WT161

WT161 selectively inhibits HDAC6 and dramatically increases levels of acetylated α-tubulin (Ac-α-tubulin) with little effect on global lysine acetylation. It induces accumulation of acetylated tubulin and cytotoxicity in multiple myeloma (MM) cells. WT161 as a single agent does not induce ER stress, the UPR, or ER stress-mediated apoptosis^[1]. Consistent with WT-161 mediated hyperacetylation and inhibition of hsp90 chaperone function, treatment with WT-161 increases the intracellular levels of polyubiuitylated proteins in the cultured MCL JeKo-1 and Z138 cells. WT-161 also dose-dependently depletes the levels of cyclin D1 in the cultured human Mantle Cell Lymphoma (MCL) cells. Treatment with WT-161 induces ER stress response in the MCL cells, demonstrated by increase in the protein levels of Glucose regulated protein (GRP) 78, phosphorylated eIF2 (eukaryotic initation factor 2) α, and induction of the pro-apoptotic transcription factor CHOP (CAAT/Enhancer Binding Protein Homologous Protein)^[2]. WT161 triggers apoptotic cell death in MCF7, T47D, BT474, and MDA-MB231 cells, associated with decreased expression of EGFR, HER2, and ERα and downstream signaling^[3].

For annexin V-PI staining, MM.1S cells cultured for 16 h with BTZ (3 nM) and/or tubacin/WT161 (3 µM) are washed with PBS and processed.

WT161 has reasonable half-life in mice (1.4 h) and drug exposure [maximum concentration (Cmax) = 18 mg/L]. It is well tolerated as a single agent^[1]. WT161 significantly inhibits in vivo MCF7 cell growth, associated with downregulation of ERα, in a murine xenograft model^[3].