Tumor markers and rectal cancer: support for an inflammation-related pathway

Intrinsic mechanisms underlying the highly efficient removal of bacterial endotoxin and related risks in tailwater by dielectric barrier discharge plasma

Endotoxin is widely present in aquatic environments and can induce adverse health effects. In this study, dielectric barrier discharge (DBD) plasma was used to remove bacterial endotoxin from the tailwater of a wastewater treatment plant. The removal efficiency of total endotoxin activity was up to 92% with low electrical energy consumption (0.43 J mL^-1%^-1) after 180 s of the DBD plasma treatment, which was better than other previously reported methods. In the early stage of DBD plasma oxidation, the expression of genes related to cell morphology and bacterial antioxidant enzyme synthesis was distinctly down-regulated, suggesting that cell integrity was destroyed, leading to endotoxin release into the solution. Additionally, endotoxin synthesis in the cells was suppressed. The endotoxin in the solution was effectively removed by ·OH, ¹O₂, and O₂·^-generated by the DBD plasma, with second-order reaction rates of 2.69 × 10¹⁰, 2.20 × 10⁷, and 8.60 × 10⁸ mol^-1 L s^-1, respectively. The core toxic component of endotoxin (lipid A) was attacked by these strong oxidative species, generating smaller molecular fragments with low toxicity. Consequently, the inflammatory factors IL-6, IL-β, and TNF-α of endotoxin decreased by 3.4-4.8 folds after the DBD plasma treatment, implying that the health risks posed by endotoxin were greatly reduced. This study revealed the intrinsic mechanisms of the highly efficient removal of bacterial endotoxin by DBD plasma oxidation.

A multicentre cohort study assessing the utility of routine blood tests as adjuncts to identify complete responders in rectal cancer following neoadjuvant chemoradiotherapy

PURPOSE

Management of rectal cancer with a complete clinical response (cCR) to neoadjuvant chemoradiotherapy (NACRT) is controversial. Some advocate "watch and wait" programmes and organ-preserving surgery. Central to these strategies is the ability to accurately preoperatively distinguish cCR from residual disease (RD). We sought to identify if post-NACRT (preoperative) inflammatory markers act as an adjunct to MRI and endoscopy findings for distinguishing cCR from RD in rectal cancer.

METHODS

Patients from three specialist rectal cancer centres were screened for inclusion (2010-2015). For inclusion, patients were required to have completed NACRT, had a post-NACRT MRI (to assess mrTRG) and proceeded to total mesorectal excision (TME). Endoluminal response was assessed on endoscopy at 6-8 weeks post-NACRT. Pathological response to therapy was calculated using a three-point tumour regression grade system (TRG1-3). Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), serum albumin (SAL), CEA and CA19-9 levels post-NACRT (preoperatively) were recorded. Variables were compared between those who had RD on post-operative pathology and those with ypCR. Statistical analysis was performed using SPSS (version 21).

RESULTS

Six hundred forty-six patients were screened, of which 422 were suitable for inclusion. A cCR rate of 25.5% (n = 123) was observed. Sixty patients who achieved cCR were excluded from final analysis as they underwent organ-preserving surgery (local excision) leaving 63 ypCR patients compared to 359 with RD. On multivariate analysis, combining cCR on MRI and endoscopy with NLR < 5 demonstrated the greatest odds of ypCR on final histological assessment [OR 6.503 (1.594-11.652]) p < 0.001]. This method had the best diagnostic accuracy (AUC = 0.962 95% CI 0.936-0.987), compared to MRI (AUC = 0.711 95% CI 0.650-0.773) or endoscopy (AUC = 0.857 95% CI 0.811-0.902) alone or used together (AUC = 0.926 95% CI 0.892-0.961).

CONCLUSION

Combining post-NACRT inflammatory markers with restaging MRI and endoscopy findings adds another avenue to aid distinguishing RD from cCR in rectal cancer.

Statistical meta-analysis to investigate the association between the Interleukin-6 (IL-6) gene polymorphisms and cancer risk

A good number of genome-wide association studies (GWAS), including meta-analyses, reported that single nucleotide polymorphisms (SNPs) of the IL-6 gene are significantly associated with various types of cancer risks, though some other studies reported insignificant association with cancers, in the literature. These contradictory results may be due to variations in sample sizes and/or deficiency of statistical modeling. Therefore, an attempt is made to provide a more comprehensive understanding of the association between the IL-6 gene SNPs (rs1800795, rs1800796, rs1800797) and different cancer risks, giving the weight on a large sample size, including different cancer types and appropriate statistical modeling with the meta-dataset. In order to attain a more reliable consensus decision about the association between the IL-6 gene polymorphisms and different cancer risks, in this study, we performed a multi-case statistical meta-analysis based on the collected information of 118 GWAS studies comprising of 50053 cases and 65204 control samples. Results from this Meta-analysis indicated a significant association (p-value < 0.05) of the IL-6 gene rs1800796 polymorphism with an overall increased cancer risk. The subgroup analysis data based on cancer types exhibited significant association (p-value < 0.05) of the rs1800795 polymorphism with an overall increased risk of cervical, liver and prostate cancers; the rs1800796 polymorphism with lung, prostate and stomach cancers; and the rs1800797 polymorphism with cervical cancer. The subgroup analysis of ethnicity data showed a significant association (p-value < 0.05) of an overall cancer risk with the rs1800795 polymorphism for the African and Asian populations, the rs1800796 polymorphism for the Asian only and the rs1800797 polymorphism in the African population. Comparative discussion showed that our multi-case meta-analyses received more support than any previously reported individual meta-analysis about the association between the IL-6 gene polymorphisms and cancer risks. Results from this study, more confidently showed that the IL-6 gene SNPs (rs1800795, rs1800796 and rs1800797) in humans are associated with increased cancer risks. Therefore, these three polymorphisms of the IL-6 gene have the potential to be evaluated as a population based rapid, low-cost PCR prognostic biomarkers for different types of cancers diagnosis and research.

Evaluation of Alpha 1-Antitrypsin for the Early Diagnosis of Colorectal Cancer

Previous proteomic studies have identified alpha 1-antitrypsin (A1AT) as a potential serum biomarker for colorectal cancer (CRC). In this case-control study, we evaluated plasma A1AT concentration and activity as a biomarker for the early diagnosis of colorectal cancer in a group of 113 sporadic CRC patients. We also analyzed A1AT gene promoter methylation, and genotypes in this group of CRC patients. The plasma A1AT and CEA concentrations were measured using the nephelometric and ELISA methods, respectively. A1AT activity was determined by Trypsin Inhibitor Capacity assay. The genomic DNA from blood samples were subjected to Z and S genotype analysis using PCR-RFLP method and the gene promoter methylation in tumors and their adjacent normal tissues was determined by methylation specific-PCR assay. The plasma levels of A1AT and CEA in patients (median, 2.3 g/L and 5.96 ng/ml, respectively) were significantly higher than those in healthy controls (medians, 1.43 g/L and 2.57 ng/ml, respectively) (p = 0.0001). The plasma A1AT activity and concentrations were positively correlated with the tumor stage and well-discriminated between early and advanced stages. The A1AT activity in plasma was the most useful marker for CRC diagnosis (median 4.8 mmol/min/ml in cases vs 1.91 mmol/min/ml in controls, p = 0.0001). No deficient Z or S alleles of A1AT was observed in patients' genotype and the gene promoter tends to be more methylated in normal mucosa than in tumor tissues. We conclude that plasma A1AT activity has better sensitivity and specificity than CEA measurement for the early detection of CRC. Promoter demethylation might play a role in increasing plasma A1AT levels in CRC patients.

Effect of Coexisting KRAS and TP53 Mutations in Patients Treated With Chemotherapy for Non-small-cell Lung Cancer

BACKGROUND

KRAS and TP53 are common mutations in non-small-cell lung cancer (NSCLC). The Lung Adjuvant Cisplatin Evaluation Biological Program group found adjuvant chemotherapy to be deleterious in patients with coexisting KRAS/TP53 mutations.

PATIENTS AND METHODS

To validate these results, patients with NSCLC tested for KRAS and TP53 mutations and receiving chemotherapy for any stage NSCLC were selected. Mutation status was analyzed using next generation sequencing (Illumina) or multiplex recurrent mutation detection (MassARRAY, Agena Biosciences) assays, and was correlated with clinical and demographic data. Disease-free (DFS) or progression-free survival (PFS) was the main endpoint, and overall survival (OS) was the secondary endpoint.

RESULTS

Among 218 patients, 28 had coexisting KRAS/TP53 mutations, 77 TP53, 37 KRAS, 76 had neither KRAS nor TP53 mutation (WT/WT). There was no DFS/PFS difference for the KRAS/TP53 group versus all others among 99 patients who received adjuvant chemotherapy (hazard ratio [HR], 1.22; 95% confidence interval [CI], 0.61-2.44; P = .57), 27 stage III patients who received chemo-radiation (HR, 0.87; 95% CI, 0.32-2.38; P = .8), and 63 patients who received palliative chemotherapy (HR, 0.68; 95% CI, 0.31-1.48; P = .33). OS was longer in the WT/WT group compared with any other group (KRAS: HR, 1.87; 95% CI, 1.02-3.43; P = .043; TP53: HR, 2.17; 95% CI, 1.3-3.61; P = .0028; KRAS/TP53: HR, 2.06; 95% CI, 1.09-3.88; P = .026). No OS difference was seen for KRAS/TP53 compared with the other groups (HR, 1.26; 95% CI, 0.75-2.13; P = .38).

CONCLUSIONS

There was no significant difference in DFS/PFS between the 4 groups. However, OS was longer for patients with TP53 and KRAS wild-type NSCLC who received chemotherapy for any stage compared with patients with KRAS, TP53 mutation, or double mutant tumors.

Genetic polymorphisms of IL-6 promoter in cancer susceptibility and prognosis: a meta-analysis

IL-6 is critical for tumorigenesis. However, previous studies on the association of IL-6 promoter polymorphisms with predisposition to different cancer types are somewhat contradictory. Therefore, we performed this meta-analysis regarding the relationship between IL-6 promoter single nucleotide polymorphisms and cancer susceptibility and prognosis. Up to April 2017, 97 original publications were identified covering three IL-6 promoter SNPs. Our results showed statistically significant association between IL-6 promoter and cancer risk and prognosis. Subgroup analysis indicated that rs1800795 was significantly associated with increased risk of cervical cancer, colorectal cancer, breast cancer, prostate cancer, lung cancer, glioma, non-Hodgkin’s lymphoma and Hodgkin’s lymphoma but not gastric cancer and multiple myeloma. Furthermore, rs1800796 was significantly associated with increased risk of lung cancer, prostate cancer and colorectal cancer but not gastric cancer. Additionally, rs1800797 was significantly association with breast cancer, non-Hodgkin’s lymphoma, B-cell lymphoma and diffuse large B-cell lymphoma but not gastric cancer. Simultaneously, rs1800795 and rs1800796 were associated with a significantly higher risk of cancer in Asia and Caucasian, rs1800797 was associated with a significantly risk of cancer in Caucasian but not in Asia. Furthermore, IL-6 promoter polymorphisms were significantly associated with the prognosis of cancer. Considering these promising results, IL-6 promoter including rs1800795, rs1800796 and rs1800797 may be a tumor marker for cancer therapy.

Inflammatory Molecule, PSGL-1, Deficiency Activates Macrophages to Promote Colorectal Cancer Growth through NFκB Signaling

P-selectin glycoprotein ligand 1 (SELPLG/PSGL-1) is an inflammatory molecule that is functionally related to immune cell differentiation and leukocyte mobilization. However, the role of PSGL-1 in tumor development remains unknown. Therefore, this study investigates the mechanistic role of PSGL-1 in the development of intestinal tumors in colorectal cancer. Apc^Min/+ mice are highly susceptible to spontaneous intestinal adenoma formation, and were crossbred with PSGL1-null mice to generate compound transgenic mice with a Apc^Min/+;PSGL-1^-/- genotype. The incidence and pathologic features of the intestinal tumors were compared between the Apc^Min/+ mice and Apc^Min/+;PSGL-1^-/- mice. Importantly, PSGL-1-deficient mice showed increased susceptibility to develop intestinal tumors and accelerated tumor growth. Mechanistically, increased production of the mouse chemokine ligand 9 (CCL9/MIP-1γ) was found in the PSGL-1-deficient mice, and the macrophages are likely the major source of macrophage inflammatory protein-1 gamma (MIP-1γ). Studies in vitro demonstrated that macrophage-derived MIP-1γ promoted colorectal cancer tumor cell growth through activating NFκB signaling. Conversely, restoration of the PSGL-1 signaling via bone marrow transplantation reduced MIP-1γ production and attenuated the ability of Apc^Min/+;PSGL-1^-/- mice to generate intestinal tumors. In human colorectal cancer clinical specimens, the presence of PSGL-1-positive cells was associated with a favorable tumor-node-metastasis staging and decreased lymph node metastasis.Implications:PSGL-1 deficiency and inflammation render intestinal tissue more vulnerable to develop colorectal tumors through a MIP-1γ/NFκB signaling axis. Mol Cancer Res; 15(4); 467-77. ©2017 AACR.

Candida albicans and cancer: Can this yeast induce cancer development or progression?

There is currently increasing concern about the relation between microbial infections and cancer. More and more studies support the view that there is an association, above all, when the causal agents are bacteria or viruses. This review adds to this, summarizing evidence that the opportunistic fungus Candida albicans increases the risk of carcinogenesis and metastasis. Until recent years, Candida spp. had fundamentally been linked to cancerous processes as it is an opportunist pathogen that takes advantage of the immunosuppressed state of patients particularly due to chemotherapy. In contrast, the most recent findings demonstrate that C. albicans is capable of promoting cancer by several mechanisms, as described in the review: production of carcinogenic byproducts, triggering of inflammation, induction of Th17 response and molecular mimicry. We underline the need not only to control this type of infection during cancer treatment, especially given the major role of this yeast species in nosocomial infections, but also to find new therapeutic approaches to avoid the pro-tumor effect of this fungal species.

Epidemiological transition of colorectal cancer in developing countries: Environmental factors, molecular pathways, and opportunities for prevention

Colorectal cancer (CRC) is one of the leading causes of cancer and cancer-related mortality worldwide. The disease has been traditionally a major health problem in industrial countries, however the CRC rates are increasing in the developing countries that are undergoing economic growth. Several environmental risk factors, mainly changes in diet and life style, have been suggested to underlie the rise of CRC in these populations. Diet and lifestyle impinge on nuclear receptors, on the intestinal microbiota and on crucial molecular pathways that are implicated in intestinal carcinogenesis. In this respect, the epidemiological transition in several regions of the world offers a unique opportunity to better understand CRC carcinogenesis by studying the disease phenotypes and their environmental and molecular associations in different populations. The data from these studies may have important implications for the global prevention and treatment of CRC.

-174G/C polymorphism in the interleukin-6 promoter is differently associated with prostate cancer incidence depending on race

Interleukin-6 (IL-6), a pro-inflammatory cytokine, is involved in prostate cancer progression, including androgen independence. Serum IL-6 levels also correlate with prostate tumor burden, prostate-specific antigen levels and metastasis. Since circulating cytokine levels vary considerably inter-individually, such variation could be linked to genetic factors, including genetic polymorphism. The -174G>C/rs1800795 polymorphism in the IL-6 promoter is functionally relevant in terms of transcriptional regulation and disease association. We investigated a possible association of the -174G/C polymorphism with prostate cancer. Since significant racial disparities exist in prostate cancer incidence, we also investigated this association between the -174G/C polymorphism and prostate cancer in Caucasians and African-Americans, separately. Direct sequencing of the PCR amplicon from genomic DNA was used for genotyping rs1800795 in all subjects [age-matched controls (N = 140) and prostate cancer patients (N = 164)]. Sample size and power was calculated using the PGA software. We found the GG genotype to be associated with increased risk of prostate cancer in Caucasian subjects, whereas the CC genotype was associated with increased risk in the African-American sample set. Such a dimorphic genotypic association with cancer and race is unique and suggests a complex gene-gene and gene-environment interaction.

Dietary patterns during high school and risk of colorectal adenoma in a cohort of middle-aged women

Adolescent diet may be etiologically relevant for later risk of colorectal adenoma, a precursor of colorectal cancer. We aimed to examine associations between adolescent dietary patterns (derived using factor analysis) and risk of colorectal adenoma in middle adulthood. We analyzed data from 17,221 women participating in the Nurses' Health Study II, who had completed a validated high school (HS) food frequency questionnaire in 1998 when they were 34-51 years old, and had subsequently undergone at least one lower bowel endoscopy. Between 1998 and 2007, 1,299 women were diagnosed with at least one colorectal adenoma. In multivariable models adjusted for adult dietary patterns, a higher "prudent" pattern during HS, characterized by high consumption of vegetables, fruit and fish was associated with a statistically significantly lower risk of rectal (odds ratio [OR] highest vs. lowest quintile, 0.45, 95% CI 0.27-0.75, p-trend = 0.005), but not colon adenomas. A higher "Western" pattern during HS, characterized by high consumption of desserts and sweets, snack foods and red and processed meat, was significantly associated with rectal (OR 1.78, 95% CI 1.12-2.85, p-trend = 0.005) and advanced (OR 1.58, 95% CI 1.07-2.33, p-trend = 0.08), but not associated with colon or non-advanced adenomas. This study suggests that overall eating patterns during high school may influence later risk of rectal and advanced adenoma, independent of adult diet. Our results support the hypothesis that diet during early life may influence colorectal carcinogenesis.

KRAS, BRAF genotyping reveals genetic heterogeneity of ovarian borderline tumors and associated implants

Background

Patients diagnosed for a serous ovarian borderline tumor (s-BOT) typically present with an excellent clinical outcome. However there have been controversies concerning the prognostic impact of so-called implants, an extra ovarian spread occurring alongside the s-BOT in certain cases. It remains obscure whether these implants actually resemble metastasis owning the same genetic pattern as the ovarian primary or whether they develop independently.

Methods

The current study, in the aim of further clarifying the genetic origin of implants, assessed BRAF/KRAS hot spot mutations and the p53/p16^INK4a immunophenotype of s-BOTs and corresponding implants (n = 49) of 15 patients by pyro-sequencing and immunostaining, respectively.

Results

A significant proportion of both s-BOTs and implants showed KRAS or BRAF mutation and though p16^INK4a was found to be abundantly expressed, p53 immunoreactivity was rather low. When genotypes of BRAF/KRAS mutated s-BOTs and corresponding implants were compared no patient presented with a fully matching mutation profile of s-BOTs and all corresponding implants.

Conclusions

The current study reveals genetic heterogeneity of s-BOTs and implants, as none of the markers examined showed constant reciprocity. Hence, our findings may assist to explain the different clinical presentation of s-BOTs and implants and might encourage to applying more individualized follow up protocols.

Links demystified: Periodontitis and cancer

Cancer is marked by the uncontrolled growth of cells, tissue invasion and metastasis to various organs via the circulatory and lymphatic systems. Recent data have expanded the concept that inflammation is a critical component of tumor progression. Many cancers arise from sites of infection, chronic irritation, and inflammation. The tumor microenvironment, which is largely orchestrated by inflammatory cells, is an indispensable participant in the neoplastic process, fostering proliferation, survival, and migration. Periodontal disease, a chronic inflammatory condition is characterized by an oral bacterial infection leading to inflammation within the supporting tissues of the teeth, which often leads to the destruction of the periodontal tissues and alveolar bone that support the teeth. This oral inflammation often has systemic effects leading to an increased concentration of circulating inflammatory markers with the severity of disease being correlated directly with levels of serum inflammatory markers. Periodontal infection has been linked to organ and systemic diseases. There is documented evidence of significant associations between cancer of the lung, kidney, pancreas, hematological and oral cancers, and periodontal disease. This articles reviews and summarizes the possible biological mechanisms involved between periodontal infection and cancer.

A two-SNP IL-6 promoter haplotype is associated with increased lung cancer risk

BACKGROUND

Aberrant expression of interleukin-6 (IL-6) may play an important role in lung carcinogenesis. Whether IL-6 promoter haplotypes are associated with lung cancer risk and their functions have not yet been studied. We tested the hypothesis that single-nucleotide polymorphism (SNP) and/or haplotypes of IL-6 promoter are associated with risk of lung cancer.

METHODS

Two functional IL-6 promoter SNPs (-6331T>C and -572C>G) were genotyped in the discovery group including 622 patients and 614 controls, and the results were replicated in an independent validation group including 615 patients and 638 controls. Luciferase reporter gene assays were conducted to examine the function of IL-6 promoter haplotypes.

RESULTS

None of the functional IL-6 promoter SNPs were associated with lung cancer risk in either study. However, a two-SNP CC (-6331C and -572C) IL-6 promoter haplotype was significantly more common among cases than among controls in both groups (P = 0.031 and P = 0.035, respectively), indicating that this haplotype is associated with increased lung cancer risk {adjusted odds ratio [OR], 1.56 [95 % confidence interval (95 % CI), 1.04-2.34] and 1.51 [95 % CI, 1.03-2.22], respectively}. Combined analysis of both studies showed a strong association of this two-SNP haplotype with increased lung cancer risk (adjusted OR, 1.53; 95 % CI, 1.16-2.03; P = 0.003). Comparably, luciferase reporter assays of A549 lung cancer cell lines transfected with the CC haplotype revealed that the two-SNP haplotype had significantly higher IL-6 transcriptional activity compared with cells transfected with the common haplotype.

CONCLUSIONS

This is the first evidence of identifying an IL-6 promoter haplotype (CC) associated with increased risk of lung cancer.

Association of the OCTN1/1672T variant with increased risk for colorectal cancer in young individuals and ulcerative colitis patients

BACKGROUND

Ulcerative colitis (UC) is associated with colorectal cancer. Chronic inflammation may also play a role in the pathogenesis of sporadic colorectal cancer (SCC), particularly in younger patients (<55 years). We evaluated whether single nucleotide polymorphisms of the OCTN1 and OCTN2 genes are associated with UC, SCC, and with UC cases with cancer progression (UCCP).

METHODS

We evaluated the OCTN1 and OCTN2 polymorphisms in 200 patients with UC, 59 patients with UCCP, 200 patients with SCC, and 200 controls (HC). IL-8 expression was also assessed by real-time polymerase chain reaction (PCR). Additionally, we transfected human colon carcinoma Caco2 cells, homozygous for OCTN1/1672T variant, with the OCTN1/1672C allele and NF-κB activity was evaluated by luciferase based reporter assay and IL-8 mRNA expression by real-time PCR.

RESULTS

OCTN2 polymorphisms did not present a significant association with any group of patients compared to normal controls. Conversely, homozygosity for the OCTN1/1672T variant was significantly associated with UC (P = 0.047 vs. HC), with UCCP (UCCP vs. HC, P < 0.001), and with SCC developing in early age (<55 years) (P = 0.021 vs. HC). Importantly, IL-8 mRNA expression was higher in UC and UCCP patients homozygous for the OCTN1 1672T variant compared to the other genotypes. Moreover, in Caco2 cells transfection of the OCTN1/1672C variant reduced the activity of the proinflammatory factor NF-κB.

CONCLUSION

Our data demonstrate that OCTN1 could have a role in modulating the severity of chronic inflammation associated with SCC in early age and in UC patients, and that its polymorphisms may help to predict malignant progression of IBD.

Genetic variation in C-reactive protein in relation to colon and rectal cancer risk and survival

C-reactive protein (CRP), a biomarker of inflammation, has been shown to be influenced by genetic variation in the CRP gene. In this study, we test the hypothesis that genetic variation in CRP influences both the risk of developing colon and rectal cancer and survival. Two population-based studies of colon cancer (n = 1,574 cases, 1,970 controls) and rectal (n = 791 cases, 999 controls) were conducted. We evaluated four CRP tagSNPs: rs1205 (G > A, 3' UTR); rs1417938 (T > A, intron); rs1800947 (G > C, L184L); and rs3093075 (C > A, 3' flanking). The CRP rs1205 AA genotype was associated with an increased risk of colon cancer (OR 1.3, 95%CI 1.1-1.7), whereas the rs3093075 A allele was associated with a reduced risk of rectal cancer (OR 0.7, 95%CI 0.5-0.9). The strongest association for the rs1205 polymorphism and colon cancer was observed among those with KRAS2 mutations (OR 1.5, 95%CI 1.1-2.0). The CRP rs1205 AA genotype also was associated with an increased risk of CIMP+ rectal tumors (OR 2.5, 95%CI 1.2-5.3); conversely, the rs1417938 A allele was associated with a reduced risk of CIMP+ rectal tumors (OR 0.5, 95%CI 0.3-0.9). We observed interactions between CRP rs1800947 and BMI and family history of CRC in modifying risk of both colon and rectal cancer. These data suggest that genetic variation in the CRP gene influences risk of both colon and rectal cancer development.

Nutrients in folate-mediated, one-carbon metabolism and the risk of rectal tumors in men and women

In an investigation of rectal tumors characterized by CpG island methylator phenotype (CIMP), KRAS2 mutation, and TP53 mutation, we examined associations with dietary and supplemental folate, riboflavin, vitamins B(6) and B(12), and methionine, nutrients involved in folate-mediated 1-carbon metabolism. We also examined folate intake and common MTHFR polymorphisms in relation to CIMP. Data from a population-based study of 951 cases (750 with tumor markers) and 1,205 controls were evaluated using multiple logistic regression models and generalized estimating equations. Reduced risk of methylated tumors was suggested in women with the upper tertile of folate intake (≥0.42 mg/day) vs. the lower tertile: OR = 0.6, 95%CI = 0.3-1.2. In men, a significant 3-fold increased risk of CIMP+ tumor was observed for the upper tertile of folate (≥0.75 mg/day) vs. the lower tertile (<0.44 mg/day): OR = 3.2, 95%CI = 1.5-6.7. These men consumed a greater proportion of folic acid fortified foods relative to natural, primarily plant-based sources (52% vs. 48%) than women with CIMP+ tumors (22% vs. 78%). MTHFR 1298A>C influenced folate in male CIMP+ risk (P interaction < 0.01). Our findings suggest folate supplementation effects may differ between genders, perhaps due to variation in MTHFR and/or endogenous/exogenous hormones, and may be important in the initiation and progression of methylated rectal tumors in men.

Candidate pathway polymorphisms in one-carbon metabolism and risk of rectal tumor mutations

We examined candidate polymorphisms in genes involved in the folate-mediated, one-carbon metabolism pathway, DNMT1 1311V, MTHFD1 R134K and R653Q, MTHFR R594Q, MTR D919G, MTRR H595Y and I22M, SHMT1 L474F, SLC19A1 H27R, and TDG G199S, and associations with rectal tumor characteristics. We hypothesized that these candidate genes would influence CpG Island Methylator Phenotype and potentially KRAS2 or TP53 tumors. Data from a population-based study of 747 rectal cases (593 with tumor markers) and 956 controls were evaluated using generalized estimating equations. We observed an increased risk of TP53 tumor mutations in homozygous carriers of the MTHFD1 134K allele (0R=2.0, 95%CI 1.2-3.1, P- trend=0.02). In the presence of low folate intake, the R134K variant was associated with increased risk of CIMP+ tumors (OR=2.8, 95%CI 1.04-7.7). The MTRR I22M variant genotype was associated with a modest increased risk of TP53 mutations (OR=1.7, 95%CI 1.2-2.5, P-trend=0.001). Our findings offer limited support that polymorphisms in one-carbon metabolism genes influence rectal tumor phenotype, and that folate may interact with MTHFD1 to alter CIMP+ risk.

Genetic variation in RPS6KA1, RPS6KA2, RPS6KB1, RPS6KB2, and PDK1 and risk of colon or rectal cancer

RPS6KA1, RPS6KA2, RPS6KB1, RPS6KB2, and PDK1 are involved in several pathways central to the carcinogenic process, including regulation of cell growth, insulin, and inflammation. We evaluated genetic variation in their candidate genes to obtain a better understanding of their association with colon and rectal cancer. We used data from two population-based case-control studies of colon (n=1574 cases, 1940 controls) and rectal (n=791 cases, 999 controls) cancer. We observed genetic variation in RPS6KA1, RPS6KA2, and PRS6KB2 were associated with risk of developing colon cancer while only genetic variation in RPS6KA2 was associated with altering risk of rectal cancer. These genes also interacted significantly with other genes operating in similar mechanisms, including Akt1, FRAP1, NFκB1, and PIK3CA. Assessment of tumor markers indicated that these genes and this pathway may importantly contributed to CIMP+ tumors and tumors with KRAS2 mutations. Our findings implicate these candidate genes in the etiology of colon and rectal cancer and provide information on how these genes operate with other genes in the pathway. Our data further suggest that this pathway may lead to CIMP+ and KRAS2-mutated tumors.

Genetic variation in a metabolic signaling pathway and colon and rectal cancer risk: mTOR, PTEN, STK11, RPKAA1, PRKAG2, TSC1, TSC2, PI3K and Akt1

Serine/threonine protein kinase 11 (STK11) and phosphatase tensin homolog deleted on chromosome 10 (PTEN) link insulin sensitivity and metabolic signaling to inflammation and other hormonal factors and colorectal cancer. We evaluate genetic variation in nine genes in a candidate pathway as follows: STK11 (3 tagSNPs), PTEN (9 tagSNPs), FRAP1 (mTOR) (4 tagSNPs), TSC1 (14 tagSNPs), TSC2 (8 tagSNPs), Akt1 (2 tagSNPs), PIK3CA (7 tagSNPs), PRKAA1 (13 tagSNPs) and PRKAG2 (68 tagSNPs) in two population-based case-control studies of colon (n = 1574 cases, 1940 controls) and rectal (n = 91 cases, 999 controls) cancer. FRAP1, PRKAA1, PRKAG2 and TSC2 genes were significantly associated with colon cancer; risk estimates ranged from 1.21 [95% confidence interval (CI) 1.05-1.38] for FRAP1rs1057079 for the AG/GG genotype to 1.51 (95% CI 1.09-2.09) for PRKAG2rs9648723 CC genotype. PIK3CA, PRKAG2, PTEN, STK11 and TSC1 were significantly associated with rectal cancer overall. The strongest association was observed for PIK3CA rs7651265 GG genotype (odds ratio 2.32 95% CI 1.02-5.30). FRAP1 was associated with microsatellite instability (MSI)+ colon tumors; PRKAA1, CpG island methylator phenotype (CIMP)+ and MSI+ colon tumors; PRKAG2 and KRAS2 colon tumors; TSC1 and CIMP+ and MSI+ colon tumors; TSC2 with MSI+ colon tumors; PIK3CA with KRAS2-mutated rectal tumors; PRKAG2 (rs6964824) with KRAS2- and TP53-mutated rectal tumors and with PRKAG2 (rs412396 and rs4725431) with CIMP+ rectal tumors. These data suggest that genetic variation in a predefined candidate pathway for colorectal cancer contributes to both colon and rectal cancer risk. Associations appear to be strongest for CIMP+ and MSI+ tumors.

Diet, physical activity, and body size associations with rectal tumor mutations and epigenetic changes

Diet and lifestyle factors have been inconsistently associated with rectal tumors. It is possible that evaluation of specific tumor markers with these factors may help clarify these associations. In this study, we examine energy contributing nutrients, dietary fiber, BMI (kg/m2), and long-term physical activity with TP53 mutations, KRAS2 mutations, and CpG Island Methylator Phenotype (CIMP) in 750 population-based cases of rectal cancer compared to healthy controls. We observed that high levels of physical activity reduced the risk of having TP53 and KRAS2 rectal tumor mutations. Dairy products rich in fat were associated with an increased risk of CIMP+ tumors (OR 1.88 95% CI 0.92, 3.84), while low-fat dairy products reduced risk of CIMP+ tumors (OR 0.56 95% CI 0.29, 1.09). Omega-3 fatty acids were associated with a twofold increased risk of a CIMP+ tumor. High levels of vegetable intake reduced risk of both TP53 mutations (OR 0.73 95% CI 0.54, 1.00; p trend 0.02) and KRAS2 mutations (OR 0.60 95% CI 0.40, 0.89; p trend <0.01). High intake of whole grains reduced the likelihood of a TP53 mutation (OR 0.74 95% CI 0.56, 0.99), while high intake of refined grains increased the likelihood of a TP53 mutation (OR 1.41 95% CI 1.02, 1.96). Dietary fiber also was associated with reduced risk of TP53 and KRAS2 rectal tumor mutations. Overall, a prudent dietary pattern significantly reduced the likelihood of a KRAS2 tumor mutation (OR 0.68 95% CI 0.47, 0.98; p linear trend 0.03). These data suggest that diet and lifestyle factors are associated with specific types of rectal tumor mutations and epigenetic changes. Findings need confirmation in other studies.