Even though some studies have shown possible clinical relationship between molecular subtypes and tumor infiltrating natural killer (NK) cells around tumors, there are few studies showing the clinical relevance of peripheral NK cell activity at diagnosis in female patients with invasive breast cancer. A total of 396 female invasive breast cancer patients who received curative surgical treatment from March 2017 to July 2021 were retrospectively analyzed. NK cell activation-induced interferon-gamma (IFN-γ) secretion measured by enzyme-linked immunosorbent assay was used to measure the activity of peripheral NK cells. Statistical analyses were performed to determine clinical relationships with major clinicopathologic parameters. Quadripartite NK cell activity measured by induced interferon-gamma showed significant relevance with staging and body mass index, and some of the inflammatory serological markers, namely N/L (neutrophil/lymphocyte), P/N (platelet/neutrophil), and P/L (platelet/lymphocyte), showed significantly different NK activity in each interval by univariate analysis. A binary subgroup analysis, setting the IFN-γ secretion cut-off at 100 pg/mL, showed that stage III was significantly increased and axillary lymph node metastasis positivity was increased in the group of IFN-γ < 100 pg/mL, and IFN-γ secretion decreased with an increasing N stage, increased BMI (body mass index), and decreased production of IFN-γ. Following this, the same binary analysis, but with the IFN-γ secretion cut-off at 250 pg/mL, also showed that secretion in stage III was increased in those concentrations with <250 pg/mL, axillary lymph node positivity appeared to be correlated, and BMI ≥ 30 increased in prevalence. Additional ANOVA post hoc tests (Bonferroni) were performed on some serological markers that tended to be somewhat inconsistent. By subgroup analysis with Bonferroni adjustment between the IFN-γ secretion and TNM stage, no significant difference in IFN-γ secretion could be identified at stages I, II, and IV, but at stage III, the IFN-γ secretion < 100 pg/mL was significantly higher than 250 ≤ IFN-γ secretion < 500 pg/mL or IFN-γ secretion ≥ 500 pg/mL. According to this study, stage III was significantly associated with the lowest IFN-γ secretion. Compared to a higher level of IFN-γ secretion, a lower level of IFN-γ secretion seemed to be associated with increased body mass index. Unlike when IFN-γ secretion was analyzed in quartiles, as the IFN-γ secretion fell below 100 pg/mL, the correlation between axillary lymph node positivity and increased N stage, increased BMI, and increased N/L and P/L, which are suggested poor prognostic factors, became more pronounced. We think a peripheral IFN-γ secretion test might be convenient and useful tool for pretreatment risk assessment and selecting probable candidates for further treatment such as immunotherapy in some curable but high-risk invasive breast cancer patients, compared to other costly assaying of tissue NK cell activity at diagnosis.
Keywords: NK cells; breast cancer; interferon-gamma; natural killer cells.