Immunohistochemical analysis reveals a protective effect of H-ras expression mediated via apoptosis in node-negative breast cancer patients.

Recently, we were able to demonstrate the favourable indication of H-ras expression in the clinically very important group of node-negative breast cancer patients. In order to further resolve a conceivable cellular effect mediated by the H-ras signal transduction pathway, we ascertained the apoptotic activity of the tumor cells of this overall 298 patients group. To this end, fragmented genomic DNA of breast cancer tissue was determined by specific DNA-end-labelling and subsequent visualization, thereby indicating early apoptosis induction. Tissues were considered apoptotic by means of the apoptotic index (quotient of apoptotic tumor cells and total tumor cells). One hundred and eighty-nine tumors (63.4%) were negative for apoptosis and 109 tissues (36.6%) were considered apoptotic (mean apoptotic index 11.9%, range, 0 to 90%). H-ras expression correlated significantly (chi2-test, p=0.004) to apoptosis. Furthermore, restricted to the node-negative subgroup, both H-ras expression and apoptosis were indicative of a better outcome (log-rank test p=0.0001, and p=0.012, respectively) during the observation time (median 87 months). These data suggest that H-ras expression effects the particular breast tumor cells by induction of apoptosis in breast cancer patients in an early stage without node involvement. The study indicates a possible mechanism, by which H-ras may act protectively.

High apoptotic index correlates to p21 and p27 expression indicating a favorable outcome of primary breast cancer patients, but lacking prognostic significance in multivariate analysis.

This study was performed in order to investigate the role of the apoptotic index (AI) as a prediction parameter for the prognosis of patients with primary breast cancer. AI was determined by DNA fragmentation on 298 primary breast cancer samples and compared to clinically established breast cancer parameters. Additionally, we determined the expression of functional parameters including proliferating cell nuclear antigen, p21waf and p27kip by immunohistochemistry. The mean AI was found to be 11.9% (range, 0-90%). 189 tumors (63.4%) were negative for apoptosis, while 109 tissue samples (36.6%) were apoptotic with >5% positive cells. Using univariate analysis (chi2 test), the AI did not show any significant correlation to one of the established prognostic parameters of primary breast cancer (p > 0.05). In contrast, we found a significant positive correlation to the expression of the cell cycle inhibitors p21waf (p = 0.04) and p27kip (p = 0.024). During the clinical follow-up (median observation time for disease-free survival 87 months), several clinically established prognostic parameters including menopausal status, nodal status, tumor size, tumor grade, and hormone receptor expression could be confirmed and were analyzed with respect to the AI in the tumor. Furthermore, AI displayed a significant positive correlation to disease-free survival using Kaplan-Meier survival analysis (log-rank test, p = 0.04). However, AI lost its prognostic significance in multivariate analysis based on the Cox proportional hazard model (relative risk 0.8, confidence interval 0.52-1.33, p = 0.44). Our data indicate that high apoptotic rates in cancer tissues are indicative of a favorable patient outcome. However, the AI was not an independent factor. The study provides indirect evidence that this process may involve cell cycle inhibitors physiologically.