pf-477736 and Lymphoma--Mantle-Cell

Mantle cell lymphoma (MCL) is an aggressive, incurable disease, characterized by a deregulated cell cycle. Chk1 and Wee1 are main regulators of cell cycle progression and recent data on solid tumors suggest that simultaneous inhibition of these proteins has a strong synergistic cytotoxic effect. The effects of a Chk1 inhibitor (PF-00477736) and a Wee1 inhibitor (MK-1775) have been herein investigated in a large panel of mature B-cell lymphoma cell lines. We found that MCL cells were the most sensitive to the Chk1 inhibitor PF-00477736 and Wee1 inhibitor MK-1775 as single agents. Possible involvement of the translocation t(11;14) in Chk1 inhibitor sensitivity was hypothesized. The combined inhibition of Chk1 and Wee1 was strongly synergistic in MCL cells, leading to deregulation of the cell cycle, with increased activity of CDK2 and CDK1, and activation of apoptosis. In vivo treatment with the drug combination of mice bearing JeKo-1 xenografts (MCL) had a marked antitumor effect with tumor regressions observed at non-toxic doses (best T/C%=0.54%). Gene expression profiling suggested effect on genes involved in apoptosis. The strong synergism observed by combining Chk1 and Wee1 inhibitors in preclinical models of MCL provides the rationale for testing this combination in the clinical setting.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Apoptosis Regulatory Proteins; Benzodiazepinones; CDC2 Protein Kinase; Cell Cycle Checkpoints; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Checkpoint Kinase 1; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinases; Dose-Response Relationship, Drug; Drug Synergism; Female; Gene Expression Profiling; Humans; Inhibitory Concentration 50; Lymphoma, Mantle-Cell; Mice, Nude; Molecular Targeted Therapy; Nuclear Proteins; Protein Kinase Inhibitors; Protein Kinases; Protein-Tyrosine Kinases; Pyrazoles; Pyrimidines; Pyrimidinones; Time Factors; Xenograft Model Antitumor Assays

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma characterized by the chromosomal translocation t(11;14) that leads to constitutive expression of cyclin D1, a master regulator of the G1-S phase. Chk1 inhibitors have been recently shown to be strongly effective as single agents in MCL. To investigate molecular mechanisms at the basis of Chk1 inhibitor activity, a MCL cell line resistant to the Chk1 inhibitor PF-00477736 (JEKO-1 R) was obtained and characterized. The JEKO-1 R cell line was cross resistant to another Chk1 inhibitor (AZD-7762) and to the Wee1 inhibitor MK-1775. It displayed a shorter doubling time than parental cell line, likely due to a faster S phase. Cyclin D1 expression levels were decreased in resistant cell line and its re-overexpression partially re-established PF-00477736 sensitivity. Gene expression profiling showed an enrichment in gene sets involved in pro-survival pathways in JEKO-1 R. Dasatinib treatment partly restored PF-00477736 sensitivity in resistant cells suggesting that the pharmacological interference of pro-survival pathways can overcome the resistance to Chk1 inhibitors. These data further corroborate the involvement of the t(11;14) in cellular sensitivity to Chk1 inhibitors, fostering the clinical testing of Chk1 inhibitors as single agents in MCL.

Topics: Antineoplastic Agents; Benzodiazepinones; Cell Cycle; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Checkpoint Kinase 1; Cyclin D1; Dasatinib; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Humans; Lymphoma, Mantle-Cell; Molecular Targeted Therapy; Nuclear Proteins; Protein Kinase Inhibitors; Protein Kinases; Protein-Tyrosine Kinases; Pyrazoles; Pyrimidines; Pyrimidinones; Signal Transduction; src-Family Kinases; Thiophenes; Time Factors; Urea