The Prognostic Significance of Intratumoral Natural Killer Cells in Colorectal Cancer

ABSTRACT

PURPOSE: Natural killer (NK) cells have a spontaneous cytotoxic capacity against tumor cells. NK cell infiltration is known to be related to the prognosis of colorectal cancer, but their prognostic significance has not been determined. The purpose of this study was to determine the prognostic importance of NK cell infiltration in colorectal cancer. METHODS: Ninety-one patients, diagnosed with colorectal cancer, between Jan. 1994 to Dec. 1995, and consequently operated on at the Department of surgery, Korea University college of medicine, were retrospectively reviewed. Immunohistochemical stains were performed for NK cells using the monoclonal antibody CD57 (IOT-10; 1 50 diluted; Chemicon, Temccula, U.S.A.). The intratumoral CD57 expressions were divided into 4 grades. Intensity 0 was defined as a total absence of CD57 expression in the tumor cells, Intensities 1+, 2+ and 3+ were defined as less than 25, 25~50 and more than 50% expression, respectively. Consecutively, intensities 0, 1+ and 2+ were regarded as low CD57 expression, with 3 regarded as high CD57 expression. The clinical characteristics, 5-year survival rates and recurrence rates by stage, according to the CD57 expression, were then analyzed. RESULTS: Patients with high CD57 expression showed better survival rates and lower recurrence rates than those with low CD57 expressions (77.8 versus 53.4% and 14.8 versus 25.0%, respectively, P=0.0856). According to stage, the patient with high CD57 expressions showed better survival rates than those with low CD57 expressions in stages II and III (76.4 versus 69.9% [P=0.6802] and 66.7 versus 40.0% [P=0.4496], respectively). CONCLUSION: Although there was not statistical significance, these data suggest that high intratumoral infiltration of NK cells, as determined by the CD57 expression, seems to be a favorable prognostic factor in colorectal cancer, although further study will be needed.