Genetic pathways in colorectal and other cancers

Overexpression of OATP1B3 confers apoptotic resistance in colon cancer

Organic anion transporting polypeptide 1B3 (OATP1B3, SLCO1B3) is normally expressed in hepatocytes. In this study, we showed frequent overexpression of OATP1B3 in colorectal adenocarcinomas. Quantitative reverse transcription-PCR analysis of 17 colon tumors indicated tumoral overexpression of OATP1B3 by approximately 100-fold, compared with 20 normal colon samples (P < 0.0001). Using immunohistochemistry on a tissue microarray containing 93 evaluable colon tumor specimens, we detected immunostaining of OATP1B3 in 75 colon adenocarcinomas (81%) and no immunostaining in normal samples. To determine the functional effects of OATP1B3 expression on drug-induced apoptosis, we used camptothecin and oxaliplatin on a panel of colorectal cancer cell lines stably overexpressing OATP1B3. The results indicated that OATP1B3 overexpression enhanced cell survival in RKO, HCT-8, and HCT116(p53+/+) cells that harbor wild-type p53 but not in Caco-2 and HCT116(p53-/-) cells that lack p53, compared with the respective empty vector controls (P < 0.01). The terminal deoxynucleotidyl transferase-mediated nick-end labeling assay confirmed that HCT116(p53+/+) cells overexpressing OATP1B3 had significantly lower apoptotic levels compared with empty vector control (P < 0.001). The overexpression of OATP1B3 reduced the transcriptional activity of p53, with subsequent reductions in transcript and protein levels of its downstream transcription targets (P21WAF1 and PUMA). Overexpression of a point mutation (G583E) variant of OATP1B3 lacking transport activity did not confer an antiapoptotic effect or affect p53 transcriptional activity, suggesting that the antiapoptotic effect of OATP1B3 may be associated with its transport activity. Taken together, our results suggest that OATP1B3 overexpression in colorectal cancer cells may provide a survival advantage by altering p53-dependent pathways.

Overexpression of OATP1B3 confers apoptotic resistance in colon cancer

Organic anion transporting polypeptide 1B3 (OATP1B3, SLCO1B3) is normally expressed in hepatocytes. In this study, we showed frequent overexpression of OATP1B3 in colorectal adenocarcinomas. Quantitative reverse transcription-PCR analysis of 17 colon tumors indicated tumoral overexpression of OATP1B3 by approximately 100-fold, compared with 20 normal colon samples (P < 0.0001). Using immunohistochemistry on a tissue microarray containing 93 evaluable colon tumor specimens, we detected immunostaining of OATP1B3 in 75 colon adenocarcinomas (81%) and no immunostaining in normal samples. To determine the functional effects of OATP1B3 expression on drug-induced apoptosis, we used camptothecin and oxaliplatin on a panel of colorectal cancer cell lines stably overexpressing OATP1B3. The results indicated that OATP1B3 overexpression enhanced cell survival in RKO, HCT-8, and HCT116(p53+/+) cells that harbor wild-type p53 but not in Caco-2 and HCT116(p53-/-) cells that lack p53, compared with the respective empty vector controls (P < 0.01). The terminal deoxynucleotidyl transferase-mediated nick-end labeling assay confirmed that HCT116(p53+/+) cells overexpressing OATP1B3 had significantly lower apoptotic levels compared with empty vector control (P < 0.001). The overexpression of OATP1B3 reduced the transcriptional activity of p53, with subsequent reductions in transcript and protein levels of its downstream transcription targets (P21WAF1 and PUMA). Overexpression of a point mutation (G583E) variant of OATP1B3 lacking transport activity did not confer an antiapoptotic effect or affect p53 transcriptional activity, suggesting that the antiapoptotic effect of OATP1B3 may be associated with its transport activity. Taken together, our results suggest that OATP1B3 overexpression in colorectal cancer cells may provide a survival advantage by altering p53-dependent pathways.

A molecular bar-coded DNA repair resource for pooled toxicogenomic screens

DNA damage from exogenous and endogenous sources can promote mutations and cell death. Fortunately, cells contain DNA repair and damage signaling pathways to reduce the mutagenic and cytotoxic effects of DNA damage. The identification of specific DNA repair proteins and the coordination of DNA repair pathways after damage has been a central theme to the field of genetic toxicology and we have developed a tool for use in this area. We have produced 99 molecular bar-coded Escherichia coli gene-deletion mutants specific to DNA repair and damage signaling pathways, and each bar-coded mutant can be tracked in pooled format using bar-code specific microarrays. Our design adapted bar-codes developed for the Saccharomyces cerevisiae gene-deletion project, which allowed us to utilize an available microarray product for pooled gene-exposure studies. Microarray-based screens were used for en masse identification of individual mutants sensitive to methyl methanesulfonate (MMS). As expected, gene-deletion mutants specific to direct, base excision, and recombinational DNA repair pathways were identified as MMS-sensitive in our pooled assay, thus validating our resource. We have demonstrated that molecular bar-codes designed for S. cerevisiae are transferable to E. coli, and that they can be used with pre-existing microarrays to perform competitive growth experiments. Further, when comparing microarray to traditional plate-based screens both overlapping and distinct results were obtained, which is a novel technical finding, with discrepancies between the two approaches explained by differences in output measurements (DNA content versus cell mass). The microarray-based classification of Deltatag and DeltadinG cells as depleted after MMS exposure, contrary to plate-based methods, led to the discovery that Deltatag and DeltadinG cells show a filamentation phenotype after MMS exposure, thus accounting for the discrepancy. A novel biological finding is the observation that while DeltadinG cells filament in response to MMS they exhibit wild-type sulA expression after exposure. This decoupling of filamentation from SulA levels suggests that DinG is associated with the SulA-independent filamentation pathway.

Expression of chloride intracellular channel protein 1 (CLIC1) and tumor protein D52 (TPD52) as potential biomarkers for colorectal cancer

OBJECTIVES

Unequivocal biomarkers are needed to predict susceptibility and progression of colorectal cancer.

DESIGN AND METHODS

Paired samples of tumor and normal tissue from six patients with colorectal cancer of different localization, pTNM stage and grade were employed in the present study. MS analysis was used to identify differentially regulated proteins after 2-DE separation and densitometric analysis.

RESULTS

Densitometric analysis revealed differential abundance of 55 spots in tumor as compared to normal tissues. Thirty nine out of 55 spots were unambiguously identified by MS representing 32 different proteins. CLIC1, TPD52 and FABPL were consistently overexpressed (>3-fold, P<0.05) in all tumor tissue samples, while TPM1, TPM2, TPM3, TAGL and MLRN were consistently down-regulated (>3-fold, P<0.05) compared to normal tissue.

CONCLUSIONS

CLIC1 and TPD52 were significantly (P<0.05) up-regulated in all cases of colorectal cancer investigated, irrespective of localization, pTNM stage and grade of colon cancer highlighting their potential to serve as new biomarkers.

Frequent mutations of the CA simple sequence repeat in intron 1 of EGFR in mismatch repair-deficient colorectal cancers

AIM: To investigate the polymorphic simple sequence repeat in intron 1 of the epidermal growth factor receptor gene (EGFR) (CA-SSRI), which is known to affect the efficiency of gene transcription as a putative target of the mismatch repair (MMR) machinery in colorectal tumors.

METHODS: The CA-SSR I genotype was analyzed in a total of 86 primary colorectal tumors, selected upon their microsatellite instability (MSI) status [42 with high frequency MSI (MSI-H) and 44 microsatellite stable (MSS)] and their respective normal tissue. The effect of the CA-SSR I genotype on the expression of the EGFR gene was evaluated in 18 specimens using quantitative real-time reverse transcription PCR and immunohistochemistry.

RESULTS: Mutations in CA-SSR I were detected in 86% (36 of 42) of MSI-H colorectal tumors and 0% (0 of 44) of MSS tumors, indicating the EGFR gene as a novel putative specific target of the defective MMR system (P < 0.001). Impaired expression of EGFR was detected in most of the colorectal tumors analyzed [6/12 (50%) at the mRNA level and 15/18 (83%) at the peptide level]. However, no association was apparent between EGFR expression and CA-SSR I status in tumors or normal tissues.

CONCLUSION: Our results suggest that CA-SSRI sequence does not contribute to the regulation of EGFR transcription in colon, and should thus not be considered as a promising predictive marker for response to EGFR inhibitors in patients with colorectal cancer.

Chapter 6. Mouse models to investigate anti-cancer effects of VEGF inhibitors

Angiogenesis, the growth of new blood vessels, is required for a variety of normal proliferative processes. Furthermore, it is well established that angiogenesis plays an important role also in neoplastic growth and metastasis. Numerous regulators of angiogenesis have been identified and characterized over the last decades. Among these, vascular endothelial growth factor (VEGF)-A appears especially important in several pathophysiological processes. Several VEGF inhibitors have been approved by the Food and Drug Administration for the treatment of tumors or age-related macular degeneration. This chapter examines the various mouse tumor models in which VEGF inhibitors have been tested and the lessons learned from these studies.

Trm9-catalyzed tRNA modifications link translation to the DNA damage response

Transcriptional and posttranslational signals are known mechanisms that promote efficient responses to DNA damage. We have identified Saccharomyces cerevisiae tRNA methyltransferase 9 (Trm9) as an enzyme that prevents cell death via translational enhancement of DNA damage response proteins. Trm9 methylates the uridine wobble base of tRNAARG(UCU) and tRNAGLU(UUC). We used computational and molecular approaches to predict that Trm9 enhances the translation of some transcripts overrepresented with specific arginine and glutamic acid codons. We found that translation elongation factor 3 (YEF3) and the ribonucleotide reductase (RNR1 and RNR3) large subunits are overrepresented with specific arginine and glutamic acid codons, and we demonstrated that Trm9 significantly enhances Yef3, Rnr1, and Rnr3 protein levels. Additionally, we identified 425 genes, which included YEF3, RNR1, and RNR3, with a unique codon usage pattern linked to Trm9. We propose that Trm9-specific tRNA modifications enhance codon-specific translation elongation and promote increased levels of key damage response proteins.

Sex chromosome alterations associate with tumor progression in sporadic colorectal carcinomas

PURPOSE

The X and Y chromosomes have been associated with malignancy in different types of human tumors. This study attempts to determine the involvement of X chromosome and pseudoautosomal regions (PAR) in sporadic colorectal carcinogenesis.

EXPERIMENTAL DESIGN

An allelotyping of X chromosome in 20 premalignant and 22 malignant sporadic colorectal tumors (CRC) from female patients and an analysis of losses [loss of heterozygosity (LOH)] on PARs from 44 CRCs and 12 adenomas of male patients were carried out. In male tumors, a fluorescence in situ hybridization analysis was done to identify which sex chromosome was possibly lost.

RESULTS

The LOH frequency in female CRCs was 46% with higher incidence in patients with tumor recurrence than in those who were disease-free (P < 0.01) and with a significant difference from adenomas (11%; P < 0.0001). The LOH rate of PARs in male CRCs was 37% with a frequency significantly higher in patients with recurrence (P < 0.03). These results were maintained also when data from PARs of all 66 male and female patients were cumulated (P < 0.05). LOH in PARs was significantly correlated with LOH at 5q (P < 0.01) and 18q (P < 0.01), early and late events, respectively, in colorectal carcinogenesis. Fluorescence in situ hybridization analysis in male patients with extensive PAR LOH revealed a preferential loss of the Y chromosome.

CONCLUSIONS

Our data suggest a role for sex chromosome deletions in the malignant progression of sporadic CRCs and support the presence in the PARs of putative tumor suppressor genes involved in the progression of human sporadic CRCs.

Decreased CHK protein levels are associated with Src activation in colon cancer cells

Src activation has been associated with colon cancers but the mechanism underlying Src activation is largely unknown. Csk-homologous kinase (CHK) can inhibit the kinase activity of certain Src kinase family members in vitro by phosphorylating the C-terminal tyrosine and by a non-catalytic mechanism. CHK was previously reported to be expressed primarily in brain and hematopoietic cells. We report herein that CHK is also expressed in normal colon cell lines. Furthermore, CHK protein levels are significantly decreased in various colon cancer cell lines and the decrease correlates with the increased specific activity of Src in these cell lines, while the level of the other Src inhibitory kinase, C-terminal Src kinase, is not significantly changed. CHK is also expressed in normal colon tissues but its expression level is decreased in colon cancer tissues collected from the same patients. Immunofluorescence microscopy shows that CHK colocalizes with Src in normal colon FHC cells. Overexpression of CHK in colon cancer cells results in inactivation of Src without phosphorylating Y530 at its C-terminus. In addition, CHK suppresses anchorage-independent cell growth and cell invasion of colon cancer cells. These results reveal a potentially important role for CHK in Src activation and tumorigenicity in colon cancer cells.

Epigenetic changes (aberrant DNA methylation) in colorectal neoplasia

Both genetic and epigenetic events have been implicated in the stepwise histological progression involving adenoma-carcinoma and hyperplastic polyp/serrated adenoma-carcinoma sequences in the development of colorectal cancer. Genetic changes have been observed at each step in the initiation and progression of polyps to adenocarcinomas. Epigenetic changes also occur at each step in the pathogenesis of colorectal cancers and include CpG island DNA hypermethylation in the promoter region of genes resulting in transcriptional silencing through associated changes in chromatin structure and effects on binding of transcription factors, and DNA global hypomethylation which leads to chromosomal instability. Recent studies on MLH1 and APC genes indicate that epigenetic and genetic changes cooperate to facilitate tumor initiation and progression. Since aberrant CGI DNA promoter hypermethylation can be detected not only in colorectal polyps and cancers, but also in sera and stool, hypermethylated genes may serve as molecular markers for early detection, risk assessment and diagnosis. In addition, silenced genes caused by CGI DNA promoter hypermethylation can be reactivated by demethylating agents and also by both the inhibitors of DNA methyltransferases and histone deacetylases. Therefore, these epigenetically acting drugs should be evaluated for their chemopreventive and therapeutic potential for colorectal cancers.

MLH1 -93G>A promoter polymorphism and the risk of microsatellite-unstable colorectal cancer

BACKGROUND

Although up to 30% of patients with colorectal cancer have a positive family history of colorectal neoplasia, few colorectal cancers can be explained by mutations in high-penetrance genes. We investigated whether polymorphisms in DNA mismatch repair genes are associated with the risk of colorectal cancer.

METHODS

We genotyped 929 case patients and 1098 control subjects from Ontario and 430 case patients and 275 control subjects from Newfoundland and Labrador for five polymorphisms in the mismatch repair genes MLH1 and MSH2 with the fluorogenic 5' nuclease assay. Tumor microsatellite instability (MSI) was determined with a polymerase chain reaction-based method; MSI status was assigned as high (MSI-H, > or = 30% unstable markers among all markers tested), low (MSI-L, <30% markers unstable), or stable (MSS, no unstable markers). We used unconditional logistic regression to evaluate the association between each polymorphism and colorectal cancer after adjusting for age and sex. The associations between polymorphisms and tumor clinicopathologic features were evaluated with a Pearson's chi-square or Fisher's exact test. All statistical tests were two-sided.

RESULTS

We observed strong associations between the MLH1 -93G>A polymorphism and MSI-H tumors among case patients from Ontario (P = .001) and Newfoundland (P = .003). When compared with the control populations, homozygosity for the MLH1 -93G>A variant allele was associated with MSI-H tumors among case patients in Ontario (adjusted odds ratio [OR] = 3.23, 95% confidence interval [CI] = 1.65 to 6.30) and in Newfoundland (OR = 8.88, 95% CI = 2.33 to 33.9), as was heterozygosity among case patients in Ontario (OR = 1.84, 95% CI = 1.20 to 2.83) and in Newfoundland (OR = 2.56, 95% CI = 1.14 to 5.75). Genotype frequencies were similar among case patients with MSS and MSI-L tumors and control subjects, and the majority of homozygous variant carriers had MSS tumors. Among case patients from Ontario, an association between the MLH1 -93G>A polymorphism and a strong family history of colorectal cancer (for Amsterdam criteria I and II, P = .004 and P = .02, respectively) was observed.

CONCLUSION

In two patient populations, the MLH1 -93G>A polymorphism was associated with an increased risk of MSI-H colorectal cancer.

The modifier of Min 2 (Mom2) locus: embryonic lethality of a mutation in the Atp5a1 gene suggests a novel mechanism of polyp suppression

Inactivation of the APC gene is considered the initiating event in human colorectal cancer. Modifier genes that influence the penetrance of mutations in tumor-suppressor genes hold great potential for preventing the development of cancer. The mechanism by which modifier genes alter adenoma incidence can be readily studied in mice that inherit mutations in the Apc gene. We identified a new modifier locus of ApcMin-induced intestinal tumorigenesis called Modifier of Min 2 (Mom2). The polyp-resistant Mom2R phenotype resulted from a spontaneous mutation and linkage analysis localized Mom2 to distal chromosome 18. To obtain recombinant chromosomes for use in refining the Mom2 interval, we generated congenic DBA.B6 ApcMin/+, Mom2R/+ mice. An intercross revealed that Mom2R encodes a recessive embryonic lethal mutation. We devised an exclusion strategy for mapping the Mom2 locus using embryonic lethality as a method of selection. Expression and sequence analyses of candidate genes identified a duplication of four nucleotides within exon 3 of the alpha subunit of the ATP synthase (Atp5a1) gene. Tumor analyses revealed a novel mechanism of polyp suppression by Mom2R in Min mice. Furthermore, we show that more adenomas progress to carcinomas in Min mice that carry the Mom2R mutation. The absence of loss of heterozygosity (LOH) at the Apc locus, combined with the tendency of adenomas to progress to carcinomas, indicates that the sequence of events leading to tumors in ApcMin/+ Mom2R/+ mice is consistent with the features of human tumor initiation and progression.

DNA repair pathways and mitochondrial DNA mutations in gastrointestinal carcinogenesis

This work focuses on the main DNA repair pathways, highlighting their role in gastrointestinal carcinogenesis and the role of mitochondrial DNA (mtDNA), mutations being described in several tumor types, including those of the gastrointestinal tract. The mismatch repair (MMR) system is inherently altered in patients with hereditary non-polyposis colorectal cancer, and plays a role in carcinogenesis in a subset of sporadic colorectal, gastric and esophageal cancers. Alterations in homologous recombination (HR) and non-homologous end-joining (NHEJ) also contribute to the development of pancreatic cancer. Gene polymorphisms of some X-ray cross-complementing (XRCCs), cofactor proteins involved in the base excision repair pathway, have been investigated in relation to gastric, colorectal and pancreatic cancer. Yet only one polymorphism, XRCC1 Arg194Trp, appears to be involved in smoking-related cancers and in early onset pancreatic cancer. Although evidence in the literature indicates that mtDNA somatic mutations play a role in gastric and colorectal carcinogenesis, no sound conclusions have yet been drawn regarding this issue in pancreatic cancer, although an mtDNA variant at 16519 is believed to worsen the outcome of pancreatic cancer patients, possibly because it is involved in altering cellular metabolism.

The metastasis-associated gene S100A4 is a novel target of beta-catenin/T-cell factor signaling in colon cancer

BACKGROUND & AIMS

Activation of the Wnt/beta-catenin pathway is frequently observed in colorectal cancers. Our aim was to elucidate the impact of gain-of-function beta-catenin on the metastasis-associated gene S100A4 in human colon cancer cell lines and tumors.

METHODS

We analyzed cell lines heterozygous for gain-of-function and wild-type beta-catenin, and variants homozygous for gain- or loss-of-function mutation in beta-catenin, for S100A4 expression, cell motility, and in vivo metastasis. beta-catenin-mediated S100A4 promoter activation was tested by reporter assays. For human colon carcinomas, S100A4 expression, beta-catenin genotype, and metachronous metastasis were correlated.

RESULTS

We identified S100A4 as the most regulated gene by gain-of-function beta-catenin using a 10K microarray. Cell lines with gain-of-function beta-catenin expressed up to 60-fold elevated S100A4 levels, displayed strongly increased migration and invasion in vitro, and induced metastasis in mice. S100A4 small interfering RNA, beta-catenin small interfering RNA, or dominant negative T-cell factor (TCF) knocked down S100A4 and blocked biological effects. S100A4 complementary DNA transfection increased migration and invasion. We identified a TCF binding site within the S100A4 promoter and demonstrated the direct binding of heterodimeric beta-catenin/TCF complexes. Reporter assays confirmed the beta-catenin-induced S100A4 promoter activity. Furthermore, S100A4 mRNA expression was increased in primary colon cancers, which later developed distant metastases, compared to non-metastasizing tumors. Colon tumors heterozygous for gain-of-function beta-catenin showed concomitant nuclear beta-catenin localization, high S100A4 expression, and metastases.

CONCLUSIONS

S100A4 is a direct beta-catenin/TCF target, induces migration and invasion in vitro and metastasis in vivo, and has value for prognosis of metastasis formation in colon cancer patients.

Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward

This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.

Modelling aspects of cancer dynamics: a review

Cancer is a complex disease in which a variety of factors interact over a wide range of spatial and temporal scales with huge datasets relating to the different scales available. However, these data do not always reveal the mechanisms underpinning the observed phenomena. In this paper, we explain why mathematics is a powerful tool for interpreting such data by presenting case studies that illustrate the types of insight that realistic theoretical models of solid tumour growth may yield. These range from discriminating between competing hypotheses for the formation of collagenous capsules associated with benign tumours to predicting the most likely stimulus for protease production in early breast cancer. We will also illustrate the benefits that may result when experimentalists and theoreticians collaborate by considering a novel anti-cancer therapy.

Low somatic K-ras mutation frequency in colorectal cancer diagnosed under the age of 45 years

Somatic mutation of K-ras is known to be a common event in colorectal cancer tumourigenesis however its association with age at onset has not been widely explored. In this study, we have analyzed tumours from a population-based study of colorectal cancer diagnosed before the age of 45 years, in which cases had been previously screened for germ-line mismatch repair gene mutations and for microsatellite instability. We used a micro-dissection and sequencing approach to search for somatic K-ras mutations in codons 12, 13 and 61 in 101 early-onset colorectal cancers. Six (6%) somatic K-ras mutations were detected; five in codon 12 (4 G>T transitions and 1 G>A) and one in codon 13 (G>A transition). All codon 12 mutations were identified in microsatellite stable tumours and the codon 13 mutation was identified in a MSI-high tumour. Four cases with K-ras mutations had no reported family history of colorectal cancer and two had some family history of colorectal cancer. None were known to carry a germ-line mutation in hMSH2, hMLH1, hMSH6 or hPMS2. The role of somatic K-ras mutations in early-onset colorectal cancer carcinogenesis appears to be minor, in contrast to its significant role in colorectal cancer of later age of onset.

c-Myc, genome instability, and tumorigenesis: the devil is in the details

The c-myc oncogene acts as a pluripotent modulator of transcription during normal cell growth and proliferation. Deregulated c-myc activity in cancer can lead to excessive activation of its downstream pathways, and may also stimulate changes in gene expression and cellular signaling that are not observed under non-pathological conditions. Under certain conditions, aberrant c-myc activity is associated with the appearance of DNA damage-associated markers and karyotypic abnormalities. In this chapter, we discuss mechanisms by which c-myc may be directly or indirectly associated with the induction of genomic instability. The degree to which c-myc-induced genomic instability influences the initiation or progression of cancer is likely to depend on other factors, which are discussed herein.

Colon cancer and apoptosis

BACKGROUND

The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells.

DATA SOURCES

Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article.

CONCLUSION

Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

Evidence for alternative candidate genes near RB1 involved in clonal expansion of in situ urothelial neoplasia

In this paper, we present whole-organ histologic and genetic mapping studies using hypervariable DNA markers on chromosome 13 and then integrate the recombination- and single-nucleotide polymorphic sites (SNPs)-based deletion maps with the annotated genome sequence. Using bladders resected from patients with invasive urothelial carcinoma, we studied allelic patterns of 40 microsatellite markers mapping to all regions of chromosome 13 and 79 SNPs located within the 13q14 region containing the RB1 gene. A whole-organ histologic and genetic mapping strategy was used to identify the evolution of allelic losses on chromosome 13 during the progression of bladder neoplasia. Markers mapping to chromosomal regions involved in clonal expansion of preneoplastic intraurothelial lesions were subsequently tested in 25 tumors and 21 voided urine samples of patients with bladder cancer. Four clusters of allelic losses mapping to distinct regions of chromosome 13 were identified. Markers mapping to the 13q14 region that is flanked by D13S263 and D13S276, which contains the RB1 gene, showed allelic losses associated with early clonal expansion of intraurothelial neoplasia. Such losses could be identified in approximately 32% bladder tumor tissue samples and 38% of voided urines from patients with bladder cancer. The integration of distribution patterns of clonal allelic losses revealed by the microsatellite markers with those obtained by genotyping of SNPs disclosed that the loss within an approximately 4-Mb segment centered around RB1 may represent an incipient event in bladder neoplasia. However, the inactivation of RB1 occurred later and was associated with the onset of severe dysplasia/carcinoma in situ. Our studies provide evidence for the presence of critical alternative candidate genes mapping to the 13q14 region that are involved in clonal expansion of neoplasia within the bladder antecedent to the inactivation of the RB1 gene.

Phenotype–genotype correlation: Challenge of intestinal-type adenocarcinoma of the nasal cavity and paranasal sinuses

BACKGROUND

Intestinal-type adenocarcinoma (ITAC) of the nasal cavity and paranasal sinuses shows microscopic features indistinguishable from colorectal cancer. Our aim was to verify whether the morphologic resemblances mirror genetic profile similarities.

METHODS

Twenty consecutive surgically treated ITAC cases, previously investigated for p16(INK4a) and TP53, were investigated for hMLH1, hMSH2, and beta-catenin immunoreactivity, and for adenomatous polyposis coli (APC), K-ras, and BRAF gene mutations.

RESULTS

One case was immunonegative for both hMLH1 and hMSH2, and 12 tumors (40%) revealed a strong beta-catenin overexpression. No BRAF and APC truncating mutations were identified, whereas K-ras mutations were detected in 9 ITACs (50%).

CONCLUSIONS

Our data confirm the phenotypic similarities at the genetic level between colorectal cancer and ITACs showing deregulation of K-Ras/BRAF and loss of heterozygosity (LOH) of chromosome 18q. By contrast, both frequency rate and type of inactivation of the APC-beta-catenin pathway differ in the 2 tumors, suggesting different gatekeeper events in the early development of ITAC (p16(INK4a) and TP53) and colorectal cancer (APC).

Opinion: the origin of the cancer stem cell: current controversies and new insights

Most tumours are derived from a single cell that is transformed into a cancer-initiating cell (cancer stem cell) that has the capacity to proliferate and form tumours in vivo. However, the origin of the cancer stem cell remains elusive. Interestingly, during development and tissue repair the fusion of genetic and cytoplasmic material between cells of different origins is an important physiological process. Such cell fusion and horizontal gene-transfer events have also been linked to several fundamental features of cancer and could be important in the development of the cancer stem cell.

Emerging role of KLF4 in human gastrointestinal cancer

Recent analyses revealed that Krüppel-like factors (KLFs) play important roles in both normal development and carcinogenesis. Of the 16 known KLFs, KLF4 has been shown to be involved in the regulation of proliferation, differentiation and tumorigenesis of gastrointestinal tract epithelium. Clinical, experimental and mechanistic findings indicate that KLF4 is a bona fide tumor suppressor for both gastric and colorectal cancers. In this review, we summarize how this growing area of research has formed and the challenging new frontiers for better understanding of the oncogenic potential of the KLFs.

Overexpression of CD10 and reduced MUC2 expression correlate with the development and progression of colorectal neoplasms

There are two opposing theories of the natural history of colorectal neoplasm, adenoma-carcinoma sequence and de novo carcinogenesis. To elucidate the histogenesis of colorectal carcinoma, we investigated the expression of CD10, MUC2, MUC5AC, MUC6, and p53 in colorectal neoplasms. Sixty-seven morphologically distinct neoplastic specimens were divided into the following groups according to morphology: adenoma (groups A and B), protruded-type carcinoma (group C), superficial-type carcinoma with adenomatous component (group D), or superficial-type carcinomas without any adenomatous component (group E). Diagnoses of adenomas and carcinomas were based upon the Vienna classification of gastrointestinal epithelial neoplasia. The expression of CD10 in group E lesions was more intense than in the other groups. Regardless of morphology, MUC2 expression was significantly decreased in CD10-positive carcinomas, and the p53-positive rate was much higher in CD10-positive than in CD10-negative carcinomas. The overexpression of CD10 and reduced expression of MUC2 may be associated with the development and progression of colorectal carcinoma. A specific tendency was evident in superficial-type carcinomas without any adenomatous component (de novo carcinomas). These carcinomas are considered to be more aggressive than other morphologically distinct carcinomas.

Identification of predictive factors for the occurrence of predisposing MLH1 and MSH2 germline mutations among Sardinian patients with colorectal carcinoma

Factors predictive of carrying MLH1 and MSH2 germline mutations in patients with colorectal cancer (CRC) are as yet unknown. The aim of this population-based study, was to further define the role of MLH1/MSH2 mutations through an evaluation clinic program with 362 consecutive Sardinian CRC patients. Eight MLH1/MSH2 germline mutations were detected in 21 (6%) patients. Examining family cancer history, MLH1/MSH2 mutations were found in 14/48 (29.2%) probands from CRC families and, among them, in 10/13 (76.9%) families fulfilling the Amsterdam criteria. The patients with low familial recurrence (two CRCs in the family) presented a much lower frequency of MLH1/MSH2 mutations (2/55; 3.6%). Significantly higher rates of MLH1/MSH2 mutations were found in patients with age of onset 45 years (P=0.012) or with 3 affected family members (P=0.009). While no significant predictive value was found for the presence of endometrial cancer within the family, earlier age of diagnosis and/or familial CRC recurrence should be considered as strong predictors for the occurrence of MLH1/MSH2 mutations, and therefore useful in recommending CRC patients for genetic testing.

High-resolution whole-organ mapping with SNPs and its significance to early events of carcinogenesis

We attempted to identify deleted segments in two model tumor suppressor gene loci on chromosomes 13q14 and 17p13 that were associated with clonal expansion of in situ bladder preneoplasia using single nucleotide polymorphisms (SNPs)-based whole-organ histologic and genetic mapping. For mapping with SNPs, the sequence-based maps spanning approximately 27 and 5 Mb centered around RB1 and p53, respectively, were assembled. The integrated gene and SNP maps of the regions were used to select 661 and 960 SNPs, which were genotyped by pyrosequencing. Genotyping of SNPs was performed on DNA samples corresponding to histologic maps of the entire bladder mucosa in human cystectomy specimens with invasive urothelial carcinoma. By using this approach, we have identified deleted regions associated with clonal expansion of intraurothelial neoplasia; which ranged from 0.001 to 4.3 Mb (average 0.67 Mb) and formed clusters of discontinuous deleted segments. The high resolution of such maps is a prerequisite for future positional targeting of genes involved in early phases of bladder neoplasia. This approach also permits analysis of the overall genomic landscape of the involved region and discloses that a unique composition of noncoding DNA characterized by a high concentration of repetitive sequences may predispose to deletions.

Molecular cytogenetic characterization of tenosynovial giant cell tumors

Tenosynovial giant cell tumor (TSGCT) is a disease of disputed etiology and pathogenesis. Some investigations indicate a neoplastic origin of the tumors; others indicate that they are polyclonal and inflammatory. The cytogenetic and molecular genetic features of TSGCTs are largely unknown, as only some 20 localized and 30 diffuse tumors with cytogenetic aberrations have been reported. The most common karyotypic aberrations have been trisomy for chromosomes 5 and 7 and translocations involving chromosomal area 1p11-13. We decided to screen the genomes of TSGCTs by comparative genomic hybridization (CGH) to perform interphase fluorescence in situ hybridization (IP-FISH), looking for numerical aberrations of chromosomes 1, 5, and 7, and to analyze the tumors for microsatellite instability. Except for two diffuse TSGCTs that came fresh to us, and which, by karyotyping, exhibited t(1;22)(p13;q12) and a t(1;1)(q21;p11) and +7, respectively, all studies had to be performed on formalin-fixed, paraffin-embedded material. DNA was extracted from 51 localized and nine diffuse TSGCTs. CGH was successful for 24 tumors, but none of them showed copy number changes. The IP-FISH studies showed trisomy 7 in 56% of the tumors (15/27), whereas chromosomes 1 and 5 seemed to be disomic in all TSGCTs. All informative tumors were wild-type by microsatellite instability analysis.

Sporadic colorectal cancer – role of the commensal microbiota

There are vast numbers of bacteria present within the human colon that are essential for the host's well being in terms of nutrition and mucosal immunity. While certain members of the colonic microbiota have been shown to promote the host's health there are also numerous studies that have implicated other members of the colonic microbiota in the development of colorectal cancer, a prominent malignancy within the western world. In this review we consider the evidence for the role of bacteria in colorectal cancer from molecular and animal model studies. We focus on some of the mechanisms by which the colonic microbiota drives the progression towards colorectal malignancy including generation of reactive metabolites and carcinogens, alterations in host carbohydrate expression and induction of chronic mucosal inflammation.

Colorectal cancer prevention

Colorectal cancer is the second leading cause of mortality in the United States. In the United States, the cumulative lifetime risk of developing colorectal cancer for both men and women is 6%. Despite advances in the management of this disease, the 5-year survival rate in the United States in only 62%. Because only 38% of patients are diagnosed when the cancers are localized to the bowel wall, it is likely that widespread implementation of screening could significantly improve the outcome. Colorectal cancer screening is cost effective, irrespective of the methods used. In addition to currently available methods (fecal occult blood, flexible sigmoidoscopy, colonoscopy, and double contrast barium enema), computed tomographic colonography (virtual colonoscopy) and stool-based molecular screening are under development. Four classes of chemopreventive compounds have demonstrated efficacy in reducing recurrent colorectal adenomas and/or cancer in randomized, controlled trials. They are selenium, calcium carbonate, hormone replacement therapy, and nonsteroidal anti-inflammatory drugs. The mechanisms of action of nonsteroidal anti-inflammatory drugs include inhibition of the cyclooxygenase system as well as cyclooxygenase-independent effects. Considerable effort is being expended to define chemopreventive activity, optimal dose, administration schedule, and toxicity for the coxibs in adenoma recurrence prevention trials. The threshold for tolerating toxicities is very low in asymptomatic individuals at minimally increased risk for colorectal neoplasia.

Lessons from TRAIL-resistance mechanisms in colorectal cancer cells: paving the road to patient-tailored therapy

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Intrinsic, as well as acquired, resistance to chemotherapy remains a major problem in the treatment of this disease. It is, therefore, of great importance to develop new, patient-tailored, treatment strategies for colorectal cancer patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) acts through the pro-apoptotic DR4 and DR5 receptors in tumor cells without harming normal cells and will soon be tested in clinical trials as a novel anti-cancer agent. However, not all human colon cancer cell lines are sensitive to TRAIL due to intrinsic or acquired TRAIL-resistance. This review discusses the mechanisms and modulation of TRAIL-resistance in colon cancer cells. Cell sensitivity to TRAIL can be affected by TRAIL-receptor expression at the cell membrane, DR4/DR5 ratio and functionality of TRAIL-receptors. Additional intracellular factors leading to TRAIL-resistance affect the caspase 8/c-FLIP ratio, such as loss of caspase 8 and caspase 10 due to mutations or gene methylation, CARP-dependent degradation of active caspase 8 and changes in caspase 8 or c-FLIP expression levels. Further downstream in the TRAIL apoptotic pathway, Bax mutations, or increased expression of IAP family members, in particularly XIAP and survivin, also cause resistance. Chemotherapeutic drugs, NSAIDs, interferon-gamma and proteasome inhibitors can overcome TRAIL-resistance by acting on TRAIL-receptor expression or changing the expression of pro- or anti-apoptotic proteins.

Prevention and therapy of colorectal cancer

Colorectal cancer is expected to affect more than 146,000 and kill more than 57,000 Americans in 2004. Increased understanding of carcinogenesis is transforming clinical approaches to all stages of this disease. During the last 5 years, four new drugs have been approved for colorectal cancer treatment, and substantial progress has been made in identifying and developing agents that prevent or delay carcinogenesis. These advances substantiate target-driven approaches to cancer prevention and treatment, and provide fruitful opportunities for future investigations.

Liver fatty acid binding protein expression in colorectal neoplasia

Liver fatty acid binding protein is a member of the fatty acid binding group of proteins that are involved in the intracellular transport of bioactive fatty acids and participate in intracellular signalling pathways, cell growth and differentiation. In this study we have used proteomics and immunohistochemistry to determine the changes in liver fatty acid binding protein in colorectal neoplasia. Comparative proteome analysis of paired samples colorectal cancer and normal colon identified consistent loss of liver fatty acid binding protein (L-FABP) in colorectal cancer compared with normal colon. To identify the changes in liver fatty acid binding protein expression during colorectal cancer development and progression the cell-specific expression of L-FABP was determined by immunohistochemistry in a series of colorectal cancers and colorectal adenomas. Decreased L-FABP immunoreactivity was significantly associated with poorly differentiated cancers (P<0.001). In colorectal adenomas there was a significant trend towards decreased staining of L-FABP in the larger adenomas (P<0.001). There was consistent L-FABP immunostaining of normal surface colonocytes. This study demonstrates that loss of L-FABP occurs at the adenoma stage of colorectal tumour development and also indicates that L-FABP is a marker of colorectal cancer differentiation.

Colorectal cancer chemoprevention--an overview of the science

The development and dissemination of sophisticated detection technologies have recently exposed the high prevalence of preinvasive colorectal neoplasia in the adult U.S. population. Although cancer screening and surveillance provide opportunities for risk stratification, they achieve risk reduction only when coupled with effective interventions. This review surveys the lead compounds for colorectal cancer prevention and the measures by which they may be prioritized for clinical testing. Clinical trials remain the rate-limiting step in agent development, and novel trial designs are needed to hasten agent identification and testing for cancer prevention. Innovative research models include the nesting of prevention end points within cancer treatment trials and within trials testing promising preventive compounds intended for nononcologic indications.

Promoter Methylation Inhibits APC Gene Expression by Causing Changes in Chromatin Conformation and Interfering with the Binding of Transcription Factor CCAAT-Binding Factor

As an important regulator in Wnt-signaling pathway, the APC gene is involved in apoptosis and cell cycle arrest. The loss of APC function is observed in most familial adenomatous polyposis-associated and sporadic colorectal cancer. APC gene is frequently inactivated by DNA mutations. However, hypermethylation in APC gene promoter was also observed in different cancers. In this study, by analyzing the methylation status of APC promoter in 22 colorectal cancer cell lines with different APC expression levels, we identified Regions A and B in the promoter, where the methylation of CpG sites was invariably correlated with the loss of gene expression. By nuclease accessibility assay, we also observed a correlation between the closed chromatin conformation in APC promoter and loss of gene expression. When the nonexpressing cell lines were treated with a DNA methyltransferase inhibitor, 5-Aza-2'-Deoxycytidine, the APC expression in these cells was induced, CpG sites were demethylated, and closed chromatin conformation was opened. However, when these cell lines were treated with a histone deacetylase inhibitor, Trichostatin A, no significant changes in APC expression, methylation status, and chromatin conformation were observed. Using transient transfection assay, a CCAAT box located in Region B was identified, which was involved in up-regulation of APC expression. Methylation of CpG sites around the CCAAT box resulted in a significant inhibition in the gene expression. The specific binding of a transcription factor CCAAT-binding factor (CBF) to the CCAAT box was determined by electrophoretic mobility shift analysis. The binding was inhibited after CpG sites close to the CCAAT box were methylated, indicating that DNA methylation can silence gene expression through interfering with the binding of transcription factors to the promoter. The biological function of CBF in APC gene regulation was further indicated by the decrease of luciferase activities in cells cotransfected with a plasmid carrying APC promoter/luciferase gene and a plasmid expressing dominant negative CBF mutant. In summary, methylation of CpG sites around CCAAT box in APC promoter inhibits the gene expression by changing the chromatin conformation and interfering with the binding of transcription factor CBF to CCAAT box.

Identification of a novel candidate gene,CASC2, in a region of common allelic loss at chromosome 10q26 in human endometrial cancer

Allelic deletions, which are suggestive for the presence of tumor suppressor genes, represent a common event in endometrial cancer (EC). Previous loss-of-heterozygosity studies for human chromosome 10q identified a candidate deletion interval at 10q25-q26, which we further narrowed to a 160-kb region at 10q26, bounded by markers D10S1236 and WIAF3299. Using a positional candidate approach, we identified three alternative transcripts of a novel human gene, CASC2 (cancer susceptibility candidate 2; formely C10orf5). One of such transcripts, CASC2a, encodes a short protein of 102 amino acids with no similarity to any other known gene product. Three (7%) CASC2a mutations were identified in tumor DNA from 44 EC patients. While c.-156G>T and c.22C>T (p.Pro8Ser) are sequence variants with unknown functional significance, c.84delA is a mutation with a truncation effect on the predicted protein (p. Asn28fsX50). Expression studies by real-time RT-PCR on several normal and tumor cells revealed that CASC2a mRNA is downregulated in cancer, suggesting that it may act as a potential tumor suppressor gene. The very low mutation rate seems to also indicate that inactivation of CASC2a might probably be due to mechanisms different from genetic alterations.

Microsatellite instability and mutation analysis among southern Italian patients with colorectal carcinoma: detection of different alterations accounting for MLH1 and MSH2 inactivation in familial cases

BACKGROUND

Microsatellite instability (MSI) is due to defective DNA mismatch repair (MMR) and has been detected at various rates in colorectal carcinoma (CRC). The role of MSI in colorectal tumorigenesis was assessed further in this study by both microsatellite analysis of two CRC subsets [unselected patients (n = 215) and patients <50 years of age (n = 95)], and mutation screening of the two major MMR genes MLH1 and MSH2 among familial CRC cases.

PATIENTS AND METHODS

PCR-based microsatellite analysis was performed on paraffin-embedded tissues. In CRC families, MLH1/MSH2 mutation analysis and MLH1/MSH2 immunostaining were performed on germline DNA and MSI+ tumour tissues, respectively.

RESULTS

The MSI+ phenotype was detected in 75 (24%) patients, with higher incidence in early-onset or proximally located tumours. Among 220 patients investigated for family cancer history, MSI frequency was markedly higher in familial [18/27 (67%)] than in sporadic [32/193 (17%)] cases. Three MLH1 and six MSH2 germline mutations were identified in 14 out of 36 (39%) CRC families. Prevalence of MLH1/MSH2 mutations in CRC families was significantly increased by the presence of: (i) fulfilled Amsterdam criteria; (ii) four or more CRCs; or (iii) one or more endometrial cancer. While MSH2 was found mostly mutated, almost all [8/9 (89%)] familial MSI+ cases with loss of the MLH1 protein were negative for MLH1 germline mutations.

CONCLUSIONS

Both genetic (for MSH2) and gene-silencing (for MLH1) alterations seem to be involved in CRC pathogenesis.

Identification of Krüppel-like factor 4 as a potential tumor suppressor gene in colorectal cancer

Krüppel-like factor 4 (KLF4 or GKLF) is an inhibitor of the cell cycle. The gene encoding KLF4 is localized on chromosome 9q, previously shown to exhibit allelic loss in colorectal cancer (CRC). In this study, we show that the mean level of KLF4 mRNA in a panel of 30 CRC was 52% that of paired normal colonic tissues. Similarly, the levels of KLF4 mRNA and protein in a panel of six established CRC cell lines were significantly lower than those of an untransformed colonic epithelial cell line. Using highly polymorphic DNA markers that flank the KLF4 locus, we found evidence for loss of heterozygosity (LOH) in two of eight surgically resected CRC specimens. In addition, LOH was observed in five of six CRC cell lines with one additional cell line exhibiting hemizygous deletion in the KLF4 gene. We also found that the 5'-untranslated region of KLF4 was hypermethylated in a subset of resected CRC specimens and cell lines. Lastly, the open-reading frame of KLF4 in two of three CRC cell lines examined contained several point mutations that resulted in a diminished ability to activate the p21(WAF1/Cip1) promoter. These findings indicate that KLF4 is a potential tumor suppressor gene in CRC.

Role of APC and DNA mismatch repair genes in the development of colorectal cancers

Colorectal cancer is the third most common cause of cancer-related death in both men and women in the western hemisphere. According to the American Cancer Society, an estimated 105,500 new cases of colon cancer with 57,100 deaths will occur in the U.S. in 2003, accounting for about 10% of cancer deaths. Among the colon cancer patients, hereditary risk contributes approximately 20%. The main inherited colorectal cancers are the familial adenomatous polyposis (FAP) and the hereditary nonpolyposis colorectal cancers (HNPCC). The FAP and HNPCC are caused due to mutations in the adenomatous polyposis coli (APC) and DNA mismatch repair (MMR) genes. The focus of this review is to summarize the functions of APC and MMR gene products in the development of colorectal cancers.

Differential modulation of the TRAIL receptors and the CD95 receptor in colon carcinoma cell lines

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95 ligand (CD95L) are potent inducers of apoptosis in various tumour cell types. Death receptors DR4 and DR5 can induce and decoy receptors DcR1 and DcR2 can inhibit TRAIL-mediated apoptosis. The study aim was to investigate whether anticancer agents can modulate similarly TRAIL-receptor and CD95 membrane expression and TRAIL and CD95L sensitivity. Three colon carcinoma cell lines (Caco-2, Colo320 and SW948) were treated with 5-fluorouracil (5-FU), cisplatin or interferon-gamma. TRAIL-receptor and CD95 membrane expression was determined flow cytometrically. Sensitivity to TRAIL or CD95L agonistic anti-CD95 antibody was determined with cytotoxicity and apoptosis assays. SW948 showed highest TRAIL sensitivity. The protein synthesis inhibitor cycloheximide decreased FLICE-like inhibitory protein levels in all cell lines, and the TRAIL-resistant cell lines Caco-2 and Colo320 became sensitive for TRAIL. Exposure of the cell lines to 5-FU, cisplatin and interferon-gamma left TRAIL-receptor membrane expression and TRAIL sensitivity unaffected. CD95 membrane expression and anti-CD95 sensitivity was, however, modulated by the same drugs in all lines. Cisplatin and interferon-gamma raised CD95 membrane levels 6-8-fold, interferon-gamma also increased anti-CD95 sensitivity. These results indicate that the CD95 and TRAIL pathways use different mechanisms to respond to various anticancer agents. Induced CD95 membrane upregulation was associated with increased anti-CD95 sensitivity, whereas no upregulation of TRAIL-receptor membrane expression or TRAIL sensitisation could be established. For optimal use of TRAIL-mediated apoptosis for cancer therapy in certain tumours, downregulation of intracellular inhibiting factors may be required.

Distinct chromosomal imbalances in nonpolypoid and polypoid colorectal adenomas indicate different genetic pathways in the development of colorectal neoplasms

Cytogenetic changes are widely unknown for nonpolypoid (synonymously termed as "flat" or "depressed") colorectal adenomas. A comparison with polypoid adenomas will contribute to the discussion whether different genetic pathways for colorectal tumorigenesis depending on its origin from nonpolypoid or polypoid adenomas exist. Tissue samples of nonpolypoid (n = 22), polypoid (n = 28) adenomas, carcinomas ex-nonpolypoid adenomas (n = 9), carcinomas ex-polypoid adenomas (n = 14), and normal colonic mucosa (n = 9) were investigated by comparative genomic hybridization of whole genomic DNA. Chromosomal imbalances were detected from average comparative genomic hybridization profiles for each entity. Nonpolypoid adenomas show recurrent chromosomal losses on chromosomes 16, 17p, 18, 20, and 22 and gains on chromosomes 2q, 4q, 5, 6, 8q, 12q, and 13q. In polypoid adenomas losses of whole chromosomes 16, 18, and 22 and gains of chromosomes 7q and 13 were detected. The frequency of copy number changes was higher in nonpolypoid compared to polypoid adenomas and early onset of chromosomal changes became apparent in low-grade dysplasias of nonpolypoid adenomas. Gains on chromosomes 2q, 5, 6, 8q, and 12q and losses on chromosomes 17p and 20 occurred exclusively in nonpolypoid adenomas, whereas 16p deletions are significantly more frequent in nonpolypoid than in polypoid adenomas. Carcinomas ex-nonpolypoid adenomas are characterized by more complex aberration patterns compared to nonpolypoid adenomas exhibiting frequent losses on chromosomes 8p, 12q, 14, 15q, 16, 17p, 18, and 22 and gains on 3q, 5, 6, 7, 8q, 12q, and 13, respectively. Normal colonic mucosa showed no chromosomal imbalances. Distinct differences of chromosomal imbalances between nonpolypoid and polypoid colorectal adenomas have been characterized that support the hypothesis that different genetic pathways may exist in the development of colorectal adenomas exhibiting nonpolypoid and polypoid phenotype.

Changes in apoptosis during the development of colorectal cancer: a systematic review of the literature

The development of colorectal cancer is characterised by an accumulation of molecular genetic alterations causing disorders in cell growth, differentiation and apoptosis. Although changes in apoptosis with colorectal cancer development have been studied extensively, a clear consensus of opinion has not yet emerged. In this review, the literature about changes in the frequency and distribution of apoptosis in tissue sections of normal and neoplastic colorectal tissues was reviewed systematically. Using a PUBMED search, 53 relevant articles were identified. Data from these studies are discussed with respect to the following aspects: methods used to detect apoptotic cell death; frequency and locoregional distribution of apoptosis in normal mucosa, adenomas and carcinomas; the correlation between levels of apoptosis and proliferation and the prognostic significance of the degree of apoptosis in colorectal cancer. Possible underlying mechanisms of dysregulation of apoptosis are discussed briefly. Finally, possible therapeutic implications of knowledge of the molecular regulation of apoptosis are discussed and potential options for further research are suggested.

Chromosomal abnormalities and microsatellite instability in sporadic endometrial cancer

Defective DNA mismatch repair and nonfunctional mechanisms controlling the proper progression of the cell cycle have been proposed as being responsible for the genomic instability and accumulation of karyotypic alterations in endometrial cancer (EC). To assess whether numerical chromosomal anomalies (aneuploidy) and microsatellite instability (MSI) might be representative of distinctive tumour behaviour, paraffin-embedded tissue samples from 86 patients with sporadic EC were evaluated by both fluorescence in situ hybridisation (FISH) and microsatellite analysis, using free nuclei and genomic DNAs (respectively). Approximately one-third of the tumours analysed (24/74; 32%) exhibited MSI, whereas 38/86 (44%) of the EC samples displayed aneuploidy. The majority of the unstable cases (15/24; 63%) were from advanced-stage patients. Conversely, 23 (61%) out of the 38 tumours with aneuploidy were from early-stage patients. No apparent correlation was found between MSI and aneuploidy, whereas the immunohistochemical (IHC) analysis revealed that inactivation of the MLH1 mismatch repair gene may be involved in the majority of the MSI+ sporadic ECs. No genetic or cytogenetic alteration analysed here seems to add any significant predictive value to the stage of disease.

Prevalence and prognostic role of microsatellite instability in patients with rectal carcinoma

BACKGROUND

Association between microsatellite instability (MSI) and favorable postoperative survival in patients with colorectal cancer receiving adjuvant chemotherapy has been indicated. To evaluate whether an analogous positive prognostic role of MSI could be present in rectal carcinoma (RC; most RC patients receive adjuvant radiotherapy), PCR-based microsatellite analysis of archival RCs and statistical correlation with clinico-pathological parameters were performed.

PATIENTS AND METHODS

DNA from paraffin-embedded paired samples of tumors and corresponding normal tissue from 91 RC patients was analyzed for MSI using five microsatellite markers (tumors were classified as MSI(+) when two or more markers were unstable).

RESULTS

Seventeen (19%) RC patients exhibited a MSI(+) phenotype. Prevalence of instability was found in patients with earlier RC onset (28% in cases with diagnosis age < or =55 years versus 15% in cases >55 years), whereas similar MSI frequencies were observed in patients with different disease stage or receiving different adjuvant therapies. While MSI was detected in seven (64%) of 11 familial patients, a remarkably lower MSI incidence was observed in sporadic cases (10/80; 12.5%). A significant association with better disease-free survival (DFS) and overall survival (OS) was found for MSI(+) patients (median DFS/OS, 30/32 months) in comparison to MSI(-) ones (median DFS/OS, 18/21 months) (P <0.001).

CONCLUSIONS

MSI was demonstrated to be a strong molecular prognostic marker in rectal carcinoma, independent of the administered treatment (radiotherapy, chemotherapy or both).

Reducing the risk of colorectal cancer by intervening in the process of carcinogenesis: a status report

Risk factors for colorectal cancer have been identified, and significant advances have been made in understanding the process of colorectal carcinogenesis. The transition from normal colonic mucosa to adenomatous polyp to adenocarcinoma is a gradual process involving genetic and epigenetic instability that can take decades, offering numerous opportunities for early detection (e.g., colonoscopy screenings), lifestyle changes (e.g., reduced red meat intake, increased physical activity, and reduced alcohol/ tobacco exposure), and chemopreventive interventions. Aspirin and various other nonsteroidal anti-inflammatory drugs may have chemopreventive benefits for colorectal cancer and other human epithelial carcinomas, butthe long-term use of nonsteroidal anti-inflammatory drugs is associated with serious gastrointestinal side effects. Recently, overexpression of cyclooxygenase-2 has been documented in colorectal tumors and numerous other pre-cancers and cancers. The development of selective cyclooxygenase-2 inhibitors, such as celecoxib, provides an opportunity for preventive intervention in the carcinogenic process. Celecoxib has been approved for the management of familial adenomatous polyposis and is under investigation for the management of sporadic colorectal polyps and for its potential as a chemopreventive agent for other cancers.

Stable karyotypes in epithelial cancer cell lines despite high rates of ongoing structural and numerical chromosomal instability

Most human tumors and tumor cell lines exhibit numerical and structural chromosomal abnormalities. The goal of this study was to determine the ongoing rates of structural and numerical instability in selected cancer cell lines and to investigate the consequences of these rates to karyotypic progression. We studied two colorectal (HCT-116 and HT-29) and two ovarian (SKOV-3 and OVCAR-8) cancer cell lines and their single cell subclones. We found that the signature karyotypes of all four cell lines were distinct and each aberrant. Whereas high rates of ongoing structural and/ or numerical chromosomal instability could be demonstrated in all cell lines, there was a relative stability of the consensus karyotype over many generations. No new clonal structural chromosomal reconfigurations emerged and the few numerical changes of karyotypes were restricted to abnormal chromosomes. This implies a kind of genomic optimization under the conditions of cell culture and suggests a link between genomic stabilization and cell propagation. We have been able to support this possibility by computer modeling. We did not observe a profound difference in the rates of numerical or structural instability in the cell lines with a replication error phenotype (RER+) versus the other cell lines.

Contrasting molecular pathology of colorectal carcinoma in Egyptian and Western patients

Colorectal carcinoma is uncommon in Egypt, but a high proportion of cases occurs before age 40 years and in the rectum. We compared the molecular pathology of 59 representative Egyptian patients aged 10-72 to Western patients with sporadic, young-onset, or hereditary non-polyposis colorectal cancer syndrome (HNPCC)-associated carcinoma and found significant differences. Most Egyptian cancers were rectal (51%) and poorly differentiated (58%). High levels of microsatellite instability (MSI-H) were frequent (37%) and attributable in some cases (36%) to methylation of the promoter of the hMLH1 mismatch repair gene, but no MSI-H cancer had loss of hMSH2 mismatch repair gene product of the type seen with germline hMSH2 mutation in HNPCC. K-ras mutation was uncommon (11%). In subset analyses, high frequencies of MSI-H in rectal carcinomas (36%) and p53 gene product overexpression in MSI-H cancers (50%) were found. MSI-H and K-ras mutation in Egyptians under age 40 were unusual (17% and 0%, respectively), and schistosomiasis was associated with MSI and K-ras mutation. Cluster analysis identified 2 groups: predominantly young men with poorly differentiated mucinous and signet-ring cell colorectal carcinoma lacking K-ras mutation; older patients who had well- or moderately differentiated adenocarcinoma often with MSI-H, K-ras mutation and schistosomiasis. Our findings show that the molecular pathology of colorectal cancer in older as well as younger Egyptians has unique differences from Western patients, and schistosomiasis influences the molecular pathogenesis of some tumours.

The future of colon cancer prevention

Chemoprevention science is in flux owing to rapid advances in postgenomic technology. We have witnessed enormous advances in the areas of early detection and molecular profiling of colorectal carcinogenesis; however, unique interpretive and technologic challenges persist. Neoplastic hallmarks must be iteratively tested and validated as markers of risk, targets for intervention, and/or markers of response in order to expedite the development of preventive interventions. In this review, we highlight several of the technologies that are revolutionizing our understanding of carcinogenesis and our approach to colorectal cancer prevention.