Roscovitine Sensitizes Leukemia and Lymphoma Cells to TRAIL-Induced Apoptosis and Enhances Cell-Mediated Cytotoxicity

• Published in: Blood 2010-11, Vol.116 (21), p.596-596
• Main Authors: Molinsky, Jan, Markova, Marie, Klanova, Magdalena, Koc, Michal, Beranova, Lenka, Andera, Ladislav, Ludvikova, Zdenka, Bohmova, Martina, Gasova, Zdenka, Trneny, Marek, Necas, Emanuel, Zivny, Jan, Klener, Pavel
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V116.21.596.596

Abstract 596 Roscovitine is a selective inhibitor of cyclin-dependent kinases (CDK) and it is under evaluation in several clinical trials in the treatment of diverse cancers. TNF-related apoptosis inducing ligand (TRAIL) is a death ligand important for tumor immunosurveillance with selective antitumor activity and minimal toxicity toward tissues. Soluble TRAIL is also under evaluation in several clinical trials. Unfortunatelly, many cancers are resistant to TRAIL. To circumvent TRAIL resistance, there is effort to combinate TRAIL with other cytotoxic agents. By measuring apoptosis and proliferation, we demonstrated that combination of low dose roscovitine and low dose TRAIL (low dose= up to 30% of apoptotic cells after 24h treatment) is synergistic in 20 of 21 tested hematologic cell lines including TRAIL resistant cell lines. Moreover, this combination was tested on primary cells from 9 patients with hematologic malignancies with synergism in 4 of 8 samples from patients with acute myeloid leukemia (AML) and 1 sample from patient with mantle cell lymphoma. Remaining 4 AML samples showed additive effect. Based on these results, we decided to explore molecular mechanisms responsible for the synergism between roscovitine and TRAIL using TRAIL-resistant K562 cells. Despite decreased mRNA, the surface expression of TRAIL receptors remained unaffected after 24h roscovitine treatment. Immunoprecipitation of death-inducing signaling complex (DISC) revealed distinct proapoptotic changes (enhanced CASP8 and 10, reduced FLIP at 12 and 24h). These proapoptotic changes suggested that roscovitine might synergize with other death ligands acting through the DISC, namely TNF and FASLG. Indeed, roscovitine significantly sensitized diverse cell lines (K562, DOHH2, RAMOS) to TNF or FASLG-induced apoptosis. We subsequently proved that pretreatment of the cells (K562, DOHH2, RAMOS) with roscovitine increased by approx. 20% the level of cell-mediated cytotoxicity (peripheral blood mononuclear cells from a healthy volunteer marked with carboxyfluorescein succinimidyl ester). Thus, proapoptotic changes of the DISC seem to play essential role in mediating roscovitine-induced sensitization to TRAIL. Despite detected alterations of the DISC, we decided to unveil additional potential changes in the protein levels of key apoptotic regulators by western blotting at 1.5, 3, 6, 12 and 24h timepoints. Like Ortiz-Ferron et al. we detected gradual downregulation of MCL1 that peaked at 12h,