Small Molecule PRIMA-1met Induces Apoptosis in Waldenstrom Macroglobulinemia Cells and Exhibits a Synergistic Cytotoxic Response with Dexamethasone
Kim Kwan, Manujendra N Saha, Sukhoon Koh, Lili Zhang, Christine Chen, Hong Chang. University Health Network, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; Princess Margaret Hospital, Toronto, ON, Canada
Background: Waldenstrom macroglobulinemia (WM) is a lymphoplasmacytic lymphoma characterized by IgM monoclonal gammopathy. PRIMA-1met, a small molecule with the ability to restore wild type conformation and function to p53, has previously been demonstrated its ability to induce apoptosis in several types of human cancers. Dexamethasone is a corticosteroid commonly used in combination with other chemotherapeutic agents in the treatment of WM. Here we examined the antitumor activity of PRIMA-1met alone and in combination with dexamethasone in WM.
Design: Two human WM cell lines, BCWM.1 and MWCL-1, with different p53 status were treated with PRIMA-1met alone or in combination with dexamethasone. Cells treated with these agents were assessed for cell viability by MTT assay and apoptosis induction by Annexin-V binding measured by Flow cytometry. In addition, peripheral blood mononuclear cells obtained from three healthy donors and primary samples from two WM patients were treated with PRIMA-1met and viability of the cells was measured by MTT assay. Expression of p53 and apoptotic targets was examined by Western blot analysis.
Results: Treatment of both WM cell lines with PRIMA-1met resulted in a significant decreased in the viability of WM cells, with an observed IC50 of 26 μM in BCWM.1 cells and 30 μM in MWCL-1 cells. In addition, treatment of the cells with 25 μM PRIMA-1met and 1 μM or 4 μM dexamethasone produced a synergistic cytotoxic response (CI=0.5-0.6) in these cell lines. Importantly, PRIMA-1met exhibited cytotoxicity in cells isolated from two WM patient samples in a dose-dependent manner whereas PRIMA-1met showed minimal cytotoxic response in three healthy donor samples at the same concentrations. In addition, incubation of WM cells with PRIMA-1met caused a significant increase of cells positive for Annexin-V binding compared to the cells treated with DMSO control. Furthermore, treatment of WM cells with PRIMA-1met resulted in a time and dose-dependent activation of p53, caspase-3, and PARP as well as up-regulation of a proapoptotic protein, PUMA.
Conclusions: Our results demonstrate potent antitumor activity of PRIMA-1met either alone or in combination with dexamethasone in WM cells and thus provide the preclinical framework for evaluation of PRIMA-1met as a novel therapeutic approach for the treatment of WM patients.
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 169, Tuesday Morning