Oncogene alterations in rat colon tumors induced by N-methyl-N-nitrosourea.

The authors assayed oncogene alterations in rat colon tumors induced by the direct-acting chemical carcinogen, N-methyl-N-nitrosourea (MNU). DNA isolated from 34 adenomas and eight carcinomas, as well as adjacent normal colon, of 11 rats was assayed by Southern blotting for restriction fragment length polymorphisms and gene amplifications and deletions in 13 oncogenes known to be involved in human or other animal tumors. In addition to finding apparent point mutations or other small alterations in the fos and abl genes in individual rat colon tumors, the authors observed what appear to be larger alterations (ie, rearrangements, or intragenic insertions or deletions) in the H-ras and myb loci in several tumors. In contrast, no changes in the K-ras, N-ras, myc, N-myc, neu, raf, fms, met, and hst genes were seen in any of these tumors. The frequency of myb gene alterations was higher in carcinomas than in adenomas, suggesting that these changes occurred relatively late during tumorigenesis and were not direct effects of the carcinogen. In addition, the finding of alterations in two or three oncogenes in several MNU-induced rat colon tumors suggests the possibility of more widespread genomic lesions in this model.     

15-Hydroxyprostaglandin dehydrogenase is an in vivo suppressor of colon tumorigenesis

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is a prostaglandin-degrading enzyme that is highly expressed in normal colon mucosa but is ubiquitously lost in human colon cancers. Herein, we demonstrate that 15-PGDH is active in vivo as a highly potent suppressor of colon neoplasia development and acts in the colon as a required physiologic antagonist of the prostaglandin-synthesizing activity of the cyclooxygenase 2 (COX-2) oncogene. We first show that 15-PGDH gene knockout induces a marked 7.6-fold increase in colon tumors arising in the Min (multiple intestinal neoplasia) mouse model. Furthermore, 15-PGDH gene knockout abrogates the normal resistance of C57BL/6J mice to colon tumor induction by the carcinogen azoxymethane (AOM), conferring susceptibility to AOM-induced adenomas and carcinomas in situ. Susceptibility to AOM-induced tumorigenesis is mediated by a marked induction of dysplasia, proliferation, and cyclin D1 expression throughout microscopic aberrant crypt foci arising in 15-PGDH null colons and is concomitant with a doubling of prostaglandin E(2) in 15-PGDH null colonic mucosa. A parallel role for 15-PGDH loss in promoting the earliest steps of colon neoplasia in humans is supported by our finding of a universal loss of 15-PGDH expression in microscopic colon adenomas recovered from patients with familial adenomatous polyposis, including adenomas as small as a single crypt. These models thus delineate the in vivo significance of 15-PGDH-mediated negative regulation of the COX-2 pathway and moreover reveal the particular importance of 15-PGDH in opposing the neoplastic progression of colonic aberrant crypt foci.     

Application of flow cytometry to the study of hematologic disorders: analysis of oncogene products

Flow cytometry (FCM) is a useful method for clinical research of oncogene products since it can analyze proteins quantitatively which are located at cell surfaces or inside of cells. Oncogene products are now under study by FCM not only as tumor markers but also as functioning proteins in carcinogenesis. The examples of oncogene products analyzed by FCM are ras, myc, p53, myb and fos; those of cell-proliferation-related proteins are Ki-67, PCNA and DNA polymerase alpha. In some diseases the relationship between these proteins and disease classification, stage, pathophysiology, or prognosis have been clarified. Using dual color FCM of H-ras p21 and DNA, we analyzed the expression of H-ras p21 in human multiple myeloma and leukemias and found that H-ras p21 levels in multiple myeloma strongly correlated to the prognosis of patients (p = 0.03). When AML cells were stimulated by adding G-CSF, it was found that many cells proliferated but some were dying. The percentage of dying cells was small in one AML case whose myeloblasts showed increased expression of H-ras p21 by G-CSF stimulation. Together with other papers reviewed, it is conceivable that H-ras p21 expression is related to cell proliferation and inhibition of cell autolysis. Thus FCM is useful in the classification of the role of oncogene products in carcinogenesis in clinical cases.     

Expression of cyclooxygenase‐2 protein in colon disease

OBJECTIVE : Several epidemiological studies have indicated that the long‐term administration of non‐steroidal anti‐inflammatory drugs (NSAIDs) may reduce the incidence of colorectal cancer. The best known action of NSAIDs is to block cyclooxygenase, the key enzyme required for the conversion of arachidonic acid to prostaglandins. Two cyclooxygenase isoforms have been identified and these are referred to as COX‐1 and COX‐2. Recent studies indicate that inducible COX‐2 plays an important role in gastrointestinal inflammation and carcinogenesis. The present study was undertaken to investigate the expression and clinical implications of COX‐2 and COX‐1 in normal and diseased colons. METHODS : COX‐2 and COX‐1 protein expression in specimens from normal controls and diseased colon tissues were examined semiquantitatively by using immunohistochemical methods. RESULTS : By using immunohistochemical detection methods, low COX‐2 protein expression in colonic epithelial cells was observed in 20.0% (2/10) of normal controls. Eighty percent (16/20) of specimens from inflammatory bowel disease (IBD) had a high COX‐2 expression, 46.40% (13/28) of adenomas and 64.3% of (9/14) well‐differentiated colonic carcinomas had some COX‐2 protein expression. Expression of COX‐2 protein was increased in IBD and colonic carcinomas compared with normal controls. There were no significant differences between colonic adenomas and colonic carcinomas. No correlation was found between COX‐2 protein expression and patient gender, patient age, tumor size, tumor location or the degree of differentiation/ metastasis of the tumor. Strong immunoreactive COX‐2 was expressed in clusters in interstitial cells (mainly mononuclear cells) in 53.6% (15/28) of adenomas and 64.3% (9/14) of colonic carcinomas. Strong COX‐2 protein expression was also displayed in the normal glands that were adjacent to the adenomas and carcinomas. Expression of COX‐1 protein was observed in the epithelial cells and interstitial cells or tumor cells of normal colon, IBD, colonic adenomas and colonic carcinomas. CONCLUSIONS : Our results indicated that COX‐2 protein overexpression may contribute to the development of IBD and colonic carcinogenesis.     

Oncogene alterations in primary human colon tumors

We have examined alterations in six oncogenes--H-ras, K-ras, N-ras, myc, fos, and N-myc--in nine primary human colon tumors. Tumors were obtained within an hour of resection; as a control for each tumor, adjacent normal colon tissue was also obtained. Deoxyribonucleic acid extracted from each tissue sample was assayed by digesting with appropriate restriction endonucleases and, after gel electrophoresis and transfer to nitrocellulose, hybridizing with radiolabeled oncogene probes. Amplification of the myc locus, relative to adjacent normal colon tissue, was observed in two of these tumors; by dot-blotting, it was estimated that myc was amplified twofold to fivefold in each tumor. No rearrangements of myc, however, were observed in any of these tumors. Examination of the H-ras alleles of these nine tumors revealed that eight possess only "common" alleles of this gene, and that each was identical to its control. Normal colon DNA of the ninth patient, however, was found to possess both a "common" and a "rare" allele, and the "common" allele of H-ras appeared to be deleted in the tumor DNA of this patient. A restriction polymorphism indicative of a mutation in the 12th codon of K-ras was not found in any of these tumors, and we observed no evidence of rearrangement of amplification of the N-ras, K-ras, fos, or N-myc genes.     

Induction of pancreatic tumors in male Syrian golden hamsters by intraperitoneal N-methyl-N-nitrosourea injection.

The carcinogenic effects of N-methyl-N-nitrosourea (MNU) in male Syrian golden hamsters were investigated. After single i.p. administration of MNU at doses of 50 mg/kg or 10 mg/kg, or after five fractionated i.p. injections to make a total dose of 50 mg/kg body weight (10 mg x 5), histopathological examinations were performed at the end of 40th week of the experiment. Neoplastic changes were observed in various organs, and lesions in the pancreas, forestomach, and adrenal gland were predominant. In the pancreas, three tumor types were observed: ductal adenocarcinomas, acinar cell carcinomas, and islet cell carcinomas. The incidences of pancreatic ductal carcinomas were 56, 27, and 0% in the single 50-mg, fractionated 50-mg, and single 10-mg groups, respectively. Two islet carcinomas were observed in the single 50-mg group, and an islet carcinoma and an acinar cell carcinoma were also observed in the fractionated 50-mg group. Several miscellaneous neoplastic lesions, including squamous cell papillomas/carcinomas in the forestomach, cortical adenomas in the adrenal glands, and a seminoma in the testis were also observed. These results indicate MNU to be a multipotent carcinogen with the pancreas as a target organ in the Syrian golden hamster under this experimental condition. The observed high induction rate for pancreatic ductal carcinoma suggests that this MNU protocol is a useful candidate model for experimental pancreatic ductal carcinogenesis.     

Phenotypic variability of chemically induced primary rat mammary tumors

Rat mammary tumors induced by DMBA (7,12-dimethylbenz(a)anthracene) or MNU (N-methyl-N-nitrosourea) were compared for frequency of histological types. Total tumor incidence in 50-day-old rats (Groups 3, 4, 5) was about 100% independently of the rat strain and carcinogen. There were found no distinct histological tumor types between DMBA and MNU carcinogenesis, although the distribution of fibroadenomas, adenocarcinomas and sarcomas varied markedly among rat groups. In 300-day-old female Wistar rats (Group 1) treated with DMBA, fibroadenomas and adenocarcinomas showed an incidence of 58% and 42% respectively. In 50-day-old rats (Group 3) the proportion of adenocarcinomas increased up to 72% of total DMBA tumors. MNU carcinogenesis induced adenocarcinomas in 98% of total tumors in the Lewis rat strain (Group 5), while only 53% in Wistar rats (Group 4). The rest of tumors were sarcomas occurring in opposite ratio to adenocarcinomas. The relatively high susceptibility of connective tissue to MNU as compared with mammary epithelium was due to the mode of MNU administration and seemed to be strain dependent. Both DMBA and MNU carcinogenic systems are valuable experimental models of mammary tumor. The cell phenotypes of the resulting tumors can be predicted with high probability by the choice of dose regimen of carcinogen and the route of its application.     

Absence of H-ras point mutation at codon 12 inN-methyl-N-nitrosourea-induced hepatocellular neoplasms in the rat

Summary In order to assess the possibility that activatedras-associated hepatic carcinomas might be much rarer in rats than mice because of the more frequent or rapid occurrence of powerful carcinogenic event(s) other thanras point mutations in the former animals, precancerous lesions and hepatocellular carcinomas induced by a weak hepatocarcinogenN-methyl-N-nitrosourea (MNU) in the rat liver were analyzed for the presence or absence ofras point mutations. MNU was chosen because it is well known that MNU-induced rat mammary carcinomas contain activated H-ras at very high frequency. Male Fisher rats were treated with a single dose of MNU after partial hepatectomy, and then administered dietary phenobarbital or repeated s.c. injections of carbon tetrachloride as promoting procedures. Analyses by oligonucleotide hybridization, MnlI-restriction-fragment-length polymorphism and NIH3T3 cell transfection assays revealed neither H-ras point mutations nor transforming ability of the DNA from 36 MNU-induced rat hepatic neoplasms. The results were in agreement with previous results for rat hepatocellular carcinomas induced by other potent liver carcinogens and did not support our hypothesis that the frequency of findingras activation might be dependent on the strength of the carcinogen.Abbreviations MNU N-methyl-N-nitrosourea - HCC hepatocellular carcinoma     

Testing the importance of p27 degradation by the SCFskp2 pathway in murine models of lung and colon cancer

Decreased expression of the CDK inhibitor p27kip1 in human tumors directly correlates with increased resistance to chemotherapies, increased rates of metastasis, and an overall increased rate of patient mortality. It is thought that decreased p27 expression in tumors is caused by increased proteasomal turnover, in particular activation of the pathway governed by the SCFskp2 E3 ubiquitin protein ligase. We have directly tested the importance of the SCFskp-mediated degradation of p27 in tumorigenesis by analyzing the tumor susceptibility of mice that express a form of p27 that cannot be ubiquitinated and degraded by this pathway (p27T187A). In mouse models of both lung and colon cancer down-regulation of p27 promotes tumorigenesis. However, we found that preventing p27 degradation by the SCFskp2 pathway had no impact on tumor incidence or overall survival in either tumor model. Our study unveiled a previously unrecognized role for the control of p27 mRNA abundance in the development of non-small cell lung cancers. In the colon cancer model, the frequency of intestinal adenomas was similarly unaffected by the p27T187A mutation, but, unexpectedly, we found that it inhibited progression of intestinal adenomas to carcinomas. These studies may guide the choice of clinical settings in which pharmacologic inhibitors of the Skp2 pathway might be of therapeutic value.     

Investigation of Epstein-Barr virus in Chinese colorectal tumors

AIM: To elucidate the association of Epstein-Barr virus (EBV) with colorectal tumors and to demonstrate whether infection of EBV existed in different stages of colorectal tumors involves in the carcinogenesis. METHODS: One hundred and thirty paraffin-embedded tissues of colorectal tumors were classified into 5 groups: 26 adenomas, 23 adenomas complicated with dysplasia, 22 adenomas complicated with carcinomatous, 36 colon carcinoma and 23 HNPCC, were examined by PCR, IHC and ISH, respectively. RESULTS: EBV DNA was detected by PCR in 26 cases out of the 130 specimens, including 5 cases of adenomas, 5 adenomas complicated with dysplasia, 5 adenomas complicated with carcinomatous, 7 colorectal carcinoma and 4 HNPCC. IHC detection showed the expression of LMP1 in 7 cases, including 1 adenoma, 1 adenoma with dysplasia, 1 HNPPC, 2 adenomas complicated with carcinomatous, and 2 colorectal carcinomas. The expression of EBER1 detected by ISH was positive in 6 cases, including 1 adenoma with dysplasia, 2 adenomas complicated with carcinomatous and 3 colorectal carcinomas. There were no significant differences among the results of PCR, IHC and ISH in the 5 groups. In all cases of HNPCC, none of the tumor cells showed positive signals of EBER1, but some EBV-positive tumor infiltrating lymphocytes were found in 2 of 23 cases. CONCLUSION: Our results showed that infection of EBV exists in human colorectal tumors, which indicates that EBV may be involved in the carcinogenesis of colorectal tumors but does not play an important role. The mechanisms need to be clarified further.     

Expression profiles of the glucose-dependent insulinotropic peptide receptor and LHCGR in sporadic adrenocortical tumors

Glucose-dependent insulinotropic peptide receptor (GIPR) and LHCGR are G-protein-coupled receptors with a wide tissue expression pattern. Aberrant expression of these receptors has rarely been demonstrated in adult sporadic adrenocortical tumors with a lack of data on pediatric tumors. We quantified the GIPR and LHCGR expression in a large cohort of 55 patients (25 children and 30 adults) with functioning and non-functioning sporadic adrenocortical tumors. Thirty-eight tumors were classified as adenomas whereas 17 were carcinomas. GIPR and LHCGR expression were analyzed by real-time PCR and normal human pancreatic and testicular tissue samples were used as positive controls. Mean expression values were determined by fold increase in comparison with a normal adrenal pool. GIPR mRNA levels were significantly higher in adrenocortical carcinomas than in adenomas from both pediatric and adult groups. LHCGR expression was similar in both carcinomas and adenomas from the pediatric group but significantly lower in carcinomas than in adenomas from the adult group (median 0.06 and 2.3 respectively, P<0.001). GIPR was detected by immunohistochemistry in both pediatric and adult tumors. Staining and real-time PCR results correlated positively only when GIPR mRNA levels were increased at least two-fold in comparison with normal adrenal expression levels. In conclusion, GIPR overexpression was observed in pediatric and adult adrenocortical tumors and very low levels of LHCGR expression were found in all adult adrenocortical carcinomas.     

大肠肿瘤癌基因蛋白产物同步检测的对比分析

对大肠肿瘤连续切片组织同步进行了Ｃ－ｍｙｃ．Ｐａｎ－ｒａｓ和Ｐ５３三种癌基因蛋白产物的检测，结果显示：癌基因ｍｙｃ，ｒａｓ和Ｐ５３阳性表达率在结肠腺瘤分别为６１、１％（４４／７２）、３７．５％（２７／７２和５．６％（４／７２），大肠泉癌分别为７２．９％（５１／７０）、５１．４％（３６／７０）和４０．０％（２８／７０），而正常粘膜则分别为２８．０％（７／２５）、４．０％（１／２５）和０。印戒细胞仅有     

TGF-β_1和MPO在结肠肿瘤中的表达及意义

目的探讨TGF-β1和MPO在人结肠癌组织中的表达及其意义。方法通过免疫组织化学染色法检测53例结肠癌组织,32例结肠腺瘤组织及10例癌旁结肠组织中TGF-β1和MPO的表达及其相互关系。结果TGF-β1和MPO阳性表达在结肠癌组织中为（62.26%,69.81%）均显著性高于癌旁结肠组织（10%,10%）和结肠腺瘤组织（15.63%,21.88%）,差异均有统计学意义（P〈0.05）。TGF-β1和MPO在淋巴结转移组的阳性率（78.57%,85.71%）高于无淋巴结转移组（44.0%,52.0%）,差异均有统计学意义（P〈0.05）。TGF-β1和MPO在结肠癌组织中表达有相关性（r=0.6528,P〈0.05）。结论TGF-β1和MPO可能参与了肿瘤生长和发展的共同通道,在大肠癌的发生、发展和转移过程中起着重要作用。     

Microvascular structure of benign and malignant tumors of the colon in humans

Studies of experimental tumors in rodents indicate that there are morphological abnormalities of the tumor microcirculation compared to normal tissues. The aim of this study was to examine the structure of the microvasculature in benign and malignant colonic tumors in humans using microvascular casting techniques. There were 15 adenocarcinomas, four benign sporadic adenomas, and three specimens from patients with familial adenomatous polyposis (FAP). A cast of the microvessels of these tumors was prepared by intraarterial administration of acrylic resin (Mercox) and the cast examined by scanning electron microscopy. Quantitative measures of the microvasculature were obtained from histological sections using stereological techniques in four carcinomas, two sporadic adenomas, and 12 adenomas from patients with FAP. Vascular casts of benign colonic adenomas showed that the microvasculature had a similar organization to normal colon. However, capillaries and venules were elongated and had increased diameters compared to normal. In adenomas greater than 3 mm in diameter, there was an increased density of microvessels in the spaces between tumor cells. Vascular casts of colonic carcinomas were characterized by a disorganized structure and increased density of microvessels. The organization of microvessels within carcinomas had a similar overall pattern to normal colon. However, the increased number and density of microvessels resulted in formation of nodular clusters of capillaries, formation of “sheets” of frequently anastomosing capillaries, or almost complete packing of the interstitial spaces of the tumor by capillaries in places. Most capillaries had a long and tortuous course and numerous capillary sprouts were identified. Tumor microvessels had greater mean diameters than normal. Extravasation of resin from microvessels in carcinomas was frequently seen. The vascular volume of carcinomas (23.1%±12.2), sporadic adenomas (16.3%±3.4), and adenomas >3 mm diameter in patients with FAP (17.7%±3.0) were significantly greater than in normal colon (11.0%±4.2). This study indicates that there is an increased vascular density in benign and malignant tumors of the colon compared to normal colon. The presence of profusely anastomotic microvessels and frequent capillary sprouts is evidence of active neovascularization and suggests control of tumor growth could be achieved by modifiers of angiogenesis.     

XAF1基因与p53基因在结直肠肿瘤中的表达研究

目的观察两个相邻位置的抑癌基因XIAP相关因子1(XAF1)与p53基因在结直肠肿瘤中的表达。方法选取结肠癌细胞株Colo205、Colo320、LoVo、SW1116为体外研究对象,另取41例结直肠癌、28例结直肠腺瘤/息肉以及31例正常人结肠黏膜为体内研究对象。应用逆转录聚合酶链反应检测XAF1mRNA与p53mRNA在体内外的表达,应用免疫组化法检测P53蛋白在结直肠组织中的表达。结果4种细胞株中XAF1表达均较为低下,p53mRNA表达均较高。结直肠肿瘤组织中的XAF1mRNA表达显著低于正常组织(P<0.01),结直肠癌中的表达又显著低于良性肿瘤(P<0.05)。结直肠肿瘤组织中的p53mRNA表达显著高于正常组织(P<0.01),但在良、恶性肿瘤中的表达差异无统计学意义(P<0.05)。P53蛋白在正常组织中未见表达,良、恶性肿瘤组的组织P53蛋白表达之间差异无统计学意义(P>0.05)。结论XAF1基因在结直肠肿瘤中表达降低,且结直肠癌XAF1mRNA表达显著低于良性肿瘤,可作为判断良、恶性肿瘤的鉴别指标。