Taishi Ogawa

Disruption of the p53-p53R2 DNA repair system in ulcerative colitis contributes to colon tumorigenesis

With ulcerative colitis (UC)‐associated tumorigenesis, p53 gene alteration is considered to be a key event. To clarify whether the p53‐checkpoint is operating in foci of inflammation and that its disruption is a feature of UC‐associated neoplasms, the present immunohistochemical study was conducted. Since accumulation of butyric acid with active UC is associated with apoptosis, effects of in vitro exposure of newly established UC‐cancer derived cell lines to organic acids were also assessed. The regulatory subunit of ribonucleotide reductase, p53R2, was found to be localized with p53 in situ, and levels of p53, phospho‐p53, p53R2 and inducible nitric oxide synthase were significantly intercorrelated. However, p53R2 expression was clearly reduced with progression through UC‐associated dysplasia to carcinoma, demonstrating an inverse relation with p53 overexpression. In vitro treatment with butyrate or propionic acid, but not succinic acid, elicited a positive response in the p53–p53R2 system. Moreover, p53‐dependent DNA repair, investigated by radioactive nucleotide incorporation, was induced by butyric acid and inhibited by short‐interfering p53 and p53R2 RNAs. Therefore, it was concluded that the p53–p53R2‐dependent DNA repair system is constitutively stimulated by butyric acid, which accumulates in UC inflammatory lesions. Since failure of the p53‐G1 checkpoint may cause dysfunction of repair under the influence of butyrate, gene alterations may increase and spread through the genome, leading to tumorigenesis.

Genetic instability on chromosome 17 in the epithelium of non-polypoid colorectal carcinomas compared to polypoid lesions.

Early colorectal carcinomas (submucosal invasive adenocarcinomas) can be classified into polypoid growth carcinoma (PG‐Ca) and non‐polypoid growth carcinoma (NPG‐Ca) types, the latter transforming more rapidly to advanced carcinoma. Previously, we indicated that stromal genetic instability might contribute to tumorigenesis of both sporadic and ulcerative colitis‐associated colorectal adenocarcinomas. In the present study, we analyzed genetic instability of both epithelial and surrounding stromal components in PG‐Ca and NPG‐Ca. In 99 colorectal submucosal invasive adenocarcinomas, epithelial and stromal genetic instability was analyzed with National Cancer Institute standard microsatellite markers, chromosome 17 (Chr.17) markers and tumor suppressor gene‐related markers, using a combination of the laser‐captured microdissection and GeneScan approaches. Immunohistochemical analysis was carried out for hMLH1, hMSH2, MGMT and p53. In addition, we investigated methylation of the hMLH1 and MGMT promoters. The frequencies of epithelial microsatellite instability (MSI) with Chr.17 markers were significantly higher in NPG‐Ca (33.3%) compared to PG‐Ca (10.4%), particularly with D17S579 and D17S796. For loss of heterozygosity, only D17S786 showed a significant difference. The frequencies of stromal MSI with all markers were 31.7% and 25.9% in NPG‐Ca and PG‐Ca, respectively, but D17S579 and TP53 showed higher MSI in NPG‐Ca than PG‐Ca. Immunohistochemically, p53 protein expression in PG‐Ca was significantly higher in loss of heterozygosity‐positive cases with altered Chr.17 markers overall, especially the D17S796 marker, compared to cases without genetic instability. These results suggest that epithelial and stromal MSI of Chr.17 markers contributes more to carcinogenesis in NPG‐Ca, whereas stromal genetic instability might be necessary for the development of both types of colorectal carcinoma. (Cancer Sci 2006; 97: 1335–1342)

Significant increase of colonic mutated crypts correlates with age in sporadic cancer and diverticulosis cases, with higher frequency in the left- than right-side colorectum

Mild periodic acid–Schiff (mPAS) staining can discriminate non‐O‐acetylated (mPAS‐positive) from O‐acetylated (mPAS‐negative) epithelial sialoglycoproteins in human colonic mucosa, allowing the three haplotypes expressed from a single polymorphic autosomal gene (oat) to be distinguished. In heterozygotes, we previously demonstrated wholly mPAS‐positive (stem cell mutated) crypts and clusters of two or more mPAS‐positive crypts to be significantly increased with duration of ulcerative colitis. To establish whether such an increase in the number of mutated crypts with age also occurs in normal individuals or in cases with diverticulosis, the O‐acetylation phenotype in the non‐cancerous colonic mucosa of 47 sporadic colorectal cancer patients who were heterozygotes for oat was tested with mild‐PAS staining. PAS‐positive crypts were assessed histologically in relation to age and compared between the left (sigmoid colon and rectum) and right (cecum and ascending colon) sides of the colorectum. Wholly mPAS‐positive (stem cell mutated) crypts and foci in heterozygotes were found to be increased significantly (P < 0.0001) in the left side with aging (r = 0.598 and 0.643, respectively). Such a positive correlation with aging was also confirmed in 19 diverticulosis cases without cancer (r = 0.797 and 0.793, respectively). The frequency of mutated crypts and foci on the right side was significantly lower than on the left side in both spontaneous colorectal cancer and diverticulosis cases. The results provide support for an intimate relationship between accumulation of mutated crypts with aging, possibly with significance for colorectal cancer development. Furthermore, the environment in the right side of the colon may be different from that in the left side in this regard. (Cancer Sci 2006; 97)

Clinical usefulness of single-balloon endoscopy in patients with previously incomplete colonoscopy

AIM To evaluate the clinical usefulness of single-balloon endoscopy (SBE) in patients in whom a colonoscope was technically difficult to insert previously. METHODS The study group comprised 15 patients (8 men and 7 women) who underwent SBE for colonoscopy (30 sessions). The number of SBE sessions was 1 in 7 patients, 2 in 5 patients, 3 in 1 patient, 4 in 1 patient, and 6 in 1 patient. In all patients, total colonoscopy was previously unsuccessful. The reasons for difficulty in scope passage were an elongated colon in 6 patients, severe intestinal adhesions after open surgery in 4, an elongated colon and severe intestinal adhesions in 2, a left inguinal hernia in 2, and multiple diverticulosis of the sigmoid colon in 1. Three endoscopists were responsible for SBE. The technique for inserting SBE in the colon was basically similar to that in the small intestine. The effectiveness of SBE was assessed on the basis of the success rate of total colonoscopy and the presence or absence of complications. We also evaluated the diagnostic and treatment outcomes of colonoscopic examinations with SBE. RESULTS Total colonoscopy was successfully accomplished in all sessions. The mean insertion time to the cecum was 22.9 ± 8.9 min (range 9 to 40). Abnormalities were found during 21 sessions of SBE. The most common abnormality was colorectal polyps (20 sessions), followed by radiation colitis (3 sessions) and diverticular disease of the colon (3 sessions). Colorectal polyps were resected endoscopically in 15 sessions. A total of 42 polyps were resected endoscopically, using snare polypectomy in 32 lesions, hot biopsy in 7 lesions, and endoscopic mucosal resection in 3 lesions. Fifty-six colorectal polyps were newly diagnosed on colonoscopic examination with SBE. Histopathologically, these lesions included 2 intramucosal cancers, 42 tubular adenomas, and 2 tubulovillous adenomas. The mean examination time was 48.2 ± 20.0 min (range 25 to 90). Colonoscopic examination or endoscopic treatment with SBE was not associated with any serious complications. CONCLUSION SBE is a useful and safe procedure in patients in whom a colonoscope is technically difficult to insert.