Inhibition of matrix metalloproteinase-9 expression by docosahexaenoic acid mediated by heme oxygenase 1 in 12-O-tetradecanoylphorbol-13-acetate-induced MCF-7 human breast cancer cells

Roles and therapeutic opportunities of ω-3 long-chain polyunsaturated fatty acids in lung cancer

Over the past decades, researchers have continuously investigated the potential functions of long-chain polyunsaturated fatty acids (LCPUFAs) in cancers, including lung cancer. The ω-3 LCPUFAs, primarily consisting of eicosapentaenoic acid and docosahexaenoic acid, were found to modify inflammatory tumor microenvironment, induce cancer cell apoptosis and autophagy, and suppress tumor development when administered alone or with other therapeutical strategies. Although the precise anti-tumor mechanism has not been elucidated yet, ω-3 LCPUFAs are often used in the nutritional treatment of patients with cancer due to their ability to significantly improve patient's nutritional status, increase the sensitivity of tumor cells to treatments, and alleviate cancer-related complications. Here we present the key roles of ω-3 LCPUFAs as dietary supplementations in lung cancer, comprehensively review the recent progress on the underlying mechanisms of cancer cell regulation by ω-3 LCPUFAs, and introduce the application of ω-3 LCPUFAs in the clinical management of lung cancer and its malignant complications.

Linoleic acid exhibits anti-proliferative and anti-invasive activities in endometrial cancer cells and a transgenic model of endometrial cancer

Emerging evidence has provided considerable insights into the integral function of reprogramming fatty acid metabolism in the carcinogenesis and progression of endometrial cancer. Linoleic acid, an essential fatty acid with the highest consumption in the Western diet regimen, has shown pro-tumorigenic or anti-tumorigenic effects on tumor cell growth and invasion in multiple types of cancer. However, the biological role of linoleic acid in endometrial cancer remains unclear. In the present study, we aimed to investigate the functional impact of linoleic acid on cell proliferation, invasion, and tumor growth in endometrial cancer cells and in a transgenic mouse model of endometrial cancer. The results showed that Linoleic acid significantly inhibited the proliferation of endometrial cancer cells in a dose-dependent manner. The treatment of HEC-1A and KLE cells with linoleic acid effectively increased intracellular reactive oxygen species (ROS) production, decreased mitochondrial membrane potential, caused cell cycle G1 arrest, and induced intrinsic and extrinsic apoptosis pathways. The anti-invasive ability of linoleic acid was found to be associated with the epithelial-mesenchymal transition process in both cell lines, including the decreased expression of N-cadherin, snail, and vimentin. Furthermore, treatment of Lkb1fl/flp53fl/fl transgenic mice with linoleic acid for four weeks significantly reduced the growth of endometrial tumors and decreased the expression of VEGF, vimentin, Ki67, and cyclin D1 in tumor tissues. Our findings demonstrate that linoleic acid exhibits anti-proliferative and anti-invasive activities in endometrial cancer cell lines and the Lkb1fl/flp53fl/fl mouse model of endometrial cancer, thus providing a pre-clinical basis for future dietary interventions with linoleic acid in endometrial cancer.

Protective Effect of Alpha-Linolenic Acid on Human Oral Squamous Cell Carcinoma Metastasis and Apoptotic Cell Death

Oral cancer ranks sixth among Taiwan's top 10 cancers and most patients with poor prognosis acquire metastases. The essential fatty acid alpha-linolenic acid (ALA) has been found to diminish many cancer properties. However, the anti-cancer activity of ALA in oral cancer has yet to be determined. We examined the mechanisms underlying ALA inhibition of metastasis and induction of apoptotic cell death in oral squamous cell carcinoma (OSCC). Migration and invasion assays confirmed the cancer cells' EMT capabilities, whereas flow cytometry and Western blotting identified molecular pathways in OSCC. ALA dramatically reduced cell growth in a concentration-dependent manner according to the findings. Low concentrations of ALA (100 or 200 μM) inhibit colony formation, the expression of Twist and EMT-related proteins, the expression of MMP2/-9 proteins, and enzyme activity, as well as cell migration and invasion. Treatment with high concentrations of ALA (200 or 400 μM) greatly increases JNK phosphorylation and c-jun nuclear accumulation and then upregulates the FasL/caspase8/caspase3 and Bid/cytochrome c/caspase9/caspase3 pathways, leading to cell death. Low concentrations of ALA inhibit SAS and GNM cell migration and invasion by suppressing Twist and downregulating EMT-related proteins or by decreasing the protein expression and enzyme activity of MMP-2/-9, whereas high concentrations of ALA promote apoptosis by activating the JNK/FasL/caspase 8/caspase 3-extrinsic pathway and the Bid/cytochrome c/caspase 9 pathway. ALA demonstrates potential as a treatment for OSCC patients.

The Effects of Omega-3 Polyunsaturated Fatty Acids on Breast Cancer as a Preventive Measure or as an Adjunct to Conventional Treatments

In order to understand how omega-3 polyunsaturated fatty acid (ω-3 PUFA) supplements affect breast cancer prevention and treatment, a systematic review of articles published in the last 5 years in two databases was performed. Of the 679 articles identified, only 27 were included and examined based on five topics, taking into account: the induction type of the breast cancer used in animal models; the characteristics of the induction model by cell transplantation; the experimental design of the ω-3 supplementation—combined or not with a treatment antitumor drug; the fatty acids (FAs) composition used; the analysis of the studies’ outcomes. There are diverse and well-established animal models of breast cancer in the literature, with very relevant histological and molecular similarities depending on the specific objective of the study, such as whether the method of tumor induction was transgenic, by cell transplantation, or by oncogenic drugs. The analyses of outcomes were mainly focused on monitoring tumor growth, body/tumor weight, and molecular, genetic, or histological analyses, and few studies evaluated latency, survival, or metastases. The best results occurred when supplementation with ω-3 PUFA was associated with antitumor drugs, especially in the analysis of metastases and volume/weight of tumors or when the supplementation was started early and maintained for a long time. However, the beneficial effect of ω-3 PUFA supplementation when not associated with an antitumor agent remains unclear.

Dipotassium Glycyrrhizinate on Melanoma Cell Line: Inhibition of Cerebral Metastases Formation by Targeting NF-kB Genes-Mediating MicroRNA-4443 and MicroRNA-3620-Dipotassium Glycyrrhizinate Effect on Melanoma

Glycyrrhizic acid (GA), a natural compound isolated from licorice (Glycyrrhiza glabra), has exhibited anti-inflammatory and anti-tumor effects in vitro. Dipotassium glycyrrhizinate (DPG), a dipotassium salt of GA, also has shown an anti-tumor effect on glioblastoma cell lines, U87MG and T98G. The study investigated the DPG effects in the melanoma cell line (SK-MEL-28). MTT assay demonstrated that the viability of the cells was significantly decreased in a time- and dose-dependent manner after DPG (IC50 = 36 mM; 24 h). DNA fragmentation suggested that DPG (IC50) induced cellular apoptosis, which was confirmed by a significant number of TUNEL-positive cells (p-value = 0.048) and by PARP-1 [0.55 vs. 1.02 arbitrary units (AUs), p-value = 0.001], BAX (1.91 vs. 1.05 AUs, p-value = 0.09), and BCL-2 (0.51 vs. 1.07 AUs, p-value = 0.0018) mRNA compared to control cells. The proliferation and wound-healing assays showed an anti-proliferative effect on DPG-IC50-treated cells, also indicating an inhibitory effect on cell migration (p-values < 0.001). Moreover, it was observed that DPG promoted a 100% reduction in melanospheres formation (p-value = 0.008). Our previous microRNAs (miRs) global analysis has revealed that DPG might increase miR-4443 and miR-3620 expression levels. Thus, qPCR showed that after DPG treatment, SK-MEL-28 cells presented significantly high miR-4443 (1.77 vs. 1.04 AUs, p-value = 0.02) and miR-3620 (2.30 vs. 1.00 AUs, p-value = 0.01) expression compared to control cells, which are predicted to target the NF-kB, CD209 and TNC genes, respectively. Both genes are responsible for cell attachment and migration, and qPCR revealed significantly decreased CD209 (1.01 vs. 0.54 AUs, p-value = 0.018) and TNC (1.00 vs. 0.31 AUs, p-value = 2.38 × 10−6) mRNA expression levels after DPG compared to untreated cells. Furthermore, the migration of SK-MEL-28 cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) was attenuated by adding DPG by wound-healing assay (48 h: p-value = 0.004; 72 h: p-value = 7.0 × 10−4). In addition, the MMP-9 expression level was inhibited by DPG in melanoma cells stimulated by TPA and compared to TPA-treated cells (3.56 vs. 0.99 AUs, p-value = 0.0016) after 24 h of treatment. Our results suggested that DPG has an apoptotic, anti-proliferative, and anti-migratory effect on SK-MEL-28 cells. DPG was also able to inhibit cancer stem-like cells that may cause cerebral tumor formation.

Sulforaphane Suppresses the Nicotine-Induced Expression of the Matrix Metalloproteinase-9 via Inhibiting ROS-Mediated AP-1 and NF-κB Signaling in Human Gastric Cancer Cells

Sulforaphane, a natural phytochemical compound found in various cruciferous vegetables, has been discovered to present anti-cancer properties. Matrix metalloproteinase-9 (MMP-9) plays a crucial role in gastric cancer metastasis. However, the role of sulforaphane in MMP-9 expression in gastric cancer is not yet defined. Nicotine, a psychoactive alkaloid found in tobacco, is associated with the development of gastric cancer. Here, we found that sulforaphane suppresses the nicotine-mediated induction of MMP-9 in human gastric cancer cells. We discovered that reactive oxygen species (ROS) and MAPKs (p38 MAPK, Erk1/2) are involved in nicotine-induced MMP-9 expression. AP-1 and NF-κB are the critical transcription factors in MMP-9 expression. ROS/MAPK (p38 MAPK, Erk1/2) and ROS functioned as upstream signaling of AP-1 and NF-κB, respectively. Sulforaphane suppresses the nicotine-induced MMP-9 by inhibiting ROS-mediated MAPK (p38 MAPK, Erk1/2)/AP-1 and ROS-mediated NF-κB signaling axes, which in turn inhibit cell invasion in human gastric cancer AGS cells. Therefore, the current study provides valuable evidence for developing sulforaphane as a new anti-invasion strategy for human gastric cancer therapy.

Nicotine stimulates IL-8 expression via ROS/NF-κB and ROS/MAPK/AP-1 axis in human gastric cancer cells

Nicotine, a major alkaloid found in tobacco, is a significant risk factor for gastric cancer. IL-8, a pleiotropic cytokine, plays a vital role in cancer cell metastasis. The role of nicotine in IL-8 expression and the underlying mechanism is currently unknown. Here, we examined the effects of nicotine on IL-8 expression and explored the potential mechanisms in gastric cancer cells. We found that nicotine increases IL-8 expression. Specific inhibitor and mutagenesis studies showed that ROS and MAPK (Erk1/2, p38) were involved in this process. Deletion and site-directed mutagenesis studies indicate the involvement of transcription factor NF-κB and AP-1. ROS and ROS/MAPK (Erk1/2, p38) functioned as the upstream signaling molecules in the activation of NF-κB and AP-1, respectively. AGS gastric cancer cells pretreated with nicotine stimulate angiogenesis in the tumor microenvironment, partially abrogated by silencing IL-8 in AGS cells. In this study, we found that nicotine induces IL-8 expression via ROS/NF-κB and ROS/MAPK (Erk1/2, p38)/AP-1 axis in gastric cancer cells, thus stimulating endothelial cell proliferation and angiogenesis in the tumor microenvironment.

Immunoresponsive gene 1 modulates the severity of brain injury in cerebral ischaemia

Inflammatory stimuli induce immunoresponsive gene 1 expression that in turn catalyses the production of itaconate through diverting cis-aconitate away from the tricarboxylic acid cycle. The immunoregulatory effect of the immunoresponsive gene 1/itaconate axis has been recently documented in lipopolysaccharide-activated mouse and human macrophages. In addition, dimethyl itaconate, an itaconate derivative, was reported to ameliorate disease severity in the animal models of psoriasis and multiple sclerosis. Currently, whether immunoresponsive gene 1/itaconate axis exerts a modulatory effect in ischaemic stroke remains unexplored. In this study, we investigated whether immunoresponsive gene 1 plays a role in modulating ischaemic brain injury. In addition, the molecular mechanism underlying the protective effects of immunoresponsive gene 1 in ischaemic stroke was elucidated. Our results showed that immunoresponsive gene 1 was highly induced in the ischaemic brain following ischaemic injury. Interestingly, we found that IRG1-/- stroke animals exhibited exacerbated brain injury, displayed with enlarged cerebral infarct, compared to wild-type stroke controls. Furthermore, IRG1-/- stroke animals presented aggravated blood-brain barrier disruption, associated with augmented Evans blue leakage and increased immune cell infiltrates in the ischaemic brain. Moreover, IRG1-/- stroke animals displayed elevated microglia activation, demonstrated with increased CD68, CD86 and Iba1 expression. Further analysis revealed that immunoresponsive gene 1 was induced in microglia after ischaemic stroke, and deficiency in immunoresponsive gene 1 resulted in repressed microglial heme oxygenase-1 expression and exacerbated ischaemic brain injury. Notably, the administration of dimethyl itaconate to compensate for the deficiency of immunoresponsive gene 1/itaconate axis led to enhanced microglial heme oxygenase-1 expression, alleviated ischaemic brain injury, improved motor function and decreased mortality in IRG1-/- stroke animals. In summary, we demonstrate for the first time that the induction of immunoresponsive gene 1 in microglia following ischaemic stroke serves as an endogenous protective mechanism to restrain brain injury through heme oxygenase-1 up-regulation. Thus, our findings suggest that targeting immunoresponsive gene 1 may represent a novel therapeutic approach for the treatment of ischaemic stroke.

Host-cell dependent role of phosphorylated keratin 8 during influenza A/NWS/33 virus (H1N1) infection in mammalian cells

In this study, we investigated the involvement of keratin 8 during human influenza A/NWS/33 virus (H1N1) infection in semi-permissive rhesus monkey-kidney (LLC-MK2) and permissive human type II alveolar epithelial (A549) cells. In A549 cells, keratin 8 showed major expression and phosphorylation levels. Influenza A/NWS/33 virus was able to subvert keratin 8 structural organization at late stages of infection in both cell models, promoting keratin 8 phosphorylation in A549 cells at early phases of infection. Accordingly, partial colocalizations of the viral nucleoprotein with keratin 8 and its phosphorylated form were assessed by confocal microscopy at early stages of infection in A549 cells. The employment of chemical activators of phosphorylation resulted in structural changes as well as increased phosphorylation of keratin 8 in both cell models, favoring the influenza A/NWS/33 virus's replicative efficiency in A549 but not in LLC-MK2 cells. In A549 and human larynx epidermoid carcinoma (HEp-2) cells inoculated with respiratory secretions from pediatric patients positive for, respectively, influenza A virus or respiratory syncytial virus, the keratin 8 phosphorylation level had increased only in the case of influenza A virus infection. The results obtained suggest that in A549 cells the influenza virus is able to induce keratin 8 phosphorylation thereby enhancing its replicative efficiency.

Suppression of Urokinase-Type Plasminogen Activator Receptor by Docosahexaenoic Acid Mediated by Heme Oxygenase-1 in 12-O-Tetradecanoylphorbol-13-Acetate-Induced Human Endothelial Cells

Urokinase-type plasminogen activator receptor (uPAR) plays a crucial role in inflammation and tumor metastasis. Docosahexaenoic acid (DHA), a representative omega-3 polyunsaturated fatty acid, has been shown to exhibit anti-inflammatory and anti-tumor properties. However, the mechanism by which DHA negatively regulates uPAR expression is not yet understood. The aim of this study was to investigate the effect of DHA on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced uPAR expression and potential role of heme oxygenase-1 (HO-1) in DHA-induced inhibition of uPAR in human endothelial ECV304 cells. Results showed that TPA induced uPAR expression in a time dependent manner, while DHA inhibited uPAR expression in a concentration-dependent manner. Moreover, treatment with DHA induced HO-1 expression in a time- and concentration-dependent manner. In addition, DHA-induced inhibition of uPAR expression and cell invasion in TPA-stimulated cells was reversed by si-HO-1 RNA. Induction of HO-1 by ferric protoporphyrin IX (FePP) inhibited TPA-induced uPAR expression, and this effect was abolished by treatment with the HO-1 inhibitor tin protoporphyrin IX (SnPP). Additionally, carbon monoxide, an HO-1 product, attenuated TPA-induced uPAR expression and cell invasion. Collectively, these data suggest a novel role of DHA-induced HO-1 in reducing uPAR expression and cell invasion in human endothelial ECV304 cells.

Single Cell Oil (SCO)-Based Bioactive Compounds: I-Enzymatic Synthesis of Fatty Acid Amides Using SCOs as Acyl Group Donors and Their Biological Activities

Fatty acid amides (FAAs) are of great interest due to their broad industrial applications. They can be synthesized enzymatically with many advantages over chemical synthesis. In this study, the fatty acid moieties of lipids of Cunninghamella echinulata ATHUM 4411, Umbelopsis isabellina ATHUM 2935, Nannochloropsis gaditana CCAP 849/5, olive oil, and an eicosapentaenoic acid (EPA) concentrate were converted into their fatty acid methyl esters and used in the FAA (i.e., ethylene diamine amides) enzymatic synthesis, using lipases as biocatalysts. The FAA synthesis, monitored using in situ NMR, FT-IR, and thin-layer chromatography, was catalyzed efficiently by the immobilized Candida rugosa lipase. The synthesized FAAs exhibited a significant antimicrobial activity, especially those containing oleic acid in high proportions (i.e., derived from olive oil and U. isabellina oil), against several human pathogenic microorganisms, insecticidal activity against yellow fever mosquito, especially those of C. echinulata containing gamma-linolenic acid, and anticancer properties against SKOV-3 ovarian cancer cell line, especially those containing EPA in their structures (i.e., EPA concentrate and N. gaditana oil). We conclude that FAAs can be efficiently synthesized using microbial oils of different fatty acid composition and used in specific biological applications.

DHA Attenuates Cerebral Edema Following Traumatic Brain Injury via the Reduction in Blood-Brain Barrier Permeability

Traumatic brain injury (TBI) could result in edema and cause an increase in intracranial pressure of the brain resulting in mortality and morbidity. Although there is hyperosmolarity therapy available for this pathophysiological event, it remains controversial. Recently, several groups have shown docosahexaenoic acid (DHA) to improve functional and histological outcomes following brain injury based on reduction of neuroinflammation and apoptosis. However, the effect of DHA on blood-brain barrier (BBB) dysfunction after brain injury has not been fully studied. Here, a controlled cortical impact rat model was used to test the effect of a single dose of DHA administered 30 min post injury. Modified neurological severity score (mNSS) and forelimb asymmetry were used to determine the functional outcomes. Neuroimaging and histology were used to characterize the edema and BBB dysfunction. The study showed that DHA-treated TBI rats had better mNSS and forelimb asymmetry score than vehicle-treated TBI rats. Temporal analysis of edema using MRI revealed a significant reduction in edema level with DHA treatment compared to vehicle in TBI rats. Histological analysis using immunoglobulin G (IgG) extravasation showed that there was less extravasation, which corresponded with a reduction in aquaporin 4 and astrocytic metalloprotease 9 expression, and greater endothelial occludin expression in the peri-contusional site of the TBI rat brain treated with DHA in comparison to vehicle treatment. In conclusion, the study shows that DHA can exert its functional improvement by prevention of the edema formation via prevention of BBB dysfunction after TBI.

α-Linolenic acid inhibits the migration of human triple-negative breast cancer cells by attenuating Twist1 expression and suppressing Twist1-mediated epithelial-mesenchymal transition

α-Linolenic acid (ALA), an essential fatty acid, has anticancer activity in breast cancer, but the mechanism of its effects in triple-negative breast cancer (TNBC) remains unclear. We investigated the effect of ALA on Twist1, which is required to initiate epithelial-mesenchymal transition (EMT) and promotes tumor metastasis, and Twist1-mediated migration in MDA-MB231, MDA-MB468 and Hs578T cells. Twist1 protein was constitutively expressed in these TNBC cells, particularly MDA-MB-231 cells. Treatment with 100 μM ALA and Twist1 siRNA markedly decreased the Twist1 protein level and cell migration. Moreover, ALA transiently attenuated the nuclear accumulation of STAT3α as well as Twist1 mRNA expression. Treatment with ALA significantly attenuated the phosphorylation of JNK, ERK and Akt and decreased the phosphorylation of Twist1 at serine 68 in MDA-MB-231 cells. ALA accelerated Twist1 degradation in the presence of cycloheximide, whereas the ubiquitination and degradation of Twist1 by ALA was suppressed by MG-132. Pretreatment with ALA mimicked Twist1 siRNA, increased the protein expression of epithelial markers such as E-cadherin, and decreased the protein expression of mesenchymal markers including Twist1, Snail2, N-cadherin, vimentin, and fibronectin. Our findings suggest that ALA can be used not only to abolish EMT but also to suppress Twist1-mediated migration in TNBC cells.

n-3 Polyunsaturated Fatty Acid Amides: New Avenues in the Prevention and Treatment of Breast Cancer

Over the last decades a renewed interest in n−3 very long polyunsaturated fatty acids (PUFAs), derived mainly from fish oils in the human diet, has been observed because of their potential effects against cancer diseases, including breast carcinoma. These n−3 PUFAs mainly consist of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) that, alone or in combination with anticancer agents, induce cell cycle arrest, autophagy, apoptosis, and tumor growth inhibition. A large number of molecular targets of n−3 PUFAs have been identified and multiple mechanisms appear to underlie their antineoplastic activities. Evidence exists that EPA and DHA also elicit anticancer effects by the conversion to their corresponding ethanolamide derivatives in cancer cells, by binding and activation of different receptors and distinct signaling pathways. Other conjugates with serotonin or dopamine have been found to exert anti-inflammatory activities in breast tumor microenvironment, indicating the importance of these compounds as modulators of tumor epithelial/stroma interplay. The objective of this review is to provide a general overview and an update of the current n−3 PUFA derivative research and to highlight intriguing aspects of the potential therapeutic benefits of these low-toxicity compounds in breast cancer treatment and care.

Trichothecin inhibits invasion and metastasis of colon carcinoma associating with SCD-1-mediated metabolite alteration

Lipid metabolic abnormalities have received intensified concerns and increased de novo synthesis of lipids is recognized as a common feature of many human cancers. Nevertheless, the role of lipid metabolism that confers aggressive properties on human cancers still remains to be revealed. Natural compounds represent an abundant pool of agents for the discovery of novel lead compounds. Trichothecin (TCN) is a sesquiterpenoid originating from an endophytic fungus of the herbal plant Maytenus hookeri Loes. Here, we assess the association of stearoyl-CoA desaturase 1 (SCD-1) over-expression with malignant progression of colorectal cancer (CRC). Based on this association, the effect of TCN on migration and invasion of colon carcinoma cells closely related to the inhibition of SCD-1 is evaluated. We further demonstrate that reduced production of unsaturated fatty acids (FAs) by blocking SCD-1 activity is beneficial for the anti-invasion effect of TCN. The aim of this study was to clarify the mechanistic connection between metabolite alterations induced by metabolic rewiring and the aggressive tumor phenotype and further develop novel pharmacological tools for the intervention of tumor invasion associated with SCD-1-mediated metabolite alterations.

1,25(OH)2 D3 attenuates indoxyl sulfate-induced epithelial-to-mesenchymal cell transition via inactivation of PI3K/Akt/β-catenin signaling in renal tubular epithelial cells

OBJECTIVES

Indoxyl sulfate (IS), a uremic toxin, has been shown to promote the epithelial-to-mesenchymal transition (EMT) of human proximal tubular cells and to accelerate the progression of chronic kidney disease (CKD). Despite the well-known protective role of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂ D₃] in EMT, the effect of 1,25(OH)₂ D₃ on IS-induced EMT in human proximal tubular epithelial cells and the underlying mechanism remain unclear. The aim of this study was to determine whether IS (0-1 mM) dose-dependently inhibited the protein expression of E-cadherin and increased the protein expression of alpha-smooth muscle actin, N-cadherin, and fibronectin.

METHODS

This study investigated the molecular mechanism by which 1,25(OH)₂ D₃ attenuates IS-induced EMT. HK-2 human renal tubular epithelial cells was used as the study model, and the MTT assay, Western Blotting, siRNA knockdown technique were used to explore the effects of 1,25(OH)₂ D₃ on EMT in the presence of IS.

RESULTS

Pretreatment with 1,25(OH)₂ D₃ inhibited the IS-induced EMT-associated protein expression in HK-2 cells. IS induced the phosphorylation of Akt (S473) and β-catenin (S552) and subsequently increased the nuclear accumulation of β-catenin. Pretreatment with 1,25(OH)₂ D₃ and LY294002 (phosphoinositide 3-kinase [PIK3] inhibitor) significantly inhibited the IS-induced phosphorylation of Akt and β-catenin, nuclear β-catenin accumulation, and EMT-associated protein expression.

CONCLUSIONS

Results from the present study revealed that the anti-EMT effect of 1,25(OH)₂ D₃ is likely through inhibition of the PI3K/Akt/β-catenin pathway, which leads to down-regulation of IS-driven EMT-associated protein expression in HK-2 human renal tubular epithelial cells.

Mitochondrial targeting of TR3 is involved in TPA induced apoptosis in breast cancer cells

TPA is considered to be a tumor promoting molecule that induces the expression of COX-2 protein. However, it is contradictory to find that TPA can induce tumor cell apoptosis and exert antitumor activity. Therefore, the role of TPA in tumorigenesis and development has not yet been elucidated. Here we show that TPA can promote the apoptosis of breast cancer cells and increase the ratio of Bax/Bcl-2. It is suggested that TPA may induce apoptosis of breast cancer cells through mitochondrial apoptosis pathway. Further studies showed that TPA could cause mitochondrial dysfunction and trigger mitochondrial apoptotic pathway. In mechanism, the mitochondrial targeting of TR3 is involved in TPA induced apoptosis in breast cancer cells. In conclusion, our findings suggest that TPA can play a role in inhibiting cancer by inducing apoptosis and TR3 is expected to be a new target for cancer treatment.

Nickel chloride administration prevents the growth of oral squamous cell carcinoma

The effect of NiCl₂ on oral squamous cell carcinoma-derived cell line HSC3 was examined. Incubation with 1 mM NiCl₂ significantly reduced the expression of MMPs at mRNA and protein levels. The in vivo orthotopic implantation model was established by injecting highly metastatic subcell line HSC3-M3 to nude mouse tongue. After 1 week of injection, mice were fed with or without 1 mM NiCl₂-containing water for two to three weeks. Immunohistochamical examination revealed that MMP9 expression was drastically reduced in NiCl2-fed mice. By CT images, cancer mass was observed as a translucent area in control mice. In NiCl₂-fed mice, much highly translucent area was observed within the translucent area. Histologically, this area corresponded to the necrotic area in the tumor mass. Real-time PCR analysis revealed the reduced expression of angiogenic factors such as IL-8 and VEGF mRNA in NiCl₂-fed mice. To further examine the effect of NiCl₂ on metastasis, human β-globin gene expression in regional lymphnodes was compared. The β-globin gene was totaly absent in NiCl₂-fed mice. Moreover, various cancer metastasis-related genes were inhibited in NiCl₂-fed mice by PCR array analysis. The results indicated that NiCl₂ might be a promising new anti-cancer therapeutics for the oral cancer treatment.

Halofuginone-induced autophagy suppresses the migration and invasion of MCF-7 cells via regulation of STMN1 and p53

Traditional Chinese medicines have been recognized as especially promising anticancer agents in modern anticancer research. Halofuginone (HF), an analog of quinazolinone alkaloid extracted from Dichroa febrifuga, is widely used in traditional medicine. However, whether HF inhibits the growth of breast cancer cells and/or reduces the migration and invasion of MCF-7 human breast cancer cells, as well as the underlying mechanisms in vitro, remains unclear. In this study, we report that an HF extract inhibits the growth of MCF-7 cells and reduces their migration and invasion, an important feature of potential anticancer agents. In addition, HF significantly increases the activation of autophagy, which is closely associated with tumor metastasis. As STMN1 and p53 have been closely implicated in breast cancer progression, we analyzed their expression in the context of HF extract treatment. Western blot analysis showed that HF suppresses STMN1 and p53 expression and activity in an autophagy-dependent manner. Collectively, these data indicate that activation of autophagy reduces expression of STMN1 and p53, and the migration and invasion of cancer cells contributes to the anti-cancer effects of the HF. These findings may provide new insight into breast cancer prevention and therapy.

Docosahexaenoic acid inhibits 12-O-tetradecanoylphorbol-13- acetate-induced fascin-1-dependent breast cancer cell migration by suppressing the PKCδ- and Wnt-1/β-catenin-mediated pathways

Fascin-1, an actin-bundling protein, plays an important role in cancer cell migration and invasion; however, the underlying mechanism remains unclear. On the basis of a 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced cell migration model, it was shown that TPA increased fascin-1 mRNA and protein expression and fascin-1-dependent cell migration. TPA dose- and time-dependently increased PKCδ and STAT3α activation and GSK3β phosphorylation; up-regulated Wnt-1, β-catenin, and STAT3α expression; and increased the nuclear translocation of β-catenin and STAT3α. Rottlerin, a PKCδ inhibitor, abrogated the increases in STAT3α activation and β-catenin and fascin-1 expression. WP1066, a STAT3 inhibitor, suppressed TPA-induced STAT3α DNA binding activity and β-catenin expression. Knockdown of β-catenin attenuated TPA-induced fascin-1 and STAT3α expression as well as cell migration. In addition to MCF-7, migration of Hs578T breast cancer cells was inhibited by silencing fascin-1, β-catenin, and STAT3α expression as well. TPA also induced Wnt-1 expression and secretion, and blocking Wnt-1 signaling abrogated β-catenin induction. DHA pretreatment attenuated TPA-induced cell migration, PKCδ and STAT3α activation, GSK3β phosphorylation, and Wnt-1, β-catenin, STAT3α, and fascin-1 expression. Our results demonstrated that TPA-induced migration is likely associated with the PKCδ and Wnt-1 pathways, which lead to STAT3α activation, GSK3β inactivation, and β-catenin increase and up-regulation of fascin-1 expression. Moreover, the anti-metastatic potential of DHA is partly attributed to its suppression of TPA-activated PKCδ and Wnt-1 signaling.

HMOX-1 inhibits TGF-β-induced epithelial-mesenchymal transition in the MCF-7 breast cancer cell line

Epithelial‑mesenchymal transition (EMT) is a key mechanism underlying metastatic breast cancer. Reactive oxygen species (ROS) play an important role in EMT. Heme oxygenase‑1 (HMOX‑1) can reduce oxidative stress. However, the effect of HMOX‑1 on the EMT process in breast cancer cells is unknown. We treated the MCF‑7 breast cancer cell line with the HMOX‑1 inducer hemin and observed that hemin induced HMOX‑1 expression and inhibited migration, invasion and ROS generation in transforming growth factor‑β (TGF‑β)‑treated MCF‑7 cells using quantitative RT‑qPCR, western blotting, wound‑healing and cell invasion assays as well as fluorescent probe DCFDA. Hemin inhibited TGF‑β‑induced EMT in the MCF‑7 cells, whereas HMOX‑1 siRNA attenuated the suppressive effect of hemin as determined by the expression and cellular distribution of selected EMT markers. In summary, our results revealed that hemin treatment increased HMOX‑1 expression and inhibited TGF‑β‑induced EMT in MCF‑7 cells.

12-O-Tetradecanoylphorbol-13-acetate (TPA) is anti-tumorigenic in liver cancer cells via inhibiting YAP through AMOT

TPA stimulates carcinogenesis in various types of cancers. However, we found that TPA inhibits transformative phenotypes in liver cancer cells via the translocation of YAP from the nucleus, where it functions as a transcriptional co-factor, to the cytoplasm. Such effects led to a separation of YAP from its dependent transcription factors. The inhibitory effects of TPA on YAP were AMOT dependent. Without AMOT, TPA was unable to alter YAP activity. Importantly, the depletion of YAP and AMOT blocked the TPA-reduced transformative phenotypes. In sum, TPA has been established as an anti-tumorigenic drug in liver cancer cells via YAP and AMOT.

Modulation of Ras/ERK and Phosphoinositide Signaling by Long-Chain n-3 PUFA in Breast Cancer and Their Potential Complementary Role in Combination with Targeted Drugs

A potential complementary role of the dietary long-chain n-3 polyunsaturated fatty acids (LCn-3 PUFA) in combination with innovative mono-targeted therapies has recently been proposed. These compounds are thought to act pleiotropically to prevent the development and progression of a variety of cancers, including breast cancer. We hereinafter critically analyze the reports investigating the ability of LCn-3 PUFA to modulate the Ras/ERK and the phosphoinositide survival signaling pathways often aberrantly activated in breast cancer and representing the main targets of innovative therapies. The in vitro or in vivo animal and human interventional studies published up to January 2017 investigating the effects of LCn-3 PUFA on these pathways in normal and cancerous breast cells or tissues were identified through a systematic search of literature in the PubMed database. We found that, in most cases, both the in vitro and in vivo studies demonstrated the ability of LCn-3 PUFA to inhibit the activation of these pro-survival pathways. Altogether, the analyzed results strongly suggest a potential role of LCn-3 PUFA as complementary agents in combination with mono-targeted therapies. Moreover, the results indicate the need for further in vitro and human interventional studies designed to unequivocally prove the potential adjuvant role of these fatty acids.

Synthesis, Characterization, and In Vitro and In Vivo Evaluations of 4-(N)-Docosahexaenoyl 2', 2'-Difluorodeoxycytidine with Potent and Broad-Spectrum Antitumor Activity

In this study, a new compound, 4-(N)-docosahexaenoyl 2′, 2′-difluorodeoxycytidine (DHA-dFdC), was synthesized and characterized. Its antitumor activity was evaluated in cell culture and in mouse models of pancreatic cancer. DHA-dFdC is a poorly soluble, pale yellow waxy solid, with a molecular mass of 573.3 Da and a melting point of about 96°C. The activation energy for the degradation of DHA-dFdC in an aqueous Tween 80–based solution is 12.86 kcal/mol, whereas its stability is significantly higher in the presence of vitamin E. NCI-60 DTP Human Tumor Cell Line Screening revealed that DHA-dFdC has potent and broad-spectrum antitumor activity, especially in leukemia, renal, and central nervous system cancer cell lines. In human and murine pancreatic cancer cell lines, the IC₅₀ value of DHA-dFdC was up to 10⁵-fold lower than that of dFdC. The elimination of DHA-dFdC in mouse plasma appeared to follow a biexponential model, with a terminal phase t_1/2 of about 58 minutes. DHA-dFdC significantly extended the survival of genetically engineered mice that spontaneously develop pancreatic ductal adenocarcinoma. In nude mice with subcutaneously implanted human Panc-1 pancreatic tumors, the antitumor activity of DHA-dFdC was significantly stronger than the molar equivalent of dFdC alone, DHA alone, or the physical mixture of them (1:1, molar ratio). DHA-dFdC also significantly inhibited the growth of Panc-1 tumors orthotopically implanted in the pancreas of nude mice, whereas the molar equivalent dose of dFdC alone did not show any significant activity. DHA-dFdC is a promising compound for the potential treatment of cancers in organs such as the pancreas.

Docosahexaenoic Acid Inhibits Tumor Promoter-Induced Urokinase-Type Plasminogen Activator Receptor by Suppressing PKCδ- and MAPKs-Mediated Pathways in ECV304 Human Endothelial Cells

The overexpression of urokinase-type plasminogen activator receptor (uPAR) is associated with inflammation and virtually all human cancers. Despite the fact that docosahexaenoic acid (DHA) has been reported to possess anti-inflammatory and anti-tumor properties, the negative regulation of uPAR by DHA is still undefined. Here, we investigated the effect of DHA on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced uPAR expression and the underlying molecular mechanisms in ECV304 human endothelial cells. DHA concentration-dependently inhibited TPA-induced uPAR. Specific inhibitors and mutagenesis studies showed that PKCδ, JNK1/2, Erk1/2, NF-κB, and AP-1 were critical for TPA-induced uPAR expression. Application of DHA suppressed TPA-induced translocation of PKCδ, activation of the JNK1/2 and Erk1/2 signaling pathways, and subsequent AP-1 and NF-κB transactivation. In conclusion, these observations suggest a novel role for DHA in reducing uPAR expression and cell invasion by inhibition of PKCδ, JNK1/2, and Erk1/2, and the reduction of AP-1 and NF-κB activation in ECV304 human endothelial cells.

Docosahexaenoic acid inhibits inflammation via free fatty acid receptor FFA4, disruption of TAB2 interaction with TAK1/TAB1 and downregulation of ERK-dependent Egr-1 expression in EA.hy926 cells

SCOPE

Inflammation is intimately associated with many cardiovascular events and docosahexaenoic acid (DHA) has been shown to protect against CVD. Egr-1 has emerged as a key regulator in the development of atherosclerosis. Free fatty acid receptor 4 (FFA4) is an n-3 FA membrane receptor. Tumor necrosis factor alpha (TNF-α) is an inflammatory mediator and transforming growth factor-β-activated kinase 1 (TAK1) is essential in the TNF-α-mediated activation of NF-κB. We examined the mechanisms underlying DHA inhibition of inflammation in human EA.hy926 cells.

METHODS AND RESULTS

TNF-α markedly induced the interaction between TAK1 binding protein (TAB) 2 and TAK1/TAB1, the phosphorylation of ERK, p38 MAPK and Akt, the expression of Egr-1 and ICAM-1, and HL-60 (monocyte-like) cell adhesion. Pretreatment with DHA attenuated TNF-α-induced phosphorylation of ERK, expression of Egr-1 and ICAM-1 and HL-60 cell adhesion. Transfection with siFFA4 reversed the DHA-mediated inhibition of TNF-α-induced Egr-1 and ICAM-1 expression, HL-60 cell adhesion and NF-κB and DNA-binding activity.

CONCLUSION

Our results suggest that the anti-inflammatory effect of DHA on the endothelium is at least partially linked to FFA4, disruption of TAB2 interaction with TAK1/TAB1 and downregulation of ERK-dependent Egr-1 and ICAM-1 expression, which leads to less HL-60 cell adhesion to TNF-α-stimulated EA.hy926 cells.

Cadmium induces matrix metalloproteinase-9 expression via ROS-dependent EGFR, NF-кB, and AP-1 pathways in human endothelial cells

Cadmium (Cd), a widespread cumulative pollutant, is a known human carcinogen, associated with inflammation and tumors. Matrix metalloproteinase-9 (MMP-9) plays a pivotal role in tumor metastasis; however, the mechanisms underlying the MMP-9 expression induced by Cd remain obscure in human endothelial cells. Here, Cd elevated MMP-9 expression in dose- and time-dependent manners in human endothelial cells. Cd increased ROS production and the ROS-producing NADPH oxidase. Cd translocates p47(phox), a key subunit of NADPH oxidase, to the cell membrane. Cd also activated the phosphorylation of EGFR, Akt, Erk1/2, and JNK1/2 in addition to promoting NF-кB and AP-1 binding activities. Specific inhibitor and mutagenesis studies showed that EGFR, Akt, Erk1/2, JNK1/2 and transcription factors NF-κB and AP-1 were related to Cd-induced MMP-9 expression in endothelial cells. Akt, Erk1/2, and JNK1/2 functioned as upstream signals in the activation of NF-κB and AP-1, respectively. In addition, N-acetyl-l-cystein (NAC), diphenyleneiodonium chloride (DPI) and apocynin (APO) inhibited the Cd-induced activation of EGFR, Akt, Erk1/2, JNK1/2, and p38 MAPK, indicating that ROS production by NADPH oxidase is the furthest upstream signal in MMP-9 expression. At present, it states that Cd displayed marked invasiveness in ECV304 cells, which was partially abrogated by MMP-9 neutralizing antibodies. These results demonstrated that Cd induces MMP-9 expression via ROS-dependent EGFR->Erk1/2, JNK1/2->AP-1 and EGFR->Akt->NF-κB signaling pathways and, in turn, stimulates invasiveness in human endothelial cells.

Docosahexaenoic Acid Downregulates EGF-Induced Urokinase Plasminogen Activator and Matrix Metalloproteinase 9 Expression by Inactivating EGFR/ErbB2 Signaling in SK-BR3 Breast Cancer Cells

Urokinase plasminogen activator (uPA) and matrix metalloproteinase 9 (MMP-9) play crucial roles in tumor metastasis. Despite the well-known anticancer role of docosa-hexaenoic acid (DHA), its specific effect on ErbB2-mediated breast cancer metastasis is not fully clarified. In this study, we investigated the effect of DHA on epidermal growth factor (EGF)-induced uPA and MMP-9 activity, expression and cell invasion in SK-BR3 breast cancer cells and the possible mechanisms involved. The results showed that EGF (40 ng/ml) induced uPA and MMP-9 mRNA and protein expression, enzyme activity, and 100 μM DHA significantly inhibited EGF-induced uPA and MMP-9 mRNA, protein expression, enzyme activity, cell migration, and cell invasion. EGF increased protein expression and phosphorylation of EGF receptor (EGFR) and ErbB2 as well as of JNK2, ERK1/2, and Akt, and these changes were attenuated by DHA pretreatment. AG1478, an inhibitor of EGFR, also attenuated EGF-induced activation of EGFR, JNK2, ERK1/2, and Akt. Knocked down ErbB2 expression resulted in a similar inhibition of uPA and MMP-9 expression as noted by DHA and AG1478. Taken together, these results suggest that suppression of EGF-induced metastasis by DHA is likely through an inhibition of EGFR and ErbB2 protein expression and the downstream target uPA and MMP-9 activation in SK-BR3 human breast cancer cells.

Elimination of ALDH+ breast tumor initiating cells by docosahexanoic acid and/or gamma tocotrienol through SHP-1 inhibition of Stat3 signaling

Study investigated the ability of docosahexaenoic acid (DHA) alone and in combination with gamma-tocotrienol (γT3) to eliminate aldehyde dehydrogenase positive (ALDH+) cells and to inhibit mammosphere formation, biomarker and functional assay for tumor initiating cells (TICs), respectively, in human triple negative breast cancer cells (TNBCs), and investigated possible mechanisms of action. DHA upregulated Src homology region 2 domain-containing protein tyrosine phosphatase-1 (SHP-1) protein levels and suppressed levels of phosphorylated signal transducer and activator of transcription-3 (pStat3) and its downstream mediators c-Myc, and cyclin D1. siRNA to SHP-1 enhanced the percentage of ALDH+ cells and Stat-3 signaling, as well as inhibited, in part, the ability of DHA to reduce the percentage of ALDH+ cells and Stat-3 signaling. γT3 alone and in combination with DHA reduced ALDH+ TNBCs, up-regulated SHP-1 protein levels, and suppressed Stat-3 signaling. Taken together, data demonstrate the anti-TIC potential of achievable concentrations of DHA alone as well as in combination with γT3.

Docosahexaenoic acid inhibits vascular endothelial growth factor (VEGF)-induced cell migration via the GPR120/PP2A/ERK1/2/eNOS signaling pathway in human umbilical vein endothelial cells

Cell migration plays an important role in angiogenesis and wound repair. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen that is essential for endothelial cell survival, proliferation, and migration. Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, shows both anti-inflammatory and antioxidant activities in vitro and in vivo. This study investigated the molecular mechanism by which DHA down-regulates VEGF-induced cell migration. HUVECs were used as the study model, and the MTT assay, Western blot, wound-healing assay, and phosphatase activity assay were used to explore the effects of DHA on cell migration. GPR120 is the putative receptor for DHA action. The results showed that DHA, PD98059 (an ERK1/2 inhibitor), and GW9508 (a GPR120 agonist) inhibited VEGF-induced cell migration. In contrast, pretreatment with okadaic acid (OA, a PP2A inhibitor) and S-nitroso-N-acetyl-DL-penicillamine (an NO donor) reversed the inhibition of cell migration by DHA. VEGF-induced cell migration was accompanied by phosphorylation of ERK1/2 and eNOS. Treatment of HUVECs with DHA increased PP2A enzyme activity and decreased VEGF-induced phosphorylation of ERK1/2 and eNOS. However, pretreatment with OA significantly decreased DHA-induced PP2A enzyme activity and reversed the DHA inhibition of VEGF-induced ERK1/2 and eNOS phosphorylation. These results suggest that stimulation of PP2A activity and inhibition of the VEGF-induced ERK1/2/eNOS signaling pathway may be involved in the DHA suppression of VEGF-induced cell migration. Thus, the effect of DHA on angiogenesis and wound repair is at least partly by virtue of its attenuation of cell migration.

Characterization of docosahexaenoic acid (DHA)-induced heme oxygenase-1 (HO-1) expression in human cancer cells: the importance of enhanced BTB and CNC homology 1 (Bach1) degradation

The effect of docosahexaenoic acid (DHA) on heme oxygenase-1 (HO-1) expression in cancer cells has never been characterized. This study examines DHA-induced HO-1 expression in human cancer cell model systems. DHA enhanced HO-1 gene expression in a time- and concentration-dependent manner, with maximal induction at 21 h of treatment. This induction of HO-1 expression was confirmed in vivo using a xenograft nude mouse model fed a fish-oil-enriched diet. The increase in HO-1 gene transcription induced by DHA was significantly attenuated by the antioxidant N-acetyl cysteine, suggesting the involvement of oxidative stress. This was supported by direct measurement of lipid peroxide levels after DHA treatment. Using a human HO-1 gene promoter reporter construct, we identified two antioxidant response elements (AREs) that mediate the DHA-induced increase in HO-1 gene transcription. Knockdown of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression compromised the DHA-induced increase in HO-1 gene transcription, indicating the importance of the Nrf2 pathway in this event. However, the nuclear protein levels of Nrf2 remained unchanged upon DHA treatment. Further studies demonstrated that DHA reduces nuclear Bach1 protein expression by promoting its degradation and attenuates Bach1 binding to the AREs in the HO-1 gene promoter. In contrast, DHA enhanced Nrf2 binding to the AREs without affecting nuclear Nrf2 expression levels, indicating a new cellular mechanism that mediates DHA's induction of HO-1 gene transcription. To our knowledge, this is the first characterization of DHA-induced HO-1 expression in human malignant cells.

Docosahexaenoic acid reverses angiotensin II-induced RECK suppression and cardiac fibroblast migration

The omega-3 polyunsaturated fatty acids (ω-3 fatty acids) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been reported to inhibit or delay the progression of cardiovascular diseases, including myocardial fibrosis. Recently we reported that angiotensin II (Ang II) promotes cardiac fibroblast (CF) migration by suppressing the MMP regulator reversion-inducing-cysteine-rich protein with Kazal motifs (RECK), through a mechanism dependent on AT1, ERK, and Sp1. Here we investigated the role of miR-21 in Ang II-mediated RECK suppression, and determined whether the ω-3 fatty acids reverse these effects. Ang II induced miR-21 expression in primary mouse cardiac fibroblasts (CFs) via ERK-dependent AP-1 and STAT3 activation, and while a miR-21 inhibitor reversed Ang II-induced RECK suppression, a miR-21 mimic inhibited both RECK expression and Ang II-induced CF migration. Moreover, Ang II suppressed the pro-apoptotic PTEN, and the ERK negative regulator Sprouty homologue 1 (SPRY1), but induced the metalloendopeptidase MMP2, all in a manner that was miR-21-dependent. Further, forced expression of PTEN inhibited Akt phosphorylation, Sp1 activation, and MMP2 induction. Notably, while both EPA and DHA reversed Ang II-mediated RECK suppression, DHA appeared to be more effective, and reversed Ang II-induced miR-21 expression, RECK suppression, MMP2 induction, and CF migration. These results indicate that Ang II-induced CF migration is differentially regulated by miR-21-mediated MMP induction and RECK suppression, and that DHA has the potential to upregulate RECK, and therefore may exert potential beneficial effects in cardiac fibrosis.

The induction of heme oxygenase-1 suppresses heat shock protein 90 and the proliferation of human breast cancer cells through its byproduct carbon monoxide

Heme oxygenase (HO)-1 is an oxidative stress-response enzyme which catalyzes the degradation of heme into bilirubin, ferric ion, and carbon monoxide (CO). Induction of HO-1 was reported to have antitumor activity; the inhibitory mechanism, however, is still unclear. In the present study, we found that treatment with [Ru(CO)3Cl2]2 (RuCO), a CO-releasing compound, reduced the growth of human MCF7 and MDA-MB-231 breast cancer cells. Analysis of growth-related proteins showed that treatment with RuCO down-regulated cyclinD1, CDK4, and hTERT protein expressions. Interestingly, RuCO treatment resulted in opposite effects on wild-type and mutant p53 proteins. These results were similar to those of cells treated with geldanamycin (a heat shock protein (HSP)90 inhibitor), suggesting that RuCO might affect HSP90 activity. Moreover, RuCO induced mutant p53 protein destabilization accompanied by promotion of ubiquitination and proteasome degradation. The induction of HO-1 by cobalt protoporphyrin IX (CoPP) showed consistent results, while the addition of tin protoporphyrin IX (SnPP), an HO-1 enzymatic inhibitor, diminished the RuCO-mediated effect. RuCO induction of HO-1 expression was reduced by a p38 mitogen-activated protein kinase inhibitor (SB203580). Additionally, treatment with a chemopreventive compound, curcumin, induced HO-1 expression accompanied with reduction of HSP90 client protein expression. The induction of HO-1 by curcumin inhibited 12-O-tetradecanoyl-13-acetate (TPA)-elicited matrix metalloproteinase-9 expression and tumor invasion. In conclusion, we provide novel evidence underlying HO-1's antitumor mechanism. CO, a byproduct of HO-1, suppresses HSP90 protein activity, and the induction of HO-1 may possess potential as a cancer therapeutic.

DHA is a more potent inhibitor of breast cancer metastasis to bone and related osteolysis than EPA

Breast cancer patients often develop bone metastasis evidenced by osteolytic lesions, leading to severe pain and bone fracture. Attenuation of breast cancer metastasis to bone and associated osteolysis by fish oil, rich in EPA and DHA, has been demonstrated previously. However, it was not known whether EPA and DHA differentially or similarly affect breast cancer bone metastasis and associated osteolysis. In vitro culture of parental and luciferase gene encoded MDA-MB-231 human breast cancer cell lines treated with EPA and DHA revealed that DHA inhibits proliferation and invasion of breast cancer cells more potently than EPA. Intra-cardiac injection of parental and luciferase gene encoded MDA-MB-231 cells to athymic NCr nu/nu mice demonstrated that DHA-treated mice had significantly less breast cancer cell burden in bone, and also significantly less osteolytic lesions than EPA-treated mice. In vivo cell migration assay as measured by luciferase intensity revealed that DHA attenuated cell migration specifically to the bone. Moreover, the DHA-treated group showed reduced levels of CD44 and TRAP positive area in bone compared to EPA-treated group. Breast cancer cell burden and osteolytic lesions were also examined in intra-tibially breast cancer cell injected mice and found less breast cancer cell growth and associated osteolysis in DHA-treated mice as compared to EPA-treated mice. Finally, doxorubicin-resistant MCF-7 (MCF-7dox) human breast cancer cell line was used to examine if DHA can improve sensitization of MCF-7dox cells to doxorubicin. DHA improved the inhibitory effect of doxorubicin on proliferation and invasion of MCF-7dox cells. Interestingly, drug resistance gene P-gp was also down-regulated in DHA plus doxorubicin-treated cells. In conclusion, DHA attenuates breast cancer bone metastasis and associated osteolysis more potently than EPA, possibly by inhibiting migration of breast cancer cell to the bone as well as by inhibiting osteoclastic bone resorption.