Abstract 2766: Inhibition of Chk1 and Wee1 as a new therapeutic approach in Mantle Cell Lymphoma

Abstract

Abstract Mantle Cell Lymphoma (MCL) is an aggressive lymphoma, for which there is not yet a standard therapy. Deregulation of cell cycle is its main pathogenic feature due to the presence of the t(11;14)(q13;q32) translocation, which leads to cyclin D1 over-expression and to frequent alterations in cell cycle and DNA damage response. Chk1 and Wee1 proteins regulate replication initiation, replication fork stability, and mitotic entry. Combined treatment of Chk1 and Wee1 inhibitors has a strong synergistic cytotoxic effect in solid tumors, but little is known on their effect in hematologic cancer such as lymphomas. The effects of a Chk1 inhibitor (PF-00477736) and a Wee1 inhibitor (MK-1775) alone or in combination was investigated in a panel of 10 MCL cell lines. The PF-00477736 median IC50 value was 30 nM, significantly lower than in 9 solid tumor models (337 nM, p=0.0041) and in 8 hematologic tumors (184 nM, p= 0.0057). The MK-1775 median IC50 value was 106 nM, significantly lower than in solid tumors (615 nM, p<0.0001), but not than in other hematologic cells (287 nM). A strong synergism of the combination was observed in all MCL cell lines. Detailed molecular analysis showed that the combination caused a general deregulation of cell cycle with an increased activity of CDK2 and CDK1 and an activation of apoptosis. Inhibition of the CDK4/6-CyclinD1 complex with the selective inhibitor PD0332991 either strongly or slightly neutralize the cytotoxic effect of PF-00477736 and MK-1775 respectively in Jeko-1 MCL cells. In addition, the sensitivity to PF-00477736 and MK-1775 was higher in 2 multiple myeloma (MM) cell lines bearing the t(11;14) deregulating cyclinD1 than in 3 MM cell lines without the translocation (with median IC50 values 40 times lower for PF-00477736 and two times lower for MK-1775). The combination of Chk1 and Wee1 inhibitors was then tested in vivo in nude mice bearing Jeko-1 MCL and important tumor regressions were observed at drug doses lower than the ones used in solid tumors xenografts (best T/C%=0.54%). Tumor samples obtained from xenografts untreated, treated with single drug or the combination were profiled for gene expression and the analysis corroborated that genes involved in apoptosis were up-regulated after combined treatment in vivo. In conclusion, our data provide a strong preclinical evidence for the role of Chk1 and Wee1 inhibitors as new therapeutic approach in MCL and warrant investigation in clinical setting. Citation Format: Laura Carrassa, Rosaria Chilà, Alessandra Basana, Francesca Ricci, Federica Guffanti, Monica Lupi, Andrea Rinaldi, Luciano Cascione, Francesco Bertoni, Massimo Broggini, Giovanna Damia. Inhibition of Chk1 and Wee1 as a new therapeutic approach in Mantle Cell Lymphoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2766. doi:10.1158/1538-7445.AM2014-2766