Immunotherapy of malignant melanoma in a SCID mouse model using the highlycytotoxic natural killer cell line NK-92

In this work, we evaluated the potential of the natural killer (NK) cell li ne NK-92 and its IL-2-independent variants NK-92MI and CI, as immunotherapy for melanoma, In vitro, we found that NK-92 was much more cytotoxic to a n umber of human melanoma cell lines than lymphokine-activated killer (LAK) c ells, particularly at low effector/target (E:T) ratios. In vivo treatment o f mice challenged with MEWO melanoma cells with i.v. administered NK-92 and NK-92-MI resulted in a 1.5-2.5-fold increase in average length of survival . NK-92, MI, and CI were also effective against the WM1341 cell line, causi ng a 2-5-fold increase in survival when administered before the malignant c ells. With s.c. injection, MEWO and WM1341 caused a primary tumor mass, sec ondary tumors, and metastatic cells. NK-92 cells reduced WM1341 primary tum or size by 40-90% and MEWO tumors by 30-75%, Similar results were seen with NK-92MI and CI, These data show that NK-92 cells are highly cytotoxic to h uman melanoma cells in vitro and in vivo and suggest that treatment with NK -92 cells may be a potentially effective immunotherapeutic modality in mela noma.