Fish oil targets PTEN to regulate NFkappaB for downregulation of anti-apoptotic genes in breast tumor growth

• Published in: Breast cancer research and treatment 2009-11, Vol.118 (1), p.213-228
• Main Authors: Ghosh-Choudhury, Triparna, Mandal, Chandi C, Woodruff, Kathleen, St Clair, Patricia, Fernandes, Gabriel, Choudhury, Goutam G, Ghosh-Choudhury, Nandini
• Format: Article
• Language: English
• Subjects: Adenocarcinoma - diet therapy; Adenocarcinoma - genetics; Adenocarcinoma - pathology; Animals; Apoptosis - drug effects; Apoptosis - physiology; bcl-X Protein - biosynthesis; bcl-X Protein - genetics; Breast Neoplasms - diet therapy; Breast Neoplasms - genetics; Breast Neoplasms - pathology; Cell Line, Tumor - drug effects; Cell Line, Tumor - metabolism; Cell Line, Tumor - pathology; DNA, Neoplasm - metabolism; Docosahexaenoic Acids - pharmacology; Down-Regulation - drug effects; Eicosapentaenoic Acid - pharmacology; Female; Fish Oils - pharmacology; Fish Oils - therapeutic use; Gene Expression Regulation, Neoplastic - drug effects; Genes, bcl-2; Humans; Mice; Mice, Nude; Neoplasm Proteins - biosynthesis; Neoplasm Proteins - genetics; Neoplasm Proteins - physiology; NF-kappa B - metabolism; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation - drug effects; Protein Binding - drug effects; Protein Processing, Post-Translational - drug effects; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; PTEN Phosphohydrolase - biosynthesis; PTEN Phosphohydrolase - genetics; PTEN Phosphohydrolase - physiology; Signal Transduction - drug effects; Transcription Factor RelA - biosynthesis; Transcription Factor RelA - genetics; Xenograft Model Antitumor Assays
• ISSN: 1573-7217
• DOI: 10.1007/s10549-008-0227-7

The molecular mechanism for the beneficial effect of fish oil on breast tumor growth is largely undefined. Using the xenograft model in nude mice, we for the first time report that the fish oil diet significantly increased the level of PTEN protein in the breast tumors. In addition, the fish oil diet attenuated the PI 3 kinase and Akt kinase activity in the tumors leading to significant inhibition of NFkappaB activation. Fish oil diet also prevented the expression of anti-apoptotic proteins Bcl-2 and Bcl-XL in the breast tumors with concomitant increase in caspase 3 activity. To extend these findings we tested the functional effects of DHA and EPA, the two active omega-3 fatty acids of fish oil, on cultured MDA MB-231 cells. In agreement with our in vivo data, DHA and EPA treatment increased PTEN mRNA and protein expression and inhibited the phosphorylation of p65 subunit of NFkappaB in MDA MB-231 cells. Furthermore, DHA and EPA reduced expression of Bcl-2 and Bcl-XL. NFkappaB DNA binding activity and NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes were also prevented by DHA and EPA treatment. Finally, we showed that PTEN expression significantly inhibited NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes. Taken together, our data reveals a novel signaling pathway linking the fish oil diet to increased PTEN expression that attenuates the growth promoting signals and augments the apoptotic signals, resulting in breast tumor regression.