[Metformin does not suppress the aromatase expression in breast cancer tissue of patients with concurrent type 2 diabetes].

Although there is data suggesting the in vitro inhibition of aromatase in cell lines by antidiabetic biguanide metformin (MF), there is no data on the intratumoral breast cancer (BC) aromatase expression in patients already receiving therapy for type II diabetes. Paraffinized tumor samples obtained from 57 BC pts aged 48-77 yrs, >80% of pts had stage T1-2N0-3M0 BC. Thirteen of the pts didn't have diabetes, 44 pts were previously diagnosed type II diabetes and reseaved the following therapy for at least 1 year: diet only (n=14), sulphonylurea (SU, n=14), metformin (MF, n=9) or MF with SU (n=7). Tumor samples were deparaffinized in xylene and treated with the monoclonal aromatase antibody 677. The rate and intensity of tissue staining was then analyzed by semi-quantitative method using conventional scores. Negative controls were processed with 0.01 M PBS instead of the specific antibody. For positive control paraffin-embedded human placenta samples were used. By conventional scores method the following values were obtained: 1.31 (pts without diabetes), 1.47 (all diabetic patients), 2.22 (MF), 1.50 (SU), 1.29 (MF+SU), 1.81 (MF and MF+SU), 1.07 (diet). Allred scores for progesterone receptor (PR) were the highest in the samples from pts treated with MF or MF+SU and the lowest in the samples obtained from SU-treated pts. Thus, in contrast to previous findings suggesting the suppressive effect of MF on aromatase in vitro, no such trend was discovered for aromatase expression in tumor samples from diabetic patients treated with MF. Although the investigated patients population is still small, this data combined with clinical data (higher PR levels) may suggest the better responses to hormonal therapy in MF-treated diabetic patients.