EFFECTS OF HIGH AND LOW DIETARY-FAT AND INDOMETHACIN ON TUMOR-GROWTH,HORMONE RECEPTOR STATUS AND GROWTH-FACTOR EXPRESSION IN DMBA-INDUCED RAT BREAST-CANCER

The effects of high and low dietary fat (20% vs. 0.5% com oil), and of the prostaglandin synthetase inhibitor indomethacin (0.005% w/w), on tumour incidence, tumour growth, hormone-receptor status and growth-fa ctor expression were examined in dimethylbenzanthracene (DMBA)-induced rat breast cancer. The high dietary-fat group showed a significantly higher tumour incidence, larger tumour size and larger number of bromo deoxyuridine(BrdU(-positive ce/ls of tumours as compared with those in the low dietary-fat group. Indomethacin reduced tumour incidence sign ificantly, but conversely increased the tumour size and the number of BrdU-positive cells in both the high and the low dietary-fat groups. N o significant difference was noted in the hormone-receptor status of t he tumours. Growth factors (TGF-alpha and IGF-II) were somewhat highly expressed in the high dietary-fat group as compared with the low diet ary-fat group, but indomethacin rather reduced the growth-factor expre ssion. It is concluded that high dietary fat stimulates tumour inciden ce and tumour proliferation, while indomethacin has dual effects: a st imulating effect on tumour proliferation, but an inhibiting effect on tumour incidence. It is also suggested that hormone-receptor status an d growth-factor expression do not play an important role in their stim ulating effects on tumour proliferation.