Michael Mouradian

Docosahexaenoic acid alters epidermal growth factor receptor-related signaling by disrupting its lipid raft association

Docosahexaenoic acid (DHA), a 22:6 n-3 polyunsaturated fatty acid, is the longest and most highly unsaturated fatty acid found in most membranes and has been shown to inhibit cancer cell growth in part by modifying cell signaling. In the current study, alterations to epidermal growth factor receptor (EGFR) signaling upon DHA supplementation are examined in A549 lung adenocarcinoma, WiDr colon carcinoma and MDA-MB-231 breast carcinoma cell lines. Interestingly, EGFR phosphorylation, most notably at the tyrosine 1068 residue, is dramatically upregulated, and EGFR association with the Sos1 guanine nucleotide exchange factor is concomitantly increased upon DHA supplementation. However, guanosine triphosphate-bound Ras and phosphorylated extracellular signal-regulated kinase (Erk)1/2 are paradoxically downregulated in the same treatments. Previous reports have noted changes in membrane microdomains upon DHA supplementation, and our findings confirmed that EGFR, but not Ras, is excluded from caveolin-rich lipid raft fractions in DHA-treated cells, resulting in a decreased association of Ras with Sos1 and the subsequent downregulation of Erk signaling. Xenografts of the A549 cell line implanted in athymic mice fed a control high-fat diet or a diet high in DHA confirmed our in vitro data. These results demonstrate for the first time a functional consequence of decreased EGFR protein in lipid raft microdomains as a result of DHA treatment in three different cancer models. In addition, we report the ability of DHA to enhance the efficacy of EGFR inhibitors on anchorage-independent cell growth (soft agar), providing evidence for the potential development of enhanced combination therapies.

Docosahexaenoic acid attenuates breast cancer cell metabolism and the Warburg phenotype by targeting bioenergetic function

Docosahexaenoic acid (DHA; C22:6n−3) depresses mammary carcinoma proliferation and growth in cell culture and in animal models. The current study explored the role of interrupting bioenergetic pathways in BT‐474 and MDA‐MB‐231 breast cancer cell lines representing respiratory and glycolytic phenotypes, respectively and comparing the impacts of DHA with a non‐transformed cell line, MCF‐10A. Metabolic investigation revealed that DHA supplementation significantly diminished the bioenergetic profile of the malignant cell lines in a dose‐dependent manner. DHA enrichment also resulted in decreases in hypoxia‐inducible factor (HIF‐1α) total protein level and transcriptional activity in the malignant cell lines but not in the non‐transformed cell line. Downstream targets of HIF‐1α, including glucose transporter 1 (GLUT 1) and lactate dehydrogenase (LDH), were decreased by DHA treatment in the BT‐474 cell line, as well as decreases in LDH protein level in the MDA‐MB‐231 cell line. Glucose uptake, total glucose oxidation, glycolytic metabolism, and lactate production were significantly decreased in response to DHA supplementation; thereby enhancing metabolic injury and decreasing oxidative metabolism. The DHA‐induced metabolic changes led to a marked decrease of intracellular ATP levels by 50% in both cancer cell lines, which mediated phosphorylation of metabolic stress marker, AMPK, at Thr172. These findings show that DHA contributes to impaired cancer cell growth and survival by altering cancer cell metabolism, increasing metabolic stress and altering HIF‐1α‐associated metabolism, while not affecting non‐transformed MCF‐10A cells. This study provides rationale for enhancement of current cancer prevention models and current therapies by combining them with dietary sources, like DHA.

Induced Oxidative Stress and Cell Death in the A549 Lung Adenocarcinoma Cell Line by Ionizing Radiation Is Enhanced by Supplementation With Docosahexaenoic Acid

Both ionizing radiation and docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid (PUFA), have been shown to inhibit tumor cell growth at least in part by increasing oxidative stress. In this study, the effects of ionizing radiation, DHA, or a combination of the two on cell proliferation, anchorage-independent growth, apoptosis, and lipid peroxidation in A549 lung adenocarcinoma cells were examined. In this study, significant decreases in cell proliferation and colony formation were noted for ionizing radiation or DHA treatments, whereas a combination of the two showed significant reductions over either treatment alone. Conversely, lipid peroxidation and apoptotic cell death showed significant increases with ionizing radiation and DHA treatments, whereas cells receiving both treatments demonstrated further significant increases. Moreover, addition of vitamin E, an antioxidant, was able to completely reverse lipid peroxidation and cell death due to ionizing radiation and partially reverse these changes in DHA treatments. Finally, the preferential incorporation of DHA into lung and xenograft compared to liver tissue is demonstrated in an in vivo model. These findings confirm the potential of DHA supplementation to enhance the treatment of lung cancer using ionizing radiation by increasing oxidative stress and enhancing tumor cell death.

Key roles for GRB2-associated-binding protein 1, phosphatidylinositol-3-kinase, cyclooxygenase 2, prostaglandin E2 and transforming growth factor alpha in linoleic acid-induced upregulation of lung and breast cancer cell growth

The distribution of omega-6 and omega-3 polyunsaturated fatty acid (PUFA) intake in Western diets is disproportionate, containing an overabundance of the omega-6 PUFA, linoleic acid (LA; C18:2). Increased enrichment with LA has been shown to contribute to the enhancement of tumorigenesis in several cancer models. Previous work has indicated that phosphatidylinositol 3-kinase (PI3K) may play a key role in LA-induced tumorigenesis. However, the modes by which LA affects carcinogenesis have not been fully elucidated. In this study, a mechanism for LA-induced upregulation of cancer cell growth is defined. LA treatment enhanced cellular proliferation in BT-474 human breast ductal carcinoma and A549 human lung adenocarcinoma cell lines. Enrichment of LA increased cyclooxygenase (COX) activity and led to increases in prostaglandin E2 (PGE2), followed by increases in matrix metalloproteinase (MMP) and transforming growth factor alpha (TGF-α) levels, which are all key elements involved in the enhancement of cancer cell growth. Further investigation revealed that LA supplementation in both BT-474 breast and A549 lung cancer cell lines greatly increased the association between the scaffolding protein GRB2-associated-binding protein 1 (Gab1) and epidermal growth factor receptor (EGFR), although Gab1 protein levels were significantly decreased. These LA-induced changes were associated with increases in activated Akt (pAkt), a downstream signaling component in the PI3K pathway. Treatment with inhibitors of EGFR, PI3K and Gab1-specific siRNAs reversed the upregulation of pAkt, as well as the observed increases in cell proliferation by LA in both cell lines. A549 xenograft assessment in athymic nude mice fed high levels of LA exhibited similar increases in EGFR-Gab1 association and increased levels of pAkt, while mice fed with high levels of the omega-3 PUFA, docosahexaenoic acid (DHA; C22:6), demonstrated an opposite response. The involvement of Gab1 in LA-induced tumorigenesis was further defined utilizing murine cell lines that express high levels of Gab1. Significant increases in cell proliferation were observed with the addition of increasing concentrations of LA. However, no changes in cell proliferation were detected in the murine paired cell lines expressing little or no Gab1 protein, establishing Gab1 as major target in LA-induced enhancement of tumorigenesis.

Docosahexaenoic Acid-mediated Inhibition of Heat Shock Protein 90-p23 Chaperone Complex and Downstream Client Proteins in Lung and Breast Cancer.

ABSTRACT The molecular chaperone, heat shock protein 90 (Hsp90), is a critical regulator for the proper folding and stabilization of several client proteins, and is a major contributor to carcinogenesis. Specific Hsp90 inhibitors have been designed to target the ATP-binding site in order to prevent Hsp90 chaperone maturation. The current study investigated the effects of docosahexaenoic acid (DHA; C22:6 n-3) on Hsp90 function and downstream client protein expression. In vitro analyses of BT-474 human breast carcinoma and A549 human lung adenocarcinoma cell lines revealed dose-dependent decreases in intracellular ATP levels by DHA treatment, resulting in a significant reduction of Hsp90 and p23 association in both cell lines. Attenuation of the Hsp90-p23 complex led to the inhibition of Hsp90 client proteins, epidermal growth factor receptor 2 (ErbB2), and hypoxia-inducible factor 1α (HIF-1α). Similar results were observed when employing 2-deoxyglucose (2-DG), confirming that DHA and 2-DG, both independently and combined, can disturb Hsp90 molecular chaperone function. In vivo A549 xenograft analysis also demonstrated decreased expression levels of Hsp90-p23 association and diminished protein levels of ErbB2 and HIF-1α in mice supplemented with dietary DHA. These data support a role for dietary intervention to improve cancer therapy in tumors overexpressing Hsp90 and its client proteins.

Abstract 5051: Docosahexaenoic acid inhibits cancer cell invasion and migration by modifying focal adhesion complex structure and signaling

The extracellular matrix (ECM) is responsible for the regulation of many cellular processes, including survival, proliferation, migration and invasion. Cellular-ECM contact induces a coordinated process recruiting functional protein complexes, consisting of scaffold, adapter, linking and docking proteins, to form focal adhesion (FA) structures. Once formed, FA complexes then recruit signaling proteins to activate downstream cellular pathways. Aberrations in FA structure and signaling have shown to contribute to cancer initiation, progression and cellular motility. Studies investigating the molecular mechanisms accounting for FA structure and function in cancer cells have demonstrated unique growth behavior and migratory properties in vitro. While docosahexaenoic acid (DHA), an omega-3 PUFA, has been shown to inhibit growth of a number of cancer cell lines, the effects of DHA on FA dynamics and signaling have not been investigated. In the present study, we show that DHA induced changes in the morphological growth phenotype in cancer cell lines grown in Matrigel™. DHA treatment also inhibited planar cell movement (cell migration) and amoeboid motility (invasion) in breast and lung cancer cell lines. Associated with the observed morphological changes and inhibited growth, were changes in the expression of a number of proteins involved in the FA complex. Upon further characterization, cell line specific changes in protein expression levels and protein localization of FAK, e-cadherin, paxillin and vinculin were observed with DHA treatment, which suggests that DHA is modifying FA complex structure. Additionally, changes in the phosphorylation patterns of major signaling pathways associated with the FA complex, like EGFR, ERK and c-Myc, were also observed with DHA treatment. Overall, these results provide new insight into FA activation and signaling and demonstrate a new mechanism for DHA treatment in cancer. Citation Format: Michael Mouradian, Palvinder K. Bains, Ronald S. Pardini. Docosahexaenoic acid inhibits cancer cell invasion and migration by modifying focal adhesion complex structure and signaling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5051.

Abstract 3165: Docosahexaenoic acid attenuates survival and progression in subtype-specific breast cancer by modifying Myc activity

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Overexpression of Myc in breast cancer is associated with poor prognosis and has a unique profile distribution among subtypes. Myc overexpression has been shown to be greatest in basal-like tumors, ∼50%, and least in luminal Her2-overexpressing tumors, ∼9%. Previous studies from our laboratory have identified a relationship between docosahexaenoic acid (DHA, C22:6 n-3) treatment and Myc activity and the effect seems to be specific to the breast cancer subtype and Myc overexpression profile, but is still unclear. In the current study, we investigated the effect of DHA on tumor growth, survival, and invasion in a high Myc expressing cell line, basal-like MDA-MB-231, and a low Myc expressing cell line, luminal Her2-overexpressing BT-474, in vitro. Basal expression analysis confirmed Myc overexpression levels in each cell line. While DHA treatment in the basal-like MDA-MB-231 cells significantly decreased Myc transcriptional activity and p-T58/S62-c-Myc phosphorylation status, the opposite response was observed with DHA treatment in the BT-474 luminal Her2-overexpressing cells, significantly enhancing Myc transcriptional activity and phosphorylation status. Although different responses in Myc activity existed between the two subtype-specific breast cancers, cell viability and apoptosis assays produced similar findings, revealing decreased cellular viability and increased early and late-apoptotic cellular status in response to DHA treatment. Additionally, dramatic decreases in wound healing and invasion index were observed in both cell lines with DHA supplementation compared to control treatments. Myc siRNA treatment rescued BT-474 cells from DHA treatment, confirming that DHA-induced alterations in apoptosis and invasion were initiated by Myc modification. Moreover, Myc knockdown in the MDA-MB-231 cell line displayed results similar to DHA treatment, consistent with our hypothesis that Myc activity is responsible for cellular survival and progression in subtype specific breast cancer. These results show that DHA is applying some of its anti-cancer effects by modifying Myc activity, inducing apoptosis and decreasing invasion in breast cancer, revealing new dietary targets that may enhance current therapeutics. Citation Format: Michael Mouradian, Palvinder K. Bains, Amy M. Chattin, Ronald S. Pardini. Docosahexaenoic acid attenuates survival and progression in subtype-specific breast cancer by modifying Myc activity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3165. doi:10.1158/1538-7445.AM2014-3165

Abstract 3353: Docosahexaenoic acid enhances 2-deoxyglucose treatment in breast and lung cancer cells in vitro

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Increased aerobic glycolysis is a common phenotype of cancer cells and is known as the Warburg effect. Recent studies have focused on targeting cellular metabolism to impede cancer cell growth. Previous findings in our laboratory have demonstrated that docosahexaenoic acid (DHA; C22:6 n-3), a long-chain omega-3 polyunsaturated fatty acid (PUFA), can inhibit cancer cell metabolism and reduce intracellular ATP levels. This study investigated the effects of concurrent treatment with DHA with 2-deoxyglucose (2DG), an inhibitor of glucose metabolism, in multiple cancer cell models in vitro, BT-474 human breast ductal carcinoma, MDA-MB-231 human breast adenocarcinoma, and A549 human lung adenocarcinoma. Dose-dependent decreases in intracellular ATP levels were observed with DHA and 2DG, both alone and in combination. In addition to the significant decreases in ATP levels, large decreases in extracellular lactate concentrations were observed in all three cell lines as well, suggesting that the combination of 2DG and DHA can augment treatment, mimic glucose deprivation and play a role in reducing the Warburg effect. Moreover, oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were significantly reduced with the combination of DHA and 2DG, which suggests that the combination of DHA with other metabolic inhibitors, like 2DG, may sensitize cells to current treatment. Our findings show that combining DHA with 2DG enhances the efficacy of 2DG treatment alone, which may help to reduce the cytotoxic effects by 2DG on normal cells. Other metabolic inhibitors are being employed in combination with DHA to determine the mechanisms behind the DHA-induced sensitizing effects, which will provide additional treatment strategies for oncologists and cancer patients. Citation Format: Michael Mouradian, Irvin V. Ma, Erika D. Vicente, Amy M. Chattin, Ronald S. Pardini. Docosahexaenoic acid enhances 2-deoxyglucose treatment in breast and lung cancer cells in vitro. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3353. doi:10.1158/1538-7445.AM2014-3353

Abstract 483: Docosahexaenoic acid inhibits heat shock protein 90 complex and client proteins by reducing intracellular ATP levels in breast and lung cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA A major contributor to carcinogenesis is the molecular chaperone heat shock protein 90 (Hsp90). Hsp90 regulates the proper folding and stabilization of several client proteins, including human epidermal growth factor receptor 2 (ErbB2) and hypoxia-inducible factor 1α (HIF-1α). ErbB2 is a member of the epidermal growth factor receptor (EGFR) family of receptor-proteins, and is a clinical target for the treatment of metastatic cancer, while HIF-1α is often stabilized and overexpressed in several cancers. The ability for Hsp90 to become a mature complex and to properly fold client proteins is dependent on adenosine triphosphate (ATP) binding with the co-chaperone, p23. Specific Hsp90 inhibitors, like geldanamycin, target the Hsp90 ATP-binding site to prevent formation of the mature complex. Although supplementation with docosahexaenoic acid (DHA; C22:6 n-3) has not been shown to specifically target the Hsp90 ATP-binding site, the current study demonstrates a similar effect by DHA causing a reduction in available intracellular ATP levels. DHA is the longest, most unsaturated omega-3 polyunsaturated fatty acid (PUFA) existing in biological membranes and has been shown to possess anti-cancer activity in several cancer models. Studies from our laboratory have shown that DHA enrichment can reduce cancer cell metabolism and intracellular ATP levels in both breast and lung cancer models. In this study, a novel mechanism for the ability of DHA to inhibit the Hsp90 chaperone complex is defined. In vitro analyses of BT-474 human breast ductal carcinoma, as well as the A549 human lung adenocarcinoma cell lines were used to determine the impact of DHA-induced decreases of intracellular ATP levels. We found that the reduction in ATP levels by DHA treatment resulted in significant decreases in the association of Hsp90 and p23 in both cell lines. The decreased association of the Hsp90-p23 complex led to decreased levels of ErbB2 and HIF-1α client proteins, suggesting that DHA can modify Hsp90 chaperone function and attenuate client protein levels. Additionally, similar results were found when employing 2-deoxyglucose (2-DG), a glycolytic inhibitor, which confirms that DHA and 2-DG can disrupt Hsp90 molecular chaperone function by decreasing cellular ATP levels. Consistent with these observations, when using a dose of DHA that did not significantly reduce intracellular ATP levels, no change in the Hsp90-p23 chaperone complex or protein levels of ErbB2 and HIF-1α were seen. These results demonstrate a potential use for dietary intervention to improve cancer therapy in tumors that overexpress Hsp90 client proteins. Citation Format: Michael Mouradian, Irvin V. Ma, Erika D. Vicente, Keith D. Kikawa, Amy M. Chattin, Ronald S. Pardini. Docosahexaenoic acid inhibits heat shock protein 90 complex and client proteins by reducing intracellular ATP levels in breast and lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 483. doi:10.1158/1538-7445.AM2014-483

Abstract 1303: Key roles for Gab1, phosphatidylinositol-3-kinase, COX-2, prostaglandin E2 and TGF-alpha in linoleic acid-induced upregulation of lung and breast cancer cell growth.

The omega-6 polyunsaturated fatty acid, linoleic acid (LA), is prevalent in Western diets and is known to enhance the tumorigenesis of mammary cancer models; with previous work demonstrating an upregulation of phosphatidylinositol-3-kinase (PI3K) signaling may play a key role. In this study, a mechanism for LA9s upregulation of cancer cell growth is defined. High levels of LA in animal diets or cell culture medium initiates a series of events beginning with increased cyclooxygenase (COX) activity, which leads to increased prostaglandin E2 (PGE2) production, that subsequently increases matrix metalloproteinase (MMP) levels and transforming growth factor alpha (TGF-α). TGF-α is a classic growth factor for the epidermal growth factor receptor 1 (EGFR), which plays a role in a large number of cancers. The Grb2-associated binding protein 1 (Gab1) is a scaffolding protein that can complex with EGFR to activate PI3K signaling. Recent studies in our laboratory reveal LA supplementation of the breast cancer cell line BT-474 and the lung adenocarcinoma cell line A549 greatly increases the association between Gab1 and EGFR, while at the same time dramatically decreasing Gab1 protein levels. These changes are concomitant with increases in activated Akt (pAkt), a downstream signaling component in the PI3K signaling pathway. Moreover, inhibitors of EGFR, PI3K and Gab1-specific siRNAs are capable of reversing LA-induced upregulation of pAkt, as well as observed increases in cell proliferation for these models. These data establish Gab1 as major target in LA-induced enhancement of tumorigenesis. Citation Format: Keith D. Kikawa, Clarissa R. Martins, Eric D. Johnson, Kristen Beck, Michael Mouradian, Ronald S. Pardini. Key roles for Gab1, phosphatidylinositol-3-kinase, COX-2, prostaglandin E2 and TGF-alpha in linoleic acid-induced upregulation of lung and breast cancer cell growth. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1303. doi:10.1158/1538-7445.AM2013-1303