 2.5 M inhibitor (corin2 or MS-275) for 24 h

Epigenetic regulation of gene expression by histone modification has emerged as a major facet of physiologic and disease processes. As a result, there has been intense interest in developing epigenetic therapies leading to the discovery of small molecule agents that target proteins involved in histone modification. Several histone deacetylase (HDAC) inhibitors are now approved drugs for a specialized group of hematologic malignancies but not yet for a wider range of cancer types including solid tumors. One of the conceptual challenges in targeting HDACs is that even selective class I HDAC inhibitors likely impact these deacetylase activities indiscriminately across a range of distinct HDAC-containing multiprotein complexes. Such broad cellular effects may result in a narrow therapeutic window between disease efficacy and toxicity. Among HDAC complexes, the CoREST complex, which includes HDAC1 or its close paralog HDAC2, the scaffolding protein CoREST, and lysine specific demethylase 1 (LSD1) has attracted special interest. Here we report corin2, designed to dually inhibit the CoREST complex major enzymatic activities, lysine specific demethylase 1 (LSD1) and HDACs 1/2. Corin2 is a synthetic hybrid agent derived from the class I HDAC inhibitor (entinostat) and an LSD1 inhibitor (tranylcypromine analog). Enzymologic analysis reveals that corin2 selectively targets the CoREST complex and shows more sustained inhibition of the CoREST complex HDAC activity than entinostat. Cell-based experiments demonstrate that corin2 exhibits a superior anti-proliferative profile against several melanoma lines compared to its parent monofunctional HDAC and LSD1 inhibitors (alone or in combination) but is less toxic to non-cancerous primary human melanocytes. Transcriptomics analysis shows that corin2 is a more powerful inducer of tumor suppressor genes relative to the parent HDAC and LSD1 compounds (alone or in combination). Genetic knockdown of CoREST or LSD1 in cancer cell lines abolishes the differences in potency of corin2 vs. entinostat, suggesting that corin2's favorable pharmacologic effects rely on an intact CoREST complex. Corin2 was also effective in slowing tumor growth in a melanoma mouse xenograft model. These studies highlight the promise of a new class of two-pronged hybrid agents that selectively target particular epigenetic regulatory complexes and offer unique therapeutic opportunities.

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Kalin JH, Wu M, Gomez AV, Song Y, Das J, Hayward D, Adejola N, Wu M, Panova I, Chung HJ, Kim E, Roberts HJ, Roberts JM, Prusevich P, Jeliazkov JR, Roy Burman SS, Fairall L, Milano C, Eroglu A, Proby CM, Dinkova-Kostova AT, Hancock WW, Gray JJ, Bradner JE, Valente S, Mai A, Anders NM, Rudek MA, Hu Y, Ryu B, Schwabe JWR, Mattevi A, Alani RM, Cole PA