Mitochondrial D310 mutations in colorectal adenomas: an early but not causative genetic event during colorectal carcinogenesis.

Somatic mutations of the D310 sequence of the mitochondrial DNA are reported in human cancers, including colorectal cancers (CRC). The presence of these mutations at early or late steps of colorectal carcinogenesis is unknown. Their prevalence increased significantly with the number of cytosines in the D310 sequence of the matched normal tissue (D310 polymorphism), suggesting that this polymorphism could be a risk factor for CRC. The aim of this study was (i) to investigate the prevalence of D310 mutations in 64 colorectal adenomas and 36 liver metastases from 15 CRC patients, (ii) to assess the relation between D310 polymorphism and the risk of colorectal adenoma in a case-control study including 613 cases with colorectal adenoma and 572 polyp-free (PF) controls. D310 mutations were found in colorectal adenomas and liver metastases from CRC patients in 27 and 33%, respectively and so are an early genetic event in colorectal carcinogenesis. The frequency of the mutations increased significantly with the number of cytosines in the matched normal tissue D310 sequence (p < 0.001) but the distribution of D310 polymorphisms was not significantly different between adenoma cases (large (>9 mm) and small (<5 mm) adenomas) and PF controls (C(4)-C(7)TC(6): 47, 52 and 49%; C(8)TC(6): 44, 39 and 41%; C(9)-C(10)TC(6): 9, 9 and 10%, respectively; p > 0.05), suggesting that germline D310 polymorphism is not a risk factor for colorectal adenomas. Considering their high frequency in colorectal adenomas, mitochondrial D310 mutations could represent a biomarker for early detection of CRC although their causative role in colorectal carcinogenesis remains uncertain.

Genetic polymorphisms of MMP1, MMP3 and MMP7 gene promoter and risk of colorectal adenoma.

BACKGROUND: Matrix metalloproteinases (MMP) have been shown to play a role in colorectal cancer (CRC). More recently, MMP1, MMP3 and MMP7 functional gene promoter polymorphisms have been found to be associated with CRC occurrence and prognosis. To document the role of MMP polymorphisms in the early step of colorectal carcinogenesis, we investigated their association with colorectal adenoma risk in a case-control study comprising 295 patients with large adenomas (LA), 302 patients with small adenomas (SA) and 568 polyp-free (PF) controls. METHODS: Patients were genotyped using automated fragment analysis for MMP1 -1607 ins/del G and MMP3 -1612 ins/delA (MMP3.1) polymorphisms and allelic discrimination assay for MMP3 -709 A/G (MMP3.2) and MMP7 -181 A/G polymorphisms. Association between MMP genotypes and colorectal adenomas was first tested for each polymorphism separately and then for combined genotypes using the combination test. Adjustment on relevant variables and estimation of odds ratios were performed using unconditional logistic regression. RESULTS: No association was observed between the polymorphisms and LA when compared to PF or SA. When comparing SA to PF controls, analysis revealed a significant association between MMP3 -1612 ins/delA polymorphism and SA with an increased risk associated with the 6A/6A genotype (OR = 1.67, 95% CI: 1.20-2.34). Using the combination test, the best association was found for MMP3.1-MMP1 (p = 0.001) with an OR of 1.88 (95% CI: 1.08-3.28) for the combined genotype 2G/2G-6A/6A estimated by logistic regression. CONCLUSION: These data show a relation between MMP1 -1607 ins/del G and MMP3 -1612 ins/delA combined polymorphisms and risk of SA, suggesting their potential role in the early steps of colorectal carcinogenesis.

Analysis of candidate genes in occurrence and growth of colorectal adenomas.

Predisposition to sporadic colorectal tumours is influenced by genes with minor phenotypic effects. A case-control study was set up on 295 patients treated for a large adenoma matched with polyp-free individuals on gender, age, and geographic origin in a 1 : 2 proportion. A second group of 302 patients treated for a small adenoma was also characterized to distinguish effects on adenoma occurrence and growth. We focussed the study on 38 single nucleotide polymorphisms (SNPs) encompassing 14 genes involved in colorectal carcinogenesis. Effect of SNPs was tested using unconditional logistic regression. Comparisons were made for haplotypes within a given gene and for biologically relevant genes combinations using the combination test. The APC p.Glu1317Gly variant appeared to influence the adenoma growth (P = .04, exact test) but not its occurrence. This result needs to be replicated and genome-wide association studies may be necessary to fully identify low-penetrance alleles involved in early stages of colorectal tumorigenesis.

Colonoscopic screening of first-degree relatives of patients with large adenomas: increased risk of colorectal tumors.

BACKGROUND & AIMS: The risk of developing colorectal neoplasia is not well established among family members of individuals with large adenomas, and screening strategies remain under debate in this population. This study aimed at quantifying the risk of colorectal adenomas and cancers using colonoscopic screening in first-degree relatives of patients with large adenomas. METHODS: This case-control study was performed in 18 endoscopic units of French nonuniversity hospitals. A colonoscopy was offered to first-degree relatives of 306 index cases with adenomas > or =10 mm if they were alive, aged 40-75 years, and could be contacted by the index case. Among them, 168 were examined and matched for age, sex, and geographical area with 2 controls (n = 307). Controls were randomly selected from 1362 consecutive patients aged 40-75 years having undergone a colonoscopy for minor symptoms. RESULTS: The prevalence of large adenomas and cancers was 8.4% and 4.2%, in relatives and controls, respectively. Odds ratios (ORs) associated with a history of large adenomas in relatives were 2.27 (95% confidence interval [CI], 1.01-5.09) for cancers or large adenomas, 1.21 (95% CI, 0.68-2.15) for small adenomas, and 1.56 (95% CI, 0.96-2.53) for all colorectal neoplasia. The risk of large adenomas and cancers was higher in relatives of index cases younger than 60 years (OR, 3.82; 95% CI, 0.92-15.87) and when the index case had large distal adenomas (OR, 3.14; 95% CI, 1.27-7.73). CONCLUSIONS: First-degree relatives of patients with large adenomas are at increased risk of developing colorectal cancers or large adenomas. This result has implications for screening in this high-risk population.

A family with gastrointestinal amyloidosis associated with variant lysozyme.

Hereditary nonneuropathic systemic lysozyme amyloidosis is a very rare form of amyloidosis, and only 4 families with this condition have been detailed until now in the literature. Clinical manifestations of lysozyme amyloidosis observed until now mainly concerned the kidneys, liver, and digestive tract. We report here a new family with hereditary lysozyme amyloidosis who presented predominantly with gastrointestinal involvement. The proband, a middle-aged woman, underwent partial gastrectomy for a hemorrhagic "gastric peptic ulcer" in 1984. Gastrointestinal amyloidosis was diagnosed in 1998 on biopsies performed on the gastroduodenal anastomosis, which appeared to be very congestive at presentation. Immunohistochemical stainings in tissue sections were positive for lysozyme. Amyloid was also observed in the colonic mucosa. The patient had a mutation in the lysozyme gene characterized by substitution of the amino acid at position 64 in the mature protein from tryptophan to arginine, previously described in only 1 French family with prominent nephropathy. It is interesting to note that her father had died many years before with an uncharacterized digestive amyloidosis. Our observation shows that a search for gastrointestinal amyloidosis is important, particularly when physicians are faced with congestive mucosa, unexplained abdominal hemorrhage, or abdominal symptoms. When gastrointestinal amyloidosis is diagnosed, it is important to determine with precision the nature of the amyloid fibril proteins, because various types of amyloidosis can involve the gastrointestinal tract.