Melanoma cells become resistant to NK-cell-mediated killing when exposed to NK-cell numbers compatible with NK-cell infiltration in the tumor European Journal of Immunology, 05/15/2012

Balsamo M et al. – Melanoma lesions showed a higher HLA–class I expression on tumor cells that were proximal to infiltrating NK cells. In long–term co–cultures, the “protective phenotype” acquired by melanoma cells was lost over time. However this phenomenon was counteracted by down–regulation of relevant activating receptors in co–cultured NK cells. Analysis of different NK–cell–activating cytokines indicated that IL–15 can partially overcome this novel tumor escape mechanism suggesting that IL–15, rather than IL–2, may be eligible for NK cell–based immunotherapy.