Influence of NKG2D/DNAM-1 interaction with tumor cell ligands on the ability of lenalidomide to enhance ADCC of antibody-coated solid tumor cells.

Abstract

e21008 Background: Lenalidomide has been shown to enhance the antibody- dependent cellular cytotoxicity (ADCC) of rituximab-treated B cell chronic lymphocytic leukemia (B-CLL) and non-Hodgkin lymphoma (NHL) tumor cells. The combination appears to be especially active in patients so we sought to build on these observations by determining lenalidomide's ability to enhance ADCC of solid tumor cells. Methods: Purified NK cells were used as effector cells and tumor cell lines were used as targets after pre-treatment with cetuximab or trastuzumab. 23 tumor cell lines were used; 11 colorectal (CRC), 3 breast, 3 ovary, 2 lung, 2 head and neck and 2 bone sarcoma. Cytotoxicity was assessed using a standard lactate dehydrogenase release assay and specific lysis calculated. NK cell expression of activating receptors from 30 donors and tumor cell expression of NK cell ligands were assessed by flow cytometry. Results: Lenalidomide increased NK cell-specific lysis of cetuximab-coated CRC cells; HCT- 116, from 19% to 39% (p < 0.01), HT-29, 32% to 50% (p < 0.05) and also of trastuzumab-coated breast cancer cells; SKBR-3, 32% to 44% (p < 0.01), MCF-7, 30% to 70% (p < 0.01). Variable sensitivity of CRC cell lines was dependent on EGFR expression (range 5%-96%) but independent of either KRAS or BRAF mutational status or FCγRIIIa genotype. CRC cell line expression of NK cell ligands, PVR, MIC-A, ULBP2 and ULBP3 correlated with sensitivity to ADCC. NK cell expression of DNAM-1, NKG2D, but not NKp46, correlated with the extent of ADCC and its enhancement by lenalidomide. Antibody blocking of NKG2D, and to a lesser extent DNAM-1, inhibited CRC cell killing from 70% to 31% and 48% respectively (both p < 0.05), whereas blocking of individual cognate ligands had minimal effect. Lenalidomide enhanced NK cell production of gmcsf, IL-8, MIP-1α/βm RANTES, MCP-1 and IP-10 but reversed phosphorylation of Src family kinases induced by antibody alone. Conclusions: Lenalidomide enhances the ADCC of solid tumor cells, the extent of which is largely dependent on NKG2D/NKG2D ligand interactions, providing a rationale for exploratory clinical studies and assessment of potential biomarkers predictive lenalidomide-mediated ADCC. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Celgene Celgene