Lower postoperative natural killer cell activity is associated with positive surgical margins after radical prostatectomy.

ABSTRACT

BACKGROUND/PURPOSE: The inflammatory milieu has been firmly established to affect cancer progression. However, the connection between natural killer (NK) cells and prostate cancer (PCa) has not been elucidated. METHODS: Prospective data on NK cell activity (NKA) and NK cell subset distribution patterns were evaluated from 51 patients treated with robot-assisted laparoscopic radical prostatectomy. Whole-blood samples were collected from patients preoperatively and 4-6 weeks postoperatively. The samples were subjected to NKA tests, NK cell number counts, determination of the NKG2D (activating receptor of NK cells), NKG2A (inhibiting receptor), and other surface markers. All the analyses were compared to the clinicopathological characteristics of patients. NKA was estimated by measuring interferon-γ (IFN-γ) levels after stimulation of the peripheral blood with PROMOCA™, which specifically stimulates the release of IFN-γ from NK cells. RESULTS: NKA was lower in patients with PCa than in healthy participants (484.66 vs. 1550 pg/mL). A paired comparison revealed significantly higher NKA postoperatively than preoperatively (1054 vs. 484.66 pg/mL; p = 0.011). Patients with negative surgical margins exhibited significantly higher postoperative NKA and NKA ratio (postoperative NKA/preoperative NKA) than those with positive margins (557 vs. 1921 pg/mL, p < 0.001; 3.6 vs. 1.59, p = 0.024). However, there was no difference in the postoperative NK cell number or the CD56bright/CD16-/CD3- or CD56dim/CD16+/CD3- cell numbers between the negative and positive margin groups. Postoperative NKA was significantly higher in lower-stage (1/2) than in higher-stage (3/4) PCa (1365 vs. 594 pg/mL, p = 0.014). CONCLUSION: NKA was significantly higher postoperatively than preoperatively. Patients with positive surgical margins had lower postoperative NKA than those with negative margins. Lower postoperative NKA was also observed in higher-stage PCa. NKA could be used as a supplemental marker for detecting the remaining tumor cells after prostatectomy in combination of PSA.