Combination of Enzastaurin, a PKC Inhibitor, and Revlimid ® has Synergistic Activity In Non-Hodgkin Lymphoma

Abstract 4905

A curative treatment does not exist for indolent lymphoma and eventually patients die for progression and complications related to their disease. Thus, there is a need of new less toxic and more active treatment. Enzastaurin, a novel targeted agent, inhibits PKC-β by interacting competitively as its ATP-binding site. Several studies have shown that enzastaurin exhibits growth inhibiting effects on a wide array of cultured human tumour cells. Revlimid ® (lenalidomide), an oral immunomodulatory drug, have shown antineoplastic activity in various tumours, including multiple myeloma (MM), myelodysplastic syndrome (MDS), B-CLL, renal-cell carcinoma and prostate cancer and it is approved for the treatment of patients with MM and MDS bearing a deletion 5q. In the present research, we demonstrate that Revlimid ® alone induce G0/G1 arrest in WSU-NHL cell line, but not apoptosis. This would suggest that, in vitro, Revlimid ® has more a cytostatic than a cytotoxic effect in this cell line. Further, we have demonstrated that the combination of doses as low as 1 mM of Enzastaurin and Revlimid ® exerts, in vitro, a strong synergistic anti lymphoma activity. We also have showed that the combination decreases viability and induce apoptosis in B-cell lymphoma cell lines and peripheral blood mononuclear cells (PBMCs) from follicular lymphoma (FL) patients. The combination has no effect on normal PBMC and suppresses cell proliferation of B-cell lymphoma cell lines when co-cultured with bone marrow stromal cells (BMSCs) in a system that mimics the BM microenvironment. The combination induces a significantly higher rate of apoptosis in comparison with these caused by each agents utilized alone, as showed by flow cytometry. The combination activates both the extrinsic and intrinsic pathways of apoptosis resulting in caspase-8, caspase-9, caspase-3 and PARP cleavage. Furthermore, we have evaluated whether the combination has the ability to trigger apoptosis through BAD and we have showed its ability to activate BAD. Further, we have demonstrated that the combination decreases the expression of phosphorylated AKT and of some AKT downstream targets such as GSK-3β, m-TOR and p70S6. In addition, we have found that the combination reduces the activation of phosphorylated MAPK and of the downstream effector p90RSK. The MAPK signaling pathways have a multiple roles in natural processes such as cell growth, differentiation, and apoptosis. Taken together, these observations suggest that interrupting the PI3K/AKT and MAPK pathways is a promising therapeutic strategy against B-cell lymphoma cell lines.

Therefore, these preclinical data, together with promising results obtained with Revlimid ® in the treatment of non-Hodgkin lymphoma, provide the rationale for evaluating the combination of Enzastaurin and Revlimid ® in the treatment of indolent lymphoma.

These compounds, with a favourable toxicity profile, are not classic chemotherapeutic agents causing severe side effects and could be considered an example of a new innovative attempt of an anti-cancer “soft treatment”.