Increased HDAC Activity and c-MYC Expression Mediate Acquired Resistance to WEE1 Inhibition in Acute Leukemia.

WEE1 is a cell cycle and DNA damage response kinase that is emerging as a therapeutic target for cancer. AZD1775 is a small molecule inhibitor of WEE1, currently in early phase clinical trials as a single agent and in combination with more conventional anti-neoplastic agents. As resistance to kinase inhibitors is frequent, we sought to identify mechanisms of resistance to WEE1 inhibition in acute leukemia. We found that AZD1775 resistant cell lines are dependent upon increased HDAC activity for their survival, in part due to increased KDM5A activity. In addition, gene expression analyses demonstrate HDAC dependent increase in MYC expression and c-MYC activity in AZD1775 treated resistant cells. Overexpression of c-MYC confers resistance to AZD1775 in cell lines with low baseline expression. Pharmacologic inhibition of BRD4, and thereby c-MYC, partially abrogated resistance to AZD1775. Thus, acquired resistance to WEE1 inhibition may be reversed by HDAC or BRD4 inhibition in leukemia cells.

Dismissal policies for vaccine refusal among US physicians: a literature review.

Childhood vaccination is one of the greatest public health achievements of the 20th century, yet increasingly, parents question the safety of and need for vaccines. This has led to increased rates of vaccine delay and refusal and outbreaks of vaccine-preventable diseases. Physicians struggle with how to respond to families who refuse vaccines, as there are few known effective interventions to convince a family to vaccinate. In the United States, the practice of dismissing families for vaccine refusal appears to be increasing as a strategy for dealing with vaccine refusal. In this review, we review the literature surrounding this controversial practice, starting with the impact that vaccine-refusing families have on medical practices, followed by a review of dismissal policies of US physicians, and ending with a discussion of the ethics of this practice.

Increased activity of both CDK1 and CDK2 is necessary for the combinatorial activity of WEE1 inhibition and cytarabine.

Inhibition of WEE1 is emerging as a promising chemosensitization strategy in many cancers including acute leukemia. Our lab and others have demonstrated that a small-molecule inhibitor of WEE1, AZD1775, sensitizes acute leukemia cells to cytarabine; however, a mechanism of combinatorial activity has remained elusive. Thus, we sought to determine the relative contribution of WEE1 targets CDK1 and CDK2 to the combinatorial activity of AZD1775 and cytarabine. To accomplish this, we expressed "WEE1 resistant" CDK1 (CDK1-AF) and CDK2 (CDK2-AF) constructs in a T-ALL cell line. Expression of CDK1/2-AF together, but neither alone, enhanced the anti-proliferative effects, DNA damage and apoptosis induced by cytarabine. Furthermore, pharmacologic inhibition of CDK1 alone or CDK1 and CDK2 together reduced the combinatorial activity of AZD1775 and cytarabine. Thus, increased activity of both CDK1 and CDK2 in response to WEE1 inhibition is necessary for the combinatorial activity of AZD1775 and cytarabine. This suggests the role of WEE1 in cells with accumulated DNA damage extends beyond regulation of CDK1 and the G2/M checkpoint and highlights the importance of WEE1 in mediating progression through the cell cycle.

A Small-Molecule Inhibitor of WEE1, AZD1775, Synergizes with Olaparib by Impairing Homologous Recombination and Enhancing DNA Damage and Apoptosis in Acute Leukemia.

Although some patients with acute leukemia have good prognoses, the prognosis of adult and pediatric patients who relapse or cannot tolerate standard chemotherapy is poor. Inhibition of WEE1 with AZD1775 has been shown to sensitize cancer cells to genotoxic chemotherapies, including cytarabine in acute myeloid leukemia (AML) and T-ALL. Inhibition of WEE1 impairs homologous recombination by indirectly inhibiting BRCA2. Thus, we sought to determine whether AZD1775 could sensitize cells to the PARP1/2 inhibitor olaparib. We found that combined treatment with AZD1775 and olaparib was synergistic in AML and ALL cells, and this combination impaired proliferative capacity upon drug withdrawal. AZD1775 impaired homologous recombination in olaparib-treated cells, resulting in enhanced DNA damage accumulation and apoptosis induction. This combination enhanced disease control and increased survival in a murine AML model. Furthermore, we demonstrated that combined treatment with AZD1775 and olaparib reduces proliferation and colony formation and increases apoptosis in AML patient samples. In aggregate, these studies raise the possibility of rational combinations of targeted agents for leukemia in patients for whom conventional chemotherapeutics may not be effective or well tolerated. Mol Cancer Ther; 16(10); 2058-68. ©2017 AACR.