K-ras and B-raf gene mutations are not associated with gastrin- and CCK2-receptor mRNA expression in human colorectal tumour tissues

Molecular identification of Helicobacter DNA present in human colorectal adenocarcinomas by 16S rDNA PCR amplification and pyrosequencing analysis

Seroepidemiological studies have indicated that Helicobacter pylori infection might be a possible risk factor for colorectal adenocarcinoma (CRC) development. However, limited information is available as to whether or not Helicobacter species are present in CRC tissues. In this study the presence of Helicobacter DNA in 77 CRC biopsies was investigated by means of a Helicobacter species-specific 16S rDNA PCR assay and real-time DNA pyrosequencing of the 16S rDNA variable V3 region. Pyrosequencing revealed the presence of Helicobacter DNA sequences in 21 of 77 biopsy specimens (27%). 16S rDNA sequences corresponding to H. pylori 26695 and H. pylori J99 were most commonly found. Intriguingly, one sequence belonged to Helicobacter mustelae, previously identified in ferrets. No significant correlations were found in the prevalence of Helicobacter DNA between colon and rectum tumour biopsies (P = 0.815), nor between Dukes' classes A/B and C/D (P = 0.262). 16S rDNA PCR amplification combined with pyrosequencing analysis of 16S rDNA variable V3 regions provides a powerful molecular tool to identify Helicobacter species in human biopsy specimens.

Gastrin suppresses growth of CCK2 receptor expressing colon cancer cells by inducing apoptosis in vitro and in vivo

BACKGROUND & AIMS

The role of amidated gastrin17 (G17) and the gastrin/CCKB/CCK2 receptor in colorectal carcinogenesis is still a controversial issue. Here, we investigated the effect of G17 on proliferation and apoptosis of CCK2 receptor-expressing human colon cancer cell lines in vitro and in vivo.

METHODS

Proliferation was determined by cell counting and cell cycle analysis. Apoptosis was analyzed by annexin V staining, TUNEL staining, caspase-3/7 assay, and JC1 (delta psi) assay. Signal-transduction pathways were analyzed by Western blotting and gel-shift and luciferase assays. An in vivo tumor model with subcutaneously inoculated colon cancer cells in SCID mice was used, and systemic hypergastrinemia was induced by omeprazole.

RESULTS

In Colo320 cells stably transfected with the wild-type CCK2 receptor (Colo320wt) or in Lovo cells endogenously expressing CCK2 receptors, G17 treatment inhibited proliferation along with a G2/M cell cycle arrest. Furthermore, the administration of G17 significantly augmented apoptosis of CCK2 receptor-expressing cells. In contrast, G17 had no effect on proliferation and apoptosis in Colo320 cells stably transfected with a tumor-derived CCK2 receptor mutant (Colo320mut) or in cells lacking CCK2 receptor expression. Systemic hypergastrinemia in severe combined immunodeficiency (SCID) mice suppressed the growth of Colo320wt tumors accompanied by enhanced apoptosis as compared with untreated tumors. In contrast, omeprazole did not affect Colo320mut tumors reflecting a loss-of-function state of the CCK2(mut) receptor. This is supported by the observation that, in Colo320wt cells, but not in Colo320mut cells, G17 treatment induced the MAPK/ERK/AP-1 pathway and inhibited the activity of NF-kappaB.

CONCLUSIONS

G17 exerts an antiproliferative and proapoptotic effect on human colon cancer cells expressing the wild-type CCK2 receptor. This supports the view that amidated gastrin prevents rather than promotes colorectal carcinogenesis.

Gastrointestinal hormone receptors in primary human colorectal carcinomas

BACKGROUND

In this study, the prevalence and identity of the cells expressing functional receptors for the gastrointestinal (GI) peptide hormones: gastrin, bombesin, and neurotensin in dissociated cells from 20 freshly resected human primary colorectal carcinomas were determined.

MATERIALS AND METHODS

GI peptide hormone-induced increases in the concentration of free intracellular Ca(2+) ([Ca(2+)](i)) were used as an assay for the detection of functional receptors. Reverse-transcription polymerase chain reaction (RT-PCR) was performed in a subset of tumor samples. Agonist-responsive cells were identified as either of epithelial or stromal origin by immunocytochemistry with cytokeratin and vimentin antibodies, respectively.

RESULTS

Overall, expression of GI peptide hormone receptors was more frequent in stromal cells when compared to epithelial cells. Of the three receptors, expression of bombesin receptor (95%) was most prevalent in vimentin-positive (stromal) cells; whereas, gastrin receptor expression by cytokeratin-positive (epithelial) cells was more common (39%). A single gastrin receptor splice variant differentially regulates [Ca(2+)](i) in a cell-type specific manner. The gastrin receptor-expression profile in the 11 colon cancer-derived cell lines did not reflect the prevalence of expression in primary human cancers.

CONCLUSIONS

The Ca(2+) assay is a sensitive method for detecting functional GI peptide hormone receptor expression by colon cancer cells. Because this approach utilizes living cells, it is amenable to further functional analyses of signal transduction mechanisms at the single cell level. Importantly, our data provide a rationale for examining of the role of these GI peptide hormones and their cognate receptors in mesenchymal cell biology.

New Molecular Concepts of Barrett’s Esophagus: Clinical Implications and Biomarkers

Barrett's esophagus (BE) represents the most serious histological consequence of gastroesophageal reflux disease (GERD) that develops in 5-10% of patients with GERD. Given that BE is the only known precursor to esophageal adenocarcinoma (EA), a systematic endoscopic biopsy protocol can detect EAs at an early stage. However, endoscopic and histopathological evaluation of BE are not adequate for effective screening of high risk patients. Therefore, molecular abnormalities associated with BE have been considered as surrogate markers and their use as such is proposed. Flow cytometry is the most useful adjunct to histology, and ploidy status of BE is an independent risk factor. Cyclin D1 overexpression is inversely correlated with survival in EA. C-erbB2 (+) patients have poorer prognosis. High plasma adenomatous polyposis coli levels correlate with reduced patient survival. p53 expression allows patient risk for EA stratification. Nuclear factor-kappaB overexpression inversely correlates with good response to adjuvant chemotherapy and radiotherapy in EA. Patients with cyclooxygenase-2 overexpression have reduced survival rates. Increased E-cadherin staining is associated with shorter survival in EA patients who received chemoradiotherapy. Finally, existing data cannot rule out a correlation between EA and colorectal tumors. Seventeen BE molecular alterations yielded noteworthy clinical implications. Apart from endoscopy and histology, these data allow for better risk stratification for patients with BE and for more efficient and timely therapeutic approaches.

Therapeutic effects of recombinant retrovirus mediated antisense K-ras gene on pancreatic cancer

AIM: To isolate and clone antisense K-ras gene fragments and to clarify its effect on proliferation and apoptosis of pancreatic cancer cells and expression of K-ras mRNA and p21 protein.

METHODS: Polymerase chain reaction (PCR) was used to amplify K-ras gene exon 1 and 4 as well as the flanking sequences, taking pancreatic carcinoma cell line BxPC-3 and PC-3 genomic DNA as the template. The target gene was cloned into retroviral vector pLXSN to construct the recombinant plasmid. After packaged in PT-67 cells the retrovirus was obtained. Then BxPC-3 and PC-3 cells were transfected with the recombinant retrovirus. Proliferation, apoptosis of pancreatic carcinoma cells and the expression of p21 protein were detected by MTT, flow cytometry and immunohistochemistry respectively. The therapeutic effect of retrovirus on hepatocellular carcinoma was observed in mice.

RESULTS: The antisense K-ras gene was successfully cloned into the vector pLXSN. Proliferation of PC-3 cells was significantly inhibited at day 1, 2, 3, 4, and 5 after transfected with pLXSN-AS-exon1/4B, compared with that of non-transfected cells and pLXSN-transfected group (F = 4.716, P < 0.05; F = 6.914, P < 0.05; F = 15.115, P < 0.05; F = 16.883, P < 0.05; F = 15.134, P < 0.05; repectively). BxPC-3 showed no significant difference among different groups. Expression of K-ras mRNA and p21 protein in PC-3 cells obviously decreased while those in BxPC-3 cells not so obviously. Apoptotic rates of PC-3 cells transfected with pLXSN-AS-exon1 and pLXSN-AS-exon4B were significantly higher than those with pLXSN and non-transfection (10.28%, 6.7% vs 2.86%, 3.24%; P < 0.01). Apoptosis of BxPC-3 cells were not significant among different groups. The size of hepatocellular carcinoma significantly decreased after treated with pLXSN-AS-exon1 and pLXSN-AS-exon4B, compared with that treated with pLXSN (0.32 ± 0.09 g, 0.352 ± 0.05 g vs 0.60 ± 0.09 g; P < 0.01).

CONCLUSION: The retrovius-mediated antisense K-ras gene can inhibit proliferation and induce apoptosis of pancreatic carcinoma cells. The mechanism may relate to down-regulating expression of K-ras mRNA and p21 protein.