MTHFR C677T polymorphism and anatomopathological characteristics with prognostic significance in sporadic colorectal cancer.

Methylenetetrahydrofolate reductase (MTHFR) plays a key role in folate metabolism, and folate is implicated in carcinogenesis due to its role in DNA methylation, repair and synthesis. The MTHFR C677T polymorphism is associated with decreased risk of CRC and increased sensitivity to 5-FU treatment. The present study addressed the relationship between this polymorphism and histopathological and immunohistochemical characteristics of prognostic significance in 50 patients from the Canary Islands. No differences were found between the MTHFR C677T genotypes with respect to tumor budding, tumor necrosis, desmoplastic fibrosis and tumoral eosinophilia. No significant differences were found in Ki-67, bcl-2 (cytoplasmic and nuclear), CD31, CD3+ T lymphocytes (both stromal and intraepithelial) and peritumoral CD20+ B lymphocytes. In carriers of the MTHFR CC variant, tumor margins were infiltrative more frequently (68.7%) than in CT+TT carriers (33.3%, p=0.03). In addition, wild-type CC genotype showed stromal CD20+ B lymphocytes (68.8%) more often than CT+TT carriers (33.3%, p=0.03). Both parameters indicate a better tumor prognosis when the MTHFR 677T variant is present.

Clinicopathological analysis of factors related to colorectal tumor perforation: influence of angiogenesis.

Colorectal tumor perforation is a life-threatening complication of this disease. However, little is known about the anatomopathological factors or pathophysiologic mechanisms involved. Pathological and immunohistochemical analysis of factors related with tumoral neo-angiogenesis, which could influence tumor perforation are assessed in this study. A retrospective study of patients with perforated colon tumors (Group P) and T4a nonperforated (controls) was conducted between 2001 and 2010. Histological variables (differentiation, vascular invasion, and location) and immunohistochemical (CD31, Growth Endothelial Vascular Factor (VEGF) and p53) related with tumor angiogenesis were analyzed. Of 2189 patients, 100 (4.56%) met the inclusion criteria. Of these, 49 patients had nonperforated (2.23%) and 51 had perforated tumors (2.32%). The P group had lower number of right-sided tumors (7/51, 13.7%) compared with controls (13/49, 36.7%) (P = .01). The high-grade tumors (undifferentiated) represented only 3.9% of the perforated tumors; the remaining 96.1% were well differentiated (P = .01). No differences between groups in the frequency of TP53 mutation or VEGF and CD31 expression were found. In the P group, only 2 (3.9%) had vascular invasion (P = .01). Of the 12 tumors with vascular invasion, only 2 were perforated (16.6%). The median number of metastatic lymph-nodes in P Group was 0 versus 3 in controls (Z = -4.2; P < .01). Pathological analysis of variables that indirectly measure the presence of tumor angiogenesis (differentiation, vascular invasion, and the number of metastatic lymph nodes) shows a relationship between this and the perforation, location, and tumor differentiation. We could not directly validate our hypothesis, by immunohistochemistry of TP53, VEGF, and CD31, that perforated tumors exhibit less angiogenesis.

Metastatic lymphs nodes and lymph node ratio as predictive factors of survival in perforated and non-perforated T4 colorectal tumors.

AIMS: Recently it has been hypothesized that perforation of colorectal cancer (CRC) itself is not a predictor of poor prognosis. The aim of this study was to analyze the prognostic impact, of the spontaneous perforation of the tumour, metastatic lymph nodes and lymph node ratio (LNR) after potentially curative surgery. METHODS: Retrospective analysis of oncologic outcomes of patients with T4a CRC grouped by perforated and non-perforated tumours. Between 2001 and 2010, 100 patients were included. Oncologic outcomes, disease-free survival and global survival were analyzed. RESULTS: Forty-nine patients had a non-perforated cancer and 51 presented a perforated neoplasm. Perforated cancers had a lower mean number of lymph nodes (1.16 vs. 4.14, P < 0.001), lower LNR (0.13 vs. 0.33, P = 0.001), better TNM-stage (P < 0.001), and lower metastases during follows-up (P = 0.02). The perforated-group had higher survival (P = 0.017) and higher metastasis-free time (P = 0.03). LNR cutoffs (<0.05, 0.05-0.4, and >0.4) had significant differences in overall survival (log-rank < 0.001). The predictive value of LNR and metastatic lymph nodes in mortality was similar. CONCLUSIONS: In our experience, perforated cancers had higher survival rates and metastasis-free interval that non-perforated cancers, probably by a lower number of metastatic lymph nodes, smaller LNR and better TNM stage. Moreover the predictive value, in mortality rate, of metastatic lymph nodes and LNR was similar.

Impact of the MTHFR C677T polymorphism on colorectal cancer in a population with low genetic variability.

PURPOSES: Methylenetetrahydrofolate reductase (MTHFR) plays a key role in folate metabolism, and folate is implicated in carcinogenesis by its role in DNA methylation, repair, and synthesis. We analyzed the impact of MTHFR C677T polymorphism in colorectal cancer in a region of the Tenerife Island whose population has a history of genetic isolation and a low genetic variability. This allows analyzing the effects of the polymorphism that are not due to interactions with different genetic variants. METHODS: Genomic DNA of 50 Spanish sporadic colorectal cancer (CRC) patients and 103 controls was analyzed by PCR/RFLP and sequencing. RESULTS: The T allele is more frequent in controls than in patients (P < 0.01). The variant (T) carriers displayed significant odds ratio values for the CT heterozygotes (P = 0.026) and even when grouping heterozygote (CT) and homozygotes (TT) (P = 0.015). Patients carriers of the variant T (CT y TT) show a higher survival rate after chemotherapy than the CC homozygotes (log rank; P = 0.001). CONCLUSIONS: The MTHRF C677T variant has a protective effect on CRC development in a population with low allelic variability and an optimal intake of folic acid. Moreover, patients carrying the variant (T) show a better prognosis after 5-fluorouracil/folinic acid-based chemotherapy.

Tumor spectrum in lynch syndrome, DNA mismatch repair system and endogenous carcinogens.

Inactivation of Mismatch Repair genes in Lynch Syndrome, caused by inherited mutations, decreases the ability to repair DNA errors throughout life. This deficit may allow the development of any tumor type. Nevertheless, the Syndrome develops a specific tumor spectrum associated with the disease. We think that such spectrum of tumors would be related to the action of certain endogenous carcinogens such as bile acids and estrogens that aggravate the inherited defect.

Association of polymorphisms MTHFR C677T and A1298C with risk of colorectal cancer, genetic and epigenetic characteristic of tumors, and response to chemotherapy.

BACKGROUND AND AIMS: The enzyme MTHFR plays an important role in folate metabolism, and folate is implicated in carcinogenesis due to its role in DNA methylation, repair, and synthesis. We analyze the relationship of MTHFR C677T and A1298C polymorphisms with biological, clinicopathological, genetic and epigenetic features of tumors, and the patient outcome after treatment with 5-FU-based chemotherapy to determine the contribution of MTHFR genotypes in the risk of colorectal cancer (CRC) and in the response to therapy. METHODS: Genomic DNA of 143 Spanish sporadic CRC and 103 controls was analyzed by polymerase chain reaction/restriction fragment length polymorphism and sequencing. RESULTS: The C677T polymorphism has protective effect on CRC showing TT genotype an odds ratios of 0.06 (95% confidence interval (CI): 0.10-0.32) and the CT of 0.51 (95% CI: 0.3-0.87). MTHFR A1298C polymorphism is not associated with CRC risk. Patients with 1298CC and AC genotypes exhibit worse survival than those with the wild genotype (log rank, p = 0.001), whereas C677T genotypes do not affect patient survival (log rank, p = 0.92). MTHFR 677T allele carriers responded better to 5-FU-based chemotherapy than patients with the wild CC genotype (log rank, p = 0.05). The variant C allele of A1298C affects negatively the response to 5-FU-based chemotherapy (log rank, p = 0.009). CONCLUSIONS: The variant allele of the C677T has a protective effect on CRC development, whereas the variant allele of the A1298C does not produce any effect on disease risk. Both MTHFR polymorphisms are relevant and independent factors of patient outcome after 5FU-based treatment of CRC, and MTHFR genotyping may be of predictive benefit in selecting treatment regimens.

Genealogical tree study as screening method in the Lynch syndrome prior to genetic test.

OBJECTIVES: Despite genetic advances in the study of Lynch syndrome (LS), difficulties remain in the diagnosis of the syndrome. The aim of this study was to assess the usefulness of a detailed genealogical tree as a screening method to identify Tenerife island families with a high probability of LS. METHODS: We elaborated complete genealogical trees of the families. According to the degree of fulfillment of the Amsterdam Criteria II, the genealogical trees were classified as high or low probability of LS. Additionally, we analyzed the level of tumor microsatellite instability (MSI+) and identified a mutation in exon 13 of the MSH2 gene by single-strand conformation polymorphism, sequencing, and PCR-RFLP. RESULTS: According the genealogical trees, we found 10 families with high probability of LS and 30 families with low probability of LS. The families with high probability of LS showed high MSI+ in all cases. Conversely, families with low probability were MSS (microsatellite stable). In 5 of the 10 families with high probability, we discovered a T-->G mutation in position 688 of exon 13 of MSH2, which appeared in all the family members with the tumor, except 1 patient with a retinoblastoma. CONCLUSIONS: Our results indicate that genealogical tree is a highly effective tool for classifying families with a high probability of Lynch Syndrome prior to genetic test.

A MLH1 polymorphism that increases cancer risk is associated with better outcome in sporadic colorectal cancer.

Germline mutations or the malfunctioning of postreplicative mismatch repair genes (MMR) are responsible of hereditary nonpolyposis colorectal cancer (HNPCC), and are also implied in some sporadic colorectal cancer (CRC) forms without any familial history of this disease. Besides germinal mutations and methylation, single-nucleotide polymorphisms (SNP) can predispose to nonfamilial CRC with low to moderate penetrance. In this case-control study, we analyzed three MLH1 single-nucleotide polymorphisms (exon 5: 415G-->C, rs28930073; exon 8: 655A-->G, rs1799977 and exon 16: 1852-1853AA-->GC) in 140 sporadic colorectal cancer cases and 125 healthy individuals to evaluate the relationship among CRC risk and clinicopathologic and genetic characteristics of the tumors. In our study, no 415G-->C variant carrier was found among all analyzed samples. The 1852-1853AA-->GC is a rare variant detected in heterozygoses in five controls and one case. In relation to the more frequent 655A-->G polymorphism, association analyses revealed that G carriers (AG or GG genotype) displayed a higher risk of CRC compared with AA homozygous [odds ratio (OR) AG=2.55, 95% confidence interval (CI)=1.48-4.39; P=0.01 and OR GG=2.48, 95% CI=1.20-5.11; P=0.01, respectively]. G-carrier males showed high CRC risk compared with homozygous AA wild-type individuals (OR: AG=3.05; 95% CI=1.49-6.26, P=0.002; OR: GG=3.60; 95% CI=1.29-10.03). Nevertheless, patients carrying the G allele displayed a better outcome than wild-type genotype carriers (log rank=7.26; P=0.007) and did not present vascular invasion (P=0.03), distant metastasis (P=0.004), or recurrence (P=0.01). MLH1 655A-->G change is associated with an increased risk, although it seems to have a favorable effect on patients, providing a better outcome. Moreover, our results suggest that for genomic profiling to predict the clinical outcome of patients with colorectal cancer, gender must also be considered.

Effect of COX2 -765G>C and c.3618A>G polymorphisms on the risk and survival of sporadic colorectal cancer.

BACKGROUND: The COX2 gene (also known as PTGS2) encodes one of the essential cyclooxygenases for the prostanoid synthesis, and its expression is tightly regulated at both transcriptional and posttranscriptional levels. COX2 overexpression has been detected in up to 90% of colon carcinomas, and its downregulation inhibits polyp formation. Several polymorphisms located in both 5'- and 3'- flanking regions of COX2 have been described, but their functional significance and their use as prognostic indicators are still unclear. METHOD: We analyzed in Spanish population the risk contribution and the prognostic significance for colorectal cancer (CRC) with five polymorphisms (rs20417, rs20426, rs5276, rs13306035 and rs4648298) located in the coding and regulatory regions of COX2. RESULTS: Only two variants appear in Spanish population: -765G>C (rs20417) located at the promoter and c.3618A>G (rs4648298) in the 3'UTR. None of the two polymorphisms associate with colon cancer risk (HR of 1.42; 95% CI = 0.46-4.47 and 0.62; 95% CI: 0.305-1.267, respectively). Moreover, the multifactor dimensionality reduction method does not detect high- or low-risk genotype combinations (training accuracy: 0.52; testing accuracy: 0.45; cross-validation consistency (CVC): 10/10; p = 0.37), indicating that there are no synergist interactions between these polymorphisms that alter the risk of cancer. However, the variant of the c.3618A>G polymorphism is associated with the presence of several clinicopathological features that have been shown to be good prognostic indicators. In addition, patients with the c.3618A>G polymorphism also show improved survival rates (log rank, p = 0.026). CONCLUSION: The current results suggested that c.3618A>G polymorphism in COX2 is a good prognostic indicator for patients with CRC. Genotyping this polymorphism may be useful for predicting the clinical outcome of sporadic CRC.

Do MSI-L sporadic colorectal tumors develop through "mild mutator pathway"?

BACKGROUND: The mutator pathway implied in the development of colorectal cancer (CRC) is characterized by microsatellite instability (MSI). MSI tumors can be subdivided according to the level of instability: MSI-H (high), MSI-L (low) or stable MSS. MSI-H CRC displays a well described distinct phenotype, but the true biologic significance of MSI-L is still uncertain. The objective of this study was to further clarify if the MSI-L phenotype could reflect a distinct pathway of tumor development with a different clinical behavior. METHODS: We analyzed the clinicopathological and genetic variables of 156 patients with sporadic CRC in relation with the level of MSI of the tumors. RESULTS: We have found that MSI-L tumors are someway in the middle of MSI-H and MSS CRC, as they share some features with each of the other 2 subgroups: left side location, lower incidence of LOH at MSH2 as MSS and Dukes B (stage II TNM) like MSI-H. Moreover, MSI-L tumors show higher incidence of KRAS mutations. CONCLUSION: We believe that MSI-L tumors could be considered a distinct phenotype that develops through a "mild mutator pathway."

RIS1, a gene with trinucleotide repeats, is a target in the mutator pathway of colorectal carcinogenesis.

Microsatellite instability (MSI) due to mismatch repair system (MMR) alterations characterizes the mutator pathway implied in colorectal cancer development. In the present study, we have analyzed the gene RIS1 (Ras-induced senescence 1) in relation to loss of heterozygosity (LOH) and its frameshift mutations for an imperfect trinucleotide repeat (GCN) located at the 3'-OH end. Additionally, we have compared the status of RIS1 with a number of genetic and clinicopathological variables. RIS1 did not display LOH in any informative tumor of our series, but exhibited frameshift mutations in a high percentage (43.8%) of high-frequency MSI tumors (MSI-H), and its alteration was correlated with mutations in two target genes: BAX and TGFBR2. Moreover, mutations in RIS1 in MSI-H tumors correlated with the epigenetic silencing of MLH1 (P = 0.04). Finally, RIS1 seemed to be functionally involved in tumor development, as low-frequency MSI tumors (MSI-L) with RIS1 mutated usually were associated with a worse prognosis: 83% of them developed metastasis, and no patient with MSI-L tumor and RIS1 mutated (35.3% of MSI-L) survived >25 months after surgery (log rank P < 0.001). All these results indicate, according to the Bethesda criteria, that RIS1 is a target gene in the mutator pathway.

New founding mutation in MSH2 associated with hereditary nonpolyposis colorectal cancer syndrome on the Island of Tenerife.

Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC) is a hereditary syndrome with genetic heterogeneity. The disease is caused by mutations or epigenetic silencing in DNA mismatch repair genes, MLH1, MSH2, MSH6, PMS2 and MLH3, although the vast majority of cases correspond to mutations of MLH1 and MSH2. We herein describe a nucleotide change, c.2063T>G in exon 13 of the MSH2 gene, present in families that fulfill the Amsterdam criteria for Lynch syndrome and originate from northern Tenerife (Canary Islands-Spain). This mutation is expected to result in a nonconservative amino acid change, M688R, at the ATPase domain of the MSH2 protein. We found five large families with this mutation, and about half the individuals heterozygous for M688R developed malignancies by the sixth decade of life. In many cases analyzed, their tumors revealed loss of the normal allele, being homozygous for M688R. There is an evidence of historical isolation for the population studied, which could have favored a considerable genetic drift. The presence of the same mutation and the disease associated-haplotype conservation in families not directly related can be probably the consequence of a bottleneck in the founding of this population (rather than a relatively recent founding of the mutation).

Significance of mutations in TGFBR2 and BAX in neoplastic progression and patient outcome in sporadic colorectal tumors with high-frequency microsatellite instability.

The mutator pathway implied in the development of colorectal cancer is characterized by microsatellite instability (MSI), which is determined by alterations of mismatch repair (MMR) genes. Defects in MMR genes affect repetitive DNA tracts interspersed mostly between coding sequences, and therefore it cannot be expected that they play a role during tumor progression. Genes containing repetitive sequences within their coding regions could be targets for MSI tumorigenesis, but this does not necessarily imply a causal role for the affected gene, because most are probably passenger mutations. We analyzed MSI and TGFBR2 and BAX frameshift mutations to further clarify the relationships between inactivation of the two genes and genomic instability in sporadic colorectal cancer (CRC), and to address how mutations in these genes influence the development of tumors and, eventually, patient outcome. One hundred and fifty-five patients with sporadic CRC were classified according to their MSI status. Frameshift mutations in the two genes were recurrent in high-frequency MSI (MSI-H) tumors, but these tended to be more common in poorly differentiated tumors. A high rate of mutations of TGFBR2 was found in tumors at Dukes' B stage, showing a greater extent of vascular invasion. Finally, in MSI-H tumors, mutations of either gene were associated with a significant decrease in survival. Our results contribute to the understanding of how the TGFBR2 and BAX gene mutations contribute to tumor progression in the mutator phenotype pathway for MSI colorectal cancers.

Simultaneous mutations in K-ras and TP53 are indicative of poor prognosis in sporadic colorectal cancer.

Despite the fact that the mutations in K-ras codon 12 and TP53 are common abnormalities in colorectal cancer, the determination of K-ras mutation combined with TP53 gene mutation, with diagnostic and prognostic purposes is still controversial. We have analyzed K-ras and TP53 mutations in 77 sporadic colorectal adenocarcinomas by means of polymerase chain reaction and sequencing. We observed a negative correlation between both K-ras and TP53 mutations. Patients with mutations in K-ras but not in TP53 exhibited worse survival rates than those with mutations in TP53 and not in K-ras. Moreover, we found the worst outcome in patients with mutations in both K-ras and TP53. These results may relate to the previously published data about primary human and rodent cells, in which transformation by Ras require either a cooperating oncogene or the inactivation of tumor suppressors such as p53 or p16. In conclusion, simultaneous mutations in K-ras and TP53 are indicative of a worse prognosis in sporadic colorectal cancer.

Genetic alterations and MSI status in primary, synchronous, and metachronous tumors in a family with hereditary nonpolyposis colorectal cancer (HNPCC).

In colorectal cancer, different levels of microsatellite instability (MSI) have been described: high-frequency MSI, low-frequency MSI, and stable microsatellites. MSI-H characterizes a unique clinical and pathologic phenotype known as hereditary nonpolyposis colorectal cancer syndrome (HNPCC). In this case, an increased incidence of synchronous and metachronous tumors has been reported, but there are few reports with standardized criteria of MSI in HNPCC-associated tumors. The authors attempted to establish whether tumors of the HNPCC spectrum with different levels of MSI could predict the development of metachronous carcinomas. We have examined the levels of MSI at loci frequently affected in colorectal cancers in primary, synchronous, and metachronous tumors in a family that fulfils the Amsterdam criteria for HNPCC. This family presents colorectal cancers, HNPCC-extracolonic tumors (endometrial and ureter), and tumors (breast and bladder) not described in the HNPCC spectrum. The tumors exhibited MSI-H, irrespective of their location and regardless whether they were primary, synchronous, or metachronous, with the only exception of both endometrial tumors that showed low-frequency MSI tumors (MSI-L). Our results suggest that not only colorectal tumors with MSI-H result in a potential marker for the determination of high-risk individuals for metachronous and synchronous tumors, but also MSI-L endometrial tumors might be considered as indicative of high-risk individuals.