Subgroups Of Colorectal Cancer Research Articles

Clusterin Expression in Normal Mucosa and Colorectal Cancer

The gene Clusterin is a target for cancer therapy in clinical trials. The indication for intervention is up-regulated Clusterin expression. Clusterin has been reported to be deregulated in multiple cancer types, including colorectal cancer (CRC). However, for CRC the studies have disagreed on whether Clusterin is up- or down-regulated by neoplastic cells. In the present study we sought to clarify the expression and distribution of Clusterin mRNAs and proteins in normal and neoplastic colorectal tissue through laser microdissection, variant-specific real time RT-PCR, immunohistochemistry, immunofluorescence, Western blotting, and array-based transcriptional profiling. At the transcript level we demonstrated the expression of two novel Clusterin transcripts in addition to the known transcript, and at the protein level we demonstrated two Clusterin isoforms. Our analysis of normal epithelial cells revealed that among these, Clusterin was only expressed by rare neuroendocrine subtype. Furthermore our analysis showed that in the normal mucosa the majority of the observed Clusterin protein originated from the stromal compartment. In tumors we found that Clusterin was de novo synthesized by non-neuroendocrine cancer cells in approximately 25% of cases. Moreover we found that the overall Clusterin level in tumors often appeared to be lower than in normal mucosa due to the stromal compartment often being suppressed in tumors. Although Clusterin in normal neuroendocrine cells showed a basal localization, the localization in cancer cells was often apical and in some cases associated with apical secretion. Collectively our results indicate that Clusterin expression is very complex. We conclude that Clusterin expression is associated with neuroendocrine differentiation in normal epithelia and that the Clusterin observed in neoplastic cells is de novo synthesized. The cases with de novo synthesized Clusterin define a distinct subgroup of CRC that may be of clinical importance as anti-Clusterin therapeutics are now in clinical trials.

Differential expression of DHHC9 in microsatellite stable and instable human colorectal cancer subgroups

Microarray analysis on pooled samples has previously identified ZDHHC9 (DHHC9) to be upregulated in colon adenocarcinoma compared to normal colon mucosa. Analyses of 168 samples from proximal and distal adenocarcinomas using U133plus2.0 microarrays validated these findings, showing a significant two-fold (log 2) upregulation of DHHC9 transcript (P<10−6). The upregulation was more striking in microsatellite stable (MSS), than in microsatellite instable (MSI), tumours. Genes known to interact with DHHC9 as H-Ras or N-Ras did not show expression differences between MSS and MSI. Immunohistochemical analysis was performed on 60 colon adenocarcinomas, previously analysed on microarrays, as well as on tissue microarrays with 40 stage I–IV tumours and 46 tumours from different organ sites. DHHC9 protein was strongly expressed in MSS compared to MSI tumours, readily detectable in premalignant lesions, compared to the rare expression seen in normal mucosa. DHHC9 was specific for tumours of the gastrointestinal tract and localised to the Golgi apparatus, in vitro and in vivo. Overexpression of DHHC9 decreased the proliferation of SW480 and CaCo2 MSS cell lines significantly. In conclusion, DHHC9 is a gastrointestinal-related protein highly expressed in MSS colon tumours. The palmitoyl transferase activity, modifying N-Ras and H-Ras, suggests DHHC9 as a target for anticancer drug design.

CpG Island Methylator Phenotype: The Third Way of Colorectal Carcinogenesis

CpG Island Methylator Phenotype: The Third Way of Colorectal Carcinogenesis

Spotlight

Schlee et al., pp. 1387–1395 Burkitt's Lymphoma (BL) is a high-grade malignancy, associated with Epstein-Barr virus, in which chromosomal translocation results in the deregulation of the proto-oncogene c-myc. Although BL cells express a limited number of EBV antigens, they are consistently ignored by cytotoxic T-cells (CTLS) in vivo. On the other hand, cells of posttransplant lymphoproliferative disease (PTLD) – an EBV-driven B-cell proliferation – elicits a robust CTL response. In this report Schlee et al. tackle an unanswered question: are BLs poorly immunogenic because they do not express the full range of EBV antigens or because c-myc is overexpressed? Using EBV-immortalized cell lines as a model of PTLD and several EBV-positive BL cell lines, the authors looked at differential gene expression. EBV-immortalized cells showed high expression levels of NF-κB target genes whereas BL showed low levels. Furthermore, BL cells showed very low expression of interferon-regulated genes such as STAT1. To pin-point the effects of c-MYC expression on immune regulators, Schlee and colleagues used cell lines in which c-MYC expression can be induced. They demonstrated that switching off c-MYC expression leads to STAT1 induction and vice versa. Furthermore, c-MYC inhibits expression of IFN- β1. Analysis of the STAT promoter showed that c-MYC could bind it directly andc-MYC could inhibit both IFN- β1-dependent and-independent STAT1 promoter activity. This detailed study shows that c-MYC is able to downregulate key players such as STAT1 and IFN- β1 in the immune response and may explain the distinct lack of immunogenicity of BL cells. Montella et al., pp. 1555–1559 Naganuma et al., pp. 1542–1547 A protective effect of coffee drinking in the cancer risk of the digestive tract and related organs has been observed. However, the evidence across studies is inconsistent. In this issue, two studies have investigated coffee consumption and cancer risk. The first group of researchers, based in Italy, investigated the association between coffee – a highly consumed national beverage – and tea consumption and the risk of developing hepatocellular carcinoma (HCC). Using a case control study comprising 185 HCC cases and a control patient group, the authors observed a significant trend (p= 0.02) of decreased HCC risk in subjects with increasing coffee consumption, starting with 14 cups/week. However, the odds ratios were not statistically significant even for consumption of 28 cups/week. No association was found with decaffeinated coffee or tea consumption. The study supports the hypothesis that coffee, but probably not caffeine, may protect against HCC. The second report uses a prospective study to work out whether coffee can protect against colorectal cancer. Although previous case-control studies have supported a protective effect, evidence from prospective studies has been much less conclusive. In this report Naganuma et al., evaluated over 38,000 people in the general Japanese population and identified 457 cases of colorectal cancer. The authors carefully analyzed hazard ratios in various subgroups of colorectal cancer according to coffee consumption. No significant decreased risk or any association was found across all subgroups and sexes. This large study should help end the debate as to whether coffee can protect against colorectal cancer. Atlasi et al., pp. 1598–1602 The cancer stem cell (CSC) hypothesis argues that only a subset of cancer cells – CSCs – initiate and maintain tumor cells. CSCs have biological properties similar to those of normal stem or progenitor cells and have a high self-renewal capacity. OCT-4, a POU domain transcription factor, is an important regulator of self-renewal and differentiation in embryonic stem cells. Although OCT-4 has been identified in human germ cell tumors, its expression in somatic cancers is not known. To investigate whether OCT-4 is expressed in bladder cancer, Atlasi et al. analyzed over 50 tumors and normal bladder tissues and found a strong correlation between the expression of OCT-4 and the presence of a tumor. Using immunohistochemistry, OCT-4 was predominantly located in the nuclei of tumor cells and no immunoreactivity was found in the neighboring normal tissue. Although it is still not known whether OCT-4 expression has any correlation with patients' prognosis, this is the first report of a link between the OCT-4 and bladder cancer. A link between stem cells' self-renewal regulatory genes, such as OCT-4, and somatic tumors adds more weight to the CSC hypothesis.

Prognostic Value of Cell Cycle and Apoptosis Regulatory Proteins in Mismatch Repair–Proficient Colorectal Cancer

Cell cycle and apoptosis regulatory proteins are markers of tumor progression in colorectal cancer. In a series of 1,274 mismatch repair-proficient colorectal cancers, immunohistochemical analysis of p21, p27, p53, and bcl-2 expression was performed using the tissue microarray technique. In univariate analysis, p21 expression was associated with tumor location and pN0; p27 expression with tumor location, lower tumor grade, early pT, and pN; p53 expression with tumor location; and bcl-2 with early pT and pN. Expression of p27 identified subgroups with worse prognosis in pT3 N0 and pT3 N+ patients. None of the 4 tumor markers were independent prognostic indicators of survival. The multimarker phenotypes p21/p27/p53 and p21/p27/bcl-2 were associated with survival. In mismatch repair-proficient colorectal cancer, p27 expression is associated with a better prognosis, and pT, pN, and vascular invasion are independent prognostic factors. In addition, multimarker phenotypes are useful to identify colorectal cancer subgroups with different prognoses.

Methylation of Serum DNA Is an Independent Prognostic Marker in Colorectal Cancer

Aberrant CpG island hypermethylation is a feature of a subgroup of colorectal cancers, which can be detected in the serum of affected patients. This study was designed to identify methylation targets with prognostic significance in the serum of patients with colorectal cancer. In a gene evaluation set consisting of sera from 24 patients with local colorectal cancers, 14 with metastasized disease, and 20 healthy controls, the genes HPP1/TPEF, HLTF, and hMLH1 were identified as potential serum DNA methylation markers. These genes were further analyzed in a test set of sera of 104 patients with colorectal cancer. Methylation of HLTF, HPP1/TPEF, and hMLH1 was found to be significantly correlated with tumor size, and methylation of HLTF and HPP1/TPEF was significantly associated with metastatic disease and tumor stage. Moreover, methylation of HPP1/TPEF was also associated with serum carcinoembryonic antigen. The prognostic relevance of methylation of these genes was tested in pretherapeutic sera of 77 patients with known follow-up. Patients with methylation of HPP1/TPEF or HLTF were found to have unfavorable prognosis (P = 0.001 and 0.008). In contrast, serum methylation of hMLH1 was not associated with a higher risk of death. Multivariate analysis showed methylated HPP1 and/or HLTF serum DNA to be independently associated with poor outcome and a relative risk of death of 3.4 (95% confidence interval, 1.4-8.1; P = 0.007). These data show that the methylation status of specific genes in the serum of patients with colorectal cancer has the potential to become a pretherapeutic predictor of outcome.

Identification of differentially expressed proteins in colorectal cancer by proteomics: Down-regulation of secretagogin

To identify proteins with colorectal cancer-specific regulation, comparative 2-DE of individual-matched normal and neoplastic colorectal tissue specimens was performed. We found 15 protein spots with concordantly increased and 20 protein spots with concordantly decreased intensity in tumor tissue (expression regulation more than fivefold). Nine of these proteins were identified by MS/MS. Interestingly, one of the proteins, which exhibited a marked down-regulation in colorectal cancer tissues, was the recently identified endocrine cell-expressed protein secretagogin. The reduction of the secretagogin content in colorectal cancer tissues was confirmed by comparative immunoblotting (n = 17) and RT-PCR (n = 22) as well as by immunohistochemistry (n = 45) of individual-matched neoplastic and normal colorectal tissue specimens. Immunohistochemistry revealed absence of secretagogin-expressing cells in most of the colorectal cancer tissue specimens. However, some colorectal cancers were characterized by secretagogin-expressing cells. In normal mucosa, positively stained cells exhibited a neuroendocrine cell-characteristic morphology and mucosal location. In colorectal cancer tissues, secretagogin-expressing cells were characterized by a malignant morphology. Our findings might represent the basis for the clinical application of secretagogin as a biomarker for a distinct subgroup of colorectal cancers.

Colorectal Cancer Prognosis Among Patients With Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is associated with an increased risk for colorectal cancer (CRC). However, the genetic, endoscopic, and histologic features of IBD-associated CRC differ from cancers that arise sporadically. The objectives of this study were to describe the clinicopathologic features of IBD-associated CRC and to compare survival rates between patients with IBD-associated CRC and patients with sporadic CRC. There were 290 patients with IBD-associated CRC (241 with chronic ulcerative colitis [CUC] and 49 with Crohn's disease) and an equal number of age- and sex-matched sporadic CRC patients who were evaluated at the Mayo Clinic between 1976 and 1996. Medical records were reviewed retrospectively for demographic features, endoscopic and histologic characteristics, and vital status at the time of the last follow-up evaluation. The actuarial survival of each group was calculated by the Kaplan-Meier method. The influence of clinical features on survival was assessed using Cox proportional hazards regression modeling. The median age at diagnosis of IBD-related CRC was 48 years. Fifty-five percent of IBD-related tumors were distal to the splenic flexure compared with 78% of sporadic tumors. During a median follow-up period of 5 years, 163 IBD-associated CRC patients died (56%), compared with 164 sporadic CRC patients (57%). The 5-year survival rates were 54% in the IBD-CRC subgroup vs 53% in the sporadic CRC subgroup (P = .94, log-rank). CUC-related CRC is diagnosed at a relatively young age, and IBD-related tumors tend to be distributed more evenly across the colorectum than sporadic tumors. The survival rates for IBD-associated and sporadic CRC were similar.

Hereditary colorectal cancer – guidelines for clinical routine

BACKGROUND: Hereditary colorectal cancer (CRC) accounts for approximately 15 % of all CRC cancers. The major subgroups of hereditary CRC are a) familial adenomatous polyposis (FAP), b) Lynch syndrome (also known as hereditary non-polyposis colon cancer syndrome (HNPCC) and c) Lynch-like syndrome. Multiple and complex definitions of the Lynch and Lynch-like syndrome have led to uncertainties within non-specialists. Therefore established knowledge is not used in clinical routine. METHODS: Review of literature. RESULTS: Assessment of the patient's family history and the genetic disposition of index patients permit custom-tailored screening for those affected by the disease. We provide simple guidelines for detection and surveillance of familiar CRC for Austria. CONCLUSIONS: A simple and clear concept should facilitate acceptance of guidelines within the medical community. The widespread use of appropriate surveillance/therapeutic programs for individuals at risk will allow prevention of cancer or detection of the disease at an early stage.

BRAF mutations are associated with distinctive clinical, pathological and molecular features of colorectal cancer independently of microsatellite instability status

BackgroundBRAF is a member of RAF family of serine/threonine kinases and mediates cellular responses to growth signals through the RAS-RAF-MAP kinase pathway. Activating mutations in BRAF have recently been found in about 10% of colorectal cancers, with the vast majority being a V600E hotspot mutation. The aim of the present study was to evaluate the clinical, pathological and molecular phenotype of colorectal tumors with BRAF mutations.ResultsMutations in BRAF were identified in 8% (23/275) of colorectal cancers. They were 5–10-fold more frequent in tumors with infiltrating lymphocytes, location in the proximal colon, poor histological grade and mucinous appearance (P < 0.002 for each). Tumors with BRAF mutation were also 10-fold more likely to show microsatellite instability and frequent DNA methylation (P < 0.0001) compared to tumors without this mutation. The characteristic morphological features of tumors with BRAF mutation (infiltrating lymphocytes, poor grade, mucinous) remained after stratification according to microsatellite instability and methylator phenotypes. Mutations in BRAF were mutually exclusive with mutations in KRAS but showed no clear association with the presence of TP53 mutation.ConclusionBRAF mutation identifies a colorectal cancer subgroup with distinctive phenotypic properties independent of microsatellite instability status and thus could be a valuable marker for studies into the clinical properties of these tumors.

Immunoprofiles of 11 Biomarkers Using Tissue Microarrays Identify Prognostic Subgroups in Colorectal Cancer

BACKGROUND, AIMS: Genomewide expression profiling has identified a number of genes expressed at higher levels in colorectal cancer (CRC) than in normal tissues. Our objectives in this study were: 1) to test whether genes were also distinct on the protein level; 2) to evaluate these biomarkers in a series of well-characterized CRCs;, 3) to apply hierarchical cluster analysis to the immunohistochemical data. METHODS: Tissue microarrays (TMAs) comprising 351 CRC specimens from 270 patients were constructed to evaluate the genes Adam10, CyclinD1, Annexinll, NFKB, Casein-kinase-2-beta (CK2B), YB-1, P32, Rad51, c-fos, IGFBP4, Connexin26 (Cx26). In total, 3,797 samples were analyzed. RESULTS: Unsupervised hierarchical clustering discovered subgroups of CRC that differed by tumor stage, survival. KaplanMeier analysis showed that reduced Cx26 expression was significantly associated with shorter patient survival, higher tumor grade (G1/G2vs G3, P = .02), Adam10 expression with a higher tumor stage (pT1/2vs pT3/4, P = .04). CONCLUSIONS: Our study highlights the potential of TMAs for a higher-dimensional analysis by evaluating serial sections of the same tissue core (three-dimensional TMA analysis). In addition, it endorses the use of immunohistochemistry supplemented by hierarchical clustering for the identification of tumor subgroups with diagnostic, prognostic signatures.

A subgroup of microsatellite stable colorectal cancers has elevated mutation rates and different responses to alkylating and oxidising agents.

An early step in the carcinogenesis of hereditary non-polyposis colorectal cancer (HNPCC) and some sporadic colorectal cancers (CRCs) is the acquisition of a ‘mutator phenotype’ resulting from defects in DNA mismatch repair (MMR) genes, which normally maintain genomic stability. This mutator phenotype causes an approximately 100–1000-fold increase in base substitutions and small insertion/deletion mutations thereby driving carcinogenesis. It also causes genome-wide microsatellite instability (MSI) due to the inability to repair mutations within these small, hard to replicate, repetitive DNA elements. In contrast, less is known about the role of mutator phenotypes in microsatellite stable (MSS) CRC. In this report, we have measured the mutation rates in 11 MSS CRC cell lines to obtain an estimate of the prevalence of mutator phenotypes in MSS carcinogenesis. Of the 11 cell lines, three of them (27%) possess spontaneous hypoxanthine phosphoribosyltransferase mutation rates approximately 10–100-fold above background. When challenged with alkylating and oxidising agents, the degree of survival and apoptotic responses are different, indicating that these cell lines may represent more than one mutator phenotype. These data demonstrate that a significant portion of MSS CRC cell lines has increased mutation rates and that this may play a role in MSS CRC carcinogenesis.

Muir-Torre-Syndrom

The Muir-Torre syndrome (MTS) is an autosomal dominant disease defined by the coincidence of at least one sebaceous skin tumor and one internal malignancy. We describe an additional case and give a review of the literature. Over a period of 7 years, 19 skin tumors were excised in a 50 year old male patient. A total of 3 colonic carcinomas, one gastric carcinoma and one laryngeal carcinoma were operated successfully. The underlying defective mutation in the hMSH2 gene and the microsatellite instability were demonstrable. MTS is graded as a subgroup of hereditary non-polyposis colorectal cancer (HNPCC). In patients with MTS and with family members with known defective mutation, regular follow-up and search for new malignancies are mandatory.

A polymorphism in the methylenetetrahydrofolate reductase gene predisposes to colorectal cancers with microsatellite instability.

The enzyme methylenetetrahydrofolate reductase (MTHFR) catalyses the formation of folate intermediates that are vital to methylation reactions. A polymorphic variant (TT) has been linked to reduced levels of plasma folate, aberrant DNA methylation in leucocytes, and increased risk of colorectal cancer (CRC) under conditions of low folate intake. The cystathionine beta-synthase (CBS) enzyme reduces homocysteine levels and thus may protect against CRC. The CBS gene has a variant, 844ins68, that has been linked with increased activity. These variants may be involved in the development of the subgroup of CRC displaying aberrant DNA methylation and frequently associated with microsatellite instability (MSI). To investigate the frequencies of the TT and 844ins68 genotypes in CRC patients with MSI+ tumours compared with those with MSI- tumours and a control population. Patients with CRC (n=501) and healthy control subjects (n=1207) were studied. CRC cases were classified as MSI+ (n=75) or MSI- (n=426) based on deletions within the BAT-26 mononucleotide repeat. Subjects were genotyped for MTHFR using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and PCR-restriction fragment length polymorphism (PCR-RFLP) techniques, and for CBS using PCR. The MTHFR TT genotype was more frequent in older CRC patients (>or=70 y) compared with equivalent aged controls (p=0.03), was associated with a significantly later age of diagnosis in patients with proximal colon tumours (p=0.02), and was almost twice as frequent in MSI+ than in MSI- tumours (p=0.05). Compared with normal controls, the 844ins68 variant of CBS was less frequent in patients with proximal tumours (p=0.02). The TT genotype of MTHFR is associated with an increased risk of CRC in older populations, possibly due to age related disturbances in folate metabolism. The TT genotype appears to predispose to CRC that is MSI+. This may reflect the involvement of aberrant DNA methylation frequently associated with MSI+. The 844ins68 CBS polymorphism may protect against proximal tumours.

Ki-ras mutation type and the survival benefit from adjuvant chemotherapy in Dukes' C colorectal cancer.

Ki-ras mutations are associated with an increased risk of relapse and death in colorectal cancer (CRC) patients, with some mutations being more aggressive than others. The present study examined the predictive value of different Ki-ras mutation types in a retrospective series of 430 Dukes' C stage CRC patients, of whom 208 (48%) had received adjuvant chemotherapy with 5-fluorouracil/levamisole or 5-fluorouracil/leucovorin. A total of 140 mutations were detected, the majority (58%, 81/140) being glycine to aspartate mutations in codons 12 and 13. Glycine to valine mutations in codon 12 (14%, 20/140) and other less frequent, non-specified mutation types (28%, 39/140) accounted for the remaining mutations. Kaplan-Meier survival analysis revealed that both Ki-ras wild-type and mutant patient groups derived significant survival benefit from chemotherapy. However, when patients were stratified according to the type of mutation, those with non-aspartate mutations appeared to gain more benefit from this treatment than those with aspartate mutations. Multivariate analysis that included other possible predictive factors in Dukes' C CRC (tumour site, patient sex, TP53 mutation) demonstrated that non-aspartate mutations in particular were associated with a significant survival benefit from chemotherapy (HR=0.11, 95% CI: 0.04-0.30, p<0.001). These results suggest that the type of Ki-ras mutation could be a clinically useful molecular marker for the identification of CRC subgroups that are likely to benefit from 5-fluorouracil-based adjuvant chemotherapy.

NAD(P)H:quinone oxidoreductase-dependent risk for colorectal cancer and its association with the presence of K-ras mutations in tumors

NAD(P)H:quinone oxidoreductase (NQO1) is a polymorphic enzyme involved in the detoxification of potentially mutagenic and carcinogenic quinones. The homozygous C609T NQO1 genotype resulting in loss of reductase activity is found in 2-20% of individuals. In the present study, the NQO1-dependent risk for sporadic colorectal cancer (CRC) was studied in 247 incident CRC cases and 296 hospital-based controls recruited during 1996-1997. Four subgroups of cases were studied: (i) all CRCs; (ii) a molecular CRC subgroup (n = 117, cases with molecular tumor analyses); (iii) within the molecular subgroup those tumors with K-ras mutations in codon 12 (CRC K12); (iv) within the molecular subgroup those tumors with K-ras mutations in codon 13 (CRC K13). The C609T NQO1 genotype was found to be twice as prevalent in all CRC patients (6.8%) compared with controls (3%) and six times more common in the subset CRC K12 (20%). Multivariant analyses in the overall population of 247 cases and 296 controls showed a significant age and gender adjusted risk for CRC associated with the C609T NQO1 genotype (OR 2.9, 95% CI 1.19-6.97; P = 0.01) or with any variant genotype (the low activity allele frequency, i.e. heterozygotes plus homozygotes) (OR 1.41, 95% CI 1.02-1.92; P = 0.03). Within cases of the molecular subgroup (n = 117) the C609T NQO1 genotype was associated with the presence of K-ras codon 12 mutation (OR 6.5 95%, CI 1.39-34.9; P = 0.003). Logistic regression showed an age and gender adjusted risk for K-ras codon 12 mutant CRC associated with the C609T NQO1 genotype (OR 10.5, 95% CI 2.99-36.7; P: = 0.0002) or with any variant NQO1 genotype (OR 2.23, 95% CI 1.23-4.00; P = 0.007) compared with the control group. Genetically determined variations in NQO1 may modify the risk for CRC and these risks may be greatest for tumors containing K-ras codon 12 mutations. CRC with K-ras codon 12 mutations may represent a distinct and etiologically more homogeneous subtype of the disease, which may be associated with toxicants that are metabolized via a NQO1-dependent pathway.

Expression of transforming growth factor β receptors in normal human colon and sporadic adenocarcinomas

Background & Aims: An absence or a presence of mutated transforming growth factor (TGF)-β receptors is a possible hypothesis explaining the resistance of cancer cells to the growth-inhibitory effect of TGF-β. Mutations involving microsatellite-like regions of the type II TGF-β receptor have been described in subgroups of colorectal cancers. The aim of this study was to investigate the expression and distribution of TGF-β receptors in sporadic colorectal cancers and normal tissues. Methods: Thirty-three sporadic colorectal cancers and 20 normal colonic tissues were explored by immunohistochemistry for the expression of type I and type II TGF-β receptors. Eighteen tumor and 20 normal samples were used for radioactive thermocycling and sequencing of the two microsatellite-like regions of the type II receptor. Results: Both receptors were overexpressed in tumors compared with normal samples. There was a relationship between the abundance of type II receptor expression and the degree of differentiation of the tumors but not the Dukes' staging or the localization of the neoplasias. No mutation was observed in the microsatellite-like regions of receptor II in any of the samples. Conclusions: Sporadic colorectal cancers do not show an absence or a presence of mutated TGF-β receptors that could explain a resistance to TGF-β–mediated growth inhibition. The pathways to tumorigenesis of sporadic colorectal cancers may be different from those of some hereditary ones. GASTROENTEROLOGY 1998;114:1211-1220

Involvement of chromosome 5 in large bowel cancer

We present here 3 of 30 cases of large bowel cancer cytogenetically studied, with deletion of chromosome 5. One of them presented a terminal deletion and the other two an interstitial deletion of chromosome 5q. In all three cases the segment 5q12–22 was deleted. Our findings may show that the segment 5q12–22 is important for a subgroup of colorectal cancers.

Evaluation of serum sialic acid and carcinoembryonic antigen for the detection of early‐stage colorectal cancer

Various expressions of elevated serum sialic acid (total sialic acid, TSA: lipid-associated sialic acid, LASA; LASA/TSA; TSA normalized to total protein, TSA/TP) have been evaluated and compared with increased serum carcinoembryonic antigen (CEA) levels for the detection of early-stage colorectal cancer. This evaluation was done blindly on a coded panel of 320 sera from staged colorectal cancer patients and controls provided by the Mayo Clinic--National Cancer Institute Diagnostic Bank. Unlike the findings of a previous preliminary study (Tautu et al., JNCI 80:1333-1337, 1988), the ratio of LASA/TSA was not useful for detecting early-stage (Dukes A and B) colorectal cancer. However, TSA and TSA/TP values were significantly elevated in each colorectal cancer subgroup compared with normal controls. TSA and TSA/TP values displayed a marginally better discriminatory power than CEA values in the case of Dukes A subgroup with respect to normal controls. CEA still appears to be the best single overall marker for discriminating between colorectal cancers and controls. However, multiple marker analysis using CEA and TSA (and related markers) appears to be more sensitive than CEA alone for detecting colorectal cancer.

Simultaneous monitoring of P53 protein and dna content of colorectal adenocarcinomas by flow cytometry

The p53 transformation-related gene is located on 17p, a chromosomal segment frequently under-represented in colorectal adenocarcinoma karyotypes. We have developed a flow cytometric method for detection of its gene product on isolated nuclei by indirect immunofluorescence. Criteria for defining the presence of p53 were established, using parameters related to the difference of fluorescence obtained by incubating nuclei with a specific monoclonal antibody (MAB) versus isotypic control. This method allowed simultaneous quantitation of p53 and DNA in tumor nuclei to be made. Twenty-two of the 41 tumors analyzed (54%) were found to overexpress p53 when compared to 13 normal mucosa specimens. Repeated preparations from different fragments of the same tumor gave reproducible results for the 21 cases tested. p53 was detected in a higher proportion of disseminated tumors (64%) compared to localized disease (39%), but the difference did not reach statistical significance (chi 2 = 2.4, p greater than 0.10). Tumors containing aneuploid cell subpopulations were also more frequently positive (65%) than diploid ones (20%), the difference being significant (Fisher's exact test, p less than 0.03). This dual parameter flow cytometric method, evaluating both DNA ploidy and p53 expression, may prove useful in identifying different biological subgroups of colorectal cancer.