Increased natural killer cell activity correlates with low or negative expression of the HER-2/neu oncogene in patients with breast cancer

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Abstract
Background. Increased expression of the HER‐2/neu oncogene in breast cancer correlates with decreased estrogen receptor concentration and seems to be an important prognostic factor. The authors investigated whether there is a correlation between HER‐2/neu expression and immunologic parameters representing tumor defense in patients with breast cancer. Method. A Western blot analysis was used to investigate HER‐2/neu expression, whereas a chromium‐release assay using the K562 cell line as target was used to measure natural killer (NK) cell activity. Results. In patients with breast cancer, NK cell activity was significantly higher compared with patients with benign tumors (P = 0.006) or healthy control subjects (P = 0.002). Moreover, 23.3% of patients with breast cancer showed an overexpression of HER‐2/neu protein. Within this group of patients, NK cell activity was significantly lower (45.6 ± 16.1%) compared with the group with no HER‐2/neu overexpression (57.3 ± 11.0%). NK cell activity did not increase in patients with HER‐2/neu overexpression. Thus, there was a statistically significant correlation of cytolytic effector cell function with HER‐2/neu expression of the tumor (P = 0.003), and HER‐2/neu overexpression correlated with a negative estrogen receptor status (P = 0.005). Conclusion. These data add further evidence to previous observations from the authors' laboratory that certain tumor characteristics may be associated with reactions of the host with breast cancer.