Genetic pathways in colorectal cancer

The model of colorectal tumorigenesis put forward by Fearon and Vogelstein has had great influence on molecular oncology. They proposed that a series of mutations occur in the progression from normal cells to colorectal cancer and that these mutations are associated with the histological features of such tumours. Several postulates of the model appear to be correct, particularly its emphasis on the stepwise accumulation of genetic changes and the inclusion of mutations at the adenomatous polyposis coli ( APC ) and TP53 loci. Since the publication of the original model, however, mutations at other loci have been identified which may be alternatives or additions. There is also evidence to suggest that some colorectal cancers develop along a different genetic pathway. In this review, we discuss how tumour development can occur as Darwinian evolution through selection of advantageous somatic mutations. The non-random nature of mutation selection gives rise to genetic pathways of tumorigenesis. In addition, we consider the Fearon and Vogelstein model, its shortcomings and possible additions to it. The evidence suggests that not all colorectal cancers follow the same genetic pathway during carcinogenesis.     

Colon carcinoma cell lines stimulate monocytes and lamina propria mononuclear cells to produce IL-10

Cytokines released from tumour cells may have function as signals to neighbouring immune and inflammatory cells. Several studies have shown that the immunoregulatory cytokines IL-10 and transforming growth factor-beta 1 (TGF-β1) as well as prostaglandin-E₂ (PGE₂) play an important role in tumour-induced immunosuppression. The aim of the study was to investigate the effect of colon carcinoma cell lines on IL-10 production in peripheral monocytes (PBMC) and lamina propria mononuclear cells (LPMC). We examined four colon carcinoma cell lines (HT-29, Caco-2, Colo-320 and HCT-116) and determined their production of TGF-β1, IL-10 and PGE₂. Peripheral monocytes were isolated by density gradient centrifugation and LPMC were isolated from surgical specimens using a collagenase digestion method. Monocytes and LPMC were cultured with colon carcinoma cell conditioned medium or in co-culture with colon carcinoma cells. Supernatants were then determined for the production of IL-10 by ELISA assays. All colon carcinoma cell lines stimulated peripheral monocytes as well as LPMC to produce markedly increased levels of IL-10. Colon cancer cells secreted negligible levels of IL-10, but high amounts of TGF-β1 and PGE₂. Neutralization of TGF-β1 by administration of anti-TGF-β as well as neutralization of PGE₂ with anti-PGE₂ antisera reduced the IL-10 production of monocytes markedly, indicating that tumour cell-derived TGF-β1 and PGE₂ are major factors for IL-10 stimulation. In vitro stimulation of monocytes with TGF-β1 and PGE₂ could confirm that TGF-β1 as well as PGF₂ at picogram concentrations were able to prime monocytes for enhanced IL-10 production. Our results demonstrate that colon carcinoma cell lines enhance the ability of monocytes and intestinal macrophages to produce IL-10. The stimulation of monocyte IL-10 by colon cancer cell-derived TGF-β1 and PGE₂ may act as a tumour-protecting mechanism by impairing the activation of anti-tumour cytokines.     

Colon lamina propria dendritic cells induce a proinflammatory cytokine response in lamina propria T cells in the SCID mouse model of colitis

Intestinal immune responses are normally regulated to maintain a state of immune balance. Dendritic cells (DC) are antigen-presenting cells, which induce immune responses against microbes and other stimuli and are key players in the regulation of tolerance in the gut. These cells influence the differentiation of cytokine responses in T cells, and in the gut, in particular, such interactions may be critical to the course of inflammatory bowel disease (IBD). Using the CD45RBhi CD4+ T cell-reconstituted severe combined immunodeficient mouse model of colitis, we investigated the ability of isolated colon DC to stimulate immune responses in syngeneic and allogeneic spleen CD4+ T cells, as well as in colon T cells isolated from the same tissue as DC in IBD mice. We found that the frequency of DC in IBD mice colons and spleens was elevated in comparison with control mice, but colon and spleen DC exhibited different phenotypic and functional properties. Colon DC stimulated significantly higher levels of interferon-gamma and interleukin-6 when cocultured with autologous colon T cells than in cocultures with syngeneic or allogeneic spleen T cells. These data suggest that in the IBD colon, DC-T cell interactions may create conditions with an abundance of proinflammatory cytokines, which favor the inflammatory state.     

Flat adenoma-carcinoma sequence with high-malignancy potential as demonstrated by CD10 and beta-catenin expression: a different pathway from the polypoid adenoma-carcinoma sequence

Aims:  CD10+ colorectal carcinomas have a high risk of giving rise to liver metastasis. The aim was to examine phenotypic expression in colorectal neoplasia and to elucidate changes in such expression through the adenoma–carcinoma sequence.
Methods and results:  We examined the expression of various proteins immunohistochemically in 111 flat [non-polypoid growth (NPG)] colorectal neoplasms, categorized into 28 low-grade (NPG-LGN), 44 high-grades (NPG-HGN) and 39 cases of invasive neoplasia (NPG-IN), as well as in 96 polypoid [polypoid growth (PG)] neoplasms, categorized into 26 PG-LGN, 39 PG-HGN and 31 PG-IN according to the Vienna classification. CD10 was more frequently expressed in NPG than in PG neoplasia. MUC2 and MUC5AC were more frequently expressed in PG than in NPG neoplasias. Nuclear β-catenin was more frequently expressed in NPG-LGN than in PG-LGN. No difference in p53 expression was found between NPG and PG neoplasia.
Conclusions:  From the viewpoint of the expression of CD10 and β-catenin, it would appear that NPG-LGN differs significantly from PG-LGN, thereby indicating that NPG-LGN is a precursor of CD10+ carcinoma. It is important to ensure that NPG neoplasia is not overlooked if cases of CD10+ carcinoma are to be detected at an early stage.     

巨噬细胞移动抑制因子在大肠黏膜癌变患者中表达增强

目的 探讨巨噬细胞移动抑制因子(MIF)表达与大肠癌临床病理因素的关系.方法 采用免疫组化法测定大肠组织中MIF的表达.ELISA测定血清中MIF水平.结果 MIF在正常大肠黏膜、大肠腺瘤、大肠癌中阳性表达强度和阳性表达率依次增高,3组之间存在显著性差异(P<0.001);组织中MIF表达强度与血清中MIF水平呈正相关性;MIF的表达与大肠癌的分化程度、淋巴结转移、肝转移有关.结论 MIF可能在大肠癌的发生和进展中起着重要的作用.     

Villous tumor of the colon and rectum with special reference to roles of p53 and bcl-2 in adenoma–carcinoma sequence

Villous tumors are rare and their histological diagnosis from biopsy specimens is often difficult. To ascertain its tumor progression, including the genetic events, would be useful for clinical treatment. Clinicopathological features and the expression of p53 and bcl-2 proteins were investigated in 50 villous tumors from 49 patients. The patients' ages ranged widely from 32 to 84 years (average, 61 years). Females were more frequently affected than males (male:female ratio, 20:29). Thirty-six (72%) of the villous tumors were present within the sigmoid colon and rectum. Histologically, 17 (34%) of these contained carcinomas in villous adenomas (CIVA), while 24 (73%) of 33 villous adenomas (VA) contained high-grade dysplasia. Most of the CIVA revealed well-differentiated adenocarcinoma, often with focal or diffuse mucin pools. Three lesions of invasive carcinomas were composed of extremely well-differentiated components. The average size of the CIVA (79 mm) was significantly larger than that of the VA (51 mm). Overexpression of p53 protein was recognized in 12% of VA, in 24% of mucosal components of CIVA and in 18% of invasive components of CIVA. Overexpression of bcl-2 was recognized in 57% of VA, 33% of mucosal components of CIVA, and 7% of invasive components of CIVA. Several characteristic features were recognized in villous tumors, which comprised: (i) a high frequency of coexistence of carcinoma; (ii) multiple foci of carcinomas arising in adenomatous tumors; (iii) a lower histological grade of carcinomas, often with mucin pools; (iv) the existence of extremely well-differentiated adenocarcinomas; and (v) less frequent expression of p53 protein in the carcinomatous components. According to these findings, the pathway of tumor progression in the villous tumors is possibly different from that of sporadic colorectal carcinomas. Because of the peculiarity of villous tumors, careful clinical management is required.     

Disturbances in apoptosis of lamina propria lymphocytes in Crohn's disease

Introduction

The aim of this study was to assess the potential mechanisms providing resistance to apoptosis of lamina propria lymphocytes (LPL) directlyin intestinal tissues from patients with Crohn''s disease (CD).

Material and methods

Fifty CD patients were enrolled in the study. The control group consisted of healthy patients who underwent surveillance colonoscopy after endoscopic polypectomy. Each CD patient underwent colonoscopy with tissue sampling from inflamed areas of the colon with the assessment of immunohistochemical expression of active caspase 3, Fas, tumour necrosis factor receptor 1 (TNFR1), Bcl-2, Bax, CD4 and CD8. This was compared with healthy intestinal mucosa.

Results

The expression of active caspase 3 was significantly lower in LPL in CD (0.4 ±0.3 vs. 2.8 ±1.5; p = 0.0002). A statistically significant increase of CD4 and CD8 positive cells was noted in CD (2.3 ±0.5 vs. 1.2 ±0.2, p < 0.0001; 2.1 ±0.3 vs. 1.1 ±0.3, p < 0.0001, respectively). It was associated with a significant increase of the Bcl-2 (6.7 ±2.7 vs. 2.9 ±0.8; p < 0.0001) and a decrease of the Bax protein expression (3.4 ±2.1 vs. 5.5 ±1.8; p < 0.0001) in CD. The expression of Fas and TNFR1 did not differ between the study groups.

Conclusions

LPL in CD are resistant to apoptosis when compared with physiological conditions. This is probably due to an imbalance in Bcl-2 family proteins. TNFR1-related pathway is probably not involved in disturbances of LPL apoptosis in CD.     

Histochemical demonstration of disulfide-groups in the lamina propria of human seminiferous tubules

Summary The distribution of disulfide-groups was investigated in the tunica propria of human seminiferous tubules by means of a thiosulfation/Alcian Blue+0.8 Mol MgCl₂-staining reaction. Controls had shown the absence of significant amounts of sulfhydryl- or sulfate-groups in the lamina propria, which groups would also be demonstrated by the method employed.The lamina propria of human seminiferous tubules is rich in disulfide-groups. The staining reaction decreases in the region of the tubulus rectus, is only faint in the connective tissue which underlies the epithelium of the rete testis, and is absent in the lamina propria of efferent ducts.It is suggested that microfibrils and type IV collagen (both rich in cystine) are the materials responsible for the histochemical reaction described. The occurrence of multiple layers of basal lamina material (type IV collagen) and bundles of microfibrils is shown in comparative electron microscopic studies.     

T lymphocytes in the intestinal epithelium and lamina propria of mice.

Mesenteric lymphoblasts have a predilection to localize selectively in the murine small intestine within 24 hr after adoptive transfer. In this report, we quantify the localization and intraintestinal distribution of radiolabelled mesenteric lymph node (MLN) T and B blasts in relation to the in situ distribution of intestinal T and B cells which were detected immunohistochemically. Our results show that, within 24 hr after transfer, MLN T blasts localized predominantly in the intestinal epithelium and villus lamina propria, whereas B blasts were found mostly in the basal lamina propria of the gut. In the epithelium and villus lamina propria, 100% and 68%, respectively, of labelled were of thymic origin; this cell type comprised 54% of labelled cells in the basal lamina propria. This pattern of localization was the reverse of the distribution of T lymphocytes and B-cell derived plasmacytes residing in the intestinal wall. These results suggest that MLN T lymphocytes may be a component of common mucosal immunological system and may be integrated with peripheral immunity according to the immunological needs of the host.     

A new in vitro model for analyzing the biological behavior of well-differentiated squamous cell carcinoma

A suitable model analyzing the behavior of well-differentiated squamous cell carcinoma has not yet been established. We tried to establish such a system using a reconstructed oral mucosa, in which T3M-1 squamous cell carcinoma cells were cultured on 3T3 fibroblast-containing collagen gel. Fibroblasts promoted the stratification and keratinization of T3M-1 cells. During growth, the Ki-67 index of T3M-1 cells with fibroblasts was higher than that of T3M-1 cells alone. Fibroblasts increased the expression of involucrin, a differentiating marker of keratinocytes, in T3M-1 cells. They also promoted the invasion of T3M-1 cells into the gel. When T3M-1 cells alone were cultured in a fibroblast-conditioned (FC) medium, the fibroblast-induced phenomena mentioned above were almost replicated. In addition, epidermal growth factqr (EGF) promoted T3M-1 cells growth, but not the invasion. cDNA microarray analysis showed that FC medium increased the expression of EGF receptor and several other mRNAs of T3M-1 cells. The data suggest that T3M-1 cells, under cancer-stromal fibroblast interaction, undergo invasive growth with their well-differentiated squamous phenotype, and that this interaction may be mediated partly by soluble molecules (e.g., EGF) in an autocrine or paracrine pathway. Our system will probably provide a useful model for analyzing the biological behavior of well-differentiated squamous cell carcinoma.     

Up-regulation of the phosphoinositide 3-kinase pathway in human lamina propria T lymphocytes

Human intestinal lamina propria T lymphocytes (LPT), when investigated ex vivo, exhibit functional properties profoundly different from those of peripheral blood T lymphocytes (PBT). One prominent feature represents their enhanced sensitivity to CD2 stimulation when compared to PBT. Given that LPT are hyporesponsive to T cell receptor (TCR)/CD3 stimulation, an alternative activation mode, as mimicked by CD2 triggering in vitro, may be functional in mucosal inflammation in vivo. This study provides insight into signalling events associated with the high CD2 responsiveness of LPT. When compared to PBT, LPT show an increased activation of the phosphoinositide 3/protein kinase B/glycogen synthase kinase 3beta (PI3-kinase/AKT/GSK-3beta) pathway in response to CD2 stimulation. Evidence is provided that up-regulation of this pathway contributes to the enhanced CD2-induced cytokine production in LPT. Given the importance of TCR-independent stimulation for the initiation of intestinal immune responses analysis of signalling pathways induced by 'co-stimulatory' receptors may provide valuable information for therapeutic drug design.     

Doxorubicin-loaded polysaccharide nanoparticles suppress the growth of murine colorectal carcinoma and inhibit the metastasis of murine mammary carcinoma in rodent models

As a synergistic drug combination, doxorubicin-loaded cisplatin crosslinked polysaccharide-based nanoparticles (Dex-SA-DOX-CDDP) have demonstrated enhanced antitumor efficacy and reduced systemic toxicity via optimized biodistribution, controlled drug release, prolonged blood circulation, and improved tolerability, compared to the non-crosslinked nanoparticles or free doxorubicin. Herein, we apply the Dex-SA-DOX-CDDP nanoparticles as an efficient antitumor agent to treat colorectal and breast tumors in three different in vivo models, i.e. subcutaneously implanted colorectal carcinoma, dimethylhydrazine-induced autochthonous colorectal carcinoma, and metastatic mammary carcinoma, which more closely simulate the natural milieu of the original tumor with intact pathological and immunological responses. Based on the properties of this combination in higher tumor accumulation and penetrating efficiency, the Dex-SA-DOX-CDDP nanoparticles significantly decreased the tumor sizes in CT26 cell line xenograft tumors compared to control. In addition, the affected animals' lifespan was significantly extended after the Dex-SA-DOX-CDDP treatment, in the autochthonous colon cancer model. Moreover, with the aid of iRGD, Dex-SA-DOX-CDDP could effectively block primary tumor growth and prevent the metastasis of 4T1 murine mammary carcinoma. In conclusion, Dex-SA-DOX-CDDP nanoparticles remarkably inhibit growth of colorectal carcinoma and metastasis of mammary carcinoma in vivo, which provides potential application as a safe and efficient antitumor agent in treatment of these cancers.     

The sequential accumulation of genetic alterations characteristic of the colorectal adenoma–carcinoma sequence does not occur between gastric adenoma and adenocarcinoma

We screened 30 gastric adenomas and 72 gastric adenocarcinomas for four genetic alterations (mutations of the K-ras, APC, and p53 genes and loss of heterozygosity at the DCC genetic locus) which are known to occur during colorectal tumourigenesis. We used polymerase chain reaction (PCR) single-strand conformation polymorphism analysis to detect mutations. Loss of heterozygosity (LOH) at the DCC locus was ascertained directly by performing PCR on the variable number of tandem repeats within the gene. Mutations of the K-ras gene were not detected in any gastric adenoma or carcinoma. APC mutations were detected in 20 per cent (6/30) of the adenomas but in only 1·4 per cent (1/72) of the carcinomas. In contrast, the p53 gene was frequently mutated in carcinomas (35 per cent; 25/72), but not in adenomas. LOH at the DCC locus was a frequent occurrence in carcinomas (58 per cent; 11/19 informative cases) but was infrequent in adenomas (14 per cent; 1/7). Alterations of the p53 and DCC genes occurred frequently both in differentiated and in undifferentiated gastric carcinomas. The considerable differences in the incidences of genetic alerations between gastric adenoma and carcinoma indicate that the sequential development of gastric carcinoma from adenoma is uncommon in gastric carcinogenesis.