TUMOR SUPPRESSIVE ACTION OF INDOMETHACIN IS NK-CELL-INDEPENDENT

This study was undertaken to determine whether NK-cells constitute a n ecessary mediator for the suppression of tumor growth by indomethacin. C57Bl mice with a methylcholantrene (MCG 101) tumor were studied. Ind omethacin treatment was provided by daily subcutaneous injections (1 m u g /g body weight). NK-cells were depleted by treatment with a monocl onal antibody to NK1.1. Consecutive indomethacin injections prolonged survival in tumor bearing animals. Indomethacin was equally effective in animals with intact NK-cells as in NK-cell-depleted animals Further , the MCG cells were apparently insensitive to the lyric activity of N K-cells in vivo. Thus, the clearance of intravenously injected MCG cel ls from lungs was nor affected by depletion of NK-cells in vivo; in co na ast, the corresponding clearance of; NK-cell-sensitive YAC-I lympho ma cells was strikingly reduced by the depletion of NK-cells. Our data suggest that NK cells are not a necessary mediator for the suppressio n of tumor growth by indomethacin.