Tobacco, alcohol, and p53 overexpression in early colorectal neoplasia

Smoking and Colorectal Cancer Risk, Overall and by Molecular Subtypes: A Meta-Analysis

INTRODUCTION

The aim of this study was to provide the most comprehensive and up-to-date evidence on the association between cigarette smoking and colorectal cancer (CRC) risk.

METHODS

We conducted a systematic review and meta-analysis of epidemiological studies on the association between cigarette smoking and CRC risk published up to September 2018. We calculated relative risk (RR) of CRC according to smoking status, intensity, duration, pack-years, and time since quitting, with a focus on molecular subtypes of CRC.

RESULTS

The meta-analysis summarizes the evidence from 188 original studies. Compared with never smokers, the pooled RR for CRC was 1.14 (95% confidence interval [CI] 1.10-1.18) for current smokers and 1.17 (95% CI 1.15-1.20) for former smokers. CRC risk increased linearly with smoking intensity and duration. Former smokers who had quit smoking for more than 25 years had significantly decreased risk of CRC compared with current smokers. Smoking was strongly associated with the risk of CRC, characterized by high CpG island methylator phenotype (RR 1.42; 95% CI 1.20-1.67; number of studies [n] = 4), BRAF mutation (RR 1.63; 95% CI 1.23-2.16; n = 4), or high microsatellite instability (RR 1.56; 95% CI 1.32-1.85; n = 8), but not characterized by KRAS (RR 1.04; 95% CI 0.90-1.20; n = 5) or TP53 (RR 1.13; 95% CI 0.99-1.29; n = 5) mutations.

DISCUSSION

Cigarette smoking increases the risk of CRC in a dose-dependent manner with intensity and duration, and quitting smoking reduces CRC risk. Smoking greatly increases the risk of CRC that develops through the microsatellite instability pathway, characterized by microsatellite instability-high, CpG island methylator phenotype positive, and BRAF mutation.

Chronic obstructive pulmonary disease and risk of lung cancer: a meta-analysis of prospective cohort studies

Background

Studies exploring the association between chronic obstructive pulmonary disease (COPD) and lung cancer have yielded mixed results. We conducted a meta-analysis of the published prospective cohort studies to have a clear understanding about this association.

Methods

We searched the MEDLINE and EMBASE databases from inception to December 31, 2016. Bibliographies were also reviewed for additional information. Random-effects model was used to calculate summary relative risk (SRR) and corresponding 95% confidence interval (CI).

Results

Eighteen prospective cohort studies were part of this meta-analysis, involving 12,442 lung cancer cases with a median duration of follow- up of 5 years (range: 1.5-20 years). A history of COPD, emphysema or chronic bronchitis conferred SRRs of 2.06 (95% CIs: 1.50-2.85; n=14 studies), 2.33 (95% CIs: 1.56-3.49; n=4 studies) and 1.17 (95%CIs: 0.79-1.73; n=3 studies), respectively. Stratification by COPD severity yielded SRR of 1.46 (95% CIs: 1.20-1.76) for mild, 2.05 (95% CIs: 1.67-2.52) for moderate and 2.44(95% CIs: 1.73-3.45) for severe COPD, respectively. There were similar risk estimations for never and ever smokers. The SRR was statistically higher for squamous cell cancer than that for adenocarcinoma and for small cell cancer of the lung (P<0.05).

Conclusion

This meta-analysis indicated a significantly increased risk of lung cancer for COPD, emphysema, but not for chronic bronchitis. For the prevention of lung cancer, it is of importance for early detection of COPD in lung cancer surveillance.

Dietary fiber intake reduces risk for colorectal adenoma: a meta-analysis

BACKGROUND & AIMS

Reports on the association between dietary fiber intake and risk of colorectal adenoma (CRA), the precursor of colorectal cancer, have been inconsistent. We conducted a meta-analysis of case-control and cohort studies to analyze this association.

METHODS

We searched the MEDLINE and EMBASE databases to identify relevant studies published through July 2013. A random-effects model was used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs) for associations between fiber intake and CRA risk. Heterogeneity among studies was assessed using the Cochran Q and I(2) statistics.

RESULTS

Our meta-analysis included 20 studies involving 10,948 subjects with CRA. The SRRs of CRA for total dietary fiber were 0.72 (95% CI, 0.63-0.83) in a high- vs low-intake analysis and 0.91 (95% CI, 0.87-0.95) per 10-g/day increase in fiber intake in a dose-response model. Subgroup analyses indicated a significant inverse association between total fiber intake and CRA risk in case-control studies (SRR, 0.66; 95% CI, 0.56-0.77), but not in cohort studies (SRR, 0.92; 95% CI, 0.76-1.10). The SRRs of CRA were 0.84 for fruit fiber (95% CI, 0.76-0.94; n = 6 studies), 0.93 for vegetable fiber (95% CI, 0.84-1.04; n = 6 studies), and 0.76 for cereal fiber (95% CI, 0.62-0.92; n = 9 studies) in high- vs low-intake analyses.

CONCLUSIONS

Our findings support the hypothesis that high dietary fiber intake is associated inversely with CRA risk. Further studies with prospective designs that use validated questionnaires and control for important confounders are warranted.

Associations between cigarette smoking, hormone therapy, and folate intake with incident colorectal cancer by TP53 protein expression level in a population-based cohort of older women

Cigarette smoking (CS), hormone therapy (HT), and folate intake (FI) are each thought to influence colorectal cancer risk, but the underlying molecular mechanisms remain incompletely defined. The TP53 (p53) protein, encoded by the TP53 tumor-suppressor gene that is commonly mutated in colorectal cancer, can be readily assessed to differentiate biologically distinct colorectal cancer subtypes. In this prospective cohort study, we examined CS-, HT-, and FI-associated colorectal cancer risks by TP53 protein expression level among Iowa Women's Health Study (IWHS) participants. The IWHS recruited 41,836 randomly selected Iowa women, ages 55 to 69 years, with a valid driver's license at study entry in 1986. Self-reported exposure variables were assessed at baseline. Incident colorectal cancer cases were ascertained by annual linkage with the Iowa Cancer Registry. Archived, paraffin-embedded tissue specimens were collected and evaluated for TP53 protein expression by immunohistochemistry. Multivariate Cox regression models were fit to estimate relative risks (RR) and 95% confidence intervals (CI) for associations between CS, HT, or FI and TP53-defined colorectal cancer subtypes. Informative environmental exposure and protein expression data were available for 492 incident colorectal cancer cases: 222 (45.1%) TP53 negative, 72 (14.6%) TP53 low, and 198 (40.2%) TP53 high. Longer duration (>5 years) of HT was inversely associated with TP53 high colorectal cancers (RR, 0.50; 95% CI, 0.27-0.94). No other statistically significant associations were observed. These data support possible heterogeneous effects from HT on TP53-related pathways of colorectal carcinogenesis in older women.

APC and KRAS mutations in distal colorectal polyps are related to smoking habits in men: results of a cross-sectional study

BACKGROUND

The purpose of this study was (a) to evaluate the association between cigarette smoking and the prevalence of distal colorectal polyps and adenocarcinoma and (b) to analyse genetic alterations representing different molecular pathways of the colorectal carcinogenesis.

METHODS

A total of 623 asymptomatic male (mean age: 53 years; 50-65) car factory workers were included. Information on smoking habits and other lifestyle factors were collected followed by a 60 cm colonoscopy. APC and KRAS mutations and microsatellite status were determined in colorectal lesions (colorectal carcinoma (CRC), hyperplastic (HP) and adenomatous polyps (AP)). Data were analysed using unconditional multiple logistic regression models.

RESULTS

Smokers had a higher prevalence of AP (OR 2.1; 95% CI 1.2-3.6; p<0.05) and HP (OR 5.4; 95% CI 2.6- 11.1; p<0.05). No differences in CRC were observed. There was a dose-response relationship with the number of cigarettes smoked. The risk of developing AP or HP decreased after smoking cessation, even among heavy smokers (≥20 packs/year). KRAS mutations were more prevalent among smokers AP (OR 5.6; 95% CI 1.6-20.4; p=0.007). There was a trend of positive association with APC mutations (OR 3.5; 95% CI 0.9-4.4; p=0.096). APC and KRAS mutations were found in 36% and 61% of the HP of smokers, but were absent in non-smokers (p=0.89 and 0.78, respectively). There were no differences in MSI between smokers and non-smokers.

CONCLUSIONS

Cigarette smoking is associated with a higher risk of developing both HP and AP and a higher prevalence of mutations in APC and KRAS.

Colorectal polyps: the scope and management of the problem

Colorectal cancer affects over 150,000 individuals yearly, and accounts for over 50,000 deaths. Much of the benefit of colorectal cancer screening has been attributed to detection and removal of adenomatous polyps, highlighting the importance of colorectal polyps as targets for intervention and as biomarkers for colorectal cancer risk. This review details the epidemiology of sporadic colorectal polyps, rationale behind use of polyps as an important surrogate for colorectal cancer risk, the benefits and limitations of secondary prevention of colorectal polyps through chemopreventive and dietary interventions, as well as colon surveillance.

p53 expression in colorectal carcinoma in relation to histopathological features in Ugandan patients

BACKGROUND

It has been shown that colorectal carcinoma is increasing in incidence in African countries. This could be due to change in life style. Molecular pathogenesis of colorectal cancer commonly involves mutation in p53 gene which leads to expression of p53 protein in tumor cells. Expression of p53 protein has been associated with poor clinical outcome and reduced survival in patients.

OBJECTIVE

This was a retrospective laboratory based study carried out in the Department of Pathology Makerere University, Kampala, Uganda. The aim of the study was to evaluate the expression of p53 protein in colorectal carcinoma in Ugandan patients, specifically its association with histological types, degree of differentiation, sites of the tumor and demographic characteristics of the patients.

METHODS

Immunohistochemistry was carried out on 109 patient's paraffin embedded tissue blocks of colorectal carcinoma diagnosed in the Pathology Department, Faculty of Medicine Makerere University Kampala during the period 1995 to 2005. The indirect immunoperoxidase method using monoclonal antibody p53 DO-7 and Envision (+) Dual link system-HRP to detect p53 expression was used. Haematoxylin and eosin stain was used for evaluation of histological types and degree of differentiation of the tumors. Topography of the tumors and demographic data were obtained from accompanying histological request forms.

RESULTS

Out of 109 patient's tissue blocks that were studied, 61 cases (56%) expressed p53 protein in the nucleus of malignant cells. Right sided colonic tumors were commoner (53.2%) than left sided colonic tumors (46.8%). p53 protein was expressed more in left sided colonic tumors with a significant difference (p<0.05), it was also expressed more in well differentiated tumors and non mucinous adenocarcinomas but with no significant difference (p>0.05). p53 expression was not affected by age or sex.

CONCLUSION

Frequency of p53 protein expression in Ugandan patients did not differ from that reported in the other parts of the world. It was expressed more in the left sided colonic tumors and this could support the hypothesis that right and left colonic tumors could have different pathogenesis and probably also responsible for difference in prognosis in these two topographic sites.

Abberant crypt foci -- importance in colorectal carcinogenesis and expression of p53 and mdm2: a changing concept

BACKGROUND

The presence of aberrant crypt foci (ACF) represents an important preneoplastic condition of the large intestine. The ACF are used extensively as the biological end point to study the effects of diet, biological agents and chemotherapeutic agents as they undergo distinct morphological and genetic changes in response to these factors. Till date, in human ACF, K-ras, beta-catenin, carcinoembryonic antigen (CEA) and adenomatous polyposis coli (APC) protein expression have been investigated, but the expression of late markers of colon carcinogenesis have not been studied in great detail.

AIMS

To study the significance of ACF in carcinogenesis, the incidence of ACF in colorectal carcinoma (CRC) patients and the expression profiles of the tumor repressor protein p53 and the murine double minute (mdm2) protein in ACF.

METHODS AND MATERIALS

The pattern of expression, histology and immunohistochemistry of the p53 and mdm2 proteins were studied in 32 colectomy specimens. Careful scoring was carried out using standard criteria. The prevalence of ACF, types of ACF, surrounding mucosal changes and the relation of ACF with tumor morphology and aggressiveness were determined, as was any difference in the staining pattern between hyperplastic and dysplastic ACF.

RESULT

Aberrant crypt foci were present in a large number of cases (84.4%), of which 65% were hyperplastic. All hyperplastic and dysplastic ACF tested positive for p53 in the nucleus. Both the nucleus and cytoplasm tested positive for mdm2 irrespective of the degree of dysplasia. No correlation was noted between ACF and tumor histology.

CONCLUSION

The p53 and mdm2 proteins are expressed during the very early stages of mucosal changes in ACF, irrespective of histological changes, but the pattern of expression can differ depending on geographical barriers, genetic factors, diet and environmental conditions. This results suggests that the conventional adenoma-carcinoma sequence is not completely correct. The detection of ACF and p53 and mdm2 expression can help to curtail the disease in its early stage by targeted therapy.

Moderate alcohol consumption protects against colorectal adenomas in smokers

BACKGROUND

Although some studies have shown an association between alcohol consumption and colorectal adenomas, the effect of moderate alcohol consumption is not well defined, nor is the interaction between alcohol and smoking.

AIM

To investigate the relationship between different levels of alcohol consumption and colorectal adenomas and to determine whether smoking modifies this relationship.

METHODS

Eligible patients who underwent a complete colonoscopy were included (179 cases and 466 controls). Alcohol consumption was obtained from a lifestyle questionnaire. Patients were divided into three groups: (1) Abstainers: 0 drinks/week; (2) Moderate drinkers: > 0 to <7 drinks/week; (3) Heavy drinkers: > or = 7 drinks/week. Odds ratios (OR) were calculated using logistic regression, controlling for gender, age, body mass index, use of non-steroidal anti-inflammatory medications. Results were stratified by the number of years smoked.

RESULTS

The proportion of patients with adenomas was 29.6% in abstainers, 22.1% in moderate drinkers, and 36.7% in heavy drinkers. The relationship between alcohol consumption and colorectal adenomas varied significantly by smoking history. For individuals who had never smoked, heavy drinkers were at significantly increased odds of having an adenoma compared to moderate drinkers (OR 3.08; 95% CI: 1.50-6.32), while no difference was seen for abstainers (OR 0.99; 95% CI: 0.52-1.89). Similarly, among individuals who had smoked 1-14 years, heavy drinkers were at increased odds of having an adenoma compared to moderate drinkers (OR 2.61; 95% CI: 1.04-6.51), and no difference was seen for abstainers (OR 1.02; 95% CI: 0.33-3.10). Somewhat unexpectedly, among individuals who had smoked for 15 or more years, abstainers were at increased odds of having an adenoma compared to moderate drinkers (OR 2.04; 95% CI: 0.91-4.59), while heavy drinkers were not at increased odds of having an adenoma (OR 0.73; 95% CI: 0.27-1.97).

CONCLUSIONS

Consumption of less than seven alcohol drinks per week does not increase the risk of having a colorectal adenoma. We found evidence in this study that moderate alcohol consumption among long-term smokers may potentially decrease the risk of an adenoma compared to abstainers.

Alcohol consumption and distinct molecular pathways to colorectal cancer

High alcohol consumption is related to colorectal cancer (CRC). Our objective was to study associations between alcohol consumption and risk of CRC according to characteristics of aetiological pathways: the chromosomal instability (CIN) and the microsatellite instability (MIN) pathway. We classified CIN+ tumours (tumours with either a truncating APC mutation, an activating K-ras mutation or overexpression of p53), MIN+ tumours (tumours lacking hMLH1 expression) and CIN- /MIN- tumours (tumours without these defects). In the Netherlands Cohort Study on diet and cancer, 120852 men and women, aged 55-69 years, completed a questionnaire on risk factors for cancer at baseline (1986). Case-cohort analyses were conducted using 573 CRC cases with complete data after 7 x 3 years of follow-up, excluding the first 2 x 3 years. Adjusted incidence rate ratios (RR) and 95 % confidence intervals (CI) were estimated. Compared with abstaining, alcohol consumption of >or=30 g/d was positively associated with the risk of CRC irrespective of genetic or molecular aberrations present, although statistical significance was not reached (RR 1 x 35 (95 % CI 0 x 9-2 x 0) for the CIN+ tumours, RR 1 x 59 (95 % CI 0 x 4-5 x 8) for the MIN+ tumours and RR 1.15 (95 % CI 0 x 5-2 x 7) for the CIN- /MIN- tumours). Beer, wine and liquor consumption were, independent of their alcoholic content, not consistently associated with the risk of CRC within the defined subgroups. In conclusion, our results indicate that a daily alcohol consumption of >or=30 g is associated with an increase in risk of CRC, independent of the presence or absence of the studied characteristics of different aetiological pathways.

Fatty acid metabolism pathway play an important role in carcinogenesis of human colorectal cancers by Microarray-Bioinformatics analysis

The present study systematically explored metabolic pathways and altered expressions of genes speculatively participating in colorectal carcinogenesis by using a Microarray-Bioinformatic analysis methods. The results revealed that 157 genes were up-regulated and 281 genes were down-regulated in colorectal cancer (CRC). Gene Ontology (GO) and relevant bioinformatics tools indicated that the functional category to which 438 genes (12%; 438/3800) of the most frequent alteration belonged was metabolism. The analysis of 10 colorectal cancer tissue specimens demonstrated that genes involved in fatty acid metabolic pathways had high rates of overexpression. In addition, we stimulated CRL-1790 cell line with linoleic acid (a polyunsaturated fatty acid) for 12, 24, 48 and 72 h. Cell proliferation was elevated by 5, 25, 28 and 31% (P<0.05), respectively. Further analyses revealed that the genes increasingly expressed in the cell line included enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase (EHHADH), enoyl Coenzyme A hydratase, short chain, 1, mitochondrial (ECHS1); glutaryl-Coenzyme A dehydrogenase (GCDH), acyl-Coenzyme A oxidase 2, branched chain (ACOX2); acyl-Coenzyme A dehydrogenase, C-2 to C-3 short chain precursor (ACADS); carnitine palmitoyltransferase 1B (CPT1B), acyl-CoA synthetase long-chain family member 5 (ACSL5), and cytochrome P450, family 4, subfamily A, and polypeptide 11 (CYP4A11) genes. This indicated that the stimulating effect of linoleic acid on cell proliferation was due to interference with the metabolic pathway of fatty acid metabolism. In conclusion, genes with altered expression levels in CRC were mainly associated with fatty acid metabolic pathways speculated to have an important role linked to carcinogenesis.