Involvement of JNK pathway in the promotion of the early stage of colorectal carcinogenesis under high-fat dietary conditions

Quercetin reverses 5-fluorouracil resistance in colon cancer cells by modulating the NRF2/HO-1 pathway

Quercetin (Que) has been proven to enhance the chemosensitivity of multiple cancers, including colon cancer (CC). However, whether the combination of Que and 5-fluorouracil (5-FU) has a synergistic effect on drug-resistant CC cells has not previously been reported. The effect of Que (5 and 10 μg/mL) on cell vitality and apoptosis of CC and CC drug-resistant cells was examined using a cell counting kit-8 (CCK-8) and flow cytometry. After cells were treated with 5-FU (10, 40 μg/mL), Que (10 μM, 40 μM), or 5-FU in combination with Que, cell proliferation, apoptosis, oxidative stress-related factors, reactive oxygen species (ROS), and nuclear factor erythroid 2-related factor (Nrf2)/heme oxygenase-1 (HO-1) pathway-related factors were examined by colony formation assay, flow cytometry, ELISA, ROS kit, immunofluorescence assay, and Western blot. The results showed that 5-FU reduced cell viability and induced apoptosis of CC as well as 5-FU-resistant CC cells. Que further restrained the proliferation, oxidative stress-related factors (SOD, CAT, GPx, and GR), ROS production, and induced apoptosis in CC cells and 5-FU-resistant CC cells induced by 5-FU. Moreover, the combination of Que and 5-FU attenuated the Nrf2/HO-1 pathway-related marker levels in CC cells and 5-FU-resistant CC cells. Therefore, our results suggest that Que reverses 5-FU resistance in CC cells via modulating the Nrf2/HO-1 pathway.

The lipid peroxidation product EKODE exacerbates colonic inflammation and colon tumorigenesis

Oxidative stress is emerging as an important contributor to the pathogenesis of colorectal cancer (CRC), however, the molecular mechanisms by which the disturbed redox balance regulates CRC development remain undefined. Using a liquid chromatography–tandem mass spectrometry-based lipidomics, we found that epoxyketooctadecenoic acid (EKODE), which is a lipid peroxidation product, was among the most dramatically increased lipid molecules in the colon of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CRC mice. This is, at least in part, due to increased oxidative stress in colon tumors, as assessed by analyzing gene expression of oxidative markers in AOM/DSS-induced CRC mice and human CRC patients in the Cancer Genome Atlas (TCGA) database. Systemic, short-time treatment with low-dose EKODE increased the severity of DSS-induced colitis, caused intestinal barrier dysfunction and enhanced lipopolysaccharide (LPS)/bacterial translocation, and exacerbates the development of AOM/DSS-induced CRC in mice. Furthermore, treatment with EKODE, at nM doses, induced inflammatory responses via JNK-dependent mechanisms in both colon cancer cells and macrophage cells. Overall, these results demonstrate that the lipid peroxidation product EKODE is an important mediator of colonic inflammation and colon tumorigenesis, providing a novel mechanistic linkage between oxidative stress and CRC development.

Repressing PDCD4 activates JNK/ABCG2 pathway to induce chemoresistance to fluorouracil in colorectal cancer cells

Background

Colorectal cancer (CRC) is the third major cause of cancer-related death worldwide, and fluorouracil (5-FU) is widely used in the treatment of CRC. However, acquired resistance to 5-FU has become an obstacle in the effective treatment of CRC. Adenosine triphosphate (ATP)-binding cassette sub-family G member 2 (ABCG2) has been found highly expressed in CRC patients with poor responsiveness to folinic acid/5-FU/irinotecan. However, the mechanisms of 5-FU resistance regulated by ABCG2 in CRC cells remain to be comprehensively understood. We aimed to explore the upstream mechanisms of ABCG2 involved in the regulation of chemoresistance in CRC cells.

Methods

We investigated the potential mechanisms of 5-FU resistance in HCT116, RKO, RKO microRNA-21 (miR-21) knockout, and acquired 5-FU-resistant HCT116 (HCT116/FUR) cells. The biochemical and biological analyses were conducted using semiquantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting, transfections, and rescue experiments, along with cell proliferation, viability, and colony formation assays. In order to investigate the efficacy of inhibiting the c-Jun NH2 terminal kinase (JNK) pathway to overcome 5-FU resistance, HCT116 and 5-FU-resistant HCT116 cells were inoculated into BALB/c-nu/nu mice to establish the cell-derived xenograft model.

Results

The results showed that ABCG2 expression in HCT116/FUR cells was higher compared to HCT116 cells. Overexpression of ABCG2 decreased sensitivity to 5-FU in HCT116 cells, but knockdown of ABCG2 decreased the survival rate in HCT116/FUR cells. Additionally, repressing programmed cell death 4 (PDCD4) activated the JNK pathway in HCT116/FUR cells. Overexpression of PDCD4 inhibited phosphorylation of c-Jun and ABCG2 expression, and recovered sensitivity to 5-FU in HCT116/FUR cells. Moreover, treatment with the JNK pathway inhibitor SP600125 downregulated ABCG2 expression and rescued sensitivity to 5-FU in HCT116/FUR cells. We also found that miR-21 expression in HCT116/FUR cells was higher compared to HCT116 cells. Finally, 5-FU treatment in combination with SP600125 significantly decreased tumorigenicity compared to other treatments in vivo.

Conclusions

Our results demonstrated that 5-FU treatment upregulated miR-21, which directly repressed PDCD4, and subsequently activated the JNK pathway, leading to the upregulation of ABCG2 in CRC cells. Inhibition of the JNK pathway overcame acquired 5-FU resistance both in vivo and in vitro.

de Pancorbo M, Palencia-Madrid L, Garcia-Etxebarria K, Rocandio AM, Arroyo-Izaga M. Gene-Diet Interactions in Colorectal Cancer: Survey Design, Instruments, Participants and Descriptive Data of a Case-Control Study in the Basque Country

Epidemiologic studies have revealed inconsistent evidence of gene-diet interaction in relation to colorectal cancer (CRC). The aim of this study was to analyze them in a sample of cases and controls from the population-based bowel cancer screening program of the Osakidetza/Basque Health Service. This study analyzed dietetic, genetic, demographic, socioeconomic factors and lifestyles. In the present manuscript, the survey design, sampling, instruments, measurements and related quality management were presented. Moreover, we analyze differences between cases and controls in some data, especially those related to diet. The participants were 308 cases and 308 age- and sex-matched subjects as controls. Cases were more likely than controls to have overweight/obesity (67.5% vs. 58.1%, p < 0.05), a lower intake of vitamin B₂ (0.86 ± 0.23 vs. 0.92 ± 0.23 mg/1000 kcal, p < 0.01) and calcium:phosphorus ratio (0.62 ± 0.12 vs. 0.65 ± 0.13, p < 0.01). A higher proportion of cases than controls did not meet the Nutritional Objectives for saturated fatty acids (85.7% vs. 67.5%, p < 0.001) or cholesterol (35.4% vs. 25.0%, p < 0.01). In conclusion, the present study provides valuable data for analyzing the complexity of gene-diet interaction in relation to CRC. The results presented here suggest that overweight/obesity and a high intake of certain dietary components, especially saturated fatty acids and cholesterol, are more frequent in cases than in controls.

Metallopanstimulin-1 (MPS-1) mediates the promotion effect of leptin on colorectal cancer through activation of JNK/c-Jun signaling pathway

Obesity is a major epigenetic cause for colorectal cancer (CRC). Leptin is implicated in obesity-associated CRC, but the underlying mechanism remains unclear. The current study identified over-expression of metallopanstimulin-1 (MPS-1) in CRC patients through microarray and histological analysis, especially in obese CRC patients. MPS-1 was correlated with advanced tumor stage, suggesting its association with CRC progression. In addition, MPS-1 over-expression was associated with poor overall survival (OS) in obese CRC patients, but not in their non-obese counterparts, suggesting its potential as a prognostic marker of obese CRC patients. MPS-1 expression was positively associated with circulating leptin levels in CRC patients, especially in obese cases. Functional experiments demonstrated that MPS-1 silencing inhibited tumor proliferation and colony formation, and induced apoptosis of CRC cells in vitro. Converse results were obtained from the experiments with MPS-1 over-expression. Mechanistically, MPS-1 executed its action through induction of c-Jun N-terminal kinase (JNK)/c-Jun pathway. Moreover, the promotion effect of MPS-1 on CRC progression was modulated by leptin. In vivo studies demonstrated that MPS-1 silencing suppressed tumor growth of CRC via inhibiting JNK/c-Jun signaling. Collectively, this study indicates that MPS-1 promotes leptin-induced CRC via activating JNK/c-Jun pathway. MPS-1 might represent a potent candidate for the treatment and prognostic prediction of obesity-associated CRC.

Obesity-associated cancer risk: the role of intestinal microbiota in the etiology of the host proinflammatory state

Obesity increases the risks of many cancers. One important mechanism behind this association is the obesity-associated proinflammatory state. Although the composition of the intestinal microbiome undoubtedly can contribute to the proinflammatory state, perhaps the most important aspect of host-microbiome interactions is host exposure to components of intestinal bacteria that stimulate inflammatory reactions. Systemic exposures to intestinal bacteria can be modulated by dietary factors through altering both the composition of the intestinal microbiota and the absorption of bacterial products from the intestinal lumen. In particular, high-fat and high-energy diets have been shown to facilitate absorption of bacterial lipopolysaccharide (LPS) from intestinal bacteria. Biomarkers of bacterial exposures that have been measured in blood include LPS-binding protein, sCD14, fatty acids characteristic of intestinal bacteria, and immunoglobulins specific for bacterial LPS and flagellin. The optimal strategies to reduce these proinflammatory exposures, whether by altering diet composition, avoiding a positive energy balance, or reducing adipose stores, likely differ in each individual. Biomarkers that assess systemic bacterial exposures therefore should be useful to (1) optimize and personalize preventive approaches for individuals and groups with specific characteristics and to (2) gain insight into the possible mechanisms involved with different preventive approaches.

Quercetin Confers Tumoricidal Activity Through Multipathway Mechanisms in A N-Methylnitrosourea Rat Model of Colon Cancer

Objective: This research was conducted to explore mechanisms behind the potency of quercetin in inhibiting colon cancer induced in an experimental model. Materials and Methods: Forty adult male rats of Wistar strain were distributed into 4 groups; a negative control group, a colon cancer bearing group, a quercetin-treated group and a 5-fluorouracil (5-FU)-treated group. Serum TAG72 and GAL3 levels were quantified by ELISA. Colonic Wnt5a and Axin-1 gene expression was estimated by PCR. In addition, colonic tissues were subjected to immunohistochemical examination of Bax expression and histological investigation of histopathological alterations. Results: Quercetin elicited significant reduction in serum TAG72 and GAL3 levels, in addition to significant suppression of colonic Wnt5a gene expression and amplification of colonic Axin-1 gene expression. Also, it caused moderate positive reaction for Bax in mucosal epithelium. Conclusion: The present research provides experimental evidence about the activity of quercetin in the colon cancer of rats. Inhibitory effects on cancer development might be ascribable to regulatory action on Wnt signaling and induction of apoptosis.

Weight loss following diet-induced obesity does not alter colon tumorigenesis in the AOM mouse model

Obesity presents a significant public health concern given its association with increased cancer incidence, unfavorable prognosis, and metastasis. However, there is very little literature on the effects of weight loss, following obesity, on risk for colon cancer or liver cancer. Therefore, we sought to study whether intentional weight loss through diet manipulation was capable of mitigating colon and liver cancer in mice. We fed mice with a high-fat diet (HFD) comprised of 47% carbohydrates, 40% fat, and 13% protein for 20 wk to mimic human obesity. Subsequently, azoxymethane (AOM) was used to promote colon and liver carcinogenesis. A subset of obese mice was then switched to a low-fat diet (LFD) containing 67.5% carbohydrate, 12.2% fat, and 20% protein to promote intentional weight loss. Body weight loss and excess fat reduction did not protect mice from colon cancer progression and liver dysplastic lesion in the AOM-chemical-cancer model even though these mice had improved blood glucose and leptin levels. Intentional weight loss in AOM-treated mice actually produced histological changes that resemble dysplastic alterations in the liver and presented a higher percentage of F4/80⁺CD206⁺ macrophages and activated T cells (CD4⁺CD69⁺) in the spleen and lymph nodes, respectively. In addition, the liver of AOM-treated mice exposed to a HFD during the entire period of the experiment exhibited a marked increase in proliferation and pNF-κB activation. Altogether, these data suggest that intentional weight loss following chemical-induced carcinogenesis does not affect colon tumorigenesis but may in fact negatively impact liver repair mechanisms.

Resveratrol affects protein kinase C activity and promotes apoptosis in human colon carcinoma cells

BACKGROUND

Resveratrol has been reported to have potential chemopreventive and apoptosis-inducing properties in a variety of tumor cell lines.

OBJECTIVE

In this study, to investigate the effects of resveratrol on protein kinase C (PKC) activity and apoptosis in human colon carcinoma cells, we used HT-29 cells and examined the PKCα and ERK1/2 signaling pathways.

METHODS

To test the effects of resveratrol on the growth of HT- 29 cells, the cells were exposed to varying concentrations and assessed with the the MTT cell-viability assay. Fluorescence-activated cell sorter (FACS) analysis was applied to determine the effects of resveratrol on cell apoptosis. Western blotting was performed to determine the protein levels of PKCα and ERK1/2. In inhibition experiments, HT-29 cells were treated with Go?6976 or PD98059 for 30 min, followed by exposure to 200 μM resveratrol for 72 h.

RESULTS

Resveratrol had a significant inhibitory effect on HT-29 cell growth. FACS revealed that resveratrol induced apoptosis. Western blotting showed that e phosphorylation of PKCα and ERK1/2 was significantly increased in response to resveratrol treatment. Pre-treatment with PKCα and ERK1/2 inhibitors (Go?6976 and PD98059) promoted apoptosis.

CONCLUSION

Resveratrol has significant anti-proliferative effects on the colon cancer cell line HT-29. The PKC- ERK1/2 signaling pathway can partially mediate resveratrol-induced apoptosis of HT-29 cells.

Inhibition of Azoxymethane-induced Colorectal Aberrant Crypt Foci in Mice Fed a High-fat Diet by Pleurotus eryngii (Eringi) and Hypsizygus marmoreus (Bunashimeji)

Obesity markedly increases the risk of colorectal cancer. Recently, the preventive effects of edible mushrooms on triglyceride elevation and visceral fat accumulation have been reported. Here, the effects of Pleurotus eryngii (Eringi) and Hypsizygus marmoreus (Bunashimeji) on azoxymethane (AOM)-induced aberrant crypt foci (ACF; precancerous lesions) in the colorectums of mice fed a high-fat diet were examined. Eringi (ER) and Bunashimeji (BU) mushroom powder samples were used. Six-week-old male C57BL/6J mice received an intraperitoneal injection of AOM (10 mg/kg) once a week for two weeks, and were sacrificed and dissected at 6 weeks after the start of the experiment. After the initiation of the experiment, they received a normal diet (ND), high-fat diet (HFD), HFD + ER (1 or 5% of diet), or HFD + BU (1 or 5% of diet). As a result, body and fat weights were significantly lower in the 5% ER and BU groups than in the HFD group. Liver triglyceride levels were also significantly lower in the 5% ER and BU groups. Total liver cholesterol levels were significantly lower in the 5% ER group. The numbers of ACF (especially large ACF) showed strong inhibitory effects in both ER and BU groups. Measurement of the cell proliferation marker Ki-67 labeling index in the colonic mucosa demonstrated more significant suppression in both ER and BU groups than in the HFD group. These results suggest that the simultaneous intake of ER and BU may inhibit colorectal tumorigenesis in HFD-fed mice.

Dietary aloe vera gel powder and extract inhibit azoxymethane- induced colorectal aberrant crypt foci in mice fed a high- fat diet

Aloe vera gel exhibits protective effects against insulin resistance as well as lipid-lowering and anti-diabetic effects. The anti-diabetic compounds in this gel were identified as Aloe-sterols. Aloe vera gel extract (AVGE) containing Aloe-sterols has recently been produced using a new procedure. We previously reported that AVGE reduced large-sized intestinal polyps in Apc-deficient Min mice fed a high fat diet (HFD), suggesting that Aloe vera gel may protect against colorectal cancer. In the present study, we examined the effects of Aloe vera gel powder (AVGP) and AVGE on azoxymethane-induced colorectal preneoplastic aberrant crypt foci (ACF) in mice fed a HFD. Male C57BL/6J mice were given a normal diet (ND), HFD, HFD containing 0.5% carboxymethyl cellulose solution, which was used as a solvent for AVGE (HFDC), HFD containing 3% or 1% AVGP, and HFDC containing 0.0125% (H-) or 0.00375% (L-) AVGE. The number of ACF was significantly lower in mice given 3% AVGP and H-AVGE than in those given HFD or HFDC alone. Moreover, 3% AVGP, H-AVGE and L-AVGE significantly decreased the mean Ki-67 labeling index, assessed as a measure of cell proliferation in the colonic mucosa. In addition, hepatic phase II enzyme glutathione S-transferase mRNA levels were higher in the H-AVGE group than in the HFDC group. These results suggest that both AVGP and AVGE may have chemopreventive effects on colorectal carcinogenesis under the HFD condition. Furthermore, the concentration of Aloe-sterols was similar between 3% AVGP and H-AVGE, suggesting that Aloe-sterols were the main active ingredients in this experiment.

Obesity promotes colonic stem cell expansion during cancer initiation

There is an urgent need to elucidate the mechanistic links between obesity and colon cancer. Convincing evidence for the role of Lgr5(+) stem cells in colon tumorigenesis has been established; however, the influence of obesity on stem cell maintenance is unknown. We assessed the effects of high fat (HF) feeding on colonic stem cell maintenance during cancer initiation (AOM induced) and the responsiveness of stem cells to adipokine signaling pathways. The number of colonic GFP(+) stem cells was significantly higher in the AOM-injected HF group compared to the LF group. The Lgr5(+) stem cells of the HF fed mice exhibited statistically significant increases in cell proliferation and decreases in apoptosis in response to AOM injection compared to the LF group. Colonic organoid cultures from lean mice treated with an adiponectin receptor agonist exhibited a reduction in Lgr5-GPF(+) stem cell number and an increase in apoptosis; however, this response was diminished in the organoid cultures from obese mice. These results suggest that the responsiveness of colonic stem cells to adiponectin in diet-induced obesity is impaired and may contribute to the stem cell accumulation observed in obesity.

Association between factors associated with colorectal cancer and rectal aberrant crypt foci in humans

Aberrant crypt foci (ACF) are regarded as potential biomarkers for colorectal cancer (CRC), and have been used as such in recent early-phase chemoprevention trials. However, the associations between the presence of ACF and other factors associated with the development of CRC, such as lifestyle factors, medication use and comorbid medical conditions, remain unknown. Thus, the present retrospective, large, cross-sectional study was conducted to evaluate the potential usefulness of ACF as a surrogate biomarker of CRC. Total colonoscopy was performed and the number of rectal ACF was counted in a total of 902 subjects. A retrospective review of the medical records of the study subjects was performed, and the factors associated with the increased prevalence of ACF was investigated using univariate and multivariate logistic regression analyses. The analysis results identified older age [odds ratio (OR), 9.24; 95% confidence interval (CI), 4.80-17.8; P<0.01], smoking habit (OR, 1.78; 95% CI, 1.20-2.63; P<0.01) and use of insulin (OR, 9.97; 95% CI, 1.28-77.5; P=0.03) as significant independent risk factors associated with the increased prevalence of ACF, regardless of the presence/absence of colon tumors. In addition, it was revealed that the prevalence and number of ACF, and the Ki-67 labeling indices of the colonic epithelial cells were significantly higher in diabetic patients receiving insulin therapy than in those not receiving insulin therapy (P<0.01, P=0.03 and P=0.01, respectively). In conclusion, the potential usefulness of ACF as a surrogate biomarker of CRC was confirmed, although useful data could not be obtained on candidate chemopreventive agents. These results indicated that insulin can enhance colonic epithelial proliferative activity and induce the formation of ACF, thereby possibly triggering CRC development.

Obesity, adipokines and cancer: an update

Obesity causes dysfunction of adipose tissue, with resultant chronic inflammation and adverse interplay of various adipokines, sex steroids and endocrine hormones. All these drive tumourigenesis and explain the epidemiological link between obesity and cancer. Over the past decade, the associations among obesity, adipokines and cancer have been increasingly recognized. Adipokines and their respective signalling pathways have drawn much research attention in the field of oncology and cancer therapeutics. This review will discuss the recent advances in the understanding of the association of several adipokines with common obesity-related cancers and the clinical therapeutic implications.

High fat diet-induced obesity increases the formation of colon polyps induced by azoxymethane in mice

BACKGROUND

Obesity has been found to be associated with colon cancer. However, the mechanism of this relationship is unclear and thus a good animal model is required. Our previous research showed that some mice developed diet-induced obesity (DIO) whilst others were diet-resistant (DR) when fed a high-fat diet.

METHODS

In the present study, we have tested the effects of a high-fat diet on the formation of colon polyps induced by azoxymethane (AOM) in both DIO and DR mice.

RESULTS

We found that the DIO mice have developed 2.5 times of polyps compared to the DR mice (P<0.05) and 3.4 times of polyps compared to the low fat fed mice (P<0.05). Although the DR mice tended to have more polyps than the low-fat diet fed mice, this was not statistically significant. The DIO mice could have an increased polyp formation due to obesity-related cancer risk factors and different gene expression from DR mice.

CONCLUSIONS

DIO mice could be used as an appropriate model for studying obesity-associated colon cancer; however DR mice are not suitable because they don't show any significant weight gains to indicate obesity.

Deficiency of iNOS-derived NO accelerates lipid accumulation-independent liver fibrosis in non-alcoholic steatohepatitis mouse model

BACKGROUND

Although many of the factors and molecules closely associated with non-alcoholic steatohepatitis (NASH) have been reported, the role of inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) on the progression of NASH remains unclear. We therefore investigated the role of iNOS-derived NO in NASH pathogenesis with a long-term follow-up study using systemic iNOS-knockout mice under high-fat diet (HFD) conditions.

METHODS

iNOS-knockout and wild-type mice were fed a basal or HFD for 10 or 48 weeks. Lipid accumulation, fibrosis, and inflammation were evaluated, and various factors and molecules closely associated with NASH were analyzed.

RESULTS

Marked fibrosis and inflammation (indicators of NASH) were observed in the livers of iNOS-knockout mice compared to wild-type mice after 48 weeks of a HFD; however, lipid accumulation in iNOS-knockout mice livers was less than in the wild-type. Increased expressions of various cytokines that are transcriptionally controlled by NF-kB in iNOS-deficient mice livers were observed during HFD conditions.

CONCLUSIONS

iNOS-derived NO may play a protective role against the progression to NASH during an HFD by preventing fibrosis and inflammation, which are mediated by NF-kB activation in Kupffer cells. A lack of iNOS-derived NO accelerates progression to NASH without excessive lipid accumulation.

Macro- and micronutrients consumption and the risk for colorectal cancer among Jordanians

OBJECTIVE

Diet and lifestyle have been reported to be important risk factors for the development of colorectal cancer (CRC). However, the association between total energy and nutrient intake and the risk of developing CRC has not been clearly explained. The aim of our study is to examine the relationship between total energy intake and other nutrients and the development of CRC in the Jordanian population.

RESEARCH METHODS AND PROCEDURES

Dietary data was collected from 169 subjects who were previously diagnosed with CRC, and 248 control subjects (matched by age, gender, occupation and marital status). These control subjects were healthy and disease free. Data was collected between January 2010 and December 2012, using interview-based questionnaires. Logistic regression was used to evaluate the association between quartiles of total energy, macro- and micronutrient intakes with the risk of developing CRC in our study population.

RESULTS

Total energy intake was associated with a higher risk of developing CRC (OR = 2.60 for the highest versus lowest quartile of intake; 95% CI: 1.21-5.56, p-trend = 0.03). Intakes of protein (OR = 3.62, 95% CI: 1.63-8.05, p-trend = 0.002), carbohydrates (OR = 1.41, 95% CI: 0.67-2.99, p-trend = 0.043), and percentage of energy from fat (OR = 2.10, 95% CI: 0.38-11.70, p-trend = 0.009) significantly increased the risk for the development of CRC. Saturated fat, dietary cholesterol and sodium intake showed a significant association with the risk of developing CRC (OR = 5.23, 95% CI: 2.33-11.76; OR = 2.48, 95% CI: 1.18-5.21; and OR = 3.42, 95% CI: 1.59-7.38, respectively), while vitamin E and caffeine intake were indicative of a protective effect against the development of CRC, OR = 0.002 (95% CI: 0.0003-0.011) and 0.023 (95%CI: 0.008-0.067), respectively.

CONCLUSION

Our results suggest an increased risk for the development of CRC in subjects with high dietary intake of energy, protein, saturated fat, cholesterol, and sodium, and diets high in vitamin E and caffeine were suggestive of a protective effect against the risk of developing CRC.

IMPACT

This is the first study in Jordan to suggest that it may be possible to reduce CRC risk by adjusting the intake of some macro-and micronutrients.

Mechanisms by Which Pleiotropic Amphiphilic n-3 PUFA Reduce Colon Cancer Risk

Colorectal cancer is one of the major causes of cancer-related mortality in both men and women worldwide. Genetic susceptibility and diet are primary determinants of cancer risk and tumor behavior. Experimental, epidemiological, and clinical data substantiate the beneficial role of n-3 polyunsaturated fatty acids (PUFA) in preventing chronic inflammation and colon cancer. From a mechanistic perspective, n-3 PUFA are pleiotropic and multifaceted with respect to their molecular mechanisms of action. For example, this class of dietary lipid uniquely alters membrane structure/ cytoskeletal function, impacting membrane receptor function and downstream signaling cascades, including gene expression profiles and cell phenotype. In addition, n-3 PUFA can synergize with other potential anti-tumor agents, such as fermentable fiber and curcumin. With the rising prevalence of diet-induced obesity, there is also an urgent need to elucidate the link between chronic inflammation in adipose tissue and colon cancer risk in obesity. In this review, we will summarize recent developments linking n-3 PUFA intake, membrane alterations, epigenetic modulation, and effects on obesity-associated colon cancer risk.

Effect of a high-fat diet in development of colonic adenoma in an animal model

AIM: To investigate the effect of a high-fat diet in the formation of the precursors of colorectal cancer using an animal model.

METHODS: Wistar rats were divided into two groups that were fed either a high-fat diet (HFD) or a normal-fat diet (ND), and 1,2-dimethylhydrazine was administered at a dose of 40 mg/kg for 10 wk. The body weight/liver weight/epididymal fat weight were recorded after rats were sacrificed, and the formation of colonic adenoma was also observed. The levels of insulin, leptin, tumor necrosis factor (TNF)-α, insulin-like growth factor (IGF)-1 and triglycerides were determined by enzyme-linked immunosorbent assay in order to compare the altered levels of biochemical indices and inflammatory cytokines in the serum between rats fed an ND and HFD. Cell proliferation activity (Ki-67) was determined by immunohistochemical analysis. Western blot and immunofluorescence staining were used to examine the expression of proliferating cell nuclear antigen (PCNA), cyclooxygenase (COX)-2, cyclin D1, β-catenin and nuclear factor (NF)-κB proteins in the adenoma and comparative control tissues.

RESULTS: The number of colonic adenomas and the colonic epithelial Ki-67 were significantly higher in the HFD group than in the ND group. The HFD group also had increased body weight, liver weight and epididymal fat weight, which were associated with increased levels of serum insulin, leptin, TNF-α, IGF-1 and triglycerides. HFD induced upregulation of PCNA, COX-2, cyclin D1, β-catenin and NF-κB proteins, as revealed by Western blot and immunofluorescence staining.

CONCLUSION: HFD promotes the formation of colonic adenoma through inflammation, metabolic abnormalities, and increases cell cycle progression.

Republished: obesity and colorectal cancer

Excess body weight, as defined by the body mass index (BMI), has been associated with several diseases and includes subjects who are overweight (BMI≥25-29.9 kg/m(2)) or obese (BMI≥30 kg/m(2)). Overweight and obesity constitute the fifth leading risk for overall mortality, accounting for at least 2.8 million adult deaths each year. In addition around 11% of colorectal cancer (CRC) cases have been attributed to overweight and obesity in Europe. Epidemiological data suggest that obesity is associated with a 30-70% increased risk of colon cancer in men, whereas the association is less consistent in women. Similar trends exist for colorectal adenoma, although the risk appears lower. Visceral fat, or abdominal obesity, seems to be of greater concern than subcutaneous fat obesity, and any 1 kg/m(2) increase in BMI confers additional risk (HR 1.03). Obesity might be associated with worse cancer outcomes, such as recurrence of the primary cancer or mortality. Several factors, including reduced sensitivity to antiangiogenic-therapeutic regimens, might explain these differences. Except for wound infection, obesity has no significant impact on surgical procedures. The underlying mechanisms linking obesity to CRC are still a matter of debate, but metabolic syndrome, insulin resistance and modifications in levels of adipocytokines seem to be of great importance. Other biological factors such as the gut microbita or bile acids are emerging. Many questions still remain unanswered: should preventive strategies specifically target obese patients? Is the risk of cancer great enough to propose prophylactic bariatric surgery in certain patients with obesity?

Chemopreventive effect of sinapic acid on 1,2-dimethylhydrazine-induced experimental rat colon carcinogenesis

Sinapic acid (SA) is a naturally occurring phenolic acid found in various herbal plants which is attributed with numerous pharmacological properties. This study was aimed to investigate the chemopreventive effect of SA on 1,2-dimethylhydrazine (DMH)-induced rat colon carcinogenesis. Rats were treated with DMH injections (20 mg kg(-1) bodyweight (b.w.) subcutaneously once a week for the first 4 consecutive weeks and SA (20, 40 and 80 mg kg(-1) b.w.) post orally for 16 weeks. At the end of the 16-week experimental period, all the rats were killed, and the tissues were evaluated biochemically. Our results reveal that DMH alone treatment decreased the levels/activities of lipid peroxidation by-products such as thiobarbituric acid reactive substances, conjugated dienes and antioxidants such as superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and reduced glutathione in the intestine and colonic tissues which were reversed on supplementation with SA. Moreover, the activities of drug-metabolizing enzymes of phase I (cytochrome P450 and P4502E1) were enhanced and those of phase II (glutathione-S-transferase, DT-diaphorase and uridine diphosphate glucuronosyl transferase) were diminished in the liver and colonic mucosa of DMH alone-treated rats and were reversed on supplementation with SA. All the above changes were supported by the histopathological observations of the rat liver and colon. These findings suggest that SA at the dose of 40 mg kg(-1) b.w. was the most effective dose against DMH-induced colon carcinogenesis, and thus, SA could be used as a potential chemopreventive agent.

Overexpressed DNA polymerase iota regulated by JNK/c-Jun contributes to hypermutagenesis in bladder cancer

Human DNA polymerase iota (pol ι) possesses high error-prone DNA replication features and performs translesion DNA synthesis. It may be specialized and strictly regulated in normal mammalian cells. Dysregulation of pol ι may contribute to the acquisition of a mutator phenotype. However, there are few reports describing the transcription regulatory mechanism of pol ι, and there is controversy regarding its role in carcinogenesis. In this study, we performed the deletion and point-mutation experiment, EMSA, ChIP, RNA interference and western blot assay to prove that c-Jun activated by c-Jun N-terminal kinase (JNK) regulates the transcription of pol ι in normal and cancer cells. Xeroderma pigmentosum group C protein (XPC) and ataxia-telangiectasia mutated related protein (ATR) promote early JNK activation in response to DNA damage and consequently enhance the expression of pol ι, indicating that the novel role of JNK signal pathway is involved in DNA damage response. Furthermore, associated with elevated c-Jun activity, the overexpression of pol ι is positively correlated with the clinical tumor grade in 97 bladder cancer samples and may contribute to the hypermutagenesis. The overexpressed pol ι-involved mutagenesis is dependent on JNK/c-Jun pathway in bladder cancer cells identifying by the special mutation spectra. Our results support the conclusion that dysregulation of pol ι by JNK/c-Jun is involved in carcinogenesis and offer a novel understanding of the role of pol ι or c-Jun in mutagenesis.

Selective modulation of Wnt ligands and their receptors in adipose tissue by chronic hyperadiponectinemia

Background

Adiponectin-transgenic mice had many small adipocytes in both subcutaneous and visceral adipose tissues, and showed higher sensitivity to insulin, longer life span, and reduced chronic inflammation. We hypothesized that adiponectin regulates Wnt signaling in adipocytes and thereby modulates adipocyte proliferation and chronic inflammation in adipose tissue.

Materials and Methods

We examined the expression of all Wnt ligands and their receptors and the activity of Wnt signaling pathways in visceral adipose tissue from wild-type mice and two lines of adiponectin-transgenic mice. The effects of adiponectin were also investigated in cultured 3T3-L1 cells.

Results

The Wnt5b, Wnt6, Frizzled 6 (Fzd6), and Fzd9 genes were up-regulated in both lines of transgenic mice, whereas Wnt1, Wnt2, Wnt5a, Wnt9b, Wnt10b, Wnt11, Fzd1, Fzd2, Fzd4, Fzd7, and the Fzd coreceptor low-density-lipoprotein receptor-related protein 6 (Lrp6) were reduced. There was no difference in total β-catenin levels in whole-cell extracts, non-phospho-β-catenin levels in nuclear extracts, or mRNA levels of β-catenin target genes, indicating that hyperadiponectinemia did not affect canonical Wnt signaling. In contrast, phosphorylated calcium/calmodulin-dependent kinase II (p-CaMKII) and phosphorylated Jun N-terminal kinase (p-JNK) were markedly reduced in adipose tissue from the transgenic mice. The adipose tissue of the transgenic mice consisted of many small cells and had increased expression of adiponectin, whereas cyclooxygenase-2 expression was reduced. Wnt5b expression was elevated in preadipocytes of the transgenic mice and decreased in diet-induced obese mice, suggesting a role in adipocyte differentiation. Some Wnt genes, Fzd genes, and p-CaMKII protein were down-regulated in 3T3-L1 cells cultured with a high concentration of adiponectin.

Conclusion

Chronic hyperadiponectinemia selectively modulated the expression of Wnt ligands, Fzd receptors and LRP coreceptors accompanied by the inhibition of the Wnt/Ca²⁺ and JNK signaling pathways, which may be involved in the altered adipocyte cellularity, endogenous adiponectin production, and anti-inflammatory action induced by hyperadiponectinemia.

Increased tumor necrosis factor receptor 1 expression in human colorectal adenomas

AIM: To determine the expression statuses of tumor necrosis factor (TNF)-α, its receptors (TNF-R) and downstream effector molecules in human colorectal adenomas.

METHODS: We measured the serum concentrations of TNF-α and its receptors in 62 colorectal adenoma patients and 34 healthy controls. The protein expression of TNF-α, TNF-R1, TNF-R2 and downstream signals of the TNF receptors, such as c-Jun N-terminal kinase (JNK), nuclear factor-κ B and caspase-3, were also investigated in human colorectal adenomas and in normal colorectal mucosal tissues by immunohistochemistry. Immunofluorescence confocal microscopy was used to investigate the consistency of expression of TNF-R1 and phospho-JNK (p-JNK).

RESULTS: The serum levels of soluble TNF-R1 (sTNF-R1) in adenoma patients were significantly higher than in the control group (3.67 ± 0.86 ng/mL vs 1.57 ± 0.72 ng/mL, P < 0.001). Receiver operating characteristic analysis revealed the high diagnostic sensitivity of TNF-R1 measurements (AUC was 0.928) for the diagnosis of adenoma, and the best cut-off level of TNF-R1 was 2.08 ng/mL, with a sensitivity of 93.4% and a specificity of 82.4%. There were no significant differences in the serum levels of TNF-α or sTNF-R2 between the two groups. Immunohistochemistry showed high levels of TNF-R1 and p-JNK expression in the epithelial cells of adenomas. Furthermore, a high incidence of co-localization of TNF-R1 and p-JNK was identified in adenoma tissue.

CONCLUSION: TNF-R1 may be a promising biomarker of colorectal adenoma, and it may also play an important role in the very early stages of colorectal carcinogenesis.

RETRACTED: Obesity-induced increase in tumor necrosis factor-α leads to development of colon cancer in mice

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief and Deputy Editor-in-Chief following an investigation into the data that were presented in several figures within the article. A number of images used in this article are believed to be duplicated images. The authors stated that they inadvertently inserted images of the wrong blots in several of the figures, resulting in the duplications; however, they did not address all of the concerns raised. Because the editors were no longer confident in the conclusions of the article based on these incorrect data, a decision was made to retract the paper. All authors have been notified of this decision. The University of Campinas (UNICAMP) in São Paulo, Brazil was contacted regarding these concerns, but to date the journal has received no response.

The role of adiponectin in cancer: a review of current evidence

Excess body weight is associated not only with an increased risk of type 2 diabetes and cardiovascular disease (CVD) but also with various types of malignancies. Adiponectin, the most abundant protein secreted by adipose tissue, exhibits insulin-sensitizing, antiinflammatory, antiatherogenic, proapoptotic, and antiproliferative properties. Circulating adiponectin levels, which are determined predominantly by genetic factors, diet, physical activity, and abdominal adiposity, are decreased in patients with diabetes, CVD, and several obesity-associated cancers. Also, adiponectin levels are inversely associated with the risk of developing diabetes, CVD, and several malignancies later in life. Many cancer cell lines express adiponectin receptors, and adiponectin in vitro limits cell proliferation and induces apoptosis. Recent in vitro studies demonstrate the antiangiogenic and tumor growth-limiting properties of adiponectin. Studies in both animals and humans have investigated adiponectin and adiponectin receptor regulation and expression in several cancers. Current evidence supports a role of adiponectin as a novel risk factor and potential diagnostic and prognostic biomarker in cancer. In addition, either adiponectin per se or medications that increase adiponectin levels or up-regulate signaling pathways downstream of adiponectin may prove to be useful anticancer agents. This review presents the role of adiponectin in carcinogenesis and cancer progression and examines the pathophysiological mechanisms that underlie the association between adiponectin and malignancy in the context of a dysfunctional adipose tissue in obesity. Understanding of these mechanisms may be important for the development of preventive and therapeutic strategies against obesity-associated malignancies.

Increased JNK1 signaling pathway is responsible for ABCG2-mediated multidrug resistance in human colon cancer

Multidrug resistance remains a major obstacle to effective chemotherapy of colon cancer. ABCG2, as a half-transporter of the G subfamily of ATP-binding cassette transporter genes (ABC transporters), is known to play a crucial role in multidrug resistance. However, the molecular mechanism of controlling ABCG2 expression in drug resistance of colon cancer is unclear and scarcely reported. In the present study, we systematically investigate the potential role of the c-Jun NH2-terminal kinase (JNK) signal pathway in ABCG2-induced multidrug resistance in colon cancer. In the hydroxycamptothecin (HCPT) resistant cell line SW1116/HCPT from human colon cancer cell line SW1116, ABCG2 is the major factor for multidrug resistance, other than well-studied ABCB1 or ABCC1. Our findings indicate that blocking the JNK pathway by pathway inhibitor SP600125 reduces the expression level and transport function of ABCG2 in drug-resistant cells SW116/HCPT. Notably, the experiments of small interfering RNA directed against JNK1 and JNK2 show that only silence of JNK1 gene has the equal effect as SP600125 on dephosphorylation of transcription factor c-Jun and the expression of ABCG2 protein, while the corresponding phenomena were not observed after silence of JNK2 gene. Meanwhile, SP600125 induces the apoptosis of SW116/HCPT cells by promoting the cleavage of PARP and suppressing the anti-apoptotic protein survivin and bcl-2, and increases the sensitivity of SW1116/HCPT to HCPT. Taken together, our work demonstrated that JNK1/c-jun signaling pathway was involved in ABCG2-mediated multidrug resistance in colon cancer cells. Definitely, inhibition of the JNK1/c-jun pathway is useful for reversing ABCG2-mediated drug resistance in HCPT-resistant colon cancer cells.

Association of total energy intake and macronutrient consumption with colorectal cancer risk: results from a large population-based case-control study in Newfoundland and Labrador and Ontario, Canada

Background

Diet is regarded as one of the most important environmental factors associated with colorectal cancer (CRC) risk. A recent report comprehensively concluded that total energy intake does not have a simple relationship with CRC risk, and that the data were inconsistent for carbohydrate, cholesterol and protein. The objective of this study was to identify the associations of CRC risk with dietary intakes of total energy, protein, fat, carbohydrate, fiber, and alcohol using data from a large case-control study conducted in Newfoundland and Labrador (NL) and Ontario (ON), Canada.

Methods

Incident colorectal cancer cases (n = 1760) were identified from population-based cancer registries in the provinces of ON (1997-2000) and NL (1999-2003). Controls (n = 2481) were a random sample of residents in each province, aged 20-74 years. Family history questionnaire (FHQ), personal history questionnaire (PHQ), and food frequency questionnaire (FFQ) were used to collect study data. Logistic regression was used to evaluate the association of intakes of total energy, macronutrients and alcohol with CRC risk.

Results

Total energy intake was associated with higher risk of CRC (OR: 1.56; 95% CI: 1.21-2.01, p-trend = 0.02, 5^th versus 1^st quintile), whereas inverse associations emerged for intakes of protein (OR: 0.85, 95%CI: 0.69-1.00, p-trend = 0.06, 5^th versus 1^st quintile), carbohydrate (OR: 0.81, 95%CI: 0.63-1.00, p-trend = 0.05, 5^th versus 1^st quintile) and total dietary fiber (OR: 0.84, 95% CI:0.67-0.99, p-trend = 0.04, 5^th versus 1^st quintile). Total fat, alcohol, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and cholesterol were not associated with CRC risk.

Conclusion

This study provides further evidence that high energy intake may increase risk of incident CRC, whereas diets high in protein, fiber, and carbohydrate may reduce the risk of the disease.

Multiple signal pathways in obesity-associated cancer

Obesity is increasing worldwide and reaches to a large proportion of the population in developed countries. Thus, obesity-associated cancer has become a major health problem. Multiple cancer risk factors in obesity have been identified including insulin/insulin-like growth factor axis, adipokines and cytokines; and multiple intracellular signal pathways have been studied. However, the role of each signal pathway in obesity-associated cancer is controversial. In this review, the recent studies on signal pathways in obesity-associated cancer are summarized and a unified explanation is provided. Multiple risk factors could initially activate phosphoinositide 3-kinase (PI3K/Akt), mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3) pathways. With increased severity of obesity, mammalian target of rapamycin (mTOR), which is down-stream of both PI3K/Akt and MAPK, is highly activated. Activated mTOR in turn inhibits the PI3K/Akt pathway and further activates the STAT3 pathway. This may explain the activation of the PI3K/Akt pathway at the early stage of obesity and its inhibition at the later stage. mTOR inhibition may be used for cancer therapy, but it may be necessary to be combined with the PI3K/Akt inhibitor as decreased mTOR activity will release its feedback inhibition on the PI3K/Akt pathway, which is under the influence of multiple cancer risk factors in obesity. Thus, dual inhibitors of PI3K and mTOR may provide a novel approach.

JNK signaling promotes intestinal tumorigenesis through activation of mTOR complex 1 in Apc(Δ716) mice

BACKGROUND & AIMS

Signaling by the mammalian target of rapamycin complex 1 (mTORC1) has been implicated in various human cancers. mTORC1 signaling is activated in intestinal tumors of adenomatous polyposis coli (Apc(Δ716)) mice, a model of familial adenomatous polyposis; in these mice, the mTORC1 inhibitor RAD001 can block tumor formation. However, the precise mechanism of mTORC1 signaling in intestinal tumors is not clear. We investigated whether c-Jun-NH(2) terminal kinase (JNK) is involved in the mTORC1 activation.

METHODS

We investigated the effects of an inhibitor and an activator of JNK, as well as small interfering RNA against JNK, on mTORC1 in Apc(Δ716) mice and colon cancer cell lines. We also determined the role of JNK in mTORC1 signaling using in vitro kinase assays.

RESULTS

JNK was activated in intestinal polyps of Apc((Δ716) mice); the JNK inhibitor SP600125 significantly suppressed tumor formation. In colorectal cancer cell lines, the JNK activator anisomycin activated mTORC1, whereas SP600125 or small interfering RNAs against JNK suppressed signaling. Importantly, JNK stimulated the mTORC1 kinase activity in vitro, through direct phosphorylation of Raptor at serine 863.

CONCLUSIONS

JNK is required for activation of mTORC1 in intestinal tumor cells. JNK inhibitors might be developed as therapeutics or to prevent development of intestinal tumors.

Targeting the JNK signaling pathway potentiates the antiproliferative efficacy of rapamycin in LS174T colon cancer cells

BACKGROUND

Targeting the mTOR signaling pathway with rapamycin in cancer therapy has been less successful than expected due in part to the removal of a negative feedback loop resulting in the over-activation of the PI3K/Akt signaling pathway. As the c-Jun N-terminal kinase (JNK) signaling pathway has been found to be a functional target of PI3K, we investigate the role of JNK in the anticancer efficacy of rapamycin.

MATERIALS AND METHODS

The colon cancer cell line LS174T was treated with rapamycin and JNK phosphorylation was analyzed by Western Blot. Overexpression of a constitutively negative mutant of JNK in LS174T cells or treatment of LS174T cells with the JNK inhibitor SP600125 were used to determine the role of JNK in rapamycin-mediated tumor growth inhibition.

RESULTS

Treatment of LS174T cells with rapamycin resulted in the phosphorylation of JNK as observed by Western Blot. The expression of a negative mutant of JNK in LS174T cells or treatment of LS174T cells with SP600125 enhanced the antiproliferative effects of rapamycin. In addition, in vivo, the antitumor activity of rapamycin was potentiated on LS174T tumor xenografts that expressed the dominant negative mutant of JNK.

CONCLUSIONS

Taken together, these results show that rapamycin-induced JNK phosphorylation and activation reduces the antitumor efficacy of rapamycin in LS174T cells.