Hypermethylation of the 5' CpG island of the p14ARF flanking exon 1ß in human colorectal cancer displaying a restricted pattern of p53 overexpression concomitant with increased MDM2 expression.

BACKGROUND: It has been suggested that inactivation of p14ARF, a tumor suppressor central to regulating p53 protein stability through interaction with the MDM2 oncoprotein, abrogates p53 activity in human tumors retaining the wild-type TP53 gene. Differences in expression of tumor suppressor genes are frequently associated with cancer. We previously reported on a pattern of restricted p53 immunohistochemical overexpression significantly associated with microsatellite instability (MSI), low TP53 mutation frequency, and MDM2 overexpression in colorectal cancers (CRCs). In this study, we investigated whether p14ARF alterations could be a mechanism for disabling the p53 pathway in this subgroup of CRCs. RESULTS: Detailed maps of the alterations in the p14ARF gene were determined in a cohort of 98 CRCs to detect both nucleotide and copy-number changes. Methylation-specific PCR combined with bisulfite sequencing was used to evaluate the prevalence and distribution of p14ARF methylation. p14ARF alterations were then correlated with MSI status, TP53 mutations, and immunohistochemical expression of p53 and MDM2. The frequency of p14ARF mutations was extremely low (1/98; 1%), whereas coexistence of methylated and unmethylated alleles in both tumors and normal colon mucosa was common (91/98; 93%). Only seven of ninety-eight tumors (7%) had a distinct pattern of methylation compared with normal colon mucosa. Evaluation of the prevalence and distribution of p14ARF promoter methylation in a region containing 27 CpG sites in 35 patients showed a range of methylated CpG sites in tumors (0 to 25 (95% CI 1 to 13) versus 0 to 17 (95% CI 0 to 2)) in adjacent colon mucosa (P = 0.004). Hypermethylation of the p14ARF promoter was significantly correlated with the restricted p53 overexpression pattern (P = 0.03), and MDM2 overexpression (P = 0.02), independently of MSI phenotype. Although no significant correlation between p14ARF methylation and TP53 mutational status was seen (P = 0.23), methylation involving the proximal CpG sites within the 5' CpG flanking exon 1ß was present more frequently in tumors with restricted p53 overexpression than in those with diffuse p53 overexpression (range of methylated clones 17 to 36% (95% CI 24 to 36%) versus range 0 to 3% (95% CI 0 to 3%), P = 0. 0003). CONCLUSION: p14ARF epigenetic silencing may represent an important deregulating mechanism of the p53-MDM2-p14ARF pathway in CRCs exhibiting a restricted p53 overexpression pattern.

Distinctive patterns of p53 protein expression and microsatellite instability in human colorectal cancer.

Although evidence suggests an inverse relationship between microsatellite instability and p53 alterations in colorectal cancer, no study has thoroughly examined the use of p53 immunohistochemistry in phenotyping colorectal cancers. We investigated the value of p53 immunohistochemistry in microsatellite instability-positive colorectal cancers prescreening and attempted to clarify the relationship between DNA mismatch repair system and p53 pathway. In a series of 104 consecutive colorectal cancers, we performed p53 immunohistochemistry, TP53 mutational analysis, DNA mismatch repair system efficiency evaluation (DNA mismatch repair system immunohistochemistry, microsatellite instability status, MLH1/MSH2 germ line, and BRAF, murine double minute 2, and p21 immunohistochemistry. Microsatellite instability high was observed in 25 of 104 colorectal cancers, with DNA mismatch repair system protein loss (24/25) and germ line (8/25) or BRAF mutations (8/25). p53 immunohistochemistry revealed 3 distinct patterns of expression: complete negative immunostaining associated with truncating TP53 mutations (P < .0001), diffuse overexpression associated with missense TP53 mutations (P < .0001), and restricted overexpression characterized by a limited number of homogenously scattered strongly positive tumor cells in 36.5% of colorectal cancers. This latest pattern was associated with wild-type TP53 and microsatellite instability high colorectal cancers (P < .0001) including all Lynch tumors (8/8), but its presence among 22% of DNA mismatch repair system-competent colorectal cancers decreased its positive predictive value (55.2% [95% confidence interval, 45%-65%]). It was also correlated with murine double minute 2 overexpression (P < .0001) and inversely with p21 loss (P = .0002), independently of microsatellite instability status. In conclusion, a restricted pattern of p53 overexpression is preferentially associated with microsatellite instability high phenotype and could, therefore, be of clinical use as signal for microsatellite instability analysis in a large-scale tumor screening. Its association with concomitant murine double minute 2 overexpression suggests an alternative mechanism of p53 pathway deregulation.

In vitro hyperresponsiveness to tumor necrosis factor-alpha contributes to adipokine dysregulation in omental adipocytes of obese subjects.

CONTEXT: In obesity, adipocyte hypertrophy and macrophage infiltration lead to overproduction of proinflammatory adipokines, which play a crucial role in the metabolic syndrome. The molecular mechanisms underlying this overproduction are still unsettled. The role of TNF-alpha also remains controversial in human obesity. OBJECTIVE: We revisited the contribution of TNF-alpha to adipokine dysregulation in central obesity. We more particularly assessed the involvement of TNF-alpha vs. other stromal-vascular cell (SVC)-secreted factors and searched for potential differential responses to TNF-alpha between adipocytes of lean and obese individuals. DESIGN AND PARTICIPANTS: Primary cultures of omental adipocytes from obese and nonobese age- and sex-matched subjects were used. For some experiments, we generated media previously conditioned by SVCs, which mimic adipocyte microenvironment. RESULTS: Adipocytes of obese subjects mainly overexpressed adipokines, in comparison with those of lean ones, when cultured in SVC-conditioned media. This was abrogated by immunoneutralization of TNF-alpha, indicating that among the numerous factors secreted by SVCs, TNF-alpha is a crucial contributor to adipokine dysregulation. Accordingly, adipocytes of obese subjects overproduced adipokines in response to direct exposure of TNF-alpha. This hyperresponsiveness was mediated by TNF-alpha receptor 1 and hyperactivation of the nuclear factor-kappaB (NF-kappaB) pathway. Correspondingly, NF-kappaB activity was increased in adipocytes of obese subjects and correlated with adipocyte size, adipokine expression, and in vivo insulin resistance. Eventually adipokine overexpression in adipocytes of obese subjects was prevented by NF-kappaB inhibitors. CONCLUSIONS: In obesity, TNF-alpha that is [corrected] over other SVC-secreted factors, a crucial determinant of adipokine dysregulation acts on enlarged adipocytes, which are hyperresponsive to this triggering signal [corrected]

Familial adenomatous polyposis predisposes to pathologic exposure of the stomach to bilirubin.

BACKGROUND: The role of duodenogastric reflux in the genesis of gastric polyps in familial adenomatous polyposis (FAP), although suggested by scintigraphy scanning studies, remains unclear. METHODS: Twenty-four hour intragastric bilirubin monitoring with the Bilitec optoelectronic device was carried out in 25 FAP patients, of whom 19 had gastric polyps (fundic gland in 13, adenomatous in 2, and both histologic types in 4) on endoscopic examination. Gastric exposure to bilirubin was expressed as the percentage of total recording time that absorbance exceeded the threshold of 0.25 and was calculated in reference to values obtained from 25 healthy volunteers. Helicobacter pylori status of the stomach was checked as well. RESULTS: Gastric exposure to bilirubin was pathologic in 14 (56%) patients. Gastric exposure to bilirubin was of longer duration in FAP patients than in healthy volunteers (mean+/-SEM: 19%+/-4% vs 6%+/-2%) (P<.005). It increased from healthy volunteers (6%+/-2%) to FAP patients without gastric polyps (10%+/-3%), and to FAP patients with gastric polyps (22%+/-5%) (P<.004). Bilirubin exposure times were similar in FAP patients with fundic gland polyps only and in those having either adenomatous polyps only or both types of polyps (24%+/-7% vs 17%+/-4%). No patient with pathologic gastric exposure to bilirubin as well as none having gastric polyps, had H. pylori in the antrum. CONCLUSIONS: This study shows that gastric exposure to bilirubin is of longer duration in FAP patients than in healthy volunteers, and in FAP patients with gastric polyps than in those without polyps. This study supports the existence of a direct correlation between pathologic duodenogastric reflux (DGR), the absence of H. pylori in the antrum, and the presence of gastric polyps in FAP patients.

Chronic stomal variceal bleeding after colonic surgery in patients with portal hypertension: efficacy of beta-blocking agents?

In patients with portal hypertension, ileostomy or colostomy carries the risk of the development of stomal varices at the site of the mucocutaneous junction of a stoma. Such varices are often the source of difficult-to-treat recurrent or chronic bleeding. In this setting, transjugular intrahepatic portosystemic shunt insertion and embolisation is considered the best therapeutic approach in spite of relatively high mortality and morbidity rates. We report the cases of three consecutive patients with portal hypertension of various causes and chronic stomal variceal bleeding in whom beta-blocking therapy resulted in the drying up of bleeding and the prevention of its recurrence for periods of time ranging between 2 and 42 months.

FDG-PET improves the staging and selection of patients with recurrent colorectal cancer.

Whole-body fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has proved effective in the diagnosis and staging of recurrent colorectal cancer. In this study, we analysed how PET affects the management of patients with recurrent colorectal cancer by permitting more accurate selection of candidates for curative resection. The data of 79 patients with known or suspected recurrent colorectal cancer were analysed. Conventional imaging modalities (CIM) and PET results were compared with regard to their accuracy in determining the extent and the resectability of tumour recurrence. Recurrence was demonstrated in 68 of the 79 patients. The data indicate that PET was superior to CIM for detection of recurrence at all sites except the liver. Based on the CIM+PET staging, surgery with curative intent was proposed in 39 patients and was indeed achieved in 31 of them (80%). PET was more accurate than CIM alone in predicting the resectability or non-resectability of the recurrence (82% vs 68%, P=0.02). It is concluded that whole-body FDG-PET is highly sensitive for both the diagnosis and the staging of patients with recurrent colorectal cancer. Its use in conjunction with conventional imaging procedures results in a more accurate selection of patients for surgical treatment with curative intent.