Modulation of arachidonic acid distribution by conjugated linoleic acid isomers and linoleic acid in MCF-7 and SW480 cancer cells

Conjugated Linoleic Acid strengthens the apoptotic effect of low-dose cisplatin in A549 cells by inducing Bcl-2 downregulation

One of the chemotherapeutic agents widely used in the treatment of non-small cell lung cancer (NSCLC) is cisplatin. However, the resistance of cancer cells to cisplatin and additionally serious side effects from cisplatin limit its use. Conjugated linoleic acid (CLA) has been shown to suppress the development of carcinogenesis in vitro and in vivo studies and has antitumoral activity in many cancers. The study aimed to investigate the potential effect of using cisplatin, the first-line treatment for NSCLC, in combination with CLA to increase its efficacy in low-dose use. MTT cytotoxicity assay was performed to determine the effects of CLA in combination with cisplatin on cell viability of NSCLC cell lines. The apoptotic effect of this combination on NSCLC cell lines and cell cycle distribution was determined by flow cytometry. At the same time, apoptosis and cell cycle-related gene expression levels were determined by Real-Time PCR. Combination treatment of low-dose cisplatin with CLA resulted in a significant decrease in cell viability compared to cisplatin alone, and an increase in the rate of apoptotic cells was observed. While cisplatin caused G1 phase arrest in cancer cells, there was an increase in cell percentages in S and G2 phases after combined application with CLA. In high-dose cisplatin administration, it was observed that the efficiency of the decrease in anti-apoptotic BCL2 expression related to resistance to chemotherapeutic agents was less than that of low-dose cisplatin administration. Combined administration of high-dose cisplatin with CLA significantly recovered BCL2 downregulation.

Anti-obesity potentiality of Tapra fish (Opisthopterus tardoore) oil

In this present investigation, we have extracted and characterized the Tapra fish oil as well as applied it to evaluate anti-obesity potentiality. The Tapra fish oil had 1.14 ± 0.10 mg KOH/g of acid value, 129.8 ± 5.09 mg KOH/g of saponification number, 2.67 ± 0.67 mEq/kg of peroxide value, 121.9 ± 2.14 mg of iodine value, and 17.67 ± 1.45 totox value. Gas Chromatography-Mass Spectrometric analysis clearly revealed the presence of nine different fatty acids. When the fish oil was applied to high-fat diet-induced obese mice, it showed significant reduction of body weight, Body Mass Index, and serum lipid profiles compared to the high-fat diet-induced obese mice. The levels of leptin and TNF-α were moderately reduced in fish oil treated high-fat diet-induced obese mice than control obese mice. In conclusion, the Tapra fish oil was enriched with essential fatty acids and it could be used as an antiobese food supplement. PRACTICAL APPLICATIONS: Considering the adverse effects of drugs used for the treatment of obesity, there is always a need to find out the alternatives. While the anti-obesity potentialities of different sea fish oil have been documented, the same for the Tapra fish (Opisthopterus tardoore) oil has not been studied at all. The extracted Tapra fish oil was found good in quality. Administration of fish oil in the mice exhibited anti-obesity effect in terms of lowering body weight, Body Mass Index, and serum lipid profiles, leptin, and TNF-α in mice model. These findings are fostering new therapeutic approaches to obesity treatment.

Use of somatic cell count as an indicator of colostrum quality

The impact of cow mammary gland diseases on the quality of colostrum is not conclusively defined; research results are conflicting. However, it is widely believed that mastitis lowers the level of immunoglobulins and the quality of the colostrum produced. Therefore, the aim of this study was to determine the influence of somatic cell counts (SCC) on the colostrum immunostimulating and chemical components. The experiment was conducted on an experimental organic dairy farm in which a herd of approximately 250 cows was kept in a freestall housing system, with the average performance exceeding 6,000 kg of milk per lactation. Colostrum and milk samples were taken individually from each cow seven times during the experiment: from the first to second day after calving–twice per day, and from the third to fifth day after calving–once per day. Therefore, after preliminary analyses, the cows were divided into two groups based on the cytological quality of their colostrum at the first collection: 1. SCC ≤400,000 cells/ml (good quality colostrum; GCC– 18 cows), 2. SCC ≥ 400,000 cells/ml (low quality colostrum; LCC– 22 cows). The study found almost double the concentration of immunoglobulins and essential fatty acids in first milking colostrum in the GCC group than in colostrum from the LCC group. In addition, an increase in the concentration of lysozyme in first milking colostrum was associated with a decrease in the concentration of immunoglobulins. In addition, the increase in the level of lysozyme was associated with a decrease in the concentration of immunoglobulins. In conclusion, the SCC of first milking colostrum can be used as an indicator of colostrum quality.

Utilization of optimized processing conditions for high yield synthesis of conjugated linoleic acid by L. plantarum AB20-961 and L. plantarum DSM2601 in semi-dry fermented sausage

The aim of this study was to utilize optimized processing conditions to obtain the highest conjugated linoleic acid (CLA) contents in semi-dry fermented sausages produced with L. plantarum AB20-961 and L. plantarum DSM 2601. Optimized conditions were 5.7 meat pH, 5% hydrolyzed safflower oil addition, 10⁸ CFU/g added starter culture, fermentation time of 73 h for L. plantarum DSM2601 and 79 h for L. plantarum AB20-961, 24 °C fermentation temperature, 65 °C internal cooking temperature and 90% relative humidity. Results indicated that CLA contents in sausages were increased 21% by L. plantarum AB20-961 and 121% by L. plantarum DSM2601 after fermentation compared to initial CLA level determined on manufacturing day (P < .05). After fermentation, an increased CLA content of sausages remained stable during heat processing and storage. Sausages incorporated with L. plantarum strains and hydrolyzed safflower oil had the highest TBARS and PUFA levels, and the lowest pH and moisture content (P < .05). Differences were not found in sensorial and other physicochemical properties among sausage treatment groups. This study demonstrated that high CLA content can be achieved in sausages by utilizing optimum processing conditions described above and starter cultures (L. plantarum AB20-961 and L. plantarum DSM2601) without any adverse effects on quality of the final product.

Anti-inflammatory potential of invasive sun corals (Scleractinia: Tubastraea spp.) from Brazil: alternative use for management?

OBJECTIVES

The objective was to analyse the anti-inflammatory potential of the invasive coral species Tubastraea coccinea and Tubastraea tagusensis.

METHODS

Methanolic extracts, fractions and synthesized compounds were evaluated for their anti-inflammatory ability, and their composition was elucidated through chemical analysis.

KEY FINDINGS

The genus Tubastraea (Order Scleractinia, Family Dendrophylliidae) (known as sun corals) presents compounds with pharmacological value. The introduction of these azooxanthellate hard corals into Brazil, initially in Rio de Janeiro state, occurred through their fouling of oil and gas platforms from the Campos oil Basin. The two invasive species have successfully expanded along the Brazilian coast and threaten endemic species and biodiversity. The HPLC-MS and GC-MS data suggest the presence of aplysinopsin analogues (alkaloids). Anti-inflammatory activity was observed in all samples tested in in-vivo assays, especially in T. coccinea. The ethyl acetate fraction from this sample was more effective in in-vitro assays for anti-inflammatory activity. Depending on the concentration, this fraction showed cytotoxic responses.

CONCLUSIONS

These species have potential pharmacological use, and considering their invasive nature, this study presents a potential alternative use, which may enhance the management of this biological invasion.

Radiolabeling of cell membrane-based nano-vesicles with 14C-linoleic acid for robust and sensitive quantification of their biodistribution

The rapid development of biomimetic cell membrane-based nanoparticles is still overshadowed by many practical challenges, one of which is the difficulty to precisely measure the biodistribution of such nanoparticles. Currently, this challenge is mostly addressed using fluorescent techniques with limited sensitivity, or radioactive labeling methods, which rarely account for the nanoparticles themselves, but their payloads instead. Here we report the development of a robust method for the innate radioactive labeling of cells and membrane-based nanoparticles and their consequent sensitive detection and biodistribution measurements. The preclinical potential of this method was demonstrated with Nano-Ghosts (NGs), manufactured from the cytoplasmic membranes of mesenchymal stem cells cultured with radioactively-labeled linoleic acid and achieving a cell labeling efficiency of 36%. Radiolabeling did not affect the physiochemical properties of the NGs, which stably retained their radiolabels. Using radioactivity measurements, we are now able to determine precisely the amount of NGs uptaken by tissues and cells, thereby providing further support to our presumed active NG targeting mechanisms. Biodistribution studies comparing radiolabeled NGs to fluorescently-labeled ones have validated our method and revealed new information, which could not be obtained otherwise, regarding the NGs' unique kinetics and rapid clearance, supporting their excellent safety profiles. The reported approach may be expanded to other membrane-based entities to facilitate and hasten their preclinical development and be used in parallel with other labeling methods to provide different and additional information.

Trans10,cis12 conjugated linoleic acid inhibits proliferation and migration of ovarian cancer cells by inducing ER stress, autophagy, and modulation of Src

The goal of this study was to investigate the anti-cancer effects of Trans10,cis12 conjugated linoleic acid (t10,c12 CLA). MTT assays and QCM™ chemotaxis 96-wells were used to test the effect of t10,c12 CLA on the proliferation and migration and invasion of cancer cells. qPCR and Western Blotting were used to determine the expression of specific factors. RNA sequencing was conducted using the Illumina platform and apoptosis was measured using a flow cytometry assay. t10,c12 CLA (IC50, 7 μM) inhibited proliferation of ovarian cancer cell lines SKOV-3 and A2780. c9,t11 CLA did not attenuate the proliferation of these cells. Transcription of 165 genes was significantly repressed and 28 genes were elevated. Genes related to ER stress, ATF4, CHOP, and GADD34 were overexpressed whereas EDEM2 and Hsp90, genes required for proteasomal degradation of misfolded proteins, were downregulated upon treatment. While apoptosis was not detected, t10,c12 CLA treatment led to 9-fold increase in autophagolysosomes and higher levels of LC3-II. G1 cell cycle arrest in treated cells was correlated with phosphorylation of GSK3β and loss of β-catenin. microRNA miR184 and miR215 were upregulated. miR184 likely contributed to G1 arrest by downregulating E2F1. miR215 upregulation was correlated with increased expression of p27/Kip-1. t10,c12 CLA-mediated inhibition of invasion and migration correlated with decreased expression of PTP1b and decreased Src activation by inhibiting phosphorylation at Tyr416. Due to its ability to inhibit proliferation and migration, t10,c12 CLA should be considered for treatment of ovarian cancer.

Phosphatidylcholine with cis-9,trans-11 and trans-10,cis-12 Conjugated Linoleic Acid Isomers: Synthesis and Cytotoxic Studies

Novel phosphatidylcholines and lysophosphatidylcholines with cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid (CLA) were synthesized in high yields (75–99 %). The in vitro cytotoxic activities of these compounds against three human cancer cell lines (HL-60, MCF-7, and HT-29) were evaluated. The results revealed that there are differences in the activity between phosphatidylcholine with cis-9,trans-11 and trans-10,cis-12 CLA acyl groups. 1,2-Di(9Z,11E)-octadecadienoyl-sn-glycero-3-phosphocholine was the most potent cytotoxic agent among all tested CLA derivatives and its IC50 (concentration of a compound that inhibits the proliferation of 50 % of the cancer cell population) was 29.4 µM against HL-60. Moreover, phosphatidylcholines with CLA acyls exhibited much lower cytotoxicity against non-cancer cells (Balb/3T3) than free CLA isomers.

Immunoregulatory mechanisms underlying prevention of colitis-associated colorectal cancer by probiotic bacteria

BACKGROUND

Inflammatory bowel disease (IBD) increases the risk of colorectal cancer. Probiotic bacteria produce immunoregulatory metabolites in vitro such as conjugated linoleic acid (CLA), a polyunsaturated fatty acid with potent anti-carcinogenic effects. This study aimed to investigate the cellular and molecular mechanisms underlying the efficacy of probiotic bacteria in mouse models of cancer.

METHODOLOGY/PRINCIPAL FINDINGS

The immune modulatory mechanisms of VSL#3 probiotic bacteria and CLA were investigated in mouse models of inflammation-driven colorectal cancer. Colonic specimens were collected for histopathology, gene expression and flow cytometry analyses. Immune cell subsets in the mesenteric lymph nodes (MLN), spleen and colonic lamina propria lymphocytes (LPL) were phenotypically and functionally characterized. Mice treated with CLA or VSL#3 recovered faster from the acute inflammatory phase of disease and had lower disease severity in the chronic, tumor-bearing phase of disease. Adenoma and adenocarcinoma formation was also diminished by both treatments. VSL#3 increased the mRNA expression of TNF-α, angiostatin and PPAR γ whereas CLA decreased COX-2 levels. Moreover, VSL#3-treated mice had increased IL-17 expression in MLN CD4+ T cells and accumulation of Treg LPL and memory CD4+ T cells.

CONCLUSIONS/SIGNIFICANCE

Both CLA and VSL#3 suppressed colon carcinogenesis, although VSL#3 showed greater anti-carcinogenic and anti-inflammatory activities than CLA. Mechanistically, CLA modulated expression of COX-2 levels in the colonic mucosa, whereas VSL#3 targeted regulatory mucosal CD4+ T cell responses.

Effects of ruminant trans fatty acids on cardiovascular disease and cancer: a comprehensive review of epidemiological, clinical, and mechanistic studies

There are 2 predominant sources of dietary trans fatty acids (TFA) in the food supply, those formed during the industrial partial hydrogenation of vegetable oils (iTFA) and those formed by biohydrogenation in ruminants (rTFA), including vaccenic acid (VA) and the naturally occurring isomer of conjugated linoleic acid, cis-9, trans-11 CLA (c9,t11-CLA). The objective of this review is to evaluate the evidence base from epidemiological and clinical studies to determine whether intake of rTFA isomers, specifically VA and c9,t11-CLA, differentially affects risk of cardiovascular disease (CVD) and cancer compared with iTFA. In addition, animal and cell culture studies are reviewed to explore potential pro- and antiatherogenic mechanisms of VA and c9,t11-CLA. Some epidemiological studies suggest that a positive association with coronary heart disease risk exists between only iTFA isomers and not rTFA isomers. Small clinical studies have been conducted to establish cause-and-effect relationships between these different sources of TFA and biomarkers or risk factors of CVD with inconclusive results. The lack of detection of treatment effects reported in some studies may be due to insufficient statistical power. Many studies have used doses of rTFA that are not realistically attainable via diet; thus, further clinical studies are warranted. Associations between iTFA intake and cancer have been inconsistent, and associations between rTFA intake and cancer have not been well studied. Clinical studies have not been conducted investigating the cause-and-effect relationship between iTFA and rTFA intake and risk for cancers. Further research is needed to determine the health effects of VA and c9,t11-CLA in humans.

Conjugated linoleic acid decreases prostaglandin synthesis in bovine luteal cells in vitro

Feeding conjugated linoleic acids (CLA) improves reproductive performance in dairy cows; however, the molecular mechanisms by which CLA improves reproduction are not understood. The effect of the CLA isomers, trans-10, cis-12 CLA and cis-9, trans-11 CLA on synthesis of progesterone, PGE(2) , and PGF(2α) , in bovine luteal cells was determined in this study. Luteal cells from three cows were cultured in medium containing 0 or 0.1 µM of trans-10, cis-12 CLA and cis-9, trans-11 CLA in varying ratios in the presence and absence of 1 µM of forskolin. Prostaglandin and progesterone concentrations were not altered by CLA isomer and ratio. Luteal cells cultured in the presence of CLA had lower PGF(2α) concentrations (62.6 ± 13.4 pg/ml vs. 55.7 ± 12.2 pg/ml; P = 0.005) and, in the absence of forskolin, lower PGE(2) concentrations (65.3 ± 15.1 pg/ml vs. 32.4 ± 14.1 pg/ml; P = 0.002) in culture media, while progesterone concentrations were not altered (P = 0.63). Relative steady-state mRNA amounts of COX-2 (1.7-fold decrease; P = 0.002), PGE synthase (1.5-fold decrease; P = 0.03) and 3β-hydroxysteroid dehydrogenase (1.6-fold decrease; P = 0.0003) were lower in CLA-treated cultures, but CLA did not significantly alter mRNA amounts of PGE(2) 9-keto-reductase, StAR, and cytochrome P450 side chain cleavage enzyme. In conclusion, a potential mechanism exists by which trans-10, cis-12 CLA and cis-9, trans-11 CLA may improve reproductive performance in dairy cows, by suppressing PGF(2α) synthesis in luteal cells via attenuation of COX-2 gene expression.

Conjugated linoleic acid suppresses colon carcinogenesis in azoxymethane-pretreated rats with long-term feeding of diet containing beef tallow

BACKGROUND

We have indicated previously that long-term feeding of beef tallow increases colorectal cancer in rats. In this study, we investigated the effects of conjugated linoleic acid (CLA) on colon carcinogenesis in rats under long-term feeding of beef tallow diets, pretreated with azoxymethane (AOM).

METHODS

Six-week-old male Sprague-Dawley rats were fed with 10% beef tallow diet only, 10% beef tallow with 1% CLA in triglyceride form (CLA-TG), or 10% beef tallow with 1% CLA in free fatty acid form (CLA-FFA). Colon carcinogenesis was induced by two intraperitoneal injections of AOM. Aberrant crypt foci (ACFs) were examined at 12 weeks. Cancer, cell proliferation, apoptosis, Wnt signaling, and the arachidonic acid cascade were examined at 44 weeks.

RESULTS

At 12 weeks, CLA-TG and CLA-FFA attenuated the increase in ACFs induced by 10% beef tallow and AOM pretreatment. At 44 weeks, both forms of CLA attenuated multiple colon cancers, and CLA-FFA reduced the incidence of colon cancer to 50% of that seen with CLA-TG. CLA-TG and CLA-FFA decreased the number of 5-bromo-2'-deoxyuridine-positive cells in AOM-pretreated rats fed with 10% beef tallow. CLA-FFA increased the number of apoptotic cells and the activity of caspase-3 in the colon mucosa, and CLA-TG enhanced the activity of caspase-3. Both forms of CLA suppressed Wnt signaling and the arachidonic acid cascade in rats treated with beef tallow and AOM.

CONCLUSION

These results suggested that CLA-TG and CLA-FFA suppressed colon carcinogenesis in rats with long-term feeding of a 10% beef tallow diet, through several mechanisms. The results of the present study with rats might be applicable to humans.

Conjugated linoleic acids as functional food: an insight into their health benefits

This review evaluates the health benefits of the functional food, conjugated linoleic acids (CLA) - a heterogeneous group of positional and geometric isomers of linoleic acid predominantly found in milk, milk products, meat and meat products of ruminants. During the past couple of decades, hundreds of reports - principally based on in vitro, microbial, animal, and of late clinical trials on humans - have been accumulating with varying biological activities of CLA isomers. These studies highlight that CLA, apart form the classical nuclear transcription factors-mediated mechanism of action, appear to exhibit a number of inter-dependent molecular signalling pathways accounting for their reported health benefits. Such benefits relate to anti-obesitic, anti-carcinogenic, anti-atherogenic, anti-diabetagenic, immunomodulatory, apoptotic and osteosynthetic effects. On the other hand, negative effects of CLA have been reported such as fatty liver and spleen, induction of colon carcinogenesis and hyperproinsulinaemia. As far as human consumption is concerned, a definite conclusion for CLA safety has not been reached yet. Parameters such as administration of the type of CLA isomer and/or their combination with other polyunsaturated fatty acids, mode of administration (eg., as free fatty acid or its triglyceride form, liquid or solid), daily dose and duration of consumption, gender, age, or ethnic and geographical backgrounds remain to be determined. Yet, it appears from trials so far conducted that CLA are functional food having prevailing beneficial health effects for humans.

t10c12 conjugated linoleic acid suppresses HER2 protein and enhances apoptosis in SKBr3 breast cancer cells: possible role of COX2

Background

HER2-targeted therapy with the monoclonal antibody trastuzumab (Herceptin®) has improved disease-free survival for women diagnosed with HER2-positive breast cancers; however, treatment resistance and disease progression are not uncommon. Current data suggest that resistance to treatment in HER2 cancers may be a consequence of NF-κB overexpression and increased COX2-derived prostaglandin E2 (PGE₂). Conjugated linoleic acid (CLA) has been shown to have anti-tumor properties and to inhibit NF-κB activity and COX2.

Methods

In this study, HER2-overexpressing SKBr3 breast cancer cells were treated with t10c12 CLA. Protein expression of the HER2 receptor, nuclear NF-κB p65, and total and phosphorylated IκB were examined by western blot and immunofluorescence. PGE₂ levels were determined by ELISA. Proliferation was measured by metabolism of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and apoptosis was measured by FITC-conjugated Annexin V staining and flow cytometry.

Results/Conclusions

We observed a significant decrease in HER2 protein expression on western blot following treatment with 40 and 80 µM t10c12 CLA (p<0.01 and 0.001, respectively) and loss of HER2 protein in cells using immunoflourescence that was most pronounced at 80 µM. Protein levels of nuclear NF-κB p65 were also significantly reduced at the 80 µM dose. This was accompanied by a significant decrease in PGE₂ levels (p = 0.05). Pretreatment with t10c12 CLA significantly enhanced TNFα-induced apoptosis and the anti-proliferative action of trastuzumab (p = 0.05 and 0.001, respectively). These data add to previous reports of an anti-tumor effect of t10c12 CLA and suggest an effect on the HER2 oncogene that may be through CLA mediated downregulation of COX2-derived PGE₂.

Conjugated linoleic acid isomers and cancer

We reviewed the literature regarding the effects of conjugated linoleic acid (CLA) preparations enriched in specific isomers, cis9, trans11-CLA (c9, t11-CLA) or trans10, cis12-CLA (t10, c12-CLA), on tumorigenesis in vivo and growth of tumor cell lines in vitro. We also examined the potential mechanisms by which CLA isomers may alter the incidence of cancer. We found no published reports that examined the effects of purified CLA isomers on human cancer in vivo. Incidence of rat mammary tumors induced by methylnitrosourea was decreased by c9, t11-CLA in all studies and by t10, c12-CLA in just a few that included it. Those 2 isomers decreased the incidence of forestomach tumors induced by benzo (a) pyrene in mice. Both isomers reduced breast and forestomach tumorigenesis. The c9, t11-CLA isomer did not affect the development of spontaneous tumors of the intestine or mammary gland, whereas t10, c12-CLA increased development of genetically induced mammary and intestinal tumors. In vitro, t10, c12-CLA inhibited the growth of mammary, colon, colorectal, gastric, prostate, and hepatoma cell lines. These 2 CLA isomers may regulate tumor growth through different mechanisms, because they have markedly different effects on lipid metabolism and regulation of oncogenes. In addition, c9, t11-CLA inhibited the cyclooxygenase-2 pathway and t10, c12-CLA inhibited the lipooxygenase pathway. The t10, c12-CLA isomer induced the expression of apoptotic genes, whereas c9, t11-CLA did not increase apoptosis in most of the studies that assessed it. Several minor isomers including t9, t11-CLA; c11, t13-CLA; c9, c11-CLA; and t7, c11-CLA were more effective than c9, t11-CLA or t10, c12-CLA in inhibiting cell growth in vitro. Additional studies with purified isomers are needed to establish the health benefit and risk ratios of each isomer in humans.

Heterologous expression of linoleic acid isomerase from Propionibacterium acnes and anti-proliferative activity of recombinant trans-10, cis-12 conjugated linoleic acid

The linoleic acid isomerase enzyme from Propionibacterium acnes responsible for bioconversion of linoleic acid to trans-10, cis-12 conjugated linoleic acid (t10, c12 CLA) was cloned and overexpressed in Lactococcus lactis and Escherichia coli, resulting in between 30 and 50 % conversion rates of the substrate linoleic acid to t10, c12 CLA. The anti-proliferative activities of the fatty acids produced following isomerization of linoleic acid by L. lactis and E. coli were assessed using the human SW480 colon cancer cell line. Fatty acids generated from both L. lactis and E. coli contained a mixture of linoleic acid and t10, c12 CLA at a ratio of ∼1.35 : 1. Following 5 days of incubation of SW480 cells with 5–20 μg ml⁻¹ (17.8–71.3 μM) of the t10, c12 CLA, there was a significant (P<0.001) reduction in growth of the SW480 cancer cells compared with the linoleic acid control. Cell viability after treatment with the highest concentration (20 μg ml⁻¹) of the t10, c12 CLA was reduced to 7.9 % (L. lactis CLA) and 19.6 % (E. coli CLA), compared with 95.4 % (control linoleic acid) and 31.7 % (pure t10, c12 CLA). In conclusion, this is believed to represent the first report in which recombinant strains are capable of producing CLA with an anti-proliferative potential.

Chronic but not acute conjugated linoleic acid treatment inhibits deoxycholic acid-induced protein kinase C and nuclear factor-kappaB activation in human colorectal cancer cells

Conjugated linoleic acid (CLA) has anti-carcinogenic effects in a variety of cancers including colon cancer. Secondary bile acids on the other hand are known as tumour promoters in colon cancer with effects on protein kinase C (PKC) and nuclear factor kappa B (NF-kappaB) signalling pathways. The aim of this study was to examine acute and chronic, isomer-specific effects of CLA on bile salt-induced PKC and NF-kappaB signal transduction in human colon cancer cells. HCT116 cells were treated with 100 mumol/l and 50 mumol/l cis-9,trans-11-CLA and trans-10,cis-12-CLA for 24 h and 14 days, respectively. The cells were then transfected with DNA coding for PKC beta1-EGFP (enhanced green fluorescent protein), PKC delta-EGFP or PKC zeta-EGFP fusion protein and activated with deoxycholic acid (DCA), phorbol myristate acetate (PMA) or C2-ceramide. PKC translocation was observed using real-time photomicroscopy and fluorescent microscopy and NF-kappaB analyses by gel shift assays. Chronic c-9,t-11-CLA and t-10,c-12-CLA treatment inhibited DCA-induced PKC beta1 and PKC delta translocation and also inhibited NF-kappaB activation. Acute CLA treatment had no effect on PKC or NF-kappaB activation. In conclusion this study indicates that chronic CLA treatment inhibits DCA-induced PKC and NF-kappaB activation in colon cancer cells. These data suggest mechanisms by which CLA may influence the course of colonic cancer.

Biological effects of conjugated linoleic acids in health and disease

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid [linoleic acid (LA), 18:2n-6] commonly found in beef, lamb and dairy products. The most abundant isomer of CLA in nature is the cis-9, trans-11 (c9t11) isomer. Commercially available CLA is usually a 1:1 mixture of c9t11 and trans-10, cis-12 (t10c12) isomers with other isomers as minor components. Conjugated LA isomer mixture and c9t11 and t10c12 isomers alone have been attributed to provide several health benefits that are largely based on animal and in vitro studies. Conjugated LA has been attributed many beneficial effects in prevention of atherosclerosis, different types of cancer, hypertension and also known to improve immune function. More recent literature with availability of purified c9t11 and t10c12 isomers suggests that t10c12 is the sole isomer involved in antiadipogenic role of CLA. Other studies in animals and cell lines suggest that the two isomers may act similarly or antagonistically to alter cellular function and metabolism, and may also act through different signaling pathways. The effect of CLA and individual isomers shows considerable variation between different strains (BALB/C mice vs. C57BL/6 mice) and species (e.g., rats vs. mice). The dramatic effects seen in animal studies have not been reflected in some clinical studies. This review comprehensively discusses the recent studies on the effects of CLA and individual isomers on body composition, cardiovascular disease, bone health, insulin resistance, mediators of inflammatory response and different types of cancer, obtained from both in vitro and animal studies. This review also discusses the latest available information from clinical studies in these areas of research.

Attenuation of breast tumor cell growth by conjugated linoleic acid via inhibition of 5-lipoxygenase activating protein

Conjugated linoleic acid (CLA) consists of a group of linoleic acid geometric isomers that have been shown to reduce tumor growth and metastasis in animal models of breast, prostate and colon cancer. To delineate a possible mechanism of action for CLA, we have recently shown that the 5-lipoxygenase product, 5-hydroxyeicosatetraenoic acid (5-HETE), could play a role in CLA alteration of mammary tumorigenesis. In this study, we determined how CLA could modulate 5-lipoxygenase activity. The t10, c12-CLA isomer reduced production of 5-HETE but not 12- and 15-HETE in MDA-MB-231 human breast tumor cells. That isomer and the c9, t11-CLA isomer decreased 5-HETE production by competition with the lipoxygenase substrate, arachidonic acid (AA). Interestingly, t10, c12-CLA reduced the expression of five-lipoxygenase activating protein (FLAP) but not the 5-lipoxygenase enzyme. Over-expression of FLAP abrogated t10, c12-CLA-reduced viability of MDA-MB-231 cells. These data suggest that the reduction of 5-HETE by t10, c12-CLA was due to competition with AA and the reduction of FLAP expression.

Isolation and characterization of the bovine Stearoyl-CoAdesaturase promoter and analysis of polymorphisms in the promoter region in dairy cows

Conjugated linoleic acid (CLA) in milk arises through microbial biohydrogenation of dietary polyunsaturated fatty acids (PUFA) in the rumen, and by the action of mammary Stearoyl-CoA desaturase (Scd). A large variation (up to tenfold) in the concentration of this fatty acid in milk has been observed, even in cows receiving the same diet. The reasons for this variation are not well understood. In this study the bovine core promoter region was isolated by a genome walking strategy from genomic DNA Genome Walker libraries and then cloned and characterized. This core promoter sequence extended approximately 600 bp upstream of the translation start site. The presence of putative transcription factor binding sites conserved in bovine, human, and mouse promoters was observed. Evidence that this promoter fragment was functional in vivo was obtained from expression studies in a mammary cell line. The promoter sequence of the scd gene was compared between cows selected for the ability to produce high fatty acid methyl esters (FAME) (2.22-2.72) in their milk, with the same promoter region of low-FAME-producing cows (0.81-1.12). However, such comparisons of the sequences of the scd promoter region of cows producing high milk CLA compared with low CLA revealed no polymorphisms in this promoter segment. Furthermore, no sequence polymorphisms were observed among the scd promoter region of Holstein Friesian, Montbeliarde, Normande, Norwegian Red, Charlois, Limousin and Kerry breeds.

Role of the Conjugated Linoleic Acid in the Prevention of Cancer

There are multiple lines of evidence that a variety of natural fatty acids are effective in health promotion. Among these fatty acids, conjugated linoleic acid (CLA)--a collective term referring to a mixture of positional and geometric isomers of linoleic acid (LA, cis-9, cis-12-octadecadienoic acid)--is currently under intensive investigation due to its health-promotion potential. The antitumor activity of CLA is of special interest, since it shows inhibitory effects against multistage carcinogenesis at relatively low dietary levels. Many studies using in vivo and in vitro models have shown that CLA suppresses the development of multistage carcinogenesis at different sites. The research to date on CLA has provided a vast amount of information about the mechanism on how CLA functions in the prevention of cancer. This article discusses characteristics of CLA in the prevention of cancer in both in vivo and in vitro studies and the possible underlying chemoprevention mechanisms.

Re-evaluation of thin layer chromatography as an alternative method for the quantification of prostaglandins from rat Kupffer cells

In contrast to conventionally used immunoassays, thin layer chromatography (TLC)--by prelabeling of cells with radioactive arachidonic acid (AA)--allows to differentiate between cellularly built and added prostanoids and thus to investigate feedback effects of prostanoids on their own release. PGD2, TXB2 and PGE2 released from zymosan-stimulated Kupffer cells were separated with distinct RF-values, corresponding to those of the pure substances. Quantification of PGD2 and PGE2 gave comparable results with TLC and immunoassays, but measurement in the presence of added prostanoids was only possible with TLC. Moreover TLC was superior to immunoassays in having a longer linear range while being comparably sensitive. Cellularly built TXB2 in its radioactively labeled form was not detectable by TLC. Inhibition of TXB2 release by externally added AA or technical artifacts were excluded, suggesting that the cellular AA-pools used for prostaglandin and thromboxane synthesis differ in their accessibility for added AA. Thus, TLC is a simple, sensitive and precise method for the quantification of cellularly built prostaglandins but not of thromboxane even in the presence of added prostanoids.

Conjugated linoleic acid reduces parathyroid hormone in health and in polycystic kidney disease in rats

BACKGROUND

Feeding conjugated linoleic acid (CLA) is reported to reduce prostaglandin E(2) synthesis, which is required for parathyroid hormone (PTH) release.

OBJECTIVE

This study was undertaken to determine whether CLA would suppress hyperparathyroidism and the resulting high-turnover bone disease in a rat model of polycystic kidney disease (PKD).

DESIGN

Outcome measurements were conducted after 8 wk of feeding diets supplemented with and without CLA (1% of dietary fat) to Han:SPRD-cy male rats (n = 52). PTH, bone formation, and resorption were assessed in addition to femur bone mass with use of dual-energy X-ray absorptiometry.

RESULTS

CLA feeding resulted in attenuation of PTH concentrations in both PKD-affected and nonaffected rats (by 60%) but did not significantly alter bone formation and resorption.

CONCLUSION

Reduction in PTH may open possibilities for CLA as an adjunctive therapy in secondary hyperparathyroidism.

Detection of conjugated C16 PUFAs in rat tissues as possible partial beta-oxidation products of naturally occurring conjugated linoleic acid and its metabolites

In a previous paper, we showed that naturally occurring conjugated linoleic acid (CLA) from butter fat is metabolized in vivo to higher metabolites such as conjugated diene (CD) 18:3, CD 20:3 and CD 20:4, all the while retaining the conjugated diene structure. In this paper, we describe the detection of two more metabolites with characteristic conjugated diene UV spectra. HPLC retention times, UV and MS spectra identified the CLA metabolites as CD 16:2 and CD 16:3. The accumulation of CD 16:2 was significantly higher than that of CD 16:3 in all tissues examined. Tissue distributions of CD 16:2 and CD 16:3 were similar, with plasma and adipose tissue showing the highest levels, while kidney had the lowest and the liver an intermediate level. CD 16 fatty acids accounted for about 20% of the total CLA metabolites. The kidney, however, was an exception where CD 16 fatty acids accounted for only 11% of total metabolites. Analyses of liver lipid classes showed that CD 16:2 and CD 16:3 were preferentially incorporated into neutral lipids. This preferential incorporation was very similar to CLA as shown previously. We hypothesize that CD 16:2 and CD 16:3 may be derived from partial beta-oxidation of CLA and CD 20:4, respectively, even though we cannot rule out that CD 16:3 may also be derived from CD 18:3 and CD 20:3. Incubation of skin human fibroblasts from X-linked adrenoleukodystrophy (ALD) patients with c9,t11 CLA showed that CD 16:2 formation in ALD cells was about 50% lower than control cells. This result may tempt to hypothesize that, at least in part, CD 16:2 is beta-oxidized in peroxisomes.

Evidence for potential mechanisms for the effect of conjugated linoleic acid on tumor metabolism and immune function: lessons from n-3 fatty acids

Conjugated linoleic acid (CLA) and the long-chain polyunsaturated n-3 fatty acids have been shown in vivo and in vitro to reduce tumor growth. Tumor growth could occur by slowing or stopping cell replication (by interfering with transition through the cell cycle), increasing cell death (via necrosis and/or apoptosis), or both. The anticancer effects of fatty acids, shown in vivo, could also be mediated by effects on the host's immune system. Although it is widely recognized that n-3 fatty acids can alter immune and inflammatory responses, considerably less is known about CLA. For n-3 fatty acids, several candidate mechanisms have been proposed for their immune effects, including changes in 1) membrane structure and composition, 2) membrane-mediated functions and signals (eg, proteins, eicosanoids), 3) gene expression, and 4) immune development. Considerable work has been done that shows the potential importance of CLA as an anticancer treatment; however, many questions remain as to how this effect occurs. This review summarizes the CLA and cancer literature and then uses the evidence for the anticancer immune and tumor properties of the long-chain n-3 fatty acids docosahexaenoic and eicosapentaenoic acids to suggest future research directions for mechanistic studies on CLA and cancer.

Conjugated linoleic acid (CLA)-enriched milk fat inhibits growth and modulates CLA-responsive biomarkers in MCF-7 and SW480 human cancer cell lines

Milk enriched in conjugated linoleic acid (CLA) was obtained from cows on pasture supplemented with full-fat rapeseeds (FFR; 2.26 g cis 9, trans 11 (c9,t11)-CLA/100 g fatty acid methyl esters) and full-fat soyabeans (1.83 g c9,t11-CLA100 g fatty acid methyl esters). A control milk fat (1.69 g c9,t11-CLA/100 g fatty acid methyl esters) was obtained from cows fed on pasture only. The present study assessed the potency of the CLA-enriched milk fats to modulate biomarkers that had previously been observed to respond to c9,t11-CLA in the MCF-7 and SW480 cell lines. Cell numbers decreased (P<0.05) by up to 61 and 58% following the incubation of MCF-7 and SW480 cells, respectively, for 4 d with milk fats (yielding CLA concentrations between 60.2 and 80.6 microM). The FFR milk fat, containing the highest CLA content, increased (P<0.05) [14C]arachidonic acid (AA) uptake into the monoacylglycerol fraction of MCF-7 and SW480 cells while it decreased (P<0.05) uptake into the phospholipid fraction of the latter. This milk fat also decreased (P<0.05) [14C]AA conversion to prostaglandin (PG) E2 while increasing conversion to PGF2alpha in both cell lines. All milk-fat samples increased (P<0.05) lipid peroxidation as measured by 8-epi-PGF2alpha in both cell lines. In SW480 cells the milk-fat samples decreased (P<0.05) bcl-2 and cytosolic glutathione levels while increasing (P<0.05) membrane-associated annexin V levels. All milk-fat samples decreased (P<0.05) the expression of ras in SW480 cells. These data suggest that milk-fat CLA was effective at modulating synthetic CLA-responsive biomarkers.

An enriched mixture of trans-10,cis-12-CLA inhibits linoleic acid metabolism and PGE2 synthesis in MDA-MB-231 cells

Conjugated linoleic acid (CLA) isomers are potent inhibitors of mammary tumor cell growth. Evidence suggests that CLA modulates essential fatty acid (EFA) metabolism; however, it is not clear which parts of this pathway are important regulatory points modulated by CLA. Enriched mixtures of D9-cis,11-trans (D9c,11t)- and D10-trans,12-cis (D10t,12c)-18:2 were used to assess outcome measures of EFA metabolism pertaining to membrane phospholipid incorporation, tumor cell growth, and prostaglandin E2 (PGE2) synthesis in the MDA-MB-231 mammary tumor cell line. Tumor cells were treated with linoleic acid (LA), an equal mixture (Mix), or enriched preparations of D9c,11t- or D10t,12c-18:2. Treatment with Mix or the enriched mixture of D10t,12c-18:2 significantly inhibited the synthesis of arachidonic acid (AA) from LA, resulting in increased levels of LA and decreased levels of AA in membrane phosphatidylcholine and phosphatidylethanolamine (P < 0.05). LA and AA levels were not altered in cells treated with enriched D9c,11t-18:2 and were similar to those in LA control treated cells. All CLA treatments reduced [3H]thymidine uptake, an indicator of tumor cell growth, by more than one-half relative to LA controls. MDA-MB-231 cells challenged with AA in the presence of all CLA mixtures resulted in significantly reduced PGE2 synthesis relative to controls treated with LA (P < 0.05). It is evident that individual isomers exert inhibitory effects at specific steps of EFA metabolism, which correspondingly leads to a reduction in PGE2 synthesis and, ultimately, tumor growth.

Conjugated Linoleic Acid Inhibits Cell Proliferation through a p53-Dependent Mechanism: Effects on the Expression of G1-Restriction Points in Breast and Colon Cancer Cells

Previous reports have documented the antiproliferative properties of a mixture of conjugated isomers (CLA) of linoleic acid [LA (18:2)]. In this study, we investigated the mechanisms of CLA action on cell cycle progression in breast and colon cancer cells. Treatment with CLA inhibited cell proliferation in breast cancer MCF-7 cells containing wild-type p53 (p53(+/+)). At cytostatic concentrations, CLA elicited cell cycle arrest in G1 and induced the accumulation of the tumor suppressors p53, p27 and p21 protein. Conversely, CLA reduced the expression of factors required for G1 to S-phase transition including cyclins D1 and E, and hyperphoshorylated retinoblastoma Rb protein. In contrast, the overexpression of mutant p53 (175Arg to His) in MFC-7 cells prevented the CLA-dependent accumulation of p21 and the reduction of cyclin E levels suggesting that the expression of wild-type p53 is required for CLA-mediated activation of the G1 restriction point. To further elucidate the role of p53, the effects of CLA in colon cancer HCT116 cells (p53(+/+)) and p53-deficient (p53(-/-)) HCT116 cells (HCTKO) were examined. The treatment of HCT116 cells with CLA increased the levels of p53, p21, p27 and hypophosphorylated (pRb) protein and reduced the expression of cyclin E, whereas these effects were not seen in p53-deficient HCTKO cells. The t10,c12-CLA isomer was more effective than c9,t11-CLA in inhibiting cell proliferation of MCF-7 breast cancer cells and enhancing the accumulation of p53 and pRb. We conclude that the antiproliferative properties of CLA appear to be a function, at least in part, of the relative content of specific isomers and their ability to elicit a p53 response that leads to the accumulation of pRb and cell growth arrest.

Dietary conjugated linoleic acid reduces PGE2 release and interstitial injury in rat polycystic kidney disease

BACKGROUND

Conjugated linoleic acid (CLA) describes positional isomers of linoleic acid (LA). Experimental health benefits of CLA include amelioration of malignancy and inflammatory disease and reduction of adiposity. The Han:SPRD-cy rat model of polycystic kidney disease (PKD) features prominent renal interstitial inflammation and fibrosis that is amenable to dietary modification. We studied CLA supplementation in the modification of inflammatory outcomes in the Han:SPRD-cy rat.

METHODS

Male offspring of Han:SPRD-cy heterozygotes were fed diets, using corn oil or corn oil with a CLA enriched oil (1% of diet by weight as CLA). After 8 weeks, measurements included renal function and morphometry, ex vivo release of renal prostaglandin E2 (PGE2), and renal and hepatic tissue fatty acid profiles.

RESULTS

Urine creatinine was significantly higher in PKD animals fed CLA (P = 0.004), but differences in serum creatinine and creatinine clearance did not quite reach significance in PKD animals. CLA feeding reduced interstitial inflammation (P < 0.001), fibrosis (P = 0.03), and renal PGE2 release (P = 0.02). Cystic change and oxidized low-density lipoprotein (LDL) staining did not change significantly. CLA feeding produced increased renal and hepatic CLA isomers. Hepatic, but not renal, LA proportion was reduced on the CLA diet. The renal proportion of the PGE2 precursor, arachidonic acid (AA), was not changed by diet, but hepatic AA proportion increased significantly with CLA feeding (P= 0.009).

CONCLUSION

CLA reduces renal production of PGE2, without reduced availability of the precursor fatty acid, AA. Short-term feeding of CLA to Han:SPRD-cy rats also has significant renal anti-inflammatory and antifibrotic effects. As inflammation and fibrosis are important components of the progression of chronic renal injury, CLA may be a useful agent in dietary amelioration of renal disease.

Vaccenic acid (t11-18:1) is converted to c9,t11-CLA in MCF-7 and SW480 cancer cells

The aims of this study were to determine whether vaccenic acid (VA; t11-18:1) is converted to c9,t11-CLA in human mammary (MCF-7) and colon (SW480) cancer cell lines and whether VA influences cell viability and other CLA-bioresponsive markers. When cells were incubated in the presence of VA at concentrations of 5 to 20 microg/mL, both VA and c9,t11-CLA increased in cellular lipids in a dose-dependent manner. After 4 d of incubation of SW480 and MCF-7 cells with VA (20 microg/mL), c9,t11-CLA increased from undetectable levels to 8.57 and 12.14 g/100 g FAME in cellular lipids, respectively. VA supplementation for 4 d at 5, 10, and 15 microg/mL had no effect on cell growth, whereas 20 microg/mL significantly (P < 0.05) reduced cell growth in both cell lines. VA (20 microg/mL) treatment induced DNA fragmentation and significantly (P < 0.05) depleted cytosolic GSH levels in the SW480 cell line after 4 d of incubation, suggesting that apoptosis was the mode of cell death induced by VA. Both VA and c9,t11-CLA reduced (P < 0.05) total ras expression in SW480 cells. 14C-Arachidonic acid uptake into the MG fraction was significantly increased (P < 0.05) in both cell lines while uptake into the phospholipid fraction decreased in response to VA. VA treatment significantly (P < 0.05) increased 8-epi-prostaglandin F2alpha in both cell lines. The data indicate that growth suppression and cellular responses of both cells lines are likely mediated by VA desaturation to c9,t11-CLA via delta9-desaturase.

Effects of cis-9, trans-11 and trans-10, cis-12 conjugated linoleic acid (CLA) isomers on immune function in healthy men

OBJECTIVES

To study the effects of two different mixtures of the main conjugated linoleic acid (CLA) isomers cis-9, trans-11 CLA and trans-10, cis-12 CLA on human immune function.

DESIGN

Double-blind, randomized, parallel, reference-controlled intervention study.

SUBJECTS AND INTERVENTION

Seventy-one healthy males aged 31-69 y received one of the following treatments: (1). mixture of 50% c9,t11 CLA and 50% t10,c12 CLA isomers (CLA 50:50); (2). mixture of 80% c9,t11 CLA and 20% t10,c12 CLA isomers (CLA 80:20); and (3). sunflower oil fatty acids (reference). The treatments were given as supplements in softgel capsules providing a total of 1.7 g (c9,t11+t10,c12) CLA fatty acids (50:50) or 1.6 g (c9,t11+t10,c12) CLA glycerides (80:20) per day in treatment groups for 12 weeks.

RESULTS

Almost twice as many subjects reached protective antibody levels to hepatitis B when consuming CLA 50:50 fatty acids (15/24, 62%) compared with subjects consuming the reference substance (7/21, 33%, P=0.075). In subjects consuming CLA 80:20 glycerides this was 8/22 (36%). Other aspects of immune function, ie DTH responses, NK cell activity, lymphocyte proliferation and production of TNF-alpha, IL1-beta, IL6, IFN-gamma, IL2, IL4, and PGE(2), were not affected.

CONCLUSION

This is the first study that suggests that CLA may beneficially affect the initiation of a specific response to a hepatitis B vaccination. This was seen in the CLA 50:50, but not in the CLA 80:20 group.

Effect of separate conjugated linoleic acid isomers on murine mammary tumorigenesis

Recent studies have linked conjugated linoleic acid (CLA) to altered tumorigenesis of several sites. We showed recently that a mixture of CLA isomers was able to significantly decrease mammary tumor metastasis in mice. That effect was seen with as little as 0.1% CLA in the diet. Other studies with dietary CLA have shown that various isomers may have differential effects. The purpose of this work was to assess which individual CLA isomers had similar effects in alteration of mouse mammary tumor metastasis. For that, we fed six 20% (w/w) total fat diets which contained either no CLA, low (0.1%, w/w) or high (0.25%, w/w) levels of cis9,trans11-CLA (c9,t11), trans10,cis12-CLA (t10,c12) or a mixture of the 2 isomers (0.125% of each, w/w) as free fatty acids. Neither the separate isomers nor the mixture had an effect on the latency or growth of primary line 4526 tumors when compared to the group without CLA. However, all diets containing CLA significantly decreased the total tumor burden (volume of tumor, mm(3)) in lungs of mice from both spontaneous metastasis (reduced by 42-73%) as well as implantation and survival of the metastatic cell (reduced by 46-61%) when compared with diets containing no CLA. Diets containing a greater concentration of either c9,t11 or t10,c12 had a significantly greater effect compared to the lower concentrations of the respective isomers when metastatic nodule size and total tumor burden were assessed. The diet containing both isomers decreased total tumor burden similarly to the diets containing the lower concentration of each of the isomers. Thus, the effects of c9,t11 and t10,c12 may not be additive and possibly share similar mechanisms for decreasing metastatic tumor burden in mice transplanted with mammary tumor cells.

Inhibition of conjugated linoleic acid on mouse forestomach neoplasia induced by benzo (a) pyrene and chemopreventive mechanisms

AIM: To explore the inhibition of conjugated linoleic acid isomers in different purity (75% purity c9, t11-, 98% purity c9, t11- and 98% purity t10,c12-CLA) on the formation of forestomach neoplasm and cheopreventive mechanisms.

METHODS: Forestomach neoplasm model induced by B (a) P in KunMing mice was established. The numbers of tumor and diameter of each tumor in forestomach were counted; the mice plasma malondialdehyde (MDA) were measured by TBARS assay; TUNEL assay was used to analyze the apoptosis in forestomach neoplasia and the expression of MEK-1, ERK-1, MKP-1 protein in forestomach neoplasm were studied by Western Blotting assay.

RESULTS: The incidence of neoplasm in B (a) P group, 75% purity c9,t11-CLA group, 98% purity c9,t11-CLA group and 98% purity t10,c12-CLA group was 100%, 75.0% (P > 0.05), 69.2% (P < 0.05) and 53.8% (P < 0.05) respectively and the effect of two CLA isomers in 98% purity on forestomach neoplasia was significant; CLA showed no influence on the average tumor numbers in tumor-bearing mouse, but significantly decreased the tumor size, the tumor average diameter of mice in 75% purity c9,t11-CLA group, 98% purity c9,t11-CLA group and 98% purity t10,c12-CLA group was 0.157 ± 0.047 cm, 0.127 ± 0.038 cm and 0.128 ± 0.077 cm (P < 0.05) and 0.216 ± 0.088 cm in B (a) P group; CLA could also significantly increase the apoptosis cell numbers by 144.00 ± 20.31, 153.75 ± 23.25, 157.25 ± 15.95 (P < 0.05) in 75% purity c9,t11-CLA group, 98% purity c9,t11-CLA group and 98% purity t10,c12-CLA group (30.88 ± 3.72 in BP group); but there were no significant differences between the effects of 75% purity c9,t11-CLA and two isomers in 98% purity on tumor size and apoptotic cell numbers; the plasma levels of MDA in were increased by 75% purity c9,t11-CLA, 98% purity c9,t11-CLA and 98% purity t10,c12-CLA. The 75% purity c9,t11-CLA showed stronger inhibition; CLA could also inhibit the expression of ERK-1 protein and promote the expression of MKP-1 protein, however no influence of CLA on MEK-1 protein was observed.

CONCLUSION: Two isomers in 98% purity show stronger inhibition on carcinogenesis. However, the inhibitory mechanisms of CLA on carcinogenesis is complicated, which may be due to the increased mice plasma MDA, the inducing apoptosis in tumor tissues. And the effect of CLA on the expression of ERK-1 and MKP-1 may be one of the mechanisms of the inhibition of CLA on the tumor.

Prevention of mammary cancer with conjugated linoleic acid: role of the stroma and the epithelium

Conjugated linoleic acid (CLA), found naturally in dairy products and ruminant meats, refers to isomers of octadecadienoic acid with conjugated double bonds. CLA inhibits both DMBA- and NMU-induced rat mammary carcinogenesis, and its antitumor efficacy is similar whether it is fed only during puberty, or continuously during promotion. Pubertal feeding is associated with a reduced proliferation of the epithelial cells within the terminal end buds (TEBs) and lobular epithelium, and results in a decrease in the epithelial density, suggesting a reduction in the carcinogen-sensitive target population. During promotion, CLA feeding induces apoptosis of preneoplastic lesions. The effects of CLA are mediated by a direct action on the epithelium, as well as by an indirect effect through the stroma. CLA is incorporated into the neutral lipids of mammary adipocytes, where it can serve as a local reservoir of CLA. Additionally, CLA induces the adipogenic differentiation of multipotent mammary stromal cells in vitro, and inhibits their development into three-dimensional capillary networks. This suggested that CLA might inhibit angiogenesis in vivo, a hypothesis that was subsequently confirmed. The antiangiogenic effect is mediated, in part, through a CLA-induced decrease in serum VEGF (vascular endothelial growth factor) and mammary gland VEGF and flk-1. Together, the data suggest that CLA may be an excellent candidate for prevention of breast cancer.

Effect of apoptosis on gastric adenocarcinoma cell line SGC-7901 induced by cis-9, trans-11-conjugated linoleic acid

AIM: To determine the effect of apoptosis on gastric cancer cells (SGC-7901) induced by cis-9, trans-11-conjugated linoleic acid (c9, t11-CLA) and its possible mechanism in the inhibition of cancer cells growth.

METHODS: Using cell culture, flow cytometery and immunocytochemical techniques, we examined the cell growth, frequency of apoptosis and distribution of cell cycle, expression of ki67, bcl-2, Fas, and c-myc of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25, 50, 100 and 200 μmol·L^-1) of c9, t11-CLA for 24 h and 48 h, with a negative control (0.1% ethanol).

RESULTS: The growth of SGC-7901 cells was inhibited by c9,t11-CLA. Eight days after treatment with various concentrations of c9,t11-CLA, as mentioned above, the inhibition rates were 5.9%, 20.2%, 75.6% and 82.4%, respectively. The frequency of apoptosis on SGC-7901 cells induced by different concentrations of c9, t11-CLA (except for 25 μmol·L^-1, 24 h) was significantly greater than that in the negative control (P < 0.01). To further investigate the influence of the cell cycle progression, we found that apoptosis induced by c9, t11-CLA may be involved in blocking the cell cycle of SGC-7901 cells. Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations for various time periods significantly decreased the expressions of ki67 (the expression rates were 18.70%-3.20%, at 24 h and 8.10%-0.20% at 48 h, respectively), bcl-2 (4.30%-0.15% at 24 h and 8.05%-0% at 48 h),and c-myc (4.85%-2.20% at 24 h and 4.75%-0.30% at 48 h) as compared with those in the controls (the expressions of ki67, bcl-2, and c-myc were 15.1% at 24 h and 13.5% at 48 h, 6.80% at 24 h and 8.00% at 48 h, 5.50% at 24 h and 5.30% at 48 h, respectively) (P < 0.01), whereas the expressions of Fas were increased (0.60%-2.75%, 24 h and 0.45%-5.95%, 48 h).

CONCLUSION: The growth and proliferation of SGC-7901 cells are inhibited by c9, t11-CLA via blocking the cell cycle, pathways of bcl-2-associated mitochondria with reduced expression of bcl-2 and Fas-associated death domain protein (FADD) with enhanced expression of Fas. But expression of c-myc on SGC-7901 cells is lower than that in negative control, which needs to be studied further.