Peroxisome proliferator-activated receptor-γ 34C>G polymorphism and colorectal cancer risk: A meta-analysis

Associations of peroxisome proliferator-activated receptor-γ Pro12Ala polymorphism with non-alcoholic fatty liver disease: A meta-analysis

BACKGROUND

Polymorphisms in peroxisome proliferator-activated receptor-γ pro12Ala (PPAR-γ Pro12Ala) have been associated with Non-alcoholic Fatty Liver Disease (NAFLD) in several studies. However, the results of these studies are not entirely consistent. Thus, we performed a meta-analysis to investigate the association between the PPAR-γ Pro12Ala polymorphisms and NAFLD.

METHODS

Studies were identified by searching PubMed database and manual assessment of the cited references in the retrieved articles. Study-specific relative risks (RRs) and 95 % confidence intervals (CIs) were estimated using a random-effect model. Study quality was assessed using the Newcastle-Ottawa scale.

RESULTS

Relevant medical researches show that 11 studies have been conducted on the analysis of NAFLD for meta-analysis, with a total of 2404 cases and 3959 participating controls. Meta-analysis results show that PPAR-γ Pro12Ala polymorphism and NALAD Ala alleles[no association between dominance model (OR = 0.968, 95%CI: 0.734-1.276, P = 0.815); Pro/Ala vs. Pro/Pro (OR = 0.930, 95 % CI: 0.701-1.233, P = 0.612); Ala/Ala vs. Pro/Pro (OR = 1.220, 95 % CI: 0.668-2.230, P = 0.518); recessive model (OR = 0.907, 95 % CI: 0.516-1.596, P = 0.736)]. Moreover, stratification by ethnicity also revealed that no matter it is in Caucasian populations or in Asian populations, NAFLD has no association with the PPAR-γ Pro12Ala polymorphism.

CONCLUSIONS

According to the meta-analysis, both in Asians and Caucasian populations, the PPAR-γ Pro12Ala polymorphism can't be demonstrated to have any link with susceptibility to NAFLD.

Contribution of Genetic Polymorphisms of Inflammation Response Genes on Sporadic Colorectal Cancer Predisposition Risk in Malaysian Patients - A Case Control Study

AIM:

To investigate the frequencies and association of polymorphic genotypes of IL-8 -251 T>A, TNF-α -308 G>A, ICAM-1 K469E, ICAM-1 R241G, IL-6 -174 G>C, and PPAR-γ 34 C>G in modulating susceptibility risk in Malaysian colorectal cancer (CRC) patients.

Methods:

In this case-control study, peripheral blood samples of 560 study subjects (280 CRC patients and 280 controls) were collected, DNA extracted and genotyped using PCR-RFLP and Allele Specific PCR. The association between polymorphic genotype and CRC susceptibility risk was determined using Logistic Regression analysis deriving Odds ratio (OR) and 95% CI.

Results:

On comparing the frequencies of genotypes of all single nucleotide polymorphisms ( SNPs ) in patients and controls, the homozygous variant genotypes IL-8 -251 AA and TNF-α -308 AA and variant A alleles were significantly higher in CRC patients. Investigation on the association of the variant alleles and genotypes singly, with susceptibility risk showed the homozygous variant A alleles and genotypes IL-8 -251 AA and TNF-α -308 AA to be at higher risk for CRC predisposition. Analysis based on age, gender and smoking habits showed that the polymorphisms IL8 -251 T>A and TNF – α 308 G>A contribute to a significantly higher risk among male and female who are more than 50 years and for smokers in this population.

Conclusion:

We observed an association between variant allele and genotypes of IL-8-251 T>A and TNF-α-308 G>A polymorphisms and CRC susceptibility risk in Malaysian patients. These two SNPs in inflammatory response genes which undoubtedly contribute to individual risks to CRC susceptibility may be considered as potential genetic predisposition factors for CRC in Malaysian population.

Genetic polymorphisms of PPAR genes and human cancers: evidence for gene-environment interactions

Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors that play a role in lipid metabolism, cell proliferation, terminal differentiation, apoptosis, and inflammation. Although several cancer models have been suggested to explain PPARs' involvement in tumorigenesis, however, their role is still unclear. In this review, we examined associations of the different PPARs, polymorphisms and various types of cancer with a focus on gene-environment interactions. Reviewed evidence suggests that functional genetic variants of the different PPARs may modulate the relationship between environmental exposure and cancer risk. In addition, this report unveils the scarcity of reliable quantitative environmental exposure data when examining these interactions, and the current gaps in studying gene-environment interactions in many types of cancer, particularly colorectal, prostate, and bladder cancers.

Effect of Proliferator-Activated Receptor-γ Pro12Ala Polymorphism on Colorectal Cancer Risk: A Meta-Analysis

Background

The association between peroxisome proliferators-activated receptor γ (PPARγ) Pro12Ala polymorphism and colorectal cancer (CRC) risk is still controversial. A meta-analysis was performed.

Material/Methods

We conducted a literature search using PubMed, EMBASE, and Cochran databases. The pooled odds ratio (OR) with 95% confidence intervals (CIs) were calculated. Fixed-effects and random-effects models were used. Dominant model, recessive model, and additive model were used in this meta-analysis.

Results

Fifteen studies including 13575 cases and 17085 controls were included in our meta-analysis. Result of this meta-analysis found that PPARγ Pro12Ala polymorphism was significantly associated with a reduced risk of CRC (OR=0.90; 95% CI 0.83–0.98; P=0.01). No significant association was found between PPARγ Pro12Ala polymorphism and CRC risk in Asians (OR=0.80; 95% CI 0.60–1.09; P=0.15). However, PPARγ Pro12Ala polymorphism was significantly associated with a reduced risk of CRC in Caucasians (OR=0.91; 95% CI 0.83–0.99; P=0.03). When stratified analysis was performed by CRC site, no positive association was found between PPARγ Pro12Ala polymorphism and rectal cancer (OR=0.95; 95% CI 0.74–1.22; P=0.71). However, a reduced risk of colon cancer was observed (OR=0.85; 95% CI 0.76–0.94; P=0.002).

Conclusions

In summary, this study suggests that PPARγ Pro12Ala polymorphism was a protective factor of CRC.

Association between the Pro12Ala polymorphism of PPAR-γ gene and the non-alcoholic fatty liver disease: a meta-analysis

Several studies have been conducted to examine the association between PPAR-γ2 Pro12Ala polymorphism and non-alcoholic fatty liver disease (NAFLD), but the results remain inconsistent. In this study, a meta-analysis was performed to assess the association of PPAR-γ Pro12Ala polymorphism with NAFLD risk. A total of 8 case-control studies, including 1697 cases and 2427 controls, were selected. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects model. Overall, no evidence has indicated that the Pro12Ala polymorphism was associated with the susceptibility to NAFLD. Besides, stratified analysis with ethnicity also indicated that no significant association between PPAR-γ Pro12Ala and the risk of NAFLD under all for genetic model in both Asian and Caucasian populations was observed. This meta-analysis indicated that the Pro12Ala polymorphism is not associated with NAFLD risk. Large and well-designed studies are warranted to validate our findings.

Therapeutic implications of targeting energy metabolism in breast cancer

PPARs are ligand activated transcription factors. PPARγ agonists have been reported as a new and potentially efficacious treatment of inflammation, diabetes, obesity, cancer, AD, and schizophrenia. Since cancer cells show dysregulation of glycolysis they are potentially manageable through changes in metabolic environment. Interestingly, several of the genes involved in maintaining the metabolic environment and the central energy generation pathway are regulated or predicted to be regulated by PPARγ. The use of synthetic PPARγ ligands as drugs and their recent withdrawal/restricted usage highlight the lack of understanding of the molecular basis of these drugs, their off-target effects, and their network. These data further underscores the complexity of nuclear receptor signalling mechanisms. This paper will discuss the function and role of PPARγ in energy metabolism and cancer biology in general and its emergence as a promising therapeutic target in breast cancer.

PPARs Signaling and Cancer in the Gastrointestinal System

Nowadays, the study of the peroxisome proliferators activated receptors (PPARs) as potential targets for cancer prevention and therapy has gained a strong interest. From a biological point of view, the overall responsibility of PPARs in cancer development and progression is still controversial since several studies report both antiproliferative and tumor-promoting actions for these signaling molecules in human cancer cells and animal models. In this paper, we discuss PPARs functions in the context of different types of gastrointestinal cancer.

Association between polymorphism of the tumor necrosis factor alpha-308 gene promoter and colon cancer in the Chinese population

Tumor necrosis factor (TNF) is a type of cytokine that inhibits tumorigenesis. Several studies have assessed the relationship between the polymorphism of TNF-alpha 308G/A and the susceptibility to colon cancer; however, the results have been controversial. A case-control study was carried out to investigate whether TNF-alpha 308G/A gene polymorphism was associated with the risk of colon cancer in a group of 180 cases and 180 controls from Heilongjiang, China. DNA was isolated from peripheral blood, and gene polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Results of our study showed that colon cancer cases had a significantly higher frequency of TNF-alpha 308AA genotype (odds ratio=9.42, 95% confidence interval=1.18, 75.15; p=0.03) than controls. When stratified by the tumor location, tumor size, growth pattern, differentiation, and stage of colon cancer, no statistically significant results was observed. The present study demonstrated that TNF-alpha 308AA genotype was associated with a higher risk of colon cancer in the Chinese population. Confirmation of these findings in other populations is required.