Search

Multiple myeloma (MM) patients who receive killer cell Ig-like receptor (KIR) ligandmismatched, T cell-depleted, allogeneic transplantation may have a reduced risk of relapse compared with patients who receive KIR ligand-matched grafts, suggesting the importance of this signaling axis in the natural killer (NK) cell-versus-MM effect. Expanding on this concept, 1P112101 (1-7F9), an anti-inhibitory KIR mAb, enhances NK-ceIl function against autologous MM cells by blocking the engagement of inhibitory KIR with cognate ligands, promoting immune complex formation and NK-ceIl cytotoxicity specifically against MM cell targets but not normal cells. IPH2101 prevents negative regulatory signals by inhibitory KIR, whereas lenalidomide augments NK-cell function and also appears to up-regulate ligands for activating NK-cell receptors on MM cells. Lenalidomide and a murine anti-inhibitory NKcell receptor Ab mediate in vivo rejection of a lenalidomide-resistant tumor. These mechanistic, preclinical data support the use of a combination of IPH2101 and lenalidomide in a phase 2 trial for MM. [ABSTRACT FROM AUTHOR]

IL-15 may have a role in the development of T cell large granular lymphocyte (T-LGL) or NKT leukemias. However, the mechanisms of action and the identity of the cell subset that undergoes leukemic transformation remain elusive. Here we show that in both mice and humans, NKp46 expression marks a minute population of WT NKT cells with higher activity and potency to become leukemic. Virtually 100% of T-LGL leukemias in IL-15 transgenic mice expressed NKp46, as did a majority of human T-LGL leukemias. The minute NKp46- NKT population, but not the NKp46 NKT population, was selectively expanded by overexpression of endogenous IL-15. Importantly, IL-15 transgenic NKp46 NKT cells did not become NKp46+ in vivo, suggesting that NKp46+ T-LGL leukemia cells were the malignant counterpart of the minute WT NKp4+ NKT population. Mechanistically, NKp46+ NKT cells possessed higher responsiveness to IL-is in vitro and in vivo compared with that of their NKp46- NKT counterparts. Furthermore, interruption of IL-15 signaling using a neutralizing antibody could prevent LGL leukemia in IL-15 transgenic mice. Collectively, our data demonstrate that NKp46 identifies a functionally distinct NKT subset in mice and humans that appears to be directly susceptible to leukemic transformation when IL-15 is overexpressed. Thus, IL-15 signaling and NKp46 may be useful targets in the treatment of patients with T-LGL or NKT leukemia. [ABSTRACT FROM AUTHOR]