Dietary flaxseed supplementation in ovarian cancer: Elucidating the molecular actions of its biologically derived active compounds.

The goal of our study is to elucidate the anti-ovarian cancer molecular mechanisms promoted by a flaxseed-supplemented diet in the laying hen. A flaxseed-supplemented diet generates a myriad of biologically active compounds that work synergistically to attack ovarian tumors. Our laboratory has demonstrated that flaxseed diet reduces the occurrence and severity of ovarian cancer in laying hen—the only spontaneous animal model for ovarian cancer. Flax diet in chicken induces the CYP1A1 pathway of estrogen metabolism increasing production of 2-hydroxy and 2-methoxy metabolites. 2-methoxyestradiol (2ME) is produced by the Catechol-O-Methyl transferase (COMT) enzyme from 2-hydroxyestradiol—a pathway that reduces estrogen toxicity, which is protective against ovarian cancer. Flaxseed is also a rich source of omega-3 fatty acids, mostly a-linoleic acid (ALA), which is converted into docosahexaenoic acid (DHA) in the gut. We have recently shown that flaxseed diet induces apoptosis and inhibits angiogenesis in the chicken ovarian tumors. 2ME promotes apoptosis and inhibits angiogenesis via activation of p38-MAPK; DHA has potent antiangiogenic and anti-inflammatory actions, however not dependent on the p38-MAPK pathway. To further investigate the molecular mechanisms of the antiangiogenic actions of flax diet, a qRT-PCR array analyzing 84 key genes involved in angiogenesis was performed. Nine key genes were significantly downregulated with flax diet. These genes are involved in hypoxia-induced endothelial cell migration, proliferation, differentiation, and lymphangiogenesis. Using human ovarian cancer cells, DNA damage was studied by TUNEL staining; DNA content and cell cycle progression were studied by PI staining and flow cytometry; apoptosis was measured by cleavage of caspase-3 by Western blot. 2ME treatment induced phosphorylation at ser139 of histone H2A (gH2Ax), a known marker for dsDNA breaks, along with phosphorylation at ser10 of histone H3 (pHH3) and ser14 of histone H2B (pHH2B). 2ME is known to bind at/near the colchicine binding site of the growing microtubules and therefore arresting cells at G2/M phase. 2ME effects were equivalent in ERa positive and negative human ovarian cancer cells. Also, the selective GPR30 agonist and antagonist, G1 and G15, did not modulate the effects of 2ME. Therefore, the anticancer actions of 2ME are not dependent on or mediated through the estrogen receptors. (NIH RO1AT005295) Citation Format: Purab Pal, Karen Hales, Dale Buchanan Hales. Dietary flaxseed supplementation in ovarian cancer: Elucidating the molecular actions of its biologically derived active compounds [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B35.