The Nucleoside Analogue Acadesine Exerts Antitumoral Activity and Cooperates with Conventional Agents In In Vitro and In Vivo Models of Mantle Cell Lymphoma

Abstract 3918

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm characterized by the t(11;14)(q13:q32) that involves cyclin D1 overexpression and consequent cell cycle deregulation at the G1 phase. This entity is generally characterized by an aggressive course and a bad prognosis. Recently, a specific subtype of MCL has been described, showing best outcomes and that might be managed more conservatively than conventional MCL. These cases are characterized by non-nodal presentation, predominantly hypermutated IgVH, lack of genomic complexity, and absence of SOX11 expression. Acadesine is a nucleoside analogue initially developed as a cardioprotective agent, and which has shown a wide range of metabolic effects, including the activation of AMP-activated protein kinase (AMPK). Acadesine was shown to induce apoptosis in primary cells from several B lymphoid neoplasms and has been entered in a phase I/II clinical trial with relapsed/refractory chronic lymphocytic leukemia (CLL) patients. This clinical study has shown that acadesine plasmatic levels in the micro molar range are achievable and safe when CLL patients are treated with the drug. To evaluate the antitumoral properties of acadesine in MCL, we exposed a set of 11 MCL primary cultures and 9 MCL cell lines for up to 48h with increasing doses of the drug. Cytotoxicity and cytostatic effects were then assessed by flow cytometry detection of annexinV/propidium iodide labeling and MTT proliferation assay, respectively. In both MCL cell lines and MCL primary cultures, we observed a heterogeneous response to the drug, with no correlation to common genetic alterations such as deletion/mutation of P53, ATM or P16 genes. JVM2, Jeko-1, Rec-1 and UPN-1 were the more sensitive cell lines, with a mean lethal dose 50 (LD50) of 1.57 mM at 24 h and 0.95 mM at 48h, while 2 cell lines (HBL-2 and Granta-519) showed a primary resistance to the compound (LD50 > 50 mM). Among MCL primary cultures, acadesine showed selective cytotoxic activity against malignant B cells while sparing accompanying T cells. Of note, those cases corresponding to the indolent MCL group showed increased sensitivity to the drug at 24h of treatment, when compared to conventional MCL cases (p=0.03). We observed that acadesine efficiently activates the intrinsic apoptotic pathway in MCL cells by modulating Bcl-2 family protein levels, leading to conformational activation of Bax and Bak, mitochondrial depolarization, generation of reactive oxygen species and caspases processing. In drug combination assays, acadesine showed a synergistic effect when combined with Rituximab, being the Rituximab-acadesine combination more potent than other Rituximab-based polychemotherapies such as R-bendamustine and R-CHOP. Finally, a daily administration of 400mg/kg acadesine in mice previously inoculated with a MCL xenotransplant significantly reduced tumor burden when compared to control animals, as soon as 7 days of treatment. In summary, these results suggest that acadesine exerts significant antitumoral activity in both in vitro and in vivo model of MCL, and may represent an attractive model for the design of a new therapeutic approach for this entity, especially in patients presenting with the indolent form.