mk-1775 and Sarcoma

Research into the biology of soft tissue sarcomas has uncovered very few effective treatment strategies that improve upon the current standard of care which usually involves surgery, radiation, and chemotherapy. Many patients with large (>5 cm), high-grade sarcomas develop recurrence, and at that point have limited treatment options available. One challenge is the heterogeneity of genetic drivers of sarcomas, and many of these are not validated targets. Even when such genes are tractable targets, the rarity of each subtype of sarcoma makes advances in research slow. Here we describe the development of a synergistic combination treatment strategy that may be applicable in both soft tissue sarcomas as well as sarcomas of bone that takes advantage of targeting the cell cycle. We show that Rb-positive cell lines treated with the CDK4/6 inhibitor palbociclib reversibly arrest in the G

Topics: Animals; Cell Cycle Checkpoints; Cell Cycle Proteins; Cell Line, Tumor; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Disease Models, Animal; Drug Resistance, Neoplasm; Gene Knockdown Techniques; Humans; Male; Mice; Nuclear Proteins; Piperazines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyrazoles; Pyridines; Pyrimidines; Pyrimidinones; Retinoblastoma Protein; Sarcoma; Xenograft Model Antitumor Assays

Wee1 is a critical component of the G(2)-M cell-cycle checkpoint control and mediates cell-cycle arrest by regulating the phosphorylation of CDC2. Inhibition of Wee1 by a selective small molecule inhibitor MK1775 can abrogate G(2)-M checkpoint, resulting in premature mitotic entry and cell death. MK1775 has recently been tested in preclinical and clinical studies of human carcinoma to enhance the cytotoxic effect of DNA-damaging agents. However, its role in mesenchymal tumors, especially as a single agent, has not been explored. Here, we studied the cytotoxic effect of MK1775 in various sarcoma cell lines and patient-derived tumor explants ex vivo. Our data show that MK1775 treatment at clinically relevant concentrations leads to unscheduled entry into mitosis and initiation of apoptotic cell death in all sarcomas tested. In MK1775-treated cells, CDC2 activity was enhanced, as determined by decreased inhibitory phosphorylation of tyrosine-15 residue and increased expression of phosphorylated histone H3, a marker of mitotic entry. The cytotoxic effect of Wee1 inhibition on sarcoma cells seems to be independent of p53 status as all sarcoma cell lines with different p53 mutation were highly sensitive to MK1775 treatment. Finally, in patient-derived sarcoma samples, we showed that MK1775 as a single agent causes significant apoptotic cell death, suggesting that Wee1 inhibition may represent a novel approach in the treatment of sarcomas.

Topics: Antineoplastic Agents; Apoptosis; CDC2 Protein Kinase; Cell Cycle Checkpoints; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Cyclin B; Cyclin-Dependent Kinases; Histones; Humans; Mitosis; Nuclear Proteins; Phosphorylation; Protein-Tyrosine Kinases; Pyrazoles; Pyrimidines; Pyrimidinones; Sarcoma; Tumor Suppressor Protein p53