The Checkpoint Kinase Inhibitor AZD7762 Potentiates Chemotherapy-Induced Apoptosis of p53-Mutated Multiple Myeloma Cells

Abstract

DNA cross-linking agents are frequently used in the treatment of multiple myeloma-generating lesions, which activate checkpoint kinase 1 (Chk1), a critical transducer of the DNA damage response. Chk1 activation promotes cell survival by regulating cell-cycle arrest and DNA repair following genotoxic stress. The ability of AZD7762, an ATP-competitive Chk1/2 inhibitor to increase the efficacy of the DNA-damaging agents bendamustine, melphalan, and doxorubicin was examined using four human myeloma cell lines, KMS-12-BM, KMS-12-PE, RPMI-8226, and U266B1. The in vitro activity of AZD7762 as monotherapy and combined with alkylating agents and the "novel" drug bortezomib was evaluated by studying its effects on cytotoxicity, signaling, and apoptotic pathways. The Chk1/2 inhibitor AZD7762 potentiated the antiproliferative effects of bendamustine, melphalan, and doxorubicin but not bortezomib in multiple myeloma cell lines that were p53-deficient. Increased gH2AX staining in cells treated with bendamustine or melphalan plus AZD7762 indicates a greater degree of DNA damage with combined therapy. Abrogation of the G 2 -M checkpoint by AZD7762 resulted in mitotic catastrophe with ensuing apoptosis evidenced by PARP and caspase-3 cleavage. In summary, the cytotoxic effects of bendamustine, melphalan and doxorubicin on p53-deficient multiple myeloma cell lines were enhanced by the coadministration of AZD7762. These data provide a rationale for testing these combinations in patients with relapsed and/or refractory multiple myeloma.

Depletion of RAD17 sensitizes pancreatic cancer cells to gemcitabine

“…The synthetic lethal effect of CHK1 and WEE1 inhibition in combination with DNA-damaging agents has been shown to be dependent on p53 deficiency (Aarts et al, 2012;Chen et al, 2006;Landau et al, 2012;Ma et al, 2012). The tumour suppressor protein p53 is a key regulator of cell-cycle arrest in response to DNA damage.…”

DNA repair pathways in human multiple myeloma

“…132 Importantly, many inhibitors targeting DNA repair pathways (PARP1, DNA-PK, ATM, ATR, MGMT, APE) or cell cycle checkpoints (CHK1, CHK2) have now been developed 66,[146][147][148] and could be useful to induce the death of MMCs in combination with DNA damage inducing drugs to develop therapeutic synthetic lethality. [148][149][150] These inhibitors could be of particular interest for improving response and survival of patients treated with high-dose melphalan and autologous stem cell transplantation. In these patients, only few MMCs (5.5 MMCs/μL after 7 days) may survive in an almost empty bone marrow 9 days after melphalan treatment.…”

Manipulating DNA damage-response signaling for the treatment of immune-mediated diseases

“…Because p53 activation potently enforces the G 1 /S checkpoint, it has been theorized that p53-null tumors are especially dependent on the S and G 2 /M checkpoints to maintain genomic integrity. Therefore, inhibitors of cell cycle checkpoint proteins have largely been developed for the treatment of p53-deficient malignancies (5,21,24,47,48). Meanwhile, MDM2 i s have been developed for use in p53-sufficient malignancies because they have little or no impact in the absence of p53.…”

“…For this reason, it has been speculated that p53-deficient malignant cells are highly dependent on the S and G 2 /M checkpoints for maintaining their genomic integrity. Accordingly, a variety of kinase inhibitors have been developed as cancer therapeutics that inhibit CHK1, CHK2, or WEE1, the known enforcers of these later checkpoints (21,22). We speculated that even though normal T cells have intact p53, their extraordinarily rapid rate of division would also make them exquisitely dependent on the S and G 2 /M checkpoints for survival.…”