Mutation accumulation in the intestine and colon of mice deficient in two intracellular glutathione peroxidases.

Mice deficient in two glutathione peroxidases (GPX), Gpx1 and Gpx2, [Gpx1/2-double knockout (DKO) mice] are prone to ileocolitis on a mixed C57BL/6 and 129S1/SvJ (B6.129) genetic background. We reported previously that approximately 25% of B6.129 Gpx1/2-DKO mice develop ileocolonic tumors by 6 to 9 months of age, when their non-DKO littermates [having at least one wild-type (WT) Gpx1 or Gpx2 allele] rarely have inflammation and none have tumors. Because genetic background affects tumor susceptibility, we have generated a B6 Gpx1/2-DKO colony and discovered that these mice have fewer inflammatory cells, milder ileocolitis, and low mortality, and only 2.5% of B6 mice developed tumors. The mutant frequency of a cII reporter gene was about 2- to 3-fold higher in 28-day-old Gpx1/2-DKO and 4-fold higher in 8-month-old Gpx1/2-DKO ileal mucosa than in controls in both genetic backgrounds. In contrast, mutant frequencies in the unaffected B6 liver were not significantly different between WT and Gpx1/2-DKO mice. The mutant frequency of 8-month-old B6.129 Gpx1/2-DKO ileum was 38.94 +/- 15.5(-5), which was not significantly higher than the age-matched B6 ileum, 25.54 +/- 10.33(-5). The mutation spectra analysis has shown that B6 Gpx1/2-DKO ileum had a 3-fold increase in small nucleotide deletions at mononucleotide repeats over control B6, which are a signature mutation associated with oxidative stress. Unexpectedly, B6 Gpx1/2-DKO mice had fewer C to T transitions at CpG dinucleotides than the WT B6 (18.0% versus 40.1%; P < 0.001). Our results suggest that inflammation drives gene mutations, which leads to neoplastic transformation of intestinal epithelium in the B6.129 Gpx1/2-DKO mice but rarely in the B6 Gpx1/2-DKO mice.

Adenoma-specific alterations of protein kinase C isozyme expression in Apc(MIN) mice.

Members of the protein kinase C (PKC) family appear to play important roles in colorectal carcinogenesis. To investigate the potential involvement of PKC isozymes in adenomatous transformation induced by inactivation of the adenomatous polyposis coli (APC) gene product, we examined protein levels and localizations of ten PKC isozymes by immunohistochemistry in normal and adenomatous ileal epithelium of ApcMIN mice. Compared with surrounding normal epithelium, adenomas showed dramatically reduced staining for PKCs a, beta1, and zeta, as well as dysplasia-specific punctate nuclear staining of PKC mu. We conclude that reduced protein expression of PKC alpha, beta1, and zeta, and nuclear localization of PKC mu are markers of, and are perhaps involved in, adenomatous transformation induced by APC inactivation in ApcMIN mice.

Primary rare anaplastic large cell lymphoma, ALK positive in small intestine: case report and review of the literature.

BACKGROUND: Primary anaplastic large cell lymphoma, ALK positive in small intestine is clinically rare ï»¿and the clinical, radiological and pathological information are generally not available. Here, we report a case of 32-year-old male with ALK positive anaplastic large cell lymphoma at the junction of jejunum and ileum, and highlight the clinicopathological features and the differential diagnosis of this type lymphoma. CASE PRESENTATION: The patient presented with right middle abdominal mass for 1 month with sporadic pain. Computed tomography (CT) showed a mass measured 8.5 × 7.4 × 4 cm at the junction of jejunum and ileum. The diagnosis was made after pathological examination of the excised tissue by enterectomy. Grossly, the mass was located predominately in intestinal wall with grayish appearance and blurry boundary. Microscopically, almost all layers of the intestinal wall were infiltrated by pleomorphic tumor cells with diffuse and cohesive growth pattern. The neoplastic cells were mainly medium to large size with moderate basophilic cytoplasm. Most of them had hyperchromatic nuclei and prominent nucleoli. "Hallmark" cells were easily detected. Immunohistochemically, tumor cells are characterized by CD30, ALK, CD5, TIA-1, Granzyme B, EMA positive staining, and CD2, CD3, CD7, CD4, CD8, CD20, CD79a negative staining. The Epstein-Barr virus encoded RNAs (EBERs) genome was also negative. A diagnosis as primary small intestinal ALK positive anaplastic large cell lymphoma was finally made. The patient received CHOP chemotherapy and is alive till now without recurrence 5 months after enterectomy. CONCLUSIONS: Primary small intestinal ALK positive anaplastic large cell lymphoma is rare. The accurate diagnosis should be based on combined consideration of clinical characteristics, CT image and pathological features, and should be distinguished from other lymphomas or solid tumors in small intestine.

Identification of zymogen and mature forms of human carboxypeptidase H. A processing enzyme for the synthesis of peptide hormones.

Carboxypeptidase H (CPH) is one of several processing enzymes required for the conversion of peptide hormone precursors into their smaller active forms. In this study, high levels of CPH activity was found in a liver metastasis of a human ileal carcinoid which expresses beta-preprotachykinin mRNA and the tachykinin neuropeptides, substance P and substance K. This human CPH showed properties of a zinc-metallopeptidase that is structurally similar to bovine and rat CPH. Immunoblots of the human ileal carcinoma with anti-bovine CPH showed that CPH activity is represented by two proteins of apparent molecular masses 57 and 55 kDa. Cell-free translation of poly(A)+ RNA followed by immunoprecipitation with anti-bovine CPH showed that human CPH mRNA encodes a precursor protein of apparent molecular mass 75 kDa. These data demonstrate that human CPH is synthesized as a zymogen, prepro-CPH, which must be cleaved to form catalytically active CPH.

Effect of Recql5 deficiency on the intestinal tumor susceptibility of Apc(min) mice.

AIM: To investigate whether Recql5, a DNA helicase that plays an important role in the maintenance of genome integrity, is a tumor suppressor in the gastrointestinal tract in mice. METHODS: We generated cohorts of both Recql5-proficient and Recql5-deficient Apc(min/+) mice and compared the tumor susceptibility in their gastrointestinal tracts. RESULTS: Recql5 deficiency in Apc(min/+) mice resulted in a significant increase in the tumor incidence in both the colon (P = 0.0162) and the small intestine (P < 0.01). These findings have provided the first genetic evidence for a tumor suppression role of Recql5 in the gastrointestinal tract of mice. Importantly, since mouse Recql5 and human RECQL5 are highly conserved, these findings also suggest that RECQL5 may be a tumor suppressor for human colon cancer. CONCLUSION: Recql5 has a tumor suppression role in the mouse gastrointestinal tract.