INCREASED NATURAL-KILLER-CELL ACTIVITY CORRELATES WITH LOW OR NEGATIVE EXPRESSION OF THE HER-2 NEU ONCOGENE IN PATIENTS WITH BREAST-CANCER/

Background. Increased expression of the HER-2/neu oncogene in breast c ancer correlates with decreased estrogen receptor concentration and se ems to be an important prognostic factor. The authors investigated whe ther there is a correlation between HER-2/neu expression and immunolog ic parameters representing tumor defense in patients with breast cance r. Method. A Western blot analysis was used to investigate HER-2/neu e xpression, whereas a chromium-release assay using the K562 cell line a s target was used to measure natural killer (NK) cell activity. Result s. In patients with breast cancer, NK cell activity was significantly higher compared with patients with benign tumors (P = 0.006) or health y control subjects (P = 0.002). Moreover, 23.3% of patients with breas t cancer showed an overexpression of HER-2/neu protein. Within this gr oup 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 correlati on of cytolytic effector cell function with HER-2/neu expression of th e tumor (P = 0.003), and HER-2/neu overexpression correlated with a ne gative estrogen receptor status (P = 0.005). Conclusion. These data ad d further evidence to previous observations from the authors' laborato ry that certain tain tumor characteristics may be associated with reac tions of the host with breast cancer.