Characterization of a 15-lipoxygenase in human breast carcinoma BT-20 cells: stimulation of 13-HODE formation by TGF alpha/EGF.

Epidemiological and experimental data suggest a role for polyunsaturated fatty acids in the etiology of breast cancer. In this report we have studied arachidonic acid and linoleic acid metabolism in the human breast carcinoma cell line BT-20 which overexpresses both EGF receptor and the homologous erbB-2 oncogene product. EGF and TGF alpha stimulated DNA synthesis in these cells which was attenuated by the addition of a lipoxygenase inhibitor, NDGA. The addition of a prostaglandin H synthase inhibitor did not alter DNA synthesis. Analytical studies reveal little arachidonic acid metabolism while linoleic acid was metabolized to 13-hydroxyoctadecadienoic acid (13-HODE). The formation of 13-HODE 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 to isolate a clone, and sequenced the cDNA for this enzyme and it was found to be identical to the human 15-lipoxygenase previously characterized from human pulmonary tissue. EGF/TGF alpha did not alter the expression of this enzyme suggesting a potential post-translational regulation of activity. This study provides a link between metabolism of linoleic acid and growth factor regulation of cell proliferation in a human breast carcinoma cell line.