CYCLIN-E OVEREXPRESSION, A NEGATIVE PROGNOSTIC FACTOR IN BREAST-CANCER WITH STRONG CORRELATION TO ESTROGEN-RECEPTOR STATUS

Cyclin E is a G1 cyclin which has been proposed to be one of the key r egulators of the important G1/S transition, and could consequently be a potential deregulated molecule in tumours. Recently, it has been obs erved that cyclin E is overexpressed in a variety of malignancies incl uding breast cancer and that several isoforms of the protein exists. I n this study we have characterised the cyclin E expression in 114 tumo ur specimens from patients with primary breast cancer using Western bl otting. Various expression of cyclin E was observed among tumours and a group of 27 patients out of 100 patients with stage I-III disease, i dentified as having tumours with high cyclin E levels, had a significa ntly increased risk of death and relapse from breast cancer (P=0.0002 and P=0.015 respectively). Even in the subgroup of axillary node-negat ive patients the cyclin E level was of prognostic importance. There wa s also a strong association between cyclin E expression and oestrogen receptor status (P<0.00001), and tumours with high cyclin E expression were in general oestrogen receptor negative, suggesting a potential r ole for cyclin E in mechanisms responsible for oestrogen-independent t umour growth.