NK cells use a variety of receptors to detect abnormal cells, including tumors and their metastases. However, in the case of melanoma, it remains to be determined what specific molecular interactions are involved and whether NK cells control metastatic progression and/or the route of dissemination. Here we show that human melanoma cell lines derived from LN metastases express ligands for natural cytotoxicity receptors (NCRs) and DNAX accessory molecule-1 (DNAM-1), two emerging NK cell receptors key for cancer cell recognition, but not NK group 2 member D (NKG2D). Compared with cell lines derived from metastases taken from other anatomical sites, LN metastases were more susceptible to NK cell lysis and preferentially targeted by adoptively transferred NK cells in a xenogeneic model of cell therapy. In mice, DNAM-1 and NCR ligands were also found on spontaneous melanomas and melanoma cell lines. Interference with DNAM-1 and NCRs by antibody blockade or genetic disruption reduced killing of melanoma cells. Taken together, these results show that DNAM-1 and NCRs are critical for NK cell–mediated innate immunity to melanoma cells and provide a background to design NK cell–based immunotherapeutic strategies against melanoma and possibly other tumors.
Tadepally Lakshmikanth, Shannon Burke, Talib Hassan Ali, Silvia Kimpfler, Francesco Ursini, Loredana Ruggeri, Marusca Capanni, Viktor Umansky, Annette Paschen, Antje Sucker, Daniela Pende, Veronika Groh, Roberto Biassoni, Petter Höglund, Masashi Kato, Kazuko Shibuya, Dirk Schadendorf, Andrea Anichini, Soldano Ferrone, Andrea Velardi, Klas Kärre, Akira Shibuya, Ennio Carbone, Francesco Colucci
Submitter: Raquel Tarazona | email@example.com
Authors: Javier G. Casado, Rafael Solana, and Graham Pawelec
University of Extremadura. Caceres, Spain
Published June 24, 2009
In a recent issue of the Journal (1), Lakshmikanth et al. analyze the role of NCRs and DNAM-1 receptors in NK cell recognition and killing of melanoma cells. Using cell lines derived from different anatomical sites they show that those from lymph node metastases express ligands for DNAM-1 (DNAM-1L), mainly CD155, and for NCRs, but low levels of ligands for NKG2D (NKG2DL). They also show that DNAM-1 and NCRs are involved in lysis of human melanoma cell lines that express DNAM-1L and NKp44L.
By analyzing the expression of ligands for activating receptors in a larger panel of melanoma cell lines (n=124), we have also shown that 95% expressed DNAM-1L, the majority also CD155, whereas CD112 expression was less frequent. However, the analysis of NKG2DL in our panel shows that eighty percent of these lines expressed MICA/B, and, in a lower extent, ULBPs (2). We also studied the contribution of NK activating receptors to the lysis of melanoma cell lines using the human NK cell line NKL. The NKL-mediated lysis of most melanoma cell lines is NKG2D-dependent (2), whereas lysis of other melanoma cell lines such as the ESTDAB-067 line mainly involves NCRs and DNAM-1 (unpublished results), indicating that both NKG2D and NCRs/DNAM-1 can be involved in NK-mediated killing of melanoma cells. NKG2D-mediated killing of melanoma cells has been previously shown, provided that the appropriate ligands are present (3-5) and several reports suggest that both NCRs and NKG2D are the major receptors contributing to NK cell-mediated lysis of melanoma (3-5). Furthermore, NKG2D has been implicated in the lysis of melanoma cell lines by NK cells expressing low levels of NCRs (3). We also found that in the absence of MHC class I-specific inhibitory signals, several DNAM-1L+/NKG2DL+ melanoma cell lines are resistant to NK cell-mediated lysis suggesting the existence of immunoescape mechanisms as the release of ligands for activating receptors that contributes to defective NK killing (2).
We therefore conclude that the expression of ligands for NK cell activating receptors is variable on different melanoma cells. Simultaneous engagement of several activating receptors contributes to efficient NK cell-mediated lysis of melanoma cells. Moreover, DNAM-1 and NKG2D crosslinking may also contribute to T cell activation. In this scenario, phenotypic characterization of melanoma cells and immunotherapeutic strategies to increase the expression of ligands for NK activating receptors may contribute to the development of more effective therapy for individual patients.