ABT-751 Induces Multiple Anticancer Effects in Urinary Bladder Urothelial Carcinoma-Derived Cells: Highlighting the Induction of Cytostasis through the Inhibition of SKP2 at Both Transcriptional and Post-Translational Levels

Abstract

The objective was to investigate the anti-cancer effects and underlying molecular mechanisms of cytostasis which were activated by an anti-microtubule drug, ABT-751, in two urinary bladder urothelial carcinoma (UBUC)-derived cell lines, BFTC905 and J82, with distinct genetic backgrounds. A series of in vitro assays demonstrated that ABT-751 induced G2/M cell cycle arrest, decreased cell number in the S phase of the cell cycle and suppressed colony formation/independent cell growth, accompanied with alterations of the protein levels of several cell cycle regulators. In addition, ABT-751 treatment significantly hurdled cell migration and invasion along with the regulation of epithelial–mesenchymal transition-related proteins. ABT-751 triggered autophagy and apoptosis, downregulated the mechanistic target of rapamycin kinase (MTOR) and upregulated several pro-apoptotic proteins that are involved in extrinsic and intrinsic apoptotic pathways. Inhibition of autophagosome and autolysosome enhanced apoptosis was also observed. Through the inhibition of the NFκB signaling pathway, ABT-751 suppressed S-phase kinase associated protein 2 (SKP2) transcription and subsequent translation by downregulation of active/phospho-AKT serine/threonine kinase 1 (AKT1), component of inhibitor of nuclear factor kappa B kinase complex (CHUK), NFKB inhibitor alpha (NFKBIA), nuclear RELA proto-oncogene, NFκB subunit (RELA) and maintained a strong interaction between NFKBIA and RELA to prevent RELA nuclear translocation for SKP2 transcription. ABT-751 downregulated stable/phospho-SKP2 including pSKP2(S64) and pSKP2(S72), which targeted cyclin-dependent kinase inhibitors for degradation through the inactivation of AKT. Our results suggested that ABT-751 may act as an anti-cancer drug by inhibiting cell migration, invasion yet inducing cell cycle arrest, autophagy and apoptosis in distinct UBUC-derived cells. Particularly, the upstream molecular mechanism of its anticancer effects was identified as ABT-751-induced cytostasis through the inhibition of SKP2 at both transcriptional and post-translational levels to stabilize cyclin dependent kinase inhibitor 1A (CDKN1A) and CDKN1B proteins.

Small-molecule compounds inhibiting S-phase kinase-associated protein 2: A review

“…ABT-751, an anti-microtubule drug ( Table 1 ), has been reported to inhibit SKP2 transcription by suppression of the AKT serine/threonine kinase–nuclear factor kappa B signaling pathway and to downregulate stable/phospho-SKP2 post-translationally by inhibition of AKT signaling in the urinary bladder urothelial carcinoma cell lines BFTC905 and J82 ( Dehghanian et al, 2021 ) ( Table 2 ).…”

Evaluation of ABT-751, a novel anti-mitotic agent able to overcome multi-drug resistance, in melanoma cells

“…It has also undergone phase I and II trials for paediatric neuroblastoma (NCT00436852), which found ABT-751 to be well tolerated but not associated with increased objective response rate or time to progression [ 23 ]. Recent pre-clinical studies have examined ABT-751 as a potential treatment for urinary bladder urothelial carcinoma and p53-deficient hepatocellular carcinoma [ 24 , 25 ]. ABT-751 has a similar mechanism of action to the taxanes, but while the taxanes are substrates for P-gp, a study using an in vivo xenograft model suggests that ABT-751 is not [ 26 ] and can overcome P-gp-mediated resistance.…”