Distinct Effects of Annexin A7 and p53 on Arachidonate Lipoxygenation in Prostate Cancer Cells Involve 5-Lipoxygenase Transcription

Tumor suppressor function for Annexin A7 (ANXA7; 10q21) is based on cancer-prone phenotype in Anxa7(+/−) mouse and ANXA7 prognostic role in human cancers. Because ANXA7-caused liposome aggregation can be promoted by arachidonic acid (AA), we hypothesized that the phospholipid-binding tumor suppressor ANXA7 is associated with AA cascade. In a comparative study of ANXA7 versus canonical tumor suppressor p53 effects on AA lipoxygenation pathway in the p53-mutant and androgen-insensitive DU145 prostate cancer cells, both tumor suppressors altered gene expression of major 5-lipoxygenase (LOX) and 15-LOXs, including response to T helper 2 (Th2)-cytokine [interleukin-4 (IL-4)] and endogenous steroids (mimicked by dexamethasone). Wild-type and mutant ANXA7 distinctly affected expression of the dexamethasone-induced 15-LOX-2 (a prostate-specific endogenous tumor suppressor) as well as the IL-4-induced 15-LOX-1. On the other hand, wild-type p53 restored 5-LOX expression in DU145 to levels comparable to benign prostate epithelial cells. Using mass spectrometry of DNA affinity–enriched nuclear proteins, we detected different proteins that were bound to adjacent p53 and estrogen response elements in the 5-LOX promoter in DU145 cells introduced with ANXA7 versus p53. Sex hormone regulator 17-β hydroxysteroid dehydrogenase 4 was identified under p53 introduction, which induced the 5-LOX expression. Meantime, nuclear proteins bound to the same 5-LOX promoter site under introduction of ANXA7 (that was associated with the repressed 5-LOX) were identified as zinc finger proteins ZNF433 and Aiolos, pyrin domain–containing NALP10, and the p53-regulating DNA repair enzyme APEX1. Thus, ANXA7 and p53 can distinctly regulate LOX transcription that is potentially relevant to the AA-mediated cell growth control in tumor suppression. (Cancer Res 2006; 66(19): 9609-16)