Association between natural killer cell activity and the risk of colorectal neoplasia

Background and Aim: Low activity of natural killer (NK) cells is known to be associated with higher risk of cancer, especially with poor prognosis and the presence of colorectal cancer (CRC). We investigated whether NK cells activity differs between subjects with and without colorectal neoplasia (CRN). Methods: A cross-sectional study was performed on 1818 asymptomatic examinees aged ≥ 30 years who underwent NK cell activity test (which quantitates the amount of interferon-γ secreted into the plasma by NK cells) and a colonoscopy as part of a health checkup. Results: The mean age of the study population was 41.4 years. The proportion of overall CRN and advanced CRN was 13.5% (n = 246) and 0.7% (n = 13), respectively. Only one subject was diagnosed with CRC. The median level of NK cell activity was lower in subjects with CRN than in those without CRN (1205 vs 1515 pg/mL, P = 0.009). It was also lower in subjects with non-advanced CRN than in those without CRN (1221 vs 1515 pg/mL; P = 0.036). Moreover, it was lower in subjects with advanced CRN than in those with non-advanced CRN (480 vs 1221 pg/mL; P = 0.028). Subjects with low levels of NK cell activity (< 250 pg/mL) had a higher prevalence of overall CRN (19.0% vs 12.9%, P = 0.024) and advanced CRN (3.4% vs 0.4%, P = 0.001) than those who demonstrated higher level (≥ 250 pg/mL). Conclusions: Natural killer cell activity seemed to decrease along with CRC progression toward the later stages in the adenoma-carcinoma sequence. Its activity may be depressed in relation to progression of neoplasia, even at precancerous stage.