Lenalidomide and pomalidomide strongly enhance tumor cell killing in vitro during antibody-dependent cellular cytotoxicity (ADCC) mediated by trastuzumab, cetuximab and rituximab

Abstract

3023 Background: Potential mechanisms of action of lenalidomide and pomalidomide (CC-4047) include anti-angiogenic, anti- proliferative and immunomodulatory activities, e.g., enhancement of T cell and NK cell function. Both drugs appear to enhance T cell activation and Th1-type cytokines in cancer patients. Also, both drugs have been shown to enhance rituximab-mediated protection in a mouse lymphoma model. Methods: We have utilized an in vitro ADCC system to assess the ability of these drugs to enhance human NK cell function in response to the approved therapeutic antibodies trastuzumab, cetuximab and rituximab. Results: Pre-treatment of NK cells with either pomalidomide or lenalidomide greatly enhanced IFN-γ production by NK cells in response to IgG in the presence of either IL-2 or IL- 12. In a series of functional ADCC assays, Her2/neu overexpressing breast cancer cells (SKBR3 & MCF-7) pre-coated with trastuzumab, EGFR positive colorectal cancer cells (HCT-116) pre-coated with cetuximab and NHL cell lines (Namalwa, Farage & Raji) pre-coated with rituximab, were exposed to NK cells pre-treated with pomalidomide, lenalidomide or thalidomide. Both pomalidomide and lenalidomide synergistically increased (up to 6-fold) NK cell-mediated killing of antibody coated tumor cells in a dose-dependent manner. Thalidomide had no effect in this system. There was minimal tumor cell killing by antibody alone or in the absence of antibody. The presence of IL-2 or IL-12 was required to see enhanced killing by either drug. Enhanced ADCC was associated with increased signaling in NK cells, specifically with inhibition of the negative regulator SHIP-1. Other downstream effects on signaling pathways are also being investigated. Monocyte-mediated tumor cell ADCC was also enhanced by both drugs. Conclusions: We have shown that pomalidomide and lenalidomide (but not thalidomide) strongly enhance the ability of therapeutic antibodies to induce ADCC via NK cell/monocyte-mediated killing of tumor cells in vitro. These results provide a strong rationale for combination of either lenalidomide or pomalidomide with antibodies to tumor-specific surface antigens in cancer patients. No significant financial relationships to disclose.