Microsatellite instability markers status in colorectal cancer

Colorectal cancer [CRC] is the third most prevalent and the third leading cause of cancer-related deaths in Iran. Our aim was to investigate five mononucleotide statuses among Iranian patients with sporadic colorectal cancer. In this experimental study investigation 80 sporadic CRC patients were evaluated for Microsatellite instability [MSI]. The pentaplex panel including 5 quasi mononucleotide microsatellite markers [NR-21, BAT-26, BAT-25, NR-27 and NR-24] was used. The MSI analysis was performed on paired tumoral DNA from cancerous tissues and genomic DNA from whole blood. MSI carriers were identified by analysis of tumor tissue using polymerase chain reaction. Our findings showed that microsatellite instability was detected in 36 of 80 cases [45%] with colorectal cancer. MSI analysis revealed that 17 cases of MSI-H [21%], 19 MSI-L [23%] and 44 MSS [55%]. Instability is observed in the tumoral DNA compared to the DNA from the normal DNA sample. The most instable markers were NR-21, NR-24 in which instability was detected in 45% of patients. Using a panel including 3 mentioned MSI markers should be more promising markers for identifying MSI status in patients with sporadic colorectal cancer

Clinical implications of BRAF mutation test in colorectal cancer

Knowledge about the clinical significance of V-Raf Murine Sarcoma Viral Oncogene Homolog B1 [BRAF] mutations in colorectal cancer [CRC] is growing. BRAF encodes a protein kinase involved with intracellular signaling and cell division. The gene product is a downstream effector of Kirsten Ras [KRAS] within the RAS/RAF/MAPK cellular signaling pathway. Evidence suggests that BRAF mutations, like KRAS mutations, result in uncontrolled, non-growth factor-dependent cellular proliferation. Similar to the rationale that KRAS mutation precludes effective treatment with anti-EGFR drugs. Recently, BRAF mutation testing has been introduced into routine clinical laboratories because its significance has become clearer in terms of effect on pathogenesis of CRC, utility in differentiating sporadic CRC from Lynch syndrome [LS], prognosis, and potential for predicting patient outcome in response to targeted drug therapy. In this review we describe the impact of BRAF mutations for these aspects

effect of 5'untranslated region polymorphism in EGF gene, rs4444903, on colorectal cancer

The purpose of this study was to determine the relationship of rs4444903 [EGF+61A/G] SNP genotype with colorectal cancer and tumor stage in an Iranian population. Epidermal growth factor [EGF] is one of the important proteins that determine survival of cells. EGF binds to its receptor on the cell surface and then activates some of the cell signaling pathway networks within cells that lead to activation or deactivation of factors which are responsible for growth and apoptosis of cells. In this study we assessed the association in EGF polymorphism rs4444903 with colorectal cancer [CRC] in Iranian population. We conducted case-control study to investigate the association of polymorphism rs4444903 in EGF, with colorectal cancer risk in Iranian population. Analyzed Polymorphism of EGF rs4444903 with restriction fragment length polymorphisms [RFLP] among two groups of subjects consisting of including 220 cases with colorectal cancer and 220 healthy individuals as controls. Mutations were confirmed in 10% of the samples by direct sequencing. The frequencies of AA, AG and GG genotypes among cases with colorectal cancer were 28.2, 46.8, and 25.0% respectively and in controls genotype frequencies were 23.2, 56.4, and 25.0%, respectively. Frequency of A allele among case group was 51.6% and for control group was 51.4%. The frequency of G allele in case and control was, respectively 48.4% and 48.6% [OR= 1.009, 95% CI= 0.775-1.315; P= 0.946]. The percentage of Stage 0, I, II, III, IV were 5%, 9.35%, 38.84%, 30.21% and 16.54%, respectively, among the cases. However, no significant association between this polymorphism and CRC stage was observed [p=0.626]. Our data suggest a SNP rs4444903 may not represent a risk factor in the development and progression of CRC among Iranian population

role of Kras mutations and MSI status in diagnosis of colorectal cancer

The aim of the current investigation was to examine the profile of Kras mutations accompanied with MSI [microsattelite instability] status in polyps and colorectal carcinoma tissues in an Iranian population. Kras mutations in colorectal cancer cause resistance to anti-Epidermal Growth Factor Receptor [EGFR]. So it can be considered as a true indicator of EGFR pathway activation status. Kras mutations can be detected in approximately 30% to 40% of all patients with colorectal cancer. The most hot spot of the gene is located in exons 2 and 3. In this study we examined exons 2 and 3 Kras gene using polymerase chain reactions and subsequent sequencing of the exons in 95 patients with sporadic colorectal cancer including 48 tumors and 47 polyps. This study was performed using biopsy samples from the patients. We sequenced the Kras gene in a panel of human colorectal tumors and polyps in addition to detecting MSI status using fluorescent technique. We could detect 6 mutations in tumors including 5 mutations in codon 12 and one mutation in codon 13. Moreover, in polyps 2 mutations were determined in codon 13 and one in codon 12. Microsatellite instability assay revealed the presence of 5 and 6 MSI in tumors and polyps, respectively. Among the MSI mononucleotide markers, NR-21 marker demonstrated the most frequency [60%] in the both groups. Our findings showed that probably the profile of mutations in tumors is not entirely compatible with the pattern of mutations in polyps. However, just one of the mutations, Gly12Asp, was similar in both groups

[Evaluation of 4-year survival in familial and non familial colorectal cancer]

Colorectal cancer in the world is located in the third position among common cancers in both sexes. It is the second cancer which has the most mortality .The incidence of this cancer in the last decades has transcended trend in our population. The aim of this study was comparison of 4-year survival between sporadic and hereditary colorectal cancer. In this descriptive-analytic study, 121 patients with colorectal cancer were collected including 61 patients with sporadic and 60 individuals with HNPCC who were referred to research cancer gastroenterology and liver diseases of Taleghani hospital during 2004-2008. Survival rate was estimated using the Kaplan Meier method and compared with log rank test. Multivariate analysis was performed using the Cox regression analysis. 4-year survival in sporadic colorectal cancer and HNPCC showed a significant difference. The rate of survival in HNPCC patients was 82.5%, while it was 56.4% [p=0.044] in sporadic colorectal cancer. Age of diagnosis in sporadic patients was higher than hereditary group. Odds ratio of sporadic colorectal cancer for tumor location was 2.93 [95%CI: 1.06-8.11] compared HNPCC [p=0.038]. The result of this study was compatible with the previous studies. The result showed that the rate of survival in patients with HNPCC is higher than sporadic cases

[ effect of o6-methyl guanine methyl teranferase in colorectal cancer]

Sporadic colorectal cancer is the fourth most common cancer in Iran. The DNA repair protein O6- methylguanine-DNA methyltransferase [MGMT] is involved in the cellular defense against alkylating agents. Genetic alterations in the MGMT gene may impair the protein's ability to remove alkyl groups from the O6-position of guanine, thereby raising the mutation rate and increasing the risk of sporadic colorectal cancer. We hypothesized that amino acid substitution polymorphisms in the MGMT gene may be associated with the genetic susceptibility to sporadic colorectal cancer. We assessed five non-synomymous polymorphisms [Pro58Ser, Leu84Phe, Arg128Gln, Ile143Val, Gly160Arg] in the MGMT gene by PCR/Pyrosequencing. The population studied consisted of 200 sporadic colorectal cancer patients and 200 healthy individuals [blood donors], all of Iranian origin. Allele frequencies and genotypes were compared between the two groups. Odds ratios were calculated and the interactions among the polymorphisms, age and sex were examined. There was a significant association between two amino acid substitution polymorphisms [Arg128Gln and Gly160Arg] of MGMT gene and sporadic colorectal cancer. We could show a significant association between the two polymorphisms and colorectal cancer. This might be a superior marker for colon cancer screening in the future

[Three novel germline mutations in the MLH1 mismatch repair gene in patients with hereditary non-polyposis colorectal cancer]

Hereditary non-polyposis colorectal cancer is the most common cause of early onset of hereditary colorectal cancer. In the majority of Hereditary non-polyposis colorectal cancer families, microsatellite instability and germline mutation in one of the DNA mismatch repair genes in clouding MSH2, MLH1, MSH6 and PMS2 are found. The Objective of this study was to determine the involvement of mismatch repair genes mutations in Iranian population, and microsatellite instability profile in patients with colorectal cancer. We analyzed 592 patients with colorectal cancer. The entire coding sequence of each gene was analyzed using direct sequencing. We were able to find three novel MLH1 germline mutations in three Iranian patients suffering from Hereditary non-polyposis colorectal cancer. The first was a transversion mutation c.346A>C [T116P], which occured in the highly conserved HATPase-c region of MLH1 protein. The second was also a transversion mutation c.736A>T [I246L], which caused an amino acid change of Isoleucine to Leucine. The third mutation [c.2145,6 delTG] was frame shift mutation, and resulted in an immature stop codon in five codons downstream. All of these three mutations were detected in MLH1 gene. In all patients, an abnormal expression of MMR proteins was related to the above mutations. MSI assay revealed high instability in microsatellite for two patients and microsatellite stability for one patient. These novel mutations may imply the different characteristics of hereditary non-polyposis colorectal cancer in Iranian population as compared to reports from the western countries