Molecular epidemiology of colon cancer

Association of Diabetes Mellitus and Alcohol Abuse with Cancer: Molecular Mechanisms and Clinical Significance

Diabetes mellitus (DM), one of the metabolic diseases which is characterized by sustained hyperglycemia, is a life-threatening disease. The global prevalence of DM is on the rise, mainly in low- and middle-income countries. Diabetes is a major cause of blindness, heart attacks, kidney failure, stroke, and lower limb amputation. Type 2 diabetes mellitus (T2DM) is a form of diabetes that is characterized by high blood sugar and insulin resistance. T2DM can be prevented or delayed by a healthy diet, regular physical activity, maintaining normal body weight, and avoiding alcohol and tobacco use. Ethanol and its metabolites can cause differentiation defects in stem cells and promote inflammatory injury and carcinogenesis in several tissues. Recent studies have suggested that diabetes can be treated, and its consequences can be avoided or delayed with proper management. DM has a greater risk for several cancers, such as breast, colorectal, endometrial, pancreatic, gallbladder, renal, and liver cancer. The incidence of cancer is significantly higher in patients with DM than in those without DM. In addition to DM, alcohol abuse is also a risk factor for many cancers. We present a review of the recent studies investigating the association of both DM and alcohol abuse with cancer incidence.

Association of XPD Lys751Gln gene polymorphism with susceptibility and clinical outcome of colorectal cancer in Pakistani population: a case-control pharmacogenetic study

BACKGROUND

XPD Lys751Gln polymorphism may modulate inter-individual variation in repair capacity of DNA, which may enhance a person's susceptibility to develop colorectal cancer (CRC). The analysis of XPD Lys751Gln polymorphism may provide important information for identifying high-risk individuals and for selecting the most appropriate treatment for poor prognostic CRC patients.

OBJECTIVE

The overall objective was to find out the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer and the ultimate clinical outcomes. In this study a total of 300 subjects (CRC and Controls), were genotyped for XPD Lys751Gln.

METHODS

Using PCR-RFLP methods, the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer was studied. In addition to overall risk assessment, genotyping results were also investigated with respect to the lifestyle risk factors, patients treated with oxaliplatin-based chemotherapy and clinicopathological characteristics.

RESULTS

The overall correlation between the XPD Lys751Gln genetic variation and the CRC risk was observed to be significant with both the homozygous variant genotype Gln/Gln as well as heterozygous genotype Lys/Gln being associated with the increased risk of CRC. Additional stratified analyses revealed that XPD Lys751Gln variants remarkably increased risk of CRC in males and younger individuals (≤ 50 years), Naswar users (8.09-fold) and high intake of red meat.

CONCLUSIONS

Our findings suggest that the relationship between the XPD Lys751Gln variants and lifestyle factors modulates the risk for CRC in Pakistani population.

Mutations in K-ras and Epidermal Growth Factor Receptor Expression in Korean Patients With Stages III and IV Colorectal Cancer

K-Ras somatic mutations in advanced colorectal cancer (CRC) can predict resistance to mAbs that target the epidermal growth factor receptor (EGFR). The relationships between K-ras mutations and the EGFR status have not yet been examined, especially in Korean patients. A total of 82 colorectal tumors (stage III-IV) were analyzed. K-Ras mutations at codons 12 and 13 were detected by polymerase chain reaction—single strand conformational polymorphism. The EGFR expressions were examined by immunohistochemistry, and these were graded according to a modified EGFR expression scoring system. The relationships between the patients’ characteristics and the survival time and the gene mutation status were analyzed. The EGFR expression was positive in 69 patients (84.1%) and negative in 13 patients (15.9%). The K-ras mutation rate was 35.4%. In all, 20 (68.9%) cases were mutated at codon 12 and 9 (31.1%) cases were mutated at codon 13. No relationship was observed between the EGFR status and K-ras mutation. The median overall survival (OS) was 68.1 months. There was no difference between the K-ras mutant group and the wild type group for overall survival (30.3% vs 21.0%, respectively, at 36 months, P = .777). K-ras mutation and the EGFR status were not independent prognostic factors for OS ( P = .105 and P = .499, respectively). For the Korean patients with CRC, the rate of an EGFR protein expression was greater than that for the patients in Western countries, and the rate of K-ras mutations was lower than that for patients in Western countries. This study found no correlation between the EGFR status and K-ras mutations in colorectal tumors.

Genetic alterations of APC, K-ras, p53, MSI, and MAGE in Korean colorectal cancer patients

BACKGROUND AND AIM

Colorectal cancer (CRC) is one of the most rapidly increasing cancers in Korea, but no comprehensive analysis has been performed to speculate the genetic basis of CRC development. We investigated the presence of adenomatous polyposis coli gene (APC), Kirsten-ras (K-ras), p53, microsatellite instability (MSI), and melanoma antigen gene (MAGE) alterations in CRC and correlated the results obtained with clinical data.

MATERIALS AND METHODS

We collected 78 cancer tissues from CRC patients. Genetic analyses were performed on APC, K-ras, p53, and MSI (BAT 25 and BAT 26), and in addition, MAGE expression was tested by reverse transcription polymerase chain reaction. Correlations between genetic markers and clinical factors were analyzed after reviewing medical records.

RESULT

The positive rates for alterations of APC, K-ras, p53, MSI, and MAGE in 78 tissue samples were 33.3, 29.5, 34.6, 9.0, and 68.4%, respectively. Mutations were frequently detected in codons 1291 and 1450 of APC, in codon 12 of K-ras and in codons 248, 282, and 176 of p53. APC mutations were frequently noted in early-stage cancer, whereas MSI was observed in right-sided and multiple cancers. No associations were found between the presence of alterations in APC, K-ras, p53, MSI, and MAGE.

INTERPRETATION

In Koreans, positive rates of alterations in APC and p53 were slightly lower than those of APC and p53 in Caucasians, and the genetic alterations including MAGE expression are involved in 92.1% of CRCs. The lack of multiple mutations and of a relation between mutation rates and clinical stage suggest that genetic alterations might have independent influences on CRC development in Koreans.