CHARACTERIZATION OF A 15-LIPOXYGENASE IN HUMAN BREAST-CARCINOMA BT-20CELLS - STIMULATION OF 13-HODE FORMATION BY TGF(ALPHA) EGF/

Epidemiological and experimental data suggest a role for polyunsaturat ed fatty acids in the etiology of breast cancer. In this report we hav e studied arachidonic acid and linoleic acid metabolism in the human b reast carcinoma cell line BT-20 which overexpresses both EGF receptor and the homologous erbB-2 oncogene product. EGF and TGF(alpha) stimula ted DNA synthesis in these cells which was attenuated by the addition of a lipoxygenase inhibitor, NDGA. The addition of a prostaglandin H s ynthase inhibitor did not alter DNA synthesis. Analytical studies reve al little arachidonic acid metabolism while linoleic acid was metaboli zed to 13-hydroxyoctadecadienoic acid (13-HODE). The formation of 13-H ODE was inhibited by the addition of NDGA and was dependent on EGF or TGF(alpha). These results suggest the metabolism of linoleic acid by a n-6 or 15-lipoxygenase regulated by EGF/TGF(alpha). RT-PCR was used t o isolate a clone, and sequenced the cDNA for this enzyme and it was f ound to be identical to the human 15-lipoxygenase previously character ized from human pulmonary tissue. EGF/TGF(alpha) did not alter the exp ression of this enzyme suggesting a potential posttranslational regula tion of activity. This study provides a link between metabolism of lin oleic acid and growth factor regulation of cell proliferation in a hum an breast carcinoma cell line. (C) 1997 Academic Press.