Inhibition of Wee1 Sensitizes Cancer Cells to Antimetabolite Chemotherapeutics In Vitro and In Vivo, Independent of p53 Functionality

Abstract

Inhibition of Wee1 is emerging as a novel therapeutic strategy for cancer, and some data suggest that cells with dysfunctional p53 are more sensitive to Wee1 inhibition combined with conventional chemotherapy than those with functional p53. We and others found that Wee1 inhibition sensitizes leukemia cells to cytarabine. Thus, we sought to determine whether chemosensitization by Wee1 inhibition is dependent on p53 dysfunction and whether combining Wee1 inhibition is tolerable and effective in vivo. Synergistic inhibition of proliferation with a Wee1 inhibitor in clinical development, MK1775, and cytarabine was observed in all acute myeloid leukemia (AML) cell lines tested, regardless of p53 functionality. Mechanistic studies indicate that inhibition of Wee1 abrogates the S-phase checkpoint and augments apoptosis induced by cytarabine. In AML and lung cancer cell lines, genetic disruption of p53 did not alter the cells' enhanced sensitivity to antimetabolites with Wee1 inhibition. Lastly, mice with AML were treated with cytarabine and/or MK1775. The combination of MK1775 and cytarabine was well-tolerated in mice and enhanced the anti-leukemia effects of cytarabine, including survival. Thus, inhibition of Wee1 sensitizes hematologic and solid tumor cell lines to antimetabolite chemotherapeutics, whether p53 is functional or not, suggesting that the use of p53 mutation as a predictive biomarker for response to Wee1 inhibition may be restricted to certain cancers and/or chemotherapeutics. These data provide preclinical justification for testing MK1775 and cytarabine in patients with leukemia.

Synergistic anti-leukemic interactions between panobinostat and MK-1775 in acute myeloid leukemia ex vivo

“…36,40,51,52 The combined cytarabine and MK-1775 treatments resulted in synergistic inhibition of proliferation, regardless of p53 status. 40 It has been demonstrated that cytarabine-induced S-phase cell cycle arrest was overcome by the addition of MK-1775.…”

“…36,40,51,52 The combined cytarabine and MK-1775 treatments resulted in synergistic inhibition of proliferation, regardless of p53 status. 40 It has been demonstrated that cytarabine-induced S-phase cell cycle arrest was overcome by the addition of MK-1775. 40, 51,52 Tibes et al used an RNAi screening approach to identify kinases involved in cytarabine sensitivity and found ATR, PKMYT1, and CHK1, among others, as kinases involved in cytarabine sensitivity.…”

“…[16][17][18]39,40 Recent studies have investigated the combination of Wee1 and CHK1 inhibitors in preclinical models of different malignancies and have also found promising activity. 39,41,42 In addition, we have previously demonstrated that activation of CHK1 was a potential mechanism of resistance to MK-1775 which could be overcome by the addition of a CHK1 selective inhibitor.…”

“…40 It has been demonstrated that cytarabine-induced S-phase cell cycle arrest was overcome by the addition of MK-1775. 40, 51,52 Tibes et al used an RNAi screening approach to identify kinases involved in cytarabine sensitivity and found ATR, PKMYT1, and CHK1, among others, as kinases involved in cytarabine sensitivity. 36 In addition, they demonstrated synergistic anti-leukemic activity for combined MK-1775 and cytarabine treatment in cell line models.…”

Cytokinetic effects of Wee1 disruption in pancreatic cancer

“…13 Several clinical trials are underway combining MK-1775 with conventional chemotherapy agents such as gemcitabine, where the effects relieving Weel 0 s restraint of Cdk2 during S-phase might be particularly relevant. 7,15,20,22 There is also a longstanding interest combining checkpoint inhibitors with radiotherapy, since this might differentially improve the radiation response of p53-deficient cancers, where the G1 checkpoint that normally facilitates repair is compromised. Here the anticipated effect of Wee1 inhibition would be to abrogate the G2 checkpoint, resulting in cells entering mitosis with unresolved radiation-induced chromosomal damage, and thereby undergoing death through mitotic catastrophe.…”