Comparison of Natural Killer (NK) Sensitivities of Two Tumor Cell Lines Established from a Cancer Patient before and after Radiation Therapy

Abstract

Major histocompatibility complex (MHC) class I positive tumor cells are 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 NK cells, whereas H42 was NK-sensitive. Both cell lines reacted with W6/32, which is an antibody to the HLA common epitope determinant. However, H42 did not react to anti-HLA-locus-specific antibodies, although H41 reacted to them. When these cell lines were treated with interferon-γ, H41 showed an increase in HLA-locus-specific antigenicity, whereas H42 did not show such a tendency. This suggests that there may have been interference in the expression of the HLA-locus-specific determinants on H42. Therefore, it was assumed that the NK 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 after the radiation therapy and the last surgery. He is now in a tumor-free state. We propose that his recovery may be related to the conversion of the tumor cells from NK-resistant to NK-sensitive.