Background and objective: Several studies have Shown the correlation of high numbers of tumor-infiltrating natural killer (NK) cells with a good prognosis for cancer patients. This study was to investigate the impact of NK cell infiltration on the survival and prognosis of patients with hepatocellular carcinoma (HCC) after resection.
Methods: The proportion of infiltrating NK cells of HCC patients was measured using flow cytometry, and the expression of CD56+ (NK) cells was investigated using immunohistochemistry. Prognostic values of intratumoral and peritumoral NK cell densities were evaluated by Kaplan-Meier method and Cox regression.
Results: The level of NK cells was significantly lower in tumor-infiltrating lymphocytes (TIL) of HCC patients than in nontumor-infiltrating lymphocytes (NIL) [(11.8 +/- 8.1)% vs. (18.0+/-7.9)%, P=0.002]. The density of NK cells was also significantly lower in cancer nests than in peritumoral lesions (2.3 +/- 2.6 vs. 8.5 +/- 4.5 cells per field, P<0.001). Patients with low intratumoral NK cells had shorter disease-free survival (P=0.027) and overall survival (P=0.005) than patients with high intratumoral NK cells. In contrast, NK cells in the peritumoral area showed no prognostic significance for either disease-free survival or overall survival. Multivariate Cox proportional hazards analysis showed that intratumoral NK cell density was an independent prognostic factor of prolonged overall survival (hazard ratio = 2.658, P=0.019).
Conclusion: Low NK cells infiltration could predict poor prognosis in patients with HCC.