The Fcp1-Wee1-Cdk1 axis affects spindle assembly checkpoint robustness and sensitivity to antimicrotubule cancer drugs

Abstract

To grant faithful chromosome segregation, the spindle assembly checkpoint (SAC) delays mitosis exit until mitotic spindle assembly. An exceedingly prolonged mitosis, however, promotes cell death and by this means antimicrotubule cancer drugs (AMCDs), that impair spindle assembly, are believed to kill cancer cells. Despite malformed spindles, cancer cells can, however, slip through SAC, exit mitosis prematurely and resist killing. We show here that the Fcp1 phosphatase and Wee1, the cyclin B-dependent kinase (cdk) 1 inhibitory kinase, play a role for this slippage/resistance mechanism. During AMCD-induced prolonged mitosis, Fcp1-dependent Wee1 reactivation lowered cdk1 activity, weakening SAC-dependent mitotic arrest and leading to mitosis exit and survival. Conversely, genetic or chemical Wee1 inhibition strengthened the SAC, further extended mitosis, reduced antiapoptotic protein Mcl-1 to a minimum and potentiated killing in several, AMCD-treated cancer cell lines and primary human adult lymphoblastic leukemia cells. Thus, the Fcp1-Wee1-Cdk1 (FWC) axis affects SAC robustness and AMCDs sensitivity.

Fighting tubulin-targeting anticancer drug toxicity and resistance

“…The two so far described APC/C Cdc20 inhibitors, TAME and Apcin, appear promising molecules as they efficiently block mitosis exit in preclinical studies, but are not yet available for clinical use (Zeng et al 2010, Sackton et al 2014. To prevent mitotic slippage, we have proposed a different strategy: inhibiting WEE1, a crucial kinase in the slippage mechanism (Visconti et al 2015a), in combination with AMCDs. Given the clinical availability of a WEE1 inhibitor, it would be worth establishing clinical trials in which the WEE1 inhibitor is combined with AMCDbased therapy.…”

“…Indeed, we have demonstrated that targeting FCP1 or WEE1 by siRNAs delayed SAC adaptation and mitotic slippage in taxane-treated cancer cell lines. Moreover, remarkably, we have shown that, in vinca alkaloid-treated primary leukemic blasts isolated from bone marrow specimens of lymphoblastic leukemia patients, the addition of AZD1775 significantly prolonged mitosis, resulting in reduced viability (Visconti et al 2015a). Thus, AZD1775, by delaying mitotic slippage, limits the occurrence of AMCD resistance in cell cultures, a promising starting point to further tests in preclinical and clinical settings.…”

“…Our suggestion is based on a novel role for WEE1 kinase at mitosis in regulating SAC adaptation (Visconti et al 2015a(Visconti et al , 2016. As illustrated in Fig.…”

“…More recently, we found that the FCP1-WEE1 pathway also has a crucial role in the mechanisms by which cells adapt to the SAC. Indeed, we found that FCP1-WEE1 pathway becomes progressively activated during SAC-dependent mitosis arrest induced by AMCDs, and this progressively lowers CDK1 activity to a point in which the mitotic state cannot be maintained, leading cells to exit mitosis despite incompletely assembled spindles (Visconti et al 2015a(Visconti et al ,b, 2016. Thus, we hypothesized that inhibiting WEE1 would enforce arrest in mitosis, synergizing with AMCDs in provoking mitotic catastrophe.…”

“…Nevertheless, strategies to increase cancer cell sensitivity to AMCDs are highly anticipated, in the hope to reduce the occurrence of resistance and toxicity. Recently, by studying the mechanisms by which cancer cells adapt to an active SAC and exit mitosis despite spindle malformation, we have been working on a new way to improve AMCD efficacy that is centered on sustaining the AMCD-induced, SACdependent, mitotic arrest to restrain mitotic slippage until the apoptotic threshold is reached (Visconti et al 2015a(Visconti et al ,b, 2016. As mechanistically detailed below, we propose to combine AMCD treatment with AZD1775, a drug that inhibits WEE1 kinase (Hirai et al 2009, Matheson et al 2016.…”