Elisabetta Piccioni

Dietary supplementation with eicosapentaenoic and docosahexaenoic acid inhibits growth of Morris hepatocarcinoma 3924A in rats: effects on proliferation and apoptosis

The effect of individual administration of low doses of highly purified eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (1 g/kg body weight) on the growth of Morris hepatocarcinoma 3924A transplanted in ACI/T rats was investigated. Both EPA and DHA inhibited growth of the hepatocarcinoma (50% reduction of tumor weight or volume at the 19th day after transplantation for both of the n‐3 PUFA groups). EPA treatment reduced the percentage of proliferating tumor cells labeled with BUdR (10‐fold), whereas DHA did not. Conversely, DHA supplementation induced a doubling of the number of cells undergoing apoptosis (labeled by TUNEL), whereas EPA treatment was much less effective. Analysis of changes in phospholipid fatty acids in tumor‐cell membranes after both treatments with EPA and DHA showed a significant reduction in arachidonic‐acid levels. EPA and docosapentaenoic acid (DPA), its elongation product, were increased in the phospholipids from EPA‐treated animals. DHA and EPA, but not DPA, were increased in the DHA‐treated group. It is concluded from the results of the present study that the anti‐tumoral effect of EPA is related mainly to its inhibition of cell proliferation, whereas that of DHA corresponds with its induction of apoptosis. The alterations in fatty‐acid composition induced by EPA or DHA appear to be factors underlying their differential actions on cell proliferation and apoptosis. Int. J. Cancer 75:699–705, 1998.© 1998 Wiley‐Liss, Inc.

Dietary polyunsaturated fatty acids as inducers of apoptosis: implications for cancer

It has recently become clear the role played by alterations in apoptosis during the development of several chronic diseases (i.e. inflammatory, neurodegenerative and neoplastic pathologies). For this reason, the research for possible therapeutic strategies involving the modulation of the apoptotic pathways has attracted considerable interest in the past few years. In particular, it has been shown that apoptosis may be induced or inhibited by a variety of nutritional compounds providing health benefits. The aim of this review is to examine the ability of different dietary polyunsaturated fatty acids (PUFAs) to induce apoptosis, especially in the cancer field. The molecular effects of different PUFAs found in dairy products, meat, fish, vegetable seeds and oils, and known to affect the incidence and progression of cancer and other chronic diseases, will be analyzed. To this aim, our effort will concentrate in critically reviewing the published works concerning the effects of: (a) the n-6 PUFAs γ-linolenic acid, arachidonic acid, and conjugated linoleic acid; (b) the n-3 PUFAs eicosapentaenoic acid and docosahexaenoic acid on the apoptotic process. We will also pay attention to the recent findings regarding the possible role of PUFAs as regulators of the endoplasmic reticulum stress-pathway of apoptosis.

Prooxidant effects of β-carotene in cultured cells

There is a growing body of interest on the role of beta-carotene and other carotenoids in human chronic diseases, including cancer. While epidemiological evidence shows that people who ingest more dietary carotenoids exhibit a reduced risk for cancer, results from intervention trials indicate that supplemental beta-carotene enhances lung cancer incidence and mortality among smokers. A possible mechanism which can explain the dual role of beta-carotene as both a beneficial and a harmful agent in cancer as well as in other chronic diseases is its ability in modulating intracellular redox status. beta-Carotene may serve as an antioxidant or as a prooxidant, depending on its intrinsic properties as well as on the redox potential of the biological environment in which it acts. This review summarizes the available evidence for a prooxidant activity of beta-carotene in cultured cells, focusing on biochemical and molecular markers of oxidative stress, which have been reported to be enhanced by the carotenoid.

n-3 Polyunsaturated Fatty Acids and the Prevention of Colorectal Cancer: Molecular Mechanisms Involved

Increasing evidence supports the hypothesis that nutrition habits play a critical role in the incidence and growth of colorectal cancer. Among dietary factors, fish-derived n-3 polyunsaturated fatty acids (PUFAs) have gained particular interest, since epidemiological studies have shown a reduced incidence of this cancer in populations consuming high levels of fish. Also a variety of experimental studies and different clinical trials substantiated the beneficial role of n-3 PUFAs. Such an anti-neoplastic activity has been related to the regulatory effects exhibited by n-3 PUFAs on cell proliferation and apoptosis. Anti-angiogenic and anti-metastatic effects have been also reported for these fatty acids. Finally, it has been suggested that they may act as adjuvant therapeutic agents sensitizing tumors, including colon cancer, to different anti-neoplastic drugs. Several molecular mechanisms have been hypothesized to explain their anti-neoplastic action and, in particular, the modulating effect on the expression of several proteins involved in the regulation of cell cycle and apoptosis, such as Bcl-2, Bax, c-Myc seem to play a central role. Their inhibitory action has been also recently suggested for the molecular pathways driven by COX-2 and beta-catenin, known to play a major role in the development and progression of colon cancer. The aim of the present review is to analyze the anti-neoplastic effect of n-3 PUFAs towards colon cancer, and examine the molecular mechanisms involved.

Cell proliferation’ differentiation’ and apoptosis are modified by n−3 polyunsaturated fatty acids in normal colonic mucosa

Supplementation with low doses of eicosapentaenoic (EPA) or docosahexaenoic (DHA) acid was used here to investigate changes in epithelial proliferation’ differentiation’ and apoptosis in normal rat colonic mucosa. ACI/T rats received by oral administration low doses of purified EPA or DHA ethyl esters (1g/kg body weight) and colonic mucosa was analyzed for cell proliferation’ differentiation’ and apoptosis. n−3 Polyunsaturated fatty acid incorporation into membrane phospholipids was investigated as reflections of fatty acid metabolism. Both EPA and DHA suppressed colonocyle proliferation and increased the numbers of differentiating and apoptotic cells without modification of the crypt morphology and the number of cells per crypt columns. A significant incorporation of the supplemented fatty acids into total phospholipids was observed. This enrichment was accompanied by a decreased content in arachidonic acid. The observation that EPA and DHA do not alter crypt morphology although they modify cell turnover in normal colonic mucosa suggests a possible use of these fatty acids as dietary chemopreventive agents.

Antineoplastic Effects of N-3 Polyunsaturated Fatty Acids in Combination With Drugs and Radiotherapy: Preventive and Therapeutic Strategies

Many data support the beneficial effect of n-3 polyunsaturated fatty acids (PUFAs) as chemopreventive and chemotherapeutic agents in the treatment of several chronic pathologies including cancer. Different molecular mechanisms have been proposed to explain their effects, including alterations in arachidonic acid oxidative metabolism and metabolic conversion of n-3 PUFAs to novel discovered bioactive derivatives; modification of oxidative stress; changes in cell membrane fluidity and structure and altered metabolism and function of membrane proteins. Considerable knowledge has been recently gathered on the possible beneficial effects of n-3 PUFAs administered in combination with different antineoplastic drugs and radiotherapy against melanoma, leukemia, neuroblastoma, and colon, breast, prostate, and lung cancer. The efficacy of these combinations has been demonstrated both in vivo and in vitro, and clinical trials have also been conducted. The aim of this review is to analyze all the n-3 PUFA combinations investigated so far, their efficacy, and the possible molecular mechanisms involved. It would be highly auspicable that the detailed analysis of the literature in this field could further support the common use of n-3 PUFAs in combination with other chemopreventive agents and warrant more clinical investigations designed to test the effectiveness of n-3 PUFA treatments coupled with conventional antineoplastic therapies.

Docosahexaenoic acid induces apoptosis in lung cancer cells by increasing MKP-1 and down-regulating p-ERK1/2 and p-p38 expression

Different agents able to modulate apoptosis have been shown to modify the expression of the MAP-kinase-phosphatase-1 (MKP-1). The expression of this phosphatase has been considered a potential positive prognostic factor in lung cancer, and smoke was shown to reduce the levels of MKP-1 in ferret lung. Our aim was to assess whether the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), known to inhibit the growth of several cancer cells mainly inducing apoptosis, may exert pro-apoptotic effect in lung cancer cells by modifying MKP-1 expression. We observed that DHA increased MKP-1 protein and mRNA expression and induced apoptosis in different lung cancer cell lines (mink Mv1Lu adenocarcinoma cells, human A549 adenocarcinoma and human BEN squamous carcinoma cells). We inhibited the pro-apoptotic effect of DHA by treating the cells with the phosphatase inhibitor Na3VO4 or by silencing the MKP-1 gene with the specific siRNA. This finding demonstrated that the induction of apoptosis by DHA involved a phosphatase activity, specifically that of MKP-1. DHA reduced also the levels of the phosphorylated MAP-kinases, especially ERK1/2 and p38. Such an effect was not observed when the MKP-1 gene was silenced. Altogether, the data provide evidence that the DHA-induced overexpression of MKP-1 and the resulting decrease of MAP-kinase phosphorylation by DHA may underlie the pro-apoptotic effect of this fatty acid in lung cancer cells. Moreover, they support the hypothesis that DHA may exert chemopreventive action in lung cancer.

DHA induces apoptosis by altering the expression and cellular location of GRP78 in colon cancer cell lines.

n-3 polyunsaturated fatty acids exert growth-inhibitory and pro-apoptotic effects in colon cancer cells. We hypothesized that the anti-apoptotic glucose related protein of 78kDa (GRP78), originally described as a component of the unfolded protein response in endoplasmic reticulum (ER), could be a molecular target for docosahexaenoic acid (DHA) in these cells. GRP78 total and surface overexpression was previously associated with a poor prognosis in several cancers, whereas its down-regulation with decreased cancer growth in animal models. DHA treatment induced apoptosis in three colon cancer cell lines (HT-29, HCT116 and SW480), and inhibited their total and surface GRP78 expression. The cell ability to undergo DHA-induced apoptosis was inversely related to their level of GRP78 expression. The transfection of the low GRP78-expressing SW480 cells with GRP78-GFP cDNA significantly induced cell growth and inhibited the DHA-driven apoptosis, thus supporting the essential role of GRP78 in DHA pro-apoptotic effect. We suggest that pERK1/2 could be the first upstream target for DHA, and demonstrate that, downstream of GRP78, DHA may exert its proapoptotic role by augmenting the expression of the ER resident factors ERdj5 and inhibiting the phosphorylation of PKR-like ER kinase (PERK), known to be both physically associated with GRP78, and by activating caspase-4. Overall, the regulation of cellular GRP78 expression and location is suggested as a possible route through which DHA can exert pro-apoptotic and antitumoral effects in colon cancer cells.

Serum tumour necrosis factor-alpha levels in cancer patients are discontinuous and correlate with weight loss.

Tumour necrosis factor‐α (TNF) has been regarded as a potential mediator of cancer cachexia. Assessment of TNF circulating levels in cancer patients and their correlation with weight loss has led to controversial results.

DHA induces apoptosis and differentiation in human melanoma cells in vitro: involvement of HuR-mediated COX-2 mRNA stabilization and β-catenin nuclear translocation

The pro-inflammatory phenotype accompanying melanoma progression includes an enhanced expression of cyclooxygenase-2 (COX-2), which plays an important role in the acquisition of apoptosis resistance, and is a suitable target for melanoma prevention and therapy. We observed that the WM266-4 metastatic melanoma cell line showed a constitutive COX-2 expression higher than that of the primary WM115 cells, an increased cytosolic level of the COX-2 messenger RNA (mRNA)-stabilizer human antigen R (HuR) and a lower susceptibility to basal apoptosis. The transfection of HuR siRNA induced apoptosis and reduced COX-2 protein abundance in both the cells. The same effects were observed treating the cells with the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), which reduced the cytoplasmic location and expression of HuR and, correspondently, decreased COX-2 protein expression and induced apoptosis. DHA also decreased the expression and stability of COX-2 mRNA, increased the β-catenin expression in the nuclei and reduced it in the cytosol, where it forms a complex with HuR and COX-2 mRNA. DHA had also a pro-differentiating effect, which is compatible with the nuclear translocation of β-catenin. These findings allow us to associate for the first time the constitutive expression of COX-2 in melanoma cells to the HuR-mediated stabilization of its mRNA and suggest that also β-catenin may play a role in HuR-mediated COX-2 stabilization in these cells. The data demonstrate that the HuR-mediated stabilization of COX-2 may represent a target of DHA action in melanoma cells and suggest the application of DHA in the prevention and therapy of melanoma.