Microsatellite instability caused by hMLH1 promoter methylation increases with tumor progression in right-sided sporadic colorectal cancer

Molecular biomarkers for the detection of metastatic colorectal cancer cells

Approximately half of all patients with colorectal cancer develop local recurrence or distant metastasis during the course of their illness. Recently, the molecular detection of metastatic cancer cells in various types of clinical samples, such as lymph nodes, bone marrow, peripheral blood, and peritoneal lavage fluid, has been investigated as a potential prognostic marker. The prognostic value of molecular tumor cell detection was independent of the type of detection method used. As assays become more sensitive and quantitative, a more thorough assessment of the cancer status of patients will be based on molecular markers alone. At present, it is difficult to conclude that one specific molecular marker is superior to others. Comparative analyses are recommended to assess the prognostic impact of molecular analyses in the same patient and determine the biomarkers that provide the most accurate prognostic information.

CDH13 and FLBN3 gene methylation are associated with poor prognosis in colorectal cancer

The aim of this study was to identify potential epigenetic prognostic biomarkers for colorectal cancer (CRC) in the Chinese population. The methylation status of five tumor suppressor genes (CDH13, DLEC1, FBLN3, hMHL1 and RUNX3) was determined using manual microdissection followed by methylation-specific PCR in 85 paired CRC specimens and adjacent normal tissue. The results showed that methylation frequencies in cancerous tissues were 31.8% for CDH13, 37.6% for DLEC1, 38.8% for FBLN3, 22.4% for hMHL1 and 27.1% for RUNX3, all of which were significantly higher than in corresponding normal tissue. Furthermore, CDH13 methylation was associated with poor differentiation (P = 0.019) and tended to be predominant in advanced stages (P = 0.084); FBLN3 methylation was associated with advanced stages (P = 0.027) and lymph node metastasis (P = 0.029). Accordingly, the methylation status of CDH13 (P = 0.022), FBLN3 (P = 0.008), CDH13 and/or FBLN3 (P = 0.001) predicted adverse overall survival in CRC, while hMHL1 methylation showed a protective role in survival (P = 0.046). Cox proportional hazard models further indicated that CDH13 and/or FBLN3 methylation, but not that of hMHL1, was an independent prognostic factor for CRC. In conclusion, we found CDH13 and FBLN3 gene methylation are potential biomarkers for poor prognosis in CRC.

Metabolomic profiling reveals a role for androgen in activating amino acid metabolism and methylation in prostate cancer cells

Prostate cancer is the second leading cause of cancer related death in American men. Development and progression of clinically localized prostate cancer is highly dependent on androgen signaling. Metastatic tumors are initially responsive to anti-androgen therapy, however become resistant to this regimen upon progression. Genomic and proteomic studies have implicated a role for androgen in regulating metabolic processes in prostate cancer. However, there have been no metabolomic profiling studies conducted thus far that have examined androgen-regulated biochemical processes in prostate cancer. Here, we have used unbiased metabolomic profiling coupled with enrichment-based bioprocess mapping to obtain insights into the biochemical alterations mediated by androgen in prostate cancer cell lines. Our findings indicate that androgen exposure results in elevation of amino acid metabolism and alteration of methylation potential in prostate cancer cells. Further, metabolic phenotyping studies confirm higher flux through pathways associated with amino acid metabolism in prostate cancer cells treated with androgen. These findings provide insight into the potential biochemical processes regulated by androgen signaling in prostate cancer. Clinically, if validated, these pathways could be exploited to develop therapeutic strategies that supplement current androgen ablative treatments while the observed androgen-regulated metabolic signatures could be employed as biomarkers that presage the development of castrate-resistant prostate cancer.

DNA methylation in patients with colorectal cancer--correlation with some clinical and morphological features and with local tumour invasion

AIM

To study quantitatively the promoter methylation of hMLH1, p16INK, TIMP3 and TPEF genes in patients with colorectal cancer and synchronous polyps, and correlate it with some clinicomorphological features.

METHODS

DNA was extracted from all studied tumours and the corresponding normal mucosa. Microsatellite instability was analysed using two mononucleotide (BAT 25 and BAT 26) and three dinucleotide markers (D2S123, D5S356, D17S250) and automated DNA sequencing. Quantitative analysis of methylation was performed using DNA bisulfite modification, PCR with biotinylated primers, visualisation by 2% agarose gel electrophoresis and pyrosequencing.

RESULTS

High methylation levels of hMLH1 and p16INK were found in elderly patients (mean age 73.8 +/- 9.5 years and 65.7 +/- 16.6 years, p < 0.03, t-test). Proximal tumours were more often associated with microsatellite instability (p < 0.05, Fisher's test) and higher level of methylation of hMLH1, p16INK and TIMP3 (p < 0.02, Kruskal-Wallis test), while tumours with poor differentiation tended to have higher methylation of the p16INK gene (p < 0.02, Kruskal-Wallis test). Local tumour invasion was correlated with the level of methylation of hMLH1, TIMP3 and the CpG island methylator phenotype (CIMP) status. Tumours with liver metastases showed a lower level of TIMP3 methylation than tumours with no systemic invasion (p < 0.05, Kruskal-Wallis test). We found concordance of methylation in 56% of the cases with colonic cancer and synchronous adenomas; the remaining 44% were discordant.

CONCLUSIONS

Tumours with microsatellite instability, high level methylation and CIMP have distinctive clinical and morphological features. The level of hMLH1 and TIMP3 methylation and CIMP status can be correlated with the local tumour invasion. Different mechanisms, even for one and the same patient, can be responsible for the development of more than one third of the synchronous polyps and carcinomas.

Serrated adenoma: a distinct form of non-polypoid colorectal neoplasia?

Until recently, 2 major forms of colorectal polyp were recognized: the adenoma and the hyperplastic polyp. Adenomas were known to represent a precursor to colorectal cancer, whereas hyperplastic polyps were viewed as nonneoplastic, having no potential for progression to malignancy. We now recognize, however, that the lesions diagnosed as hyperplastic polyps in the past represent a heterogeneous group of polyps, some of which truly are hyperplastic, and others that truly have a significant risk for transformation to colorectal cancer. These polyps have a characteristic serrated architecture, and include not only hyperplastic polyps but also the recently recognized serrated adenomas. Serrated adenomas occur in 2 forms: the traditional serrated adenoma, which is usually a polypoid lesion endoscopically, and the sessile serrated adenoma, a flat or slightly raised, usually right-sided lesion. Serrated adenomas of both types show characteristic molecular alterations not commonly seen in traditional colorectal adenomas, and probably progress to colorectal cancer by means of a different pathway, the so-called serrated neoplasia pathway. The morphologic features of serrated colorectal lesions, the molecular alterations that characterize them, and their role in colorectal cancer development are discussed.

Oxidative stress and DNA methylation in prostate cancer

The protective effects of fruits, vegetables, and other foods on prostate cancer may be due to their antioxidant properties. An imbalance in the oxidative stress/antioxidant status is observed in prostate cancer patients. Genome oxidative damage in prostate cancer patients is associated with higher lipid peroxidation and lower antioxidant levels. Oxygen radicals are associated with different steps of carcinogenesis, including structural DNA damage, epigenetic changes, and protein and lipid alterations. Epigenetics affects genetic regulation, cellular differentiation, embryology, aging, cancer, and other diseases. DNA methylation is perhaps the most extensively studied epigenetic modification, which plays an important role in the regulation of gene expression and chromatin architecture, in association with histone modification and other chromatin-associated proteins. This review will provide a broad overview of the interplay of oxidative stress and DNA methylation, DNA methylation changes in regulation of gene expression, lifestyle changes for prostate cancer prevention, DNA methylation as biomarkers for prostate cancer, methods for detection of methylation, and clinical application of DNA methylation inhibitors for epigenetic therapy.

MTHFR C677T and A1298C variant genotypes and the risk of microsatellite instability among Iranian colorectal cancer patients

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the folate metabolic pathway. We aimed to test the hypothesis that C677T and A1298C variants of MTHFR predispose to microsatellite instable (MSI) colorectal cancer. We determined MTHFR genotypes in 175 sporadic colorectal cancer patients and a total of 231 normal controls in Shiraz, Southern Iran. Among the genotypes found in our samples, MTHFR CT and CT+TT were associated with increased risk for CRC incidence [odds ratio (OR)=2.4, 95% confidence interval (95%CI)=1.8-4.4; OR=2.4, 95%CI=1.6-3.6, respectively]. Double heterozygotes 677CT/1298AC and double homozygote 677TT/1298AA and 677CC/1298CC genotypes also showed a significantly increased risk of developing CRC compared with the wild-type 677CC/1298AA genotypes of the controls. Among the 151 tumors tested, 36 (23.8%) were MSI+. MSI was more common in proximal tumors (OR=10.4; 95%CI=3.9-27.8) and in smokers (OR=2.9; 95%CI=1.3-6.7). In a case-control comparison, the MTHFR 677CT+TT genotype was strongly associated with MSI (OR=2.6; 95%CI=1.3-5.3). Hypermethylation of mismatch repair genes was positively related with MSI incidence in these tumor series (P=0.00). Our data suggest that the MTHFR 677CT+TT variant genotype may be a risk factor for MSI+ cancer.

Differential MSH2 promoter methylation in blood cells of Neurofibromatosis type 1 (NF1) patients

Neurofibromatosis type 1 (NF1) is caused by NF1 gene mutations. The phenotype is highly variable, with 'modifiers' being discussed as potential determinants. Mismatch repair deficiency was shown to cause NF1 mutations, but constitutional mutation of mismatch repair genes was identified only once in a NF1 patient. We aimed to analyze whether DNA methylation of mismatch repair gene promoters, known to lead to transcriptional silencing, is associated with increased tumor load in NF1 defined by the number of cutaneous neurofibromas. Leukocyte DNA of 79 controls and 79 NF1 patients was investigated for methylation of mismatch repair genes MLH1, MSH2, MSH6, and PMS2 by methylation-specific PCR and pyrosequencing. MLH1, MSH6, and PMS2 promoters were not methylated. By contrast, we found promoter methylation of MSH2 with a higher rate of methylation in NF1 patients compared with controls. Furthermore, when comparing NF1 patients with a low vs those with a high number of cutaneous neurofibromas, MSH2 promoter methylation was significantly different. In patients with a high tumor burden, methylation of two (out of six) CpGs was enhanced. This finding was not confounded by age. In conclusion, enhanced methylation involving transcription start points of mismatch repair genes, such as MSH2 in NF1, has not been described so far. Methylation-induced variability of MSH2 gene expression may lead to variable mismatch repair capacity. Our results may point toward a role of MSH2 as a modifier for NF1, although the amount of DNA methylation and subsequent gene expression in other cell types of NF1 patients needs to be elucidated.

Serrated polyps and colorectal cancer: new pathway to malignancy

Until recently, two major forms of colorectal epithelial polyp were recognized: the adenoma and the hyperplastic polyp. Adenomas were perceived to represent the precursor to colorectal cancer, whereas hyperplastic polyps were viewed as innocuous lesions with no potential for progression to malignancy. We now recognize, however, that the lesions formerly classified as hyperplastic actually represent a heterogeneous group of polyps, some of which have a significant risk for neoplastic transformation. These serrated polyps include not only hyperplastic polyps but also traditional serrated adenomas and sessile serrated adenomas. These polyps demonstrate characteristic molecular alterations not commonly seen in colorectal adenomas, and they probably progress to colorectal cancer by means of a new pathway: the serrated neoplasia pathway. The morphologic features of serrated colorectal lesions, the molecular alterations that characterize them, and their role in colorectal cancer development are discussed herein.

Detection of mismatch repair gene germline mutation carrier among Chinese population with colorectal cancer

Background

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant syndrome. The National Cancer Institute (NCI) has recommended the Revised Bethesda guidelines for screening HNPCC. There has been a great deal of research on the value of these tests in other countries. However, literature about the Chinese population is scarce. Our objective is to detect and study microsatellite instability (MSI) and mismatch repair (MMR) gene germline mutation carriers among a Chinese population with colorectal cancer.

Methods

In 146 prospectively recruited consecutive patients with clinically proven colorectal cancer, MSI carriers were identified by analysis of tumor tissue using multiplex fluorescence polymerase chain reaction (PCR) using the NCI recommended panel and classified into microsatellite instability-low (MSI-L), microsatellite instability-high (MSI-H) and microsatellite stable (MSS) groups. Immunohistochemical staining for MSH2, MSH6 and MLH1 on tissue microarrays (TMAs) was performed, and methylation of the MLH1 promoter was analyzed by quantitative methylation specific PCR (MSP). Germline mutation analysis of blood samples was performed for MSH2, MSH6 and MLH1 genes.

Results

Thirty-four out of the 146 colorectal cancers (CRCs, 23.2%) were MSI, including 19 MSI-H CRCs and 15 MSI-L CRCS. Negative staining for MSH2 was found in 8 CRCs, negative staining for MSH6 was found in 6 CRCs. One MSI-H CRC was negative for both MSH6 and MSH2. Seventeen CRCs stained negatively for MLH1. MLH1 promoter methylation was determined in 34 MSI CRCs. Hypermethylation of the MLH1 promoter occurred in 14 (73.7%) out of 19 MSI-H CRCs and 5 (33.3%) out of 15 MSI-L CRCs. Among the 34 MSI carriers and one MSS CRC with MLH1 negative staining, 8 had a MMR gene germline mutation, which accounted for 23.5% of all MSI colorectal cancers and 5.5% of all the colorectal cancers. Five patients harbored MSH2 germline mutations, and three patients harbored MSH6 germline mutations. None of the patients had an MLH1 mutation. Mutations were commonly located in exon 7 and 12 of MSH2 and exon 5 of MSH6. Right colonic lesions and mucinous carcinoma were not common in MSI carriers.

Conclusion

Our data may imply that the characteristics of HNPCC in the Chinese population are probably different from those of Western countries. Application of NCI recommended criteria may not be effective enough to identify Chinese HNPCC families. Further studies are necessary to echo or refute our results so as to make the NCI recommendation more universally applicable.

Colorectal serrated adenocarcinoma

Colorectal cancer (CRC) ranks among the three most common cancers in terms of both cancer incidence and cancer-related deaths in most Western countries. Serrated adenocarcinoma is a recently described, distinct variant of CRC, accounting for about 7.5% of all CRCs and up to 17.5% of most proximal CRCs. It has been postulated that about 10-15% of sporadic CRCs would have their origin in serrated polyps that harbour a significant malignant potential. These lesions include hyperplastic-type aberrant crypt foci, hyperplastic polyps, sessile serrated adenomas, admixed polyps and serrated adenomas, and constitute the so-called 'serrated pathway', which is distinct from both the conventional adenoma-carcinoma pathway and the mutator pathway of hereditary non-polyposis CRC and is characterized by early involvement of oncogenic BRAF mutations, excess CpG island methylation (CIM) and subsequent low- or high-level DNA microsatellite instability (MSI). Methylation of hMLH1 is likely to explain the increased frequency of high-level MSI (16%) and methylation of MGMT is postulated to explain the low-level MSI (29%) in serrated adenocarcinomas. Reproducible histopathological criteria for serrated adenocarcinoma have recently been established and they have been qualified by DNA expression analysis for 7928 genes, showing clustering of serrated adenocarcinomas into a molecular entity apart from conventional adenocarcinoma, and representing with distinct down-regulation of EPHB2, PTCH and up-regulation of HIF1alpha.