COMPARISON OF NATURAL-KILLER (NK) SENSITIVITIES OF 2 TUMOR-CELL LINESESTABLISHED FROM A CANCER-PATIENT BEFORE AND AFTER RADIATION-THERAPY

Major histocompatibility complex (MHC) class I positive tumor cells ar e generally resistant to natural killer (NK) cells. In this report, we compared the NK sensitivities of tumor cell lines H41 and H42, which were established from a cancer patient at surgery. H41 was established before radiation therapy and H42 was established after the radiation therapy in 1985. H41 was resistant to NH cells, whereas H42 was NH-sen sitive. Both cell lines reacted with W6/32, which is an antibody to th e HLA common epitope determinant. However, H42 did not react to anti-H LA-locus-specific antibodies, although H41 reacted to them. When these cell lines were treated with interferon-gamma, H41 showed an increase in HLA-locus-specific antigenicity, whereas H42 did not show such a t endency. This suggests that there may have been interference in the ex pression of the HLA-locus-specific determinants on H42. Therefore, it was assumed that the NH sensitivity of H42 may be due to depression of an HLA-locus-specific determinant, and this depression may be related to the radiation therapy. The patient recovered from the disease afte r the radiation therapy and the last surgery. He is now in a tumor-fre e state. We propose that his recovery may be related to the conversion of the tumor cells from NK-resistant to NK-sensitive. (C) 1997 Academ ic Press.