Effects of mutant p53 expression on human 15-lipoxygenase-promoter activity and murine 12/15-lipoxygenase gene expression: Evidence that 15-lipoxygenase is a mutator gene

Human 15-lipoxygenase (h15-LO) is present on chromosome 17p13.3 in close pr oximity to the tumor-suppressor gene, p53. IS-LO is implicated in antiinfla mmation, membrane remodeling, and cancer development/metastasis. The murine BALB/c embryo fibroblast cell line, (10)1val, expresses p53 in mutant (mt) conformation when grown at 39 degrees C and in wild-type conformation when grown at 32 degrees C. Transfection of h15-LO promoter constructs (driving luciferase reporter) into (10)1val cells and into p53-deficient (10)1 cell s resulted in a marked increase in h15-LO promoter activity in (10)1val cel ls at 39 degrees C, but not at 32 degrees C, or as compared with (10)1 cell s. Transfection of h15-LO promoter deletion constructs, however, resulted i n total loss of activity in both cell types at 32 degrees C and 39 degrees C. Cotransfection of (10)1 cells with h15-LO promoter (driving luciferase r eporter) along with increasing levels of a mt p53 expression vector demonst rated dose-dependent capacity of mt p53 to induce 15-LO promoter activity. No effect was observed with wild-type p53. In contrast to h15-LO promoter a ctivity, (10)1val cells had significantly lower levels of endogenous (murin e) 12/15-LO (mouse analog of h15-LO) mRNA and protein when grown at 39 degr ees C compared with cells grown at 32 degrees C. Our data support the hypot hesis that loss of a tumor-suppressor gene (p53), or "gain-of-function acti vities" resulting from the expression of its mutant forms, regulates 15-LO promoter activity in man and in mouse, albeit in directionally opposite man ners. The studies define a direct link between 15-LO activity and an establ ished tumor-suppressor gene located in close chromosomal proximity.