Increased p53 protein content of colorectal tumours correlates with poor survival

Colorectal liver metastases: Current management and future perspectives

The liver is the commonest site of metastatic disease for patients with colorectal cancer, with at least 25% developing colorectal liver metastases (CRLM) during the course of their illness. The management of CRLM has evolved into a complex field requiring input from experienced members of a multi-disciplinary team involving radiology (cross sectional, nuclear medicine and interventional), Oncology, Liver surgery, Colorectal surgery, and Histopathology. Patient management is based on assessment of sophisticated clinical, radiological and biomarker information. Despite incomplete evidence in this very heterogeneous patient group, maximising resection of CRLM using all available techniques remains a key objective and provides the best chance of long-term survival and cure. To this end, liver resection is maximised by the use of downsizing chemotherapy, optimisation of liver remnant by portal vein embolization, associating liver partition and portal vein ligation for staged hepatectomy, and combining resection with ablation, in the context of improvements in the functional assessment of the future remnant liver. Liver resection may safely be carried out laparoscopically or open, and synchronously with, or before, colorectal surgery in selected patients. For unresectable patients, treatment options including systemic chemotherapy, targeted biological agents, intra-arterial infusion or bead delivered chemotherapy, tumour ablation, stereotactic radiotherapy, and selective internal radiotherapy contribute to improve survival and may convert initially unresectable patients to operability. Currently evolving areas include biomarker characterisation of tumours, the development of novel systemic agents targeting specific oncogenic pathways, and the potential re-emergence of radical surgical options such as liver transplantation.

Immunohistochemical investigation of prognostic biomarkers in resected colorectal liver metastases: a systematic review and meta-analysis

Background

Many studies have investigated the prognostic role of biomarkers in colorectal liver metastases (CRLM). However, no biomarker has been established in routine clinical practice. The aim of this study was to scrutinize the current literature for biomarkers evaluated by immunohistochemistry as prognostic markers in patients with resected CRLM.

Methods

A systematic review was performed according to the PRISMA guidelines. Articles were identified in the PubMed database with selected search terms and by cross-references search. The REMARK quality criteria were applied. Markers were included if they reported the prognostic impact of immunohistochemical markers in a multivariable setting in relation to overall survival (OS). A meta-analysis was conducted when more than one original article provided survival data of a marker.

Results

In total, 26 biomarkers were identified as independent significant markers for OS in resected CRLM. These biomarkers were found to be involved in multiple oncogenic signalling pathways that control cell growth, apoptosis, angiogenesis and evasion of immune detection. Among these biomarker candidates were Ki-67, EGFR, p53, hTERT, CD34, TSP-1, KISS1, Aurora kinase A and CDX2. CD34 and TSP-1 were reported as significantly associated with survival by more than one study and where therefore pooled in a meta-analysis.

Conclusion

A number of independent prognostic biomarkers for resected CRLM were identified. However, most markers were evaluated in a retrospective setting with small patient cohorts, without external validation. Large, prospective, multicentre studies with standardised methods are needed before biomarkers can translated into the clinic.

Genetic Events Responsible for Colorectal Tumorigenesis: Achievements and Challenges

Colorectal carcinogenesis is a multistep process that is accompanied by accumulation of changes in proto-oncogenes and tumor-suppressor genes. APC/MCC, RAS, DCC, p53 mutations and/or allelic losses, hyperexpression of c-MYC and RB genes, as well as other genomic alterations appear at characteristic stages of tumor development and are observed in most neoplasms. However, consideration of each of these abnormalities leaves many unanswered questions. The striking data on recurrent amplification of the RB tumor-suppressor gene as well as suppressive activities of protein kinase C and activated RAS genes, at least in some colon carcinoma cell lines, suggest the unusual effects of some signalling pathways in colonic epithelial cells. The results obtained to date indicate that distinct sets of genetic changes may underlie the development of colorectal tumors.

ras and p53 in the prediction of survival in Dukes' stage B colorectal carcinoma

Aims-To determine possible associations between p53 allelic deletion, c-Ki-ras mutational activation, immunohistochemical detection of p53 and ras proteins, various clinicopathological variables, and patient outcome in 168 Dukes' stage B colorectal carcinomas.Methods-Allelic deletion at the p53 tumour suppressor gene locus was detected using polymerase chain reaction (PCR) based loss of heterozygosity (LOH) assays. Overexpressed proteins were detected using the CM1 polyclonal antibody. A PCR based assay was used to detect the presence of activating mutations at codon 12 of c-Ki-ras. Immunostaining was carried out using a monoclonal antibody to p21(ras).Results-p53 LOH, CM1 immunostaining, c-Ki-ras mutational activation, and p21(ras) immunostaining were not predictive of survival by logrank analysis. Multivariate analysis using Cox regression did not predict survival in this group of tumours.Conclusions-Aberrations in ras and p53 are unlikely to play an important role in the subdivision of patients with Dukes' stage B colorectal carcinoma into more accurate prognostic strata. It is possible that later genetic events are more important in conferring a specific phenotype on the resultant Dukes' stage B tumour.

Frameshift mutations in coding repeats of protein tyrosine phosphatase genes in colorectal tumors with microsatellite instability

BACKGROUND

Protein tyrosine phosphatases (PTPs) like their antagonizing protein tyrosine kinases are key regulators of signal transduction thereby assuring normal control of cellular growth and differentiation. Increasing evidence suggests that mutations in PTP genes are associated with human malignancies. For example, mutational analysis of the tyrosine phosphatase (PTP) gene superfamily uncovered genetic alterations in about 26% of colorectal tumors. Since in these studies tumors have not been stratified according to genetic instability status we hypothesized that colorectal tumors characterized by high-level of microsatellite instability (MSI-H) might show an increased frequency of frameshift mutations in those PTP genes that harbor long mononucleotide repeats in their coding region (cMNR).

RESULTS

Using bioinformatic analysis we identified 16 PTP candidate genes with long cMNRs that were examined for genetic alterations in 19 MSI-H colon cell lines, 54 MSI-H colorectal cancers, and 17 MSI-H colorectal adenomas. Frameshift mutations were identified only in 6 PTP genes, of which PTPN21 show the highest mutation frequency at all in MSI-H tumors (17%).

CONCLUSION

Although about 32% of MSI-H tumors showed at least one affected PTP gene, and cMNR mutation rates in PTPN21, PTPRS, and PTPN5 are higher than the mean mutation frequency of MNRs of the same length, mutations within PTP genes do not seem to play a common role in MSI tumorigenesis, since no cMNR mutation frequency reached statistical significance and therefore, failed prediction as a Positive Selective Target Gene.

Is there a genetic signature for liver metastasis in colorectal cancer?

Even though liver metastasis accounts for the vast majority of cancer deaths in patients with colorectal cancer (CRC), fundamental questions about the molecular and cellular mechanisms of liver metastasis still remain unanswered. Determination of gene expression profiles by microarray technology has improved our knowledge of CRC molecular pathways. However, defined gene signatures are highly variable among studies. Expression profiles and molecular markers have been specifically linked to liver metastases mechanistic paths in CRC. However, to date, none of the identified signatures or molecular markers has been successfully validated as a diagnostic or prognostic tool applicable to routine clinical practice. To obtain a genetic signature for liver metastasis in CRC, measures to improve reproducibility, to increase consistency, and to validate results need to be implemented. Alternatives to expression profiling with microarray technology are continuing to be used. In the recent past, many genes codifying for proteins that are directly or indirectly involved in adhesion, invasion, angiogenesis, survival and cell growth have been linked to mechanisms of liver metastases in CRC.

Microsatellite instability accounts for tumor site-related differences in clinicopathologic variables and prognosis in human colon cancers

OBJECTIVE

Colon cancers with high frequency microsatellite instability (MSI-H) are preferentially located in the proximal colon. Given that 15-20% of sporadic colon cancers are MSI-H, we determined whether tumor site-specific differences in clinicopathological variables, biomarkers, and prognosis are due to inclusion of MSI-H cases.

METHODS

TNM stage II and III primary colon carcinomas (N = 528) from patients enrolled in 5-fluorouracil-based adjuvant trials were analyzed for MSI using 11 microsatellite markers. Immunostaining for DNA mismatch repair (hMLH1, hMSH2, hMSH6) and p53 proteins was performed. DNA ploidy (diploid vs aneuploid/tetraploid) and proliferative indices (PI: S-phase + G(2)M) were analyzed by flow cytometry.

RESULTS

MSI-H was found in 95 (18%) colon cancers. Proximal tumors (N = 286) were associated with MSI-H, older age (>65 yr), poor differentiation, and diploid DNA content compared with distal tumors (all P< or = 0.016). Nuclear p53 staining was more frequent in distal tumors (P= 0.002); PI was unrelated to tumor site. When MSI-H tumors were excluded, no tumor site-related differences were found except for age, which remained associated with proximal cancers (P= 0.030). Proximal site was associated with improved disease-free survival in all patients (P= 0.042), but not when MSI-H cases were excluded (P= 0.236). MSI-H status or loss of mismatch repair proteins, diploidy, and lower PI were associated with improved survival rates.

CONCLUSIONS

Tumor site-related differences in clinicopathological variables, biomarkers, and prognosis of sporadic colon cancers can be explained by the inclusion of MSI-H cases. Older age, however, is associated with proximal tumor site independent of MSI status.

Differential expression of Bcl-2, Bcl-XL and p53 in colorectal cancer

AIMS

The balance between proliferation and apoptosis is often disturbed in cancer. The aim of this study was to investigate the possible role of Bcl-2 gene family members and p53 as prognostic factors in a series of colorectal cancer.

METHODS

The immunohistochemical expression of Bcl-2 gene family members (Bcl-2 and Bcl-X(L)) and p53 was evaluated in 81 surgical specimens of primary human colorectal cancers to establish the role of these genes in colorectal cancer and to evaluate their prognostic importance.

RESULTS

The expression of Bcl-2 correlated with early clinical stage and lack of lymphovascular invasion and lymph node involvement. The expression of p53 correlated with less differentiated status and with perineural invasion. p53 expression showed negative correlation with Bcl-X(L) expression (P = 0.025) and no correlation with Bcl-2 expression.

CONCLUSIONS

p53 expression may be a less favorable marker and Bcl-2 expression a more favorable marker of behavior. Bcl-2 and Bcl-X(L) may play an independent role in disease progression, and the expression of these proteins may be under independent regulatory control in colorectal cancer.

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.

Two colons-two cancers: paradigm shift and clinical implications

Embryological and physiological data suggest that proximal (in relation to the splenic flexure) and distal parts of the colon represent distinct anatomical and functional entities. Since 1990, molecular biologists have identified two distinct pathways, microsatellite instability (MSI) and chromosomal instability (CIN), which are involved in the pathogenesis of colon cancer (CC). Thus, a new paradigm has emerged with the discovery that CC is a heterogeneous disease; furthermore recent data have demonstrated that these two distinct pathways in colorectal carcinogenesis are characterized by a different clinical outcome. The implications for the clinicians are twofold; (1) tumors originating from the proximal colon have a better prognosis due to a high percentage of MSI-positive lesions; and (2) location of the neoplasm in reference to the splenic flexure should be documented before group stratification in ongoing trials of adjuvant chemotherapy for CC. In the future, clinical decision-making regarding adjuvant chemotherapy might be stratified according to the MSI status of cancers located proximally to the splenic flexure.

Systematic review of genetic influences on the prognosis of colorectal cancer

Background

In terms of genetics, colorectal cancer is one of the best understood of all malignant diseases. Genetic influences on prognosis may have far-reaching implications, especially for the design of surgical and chemoradiotherapeutic regimens. However, their significance in determining prognosis remains unclear. This study aimed to review the literature on the specific role of key genes in determining the survival of patients with colorectal cancer.

Methods

A Medline search was carried out to identify all original scientific papers relating colorectal cancer genetics to patient survival, up to December 2002. Cochrane and Embase databases were also searched. Identified articles were retrieved and searched carefully for additional information. This review includes K-ras, p53, DCC, NM23 and DNA mismatch repair genes.

Results and conclusion

Conflicting evidence exists as to the prognostic significance of genes commonly implicated in the pathogenesis of colorectal carcinoma. Possible causes for such discrepancy include differences in study methods and laboratory techniques, variable duration of follow-up, statistical differences in study power, and heterogeneity in study populations. Future studies should adopt standardized protocols to define clinically relevant genetic observations.

Expression of p53 and mdm2 and their significance in recurrence of superficial bladder cancer

The purpose of this study is to evaluate the expression of p53 and mdm2 and to determine whether they may be used as additional predictors of recurrence in superficial transitional cell carcinoma of the bladder. Paraffin sections of 80 patients with superficial transitional cell carcinoma of the bladder, who were treated with transurethral resection, were stained with p53 and mdm2 antibodies using the standard avidin biotin immunoperoxidase method. Nuclear staining for both p53 and mdm2 was calculated as the percentage of labeled nuclei out of a total number of tumor cells counted. The percentage of p53- and mdm2-positive cells showed a significant relationship with tumor grade and recurrence (p = 0.002 and p = 0.016; p = 0.01 and p = 0.003, respectively). In addition, a weak inverse relationship was found between p53 and mdm2 values (r = -0.184). p53 and mdm2 reactivities are valuable parameters in predicting recurrence in superficial bladder cancer. Thus, mdm2 expression appears to play a role in predicting biologic behavior in superficial transitional carcinoma of the bladder.

p53 protein accumulation in colorectal cancer tissue has prognostic value only in left-sided colon tumours

The aim of this paper is to describe the prospective 10-year follow-up study of prognostic value of p53 protein accumulation in cancer cells in relation to the localisation of tumour in colorectum.

METHODS

The p53 protein accumulation has been assessed immunohistochemically in tumour tissue samples obtained from 80 selected sporadic colorectal cancer patients.

RESULTS

p53 protein accumulation was detected more often in rectum than in colon tumours. Lower survival rates were observed in patients with p53 protein accumulation in cancer cells independent of primary tumour site. Significantly lower cumulative survival rate was detected in the group of patients with left-sided colon cancer. The p53 protein accumulation was an independent prognostic factor in the left-sided colon tumours.

CONCLUSIONS

The right-sided colon tumours may be developed in p53-independent manner and p53 protein accumulation in cancer cells has prognostic value only in the left-sided colorectal tumours.

Molecular lesions in colorectal cancer: impact on prognosis? Original data and review of the literature

BACKGROUND

In the Dukes' B and C stages of colorectal carcinoma there are considerable variations in the observed courses of the disease. Since post-operative chemotherapy in patients with Dukes' C (node-positive) colon carcinoma has been demonstrated to be effective in improving overall-survival, a more exact prognosis assessment gains additional significance and therapeutic relevance.

DISCUSSION

One also hopes to derive improved prognostic factors from the clarification of the molecular pathogenesis. Because of its frequency and the accessibility and recognizability of its developmental stages colorectal carcinoma is among the best investigated of all solid tumors. Despite a multitude of suggested molecular candidate markers none of these changes has yet been able enter the everyday life of the clinic. However, it is to be expected that some of the molecular alterations presently discussed will gain importance before long in the clinical treatment of patients with colorectal carcinoma.

CONCLUSION

Considering also our own findings, this review presents the latest developments in the scientific discussion of the tumor suppressor/oncogenes p53, k-ras, and DCC, biochemical determinants of the 5-fluorouracil metabolism, and defects of the DNA repair system.

Abnormal p53 immunohistochemistry is associated with an increased colorectal cancer-related mortality in patients with ulcerative colitis

OBJECTIVE

Immunohistochemical evaluation of p53 staining patterns has been considered as a complementary test for dysplasia in ulcerative colitis-related colorectal cancer surveillance, but usefulness would be particularly important if it were a marker associated with a poor prognosis. The aim of this study was to determine whether abnormal p53 staining of the tumor correlated with cancer-related mortality in ulcerative colitis patients.

METHODS

An historical cohort study was designed to examine all ulcerative colitis patients who developed colorectal cancer between 1978 and 1997 and who had tumor tissue blocks available for staining. Tissue was recut and stained for abnormal p53 immunohistochemistry using the DO-7 antibody. Tumors were considered to be p53 positive if at least 5% of nuclei in a high power field were positive for staining.

RESULTS

Among 75 patients entered in the study, 38 (50.7%) had p53 positive tumors. Fourteen patients (36.8%) with p53 positive tumors died from colorectal cancer, compared to five (13.5%) with p53 negative tumors (p < 0.04, log-rank test). The adjusted relative risk of cancer-related death among patients with p53 positive tumors was 3.03 (95% CI = 1.05-8.73).

CONCLUSIONS

Abnormal p53 immunohistochemistry of tumors is associated with a poor prognosis among ulcerative colitis patients who develop colorectal cancer. As such, p53 immunohistochemical staining could be a useful histological marker to complement routine histology in cancer surveillance programs in ulcerative colitis patients.

gamma-Glutamyl transpeptidase expression in Ewing's sarcoma cells: up-regulation by interferons

The genetic hallmark of Ewing's sarcoma family of tumours (ET) is the presence of the translocation t(11;22)(q24;q12), which creates the ET fusion gene, leading to cellular transformation. Five human gamma-glutamyl transpeptidase (gamma-GT) genes are located near the chromosomal translocation in ET. gamma-GT is a major enzyme involved in glutathione homoeostasis. Five human cell lines representative of primary or metastatic tumours were investigated to study whether gamma-GT alterations could occur at the chromosomal breaks and rearrangements in ET. As shown by enzymic assays and FACS analyses, all ET cell lines consistently expressed a functional gamma-GT which however did not discriminate steps of ET progression. As shown previously [Sancéau, Hiscott, Delattre and Wietzerbin (2000) Oncogene 19, 3372-3383], ET cells respond to the antiproliferative effects of interferons (IFNs) type I (alpha and beta) and to a much less degree to IFN type II (gamma). IFN-alpha and -beta arrested cells in the S-phase of the cell cycle. We found an enhancement of gamma-GT mRNA species with IFN-alpha and -beta by reverse transcriptase-PCR analyses. This is reflected by up-regulation of gamma-GT protein, which coincides with the increase in gamma-GT-specific enzymic activity. Similarly, IFNs up-regulate the levels of gamma-GT in another IFN-responsive B cell line. Whether this up-regulation of gamma-GT by IFNs is of physiological relevance to cell behaviour remains to be studied.

Prognostic significance of p53 mutations in colon cancer at the population level

Some studies have reported that p53 mutations or certain types of p53 mutation are associated with poor prognosis in colon cancer, while other studies have failed to show such a relationship. None of these previous studies was population-based. We therefore evaluated the prognostic significance of p53 mutations in a large, population-based study of 1,464 individuals with colon cancer from Utah and California. Mutations in exons 5-8 were detected by SSCP analysis, followed by sequencing of aberrant bands. p53 mutations were identified in colon cancers from 665 of 1,464 (45.4%) individuals. p53 mutations were significantly more common in distal tumors (p < 0.01), tumors of relatively high stage (p = 0.04), tumors without MSI (p < 0.01) and tumors without Ki-ras mutations (p < 0.01). In a univariate analysis, tumors with p53 mutations were associated with a significantly worse 5-year survival than those with wild-type p53 (53.4% vs. 58.8%, p = 0.04); significantly worse prognosis also was seen with missense mutations, transitions, transversions, mutations affecting the structure of the p53 molecule, mutations within the beta-sandwich motif and mutations in proximal tumors. In multivariate analyses, however, the only significant predictors of poor prognosis were G245 hot spot mutations (HRR = 2.16, 95% CI 1.06-4.40) and p53 mutations in proximal tumors (HRR = 1.34, 95% CI 1.07-1.63). We conclude that overall p53 mutational status is not an independent predictor of poor prognosis in colon cancer. However, specific classes of mutations, namely, the G245 hot spot mutation and mutations in proximal tumors, are related to significantly worse survival even after adjusting for age and stage.

An immunohistochemical study of p21 and p53 expression in primary node-positive breast carcinoma

AIMS

p21, an inhibitor of cyclin-dependent kinase, is involved in the p53 pathway of growth control. Its expression has been linked to cellular differentiation. It has been implicated in p53-mediated growth arrest following DNA damage and in terminally differentiated cells. This study analysed p21 and p53 expression, in a series of node-positive patients with breast carcinoma and examined histopathological parameters of the tumour and the prognostic implications of p21 and p53 expression.

METHODS

One hundred and five consecutive patients with node-positive disease and at least 3 years follow-up were identified. Sections were stained for p53 and p21 using monoclonal antibodies. Results were expressed as percentage positive cells, and over 20% considered positive for p53 and over 10% considered for p21.

RESULTS

p21 was overexpressed (>10% of cells positive) in 65% of patients and p53 was overexpressed (>20% of cells positive in 68%. The mean (SEM) level of p21 staining was 5.7(0.8)% and was 54.9(4.0)% for p53. There was no correlation between p21 and p53 expression (r=0.071 P=0.5). There were no significant differences in demographic criteria between patients that were p21 positive or negative and p53 positive or negative. There were no significant differences in tumour type, grade or stage between the groups. p21 expression did not have prognostic significance; however, p53 positivity was associated with a worse prognosis, which remained when controlled for stage.

CONCLUSIONS

This study demonstrated p21 overexpression in 65% of patients with node-positive breast carcinoma. Levels did not correlate with p53 status and unlike p53 failed to have prognostic significance.

What we could do now: molecular pathology of colorectal cancer

The contribution of molecular genetics to colorectal cancer has been largely restricted to relatively rare inherited tumours and to the detection of germ line mutations predisposing to these cancers. However, much is now known about the somatic events leading to colorectal cancer in general. Several studies have examined the relation between genetic features and prognosis. The purpose of this article is to review these studies and summarise the current state of this subject. Although many of the published studies are small and inconclusive, it is clear that several different pathways exist for the development of this cancer, and some molecular characteristics seem to correlate with clinicopathological features. At present, studies are confined to evaluating a small number of molecular markers; however, with the advent of methods for the rapid genetic profiling of large numbers of colorectal cancers, it will be possible to evaluate fully the clinical usefulness of a range of colorectal cancer genotypes.

Dukes B colorectal cancer: distinct genetic categories and clinical outcome based on proximal or distal tumor location

PURPOSE

The aim of this study was to determine whether tumor location proximal or distal to the splenic flexure is associated with distinct molecular patterns and can predict clinical outcome in a homogeneous group of patients with Dukes B (T3-T4, N0, M0) colorectal cancer. It has been hypothesized that proximal and distal colorectal cancer may arise through different pathogenetic mechanisms. Although p53 and Ki-ras gene mutations occur frequently in distal tumors, another form of genomic instability associated with defective DNA mismatch repair has been predominantly identified in the proximal colon. To date, however, the clinical usefulness of these molecular characteristics remains unproven.

METHODS

A total of 126 patients with a lymph node-negative sporadic colon or rectum adenocarcinoma were prospectively assessed with the endpoint of death by cancer. No patient received either radiotherapy or chemotherapy. p53 protein was studied by immunohistochemistry using DO-7 monoclonal antibody, and p53 and Ki-ras gene mutations were detected by single strand conformation polymorphism assay.

RESULTS

During a mean follow-up of 67 months, the overall five-year survival was 70 percent. Nuclear p53 staining was found in 57 tumors (47 percent), and was more frequent in distal than in proximal tumors (55 vs. 21 percent; chi-squared test, P < 0.001). For the whole group, p53 protein expression correlated with poor survival in univariate and multivariate analysis (log-rank test, P = 0.01; hazard ratio = 2.16; 95 percent confidence interval = 1.12-4.11, P = 0.02). Distal colon tumors and rectal tumors exhibited similar molecular patterns and showed no difference in clinical outcome. In comparison with distal colorectal cancer, proximal tumors were found to be statistically significantly different on the following factors: mucinous content (P = 0.008), degree of histologic differentiation (P = 0.012), p53 protein expression, and gene mutation (P = 0.001 and 0.01 respectively). Finally, patients with proximal tumors had a marginally better survival than those with distal colon or rectal cancers (log-rank test, P = 0.045).

CONCLUSION

In this series of Dukes B colorectal cancers, p53 protein expression was an independent factor for survival, which also correlated with tumor location. Eighty-six percent of p53-positive tumors were located in the distal colon and rectum. Distal colon and rectum tumors had similar molecular and clinical characteristics. In contrast, proximal neoplasms seem to represent a distinct entity, with specific histopathologic characteristics, molecular patterns, and clinical outcome. Location of the neoplasm in reference to the splenic flexure should be considered before group stratification in future trials of adjuvant chemotherapy in patients with Dukes B tumors.

Detection of aberrations of 17p and p53 gene in gastrointestinal cancers by dual (two-color) fluorescence in situ hybridization and GeneChip p53 assay

We performed dual (two-color) fluorescence in situ hybridization (FISH) using direct fluorescent labeling probes for p53 and chromosome 17 in six gastrointestinal (3 stomach and 3 colon) cancers. In three of these (1 stomach and 2 colon) the interphase cell nuclei showed an imbalance of signals for the p53 and chromosome 17; that is, the p53 signal count was lower than the chromosome 17 signal count, indicating deletion of the p53 gene. Moreover, metaphase FISH analysis demonstrated that those nuclei actually had a chromosome 17 with deletion of the p53 gene. Interestingly, these three cases had an abnormal chromosome 17 copy number, that is, chromosome 17 aneusomy. Furthermore, to investigate the possibility of p53 mutation in tumors with an imbalance of signals for chromosome 17 and p53 per nucleus, we performed a GeneChip p53 assay which has recently been developed. GeneChip p53 assay demonstrated that a primary tumor sample from one colon cancer case had a heterozygous point mutation of CGT (Arg) to CAT (His) at codon 273 in exon 8. In addition, a sample of metastatic tumor in the liver from the same case revealed two heterozygous point mutations. One of them was the same mutation as that is the primary tumor; the other was GTG (Val) to GGG (Gly) at codon 217 in exon 6. In conclusion, we found that the combination of dual-color FISH and GeneChip p53 assay offered reliable results and important information concerning not only deletion of the p53 gene and chromosome 17 aneusomy but also p53 mutations. Using these techniques, we demonstrated that an imbalance of signals for chromosome 17 and p53 per nucleus, chromosome 17 aneusomy, and accumulation of p53 mutations had occurred during carcinogenesis and development of gastrointestinal cancers.

The p53 tumor suppressor gene: from molecular biology to clinical investigation

The tumor suppressor p53 is a phosphoprotein barely detectable in the nucleus of normal cells. Upon cellular stress, particularly that induced by DNA damage, p53 can arrest cell cycle progression, thus allowing the DNA to be repaired; or it can lead to apoptosis. These functions are achieved, in part, by the transactivational properties of p53, which activate a series of genes involved in cell cycle regulation. In cancer cells bearing a mutant p53, this protein is no longer able to control cell proliferation, resulting in inefficient DNA repair and the emergence of genetically unstable cells. The most common changes of p53 in human cancers are point missense mutations within the coding sequences of the gene. Such mutations are found in all major histogenetic groups, including cancers of the colon (60%), stomach (60%), breast (20%), lung (70%), brain (40%), and esophagus (60%). It is estimated that p53 mutations are the most frequent genetic event in human cancers, accounting for more than 50% of cases. One of the most striking features of the inactive mutant p53 protein is its increased stability (half-life of several hours, compared to 20 min for wild-type p53) and its accumulation in the nucleus of neoplastic cells. Therefore, positive immunostaining is indicative of abnormalities of the p53 gene and its product. Several studies have shown that p53 mutations are associated with short survival in colorectal cancer, but the use of p53 as a tumoral marker is still a matter of debate.

Detection of circulating anti-p53 antibodies in esophageal cancer patients

It has been reported that circulating anti-p53 antibodies (p53-Ab) in the serum are detected in some cancers. To investigate the usefulness of detecting p53-Ab, we measured the circulating p53-Ab in comparison with squamous cell carcinoma antigen (SCC-Ag) in patients with esophageal carcinoma. Serum specimens from 46 esophageal cancer patients (42 squamous cell carcinomas, 3 mucoepidermoid carcinomas and 1 basaloid squamous carcinoma) and 13 healthy subjects were studied. Serum p53-Ab was measured by an enzyme-linked immunosorbent assay. Surgically resected specimens from 43 patients were immunohistochemically stained for p53. Serum SCC-Ag was measured by a radioimmunoassay. The results were analyzed with the clinical data and outcome. Serum p53-Ab was detected in 13 (28%) of the 46 patients, but not in any of the healthy subjects. The positive rate was 0% (0/6) in stage I, 60% (3/5) in stage IIA, 30% (3/10) in stage IIB, 29% (7/24) in stage III and 0% (0/1) in stage IV. There was no difference in the outcome between the p53-Ab-positive and p53-Ab-negative patients. Immunohistochemically, 30 (70%) of the 43 specimens stained positively for p53. Serum p53-Ab was detected in 43% (13/30) of the patients with tumors which stained positively for p53. There was a close correlation between positivity for p53 immunostaining and positivity for p53-Ab (p<0.01). An elevated level of SCC-Ag was found in only 13%of the patients, and most patients positive for SCC-Ag already had advanced disease with lymph node metastasis and invasion to the adventitia. In conclusion, serum p53-Ab was detected in Japanese esophageal cancer patients at a frequency similar to that reported in Western countries. Serum p53-Ab may be a potentially useful molecular marker for detection and screening of esophageal cancer. Further studies of a large population may be required to elucidate the true diagnostic usefulness of measuring the serum p53-Ab.

Assessment of biomarkers in paired primary and recurrent colorectal adenocarcinomas

PURPOSE

Recurrent colorectal cancers respond poorly to anticancer treatment including radiotherapy. To better understand the biological characteristics of the recurrent colorectal tumor, we investigated various biomarkers regulating cell proliferation and cell loss in paired primary and recurrent colorectal tumor specimens within each individual.

METHODS AND MATERIALS

From a total of 11 colorectal adenocarcinoma patients, 22 specimens of paired primary and recurrent tumors were obtained for analysis. Apoptosis was evaluated by TUNEL labeling of apoptotic DNA fragmentation. Other biomarkers including proliferating cell nuclear antigen (PCNA), p53, WAF1, p34cdc2, and cyclins B1 and D1 were analyzed by immunohistochemical stains.

RESULTS

PCNA index (PCNAI) showed an increase in 6 and a decrease in 5 recurrent tumors compared to primary tumors. Median PCNAI in primary and recurrent tumors were 33.5 and 48.3, respectively (p = 0.16). In contrast, the apoptotic index (AI) decreased in 9 of 11 recurrent tumors compared to primary tumors. Median AI decreased from 4.3 in primary tumors to 1.4 in recurrent tumors (p = 0.04). The p53 expression increased in more than half of recurrent tumors compared to primary tumors. Mean staining score increased from 0.7 in primary tumors to 1.2 in recurrent tumors (p = 0.059). WAF1 and cyclin B1 did not show significant change. In contrast, both cyclin D1 and p34cdc2 increased significantly in recurrent tumors. These two biomarkers showed increased expression in 8 (cyclin D1) and 7 (p34cdc2) recurrent tumors, respectively, compared to their primary counterparts. Mean staining scores of both biomarkers in recurrent tumors increased by more than twofold compared to those in primary tumors and these differences were statistically significant (cyclin D1, p = 0.007; p34cdc2, p = 0.008).

CONCLUSION

This study showed significantly decreased apoptosis in recurrent colorectal tumors compared to their primary counterparts. The underlying regulatory mechanisms included increased expression of p53 and altered cell cycle regulators such as increased cyclin D1 and p34cdc2. With further study, it may be used for developing a new therapeutic strategy for the treatment of recurrent colorectal cancer.

TP53 status and gene amplification in human colorectal carcinomas

Gene amplification is one of the characteristics of cancer cells. In vitro studies suggested that alterations of the TP53 gene might be responsible for gene amplification. We have examined the presence of TP53 mutations and looked for cytogenetic evidence of gene amplification in a series of 79 primary colorectal carcinomas. Other parameters such as the pattern of cytogenetic alterations, microsatellite instability, tumor site, and histological staging were also considered. A multiparametric study supported by statistical analyses suggests the existence of two major pathways of colorectal carcinogenesis. No relationships could be established between the presence of TP53 alterations and gene amplification.

Correlations between p53-protein accumulation, serum antibodies and gene mutation in colorectal cancer

Only half of colorectal-cancer patients elicit serum antibodies in response to intratumoral p53-gene mutations. Our study was designed to compare cellular events (p53-protein accumulation and gene mutations) with the presence of circulating anti-p53 antibodies (p53-Ab). Thirty-five colorectal-cancer patients were studied for their intratumoral p53-protein accumulation and circulating p53-Ab. Tumour DNA was analyzed for genomic mutations in a sub-set of 28 patients. In all, 18 tumours (51.4%) were positive by immunohistochemistry, and 17 tumour extracts were shown to contain "mutant" conformation p53 protein, 16 of them being were concordant by both methods. Of the 28 tumours tested by DGGE, 16 contained alterations in p53 exons 5 to 8 (57.1%). Of 12 tumours without detectable mutations, 10 were "mutant"-conformation-negative by immunohistochemistry and ELISA. Paradiploid tumors presented more frequently wild-type p53 genes and were significantly less frequently immunohistochemistry- or p53-Ab-positive than polyploid tumors. Circulating p53-Ab were detected in the serum of 11 patients (31%). In 9/11 cases, a gene mutation was found in the corresponding tumour. Three of four mutations in exon 8 and 3/3 mutations in exons 5-6 were associated with p53-Ab, in contrast with only 3/9 mutations in exon 7. We found good agreement in the detection of p53-gene alterations by different methods. However, our data suggest that all gene mutations may not be equivalent in term of immunogenicity.

Analysis of the p53/BAX pathway in colorectal cancer: low BAX is a negative prognostic factor in patients with resected liver metastases

PURPOSE

To determine the prognostic value of the central downstream apoptosis effector BAX in relation to its upstream regulator p53 in R0-resected hepatic metastases of colorectal cancer.

PATIENTS AND METHODS

Retrospective analysis of 41 patients who underwent potentially curative resection of liver metastases from colarectal cancer was performed. Tumor DNA was screened for p53 mutations by single-stranded conformational polymorphism polymerase chain reaction and for BAX frameshift mutations by fragment length analysis. Protein expression of BAX, p21, and p53 was investigated by immunohistochemistry.

RESULTS

Overall median survival was 40.2 months. Tumors with BAX frameshift mutations were considered microsatellite mutator phenotype-positive and were excluded from further prognostic analyses. Patients with high BAX protein expression had a median survival of 53.6 months compared with 35.4 months for patients with low BAX expression (P < .05). The negative prognostic value of low BAX expression was more evident in those patients with wild-type p53 (median survival, 54.0 v 23.3 months for BAX-negative tumors; P < .01). Low BAX expression was an independent negative prognostic marker in multivariate regression analysis for all patients independent of the p53 status (relative risk, 3.03, P = .03), especially for p53 wild-type tumors (relative risk, 8.21; P = .0095).

CONCLUSION

We conclude that low BAX expression is an independent negative prognostic marker in patients with hepatic metastases of colorectal cancer. The best survival was seen in patients with an intact p53-to-BAX pathway; ie, wild-type p53- and BAX-positive tumors. Thus, analysis of apoptosis signaling pathways (here, p53 in concert with its downstream death effector, BAX) might yield more prognostic power in future studies as compared with analysis of single genes such as p53 alone.

A p53 genetic polymorphism as a modulator of hepatocellular carcinoma risk in relation to chronic liver disease, familial tendency, and cigarette smoking in hepatitis B carriers

This study evaluated whether the codon 72 p53 polymorphism was related to hepatocellular carcinoma (HCC). Genotypes of p53 were determined in 80 incident cases of HCC and 328 controls nested in a cohort study of 4,841 male chronic hepatitis B carriers. No overall increase in HCC risk with the Pro variant allele of the p53 polymorphism was apparent. However, there were synergistic effects on HCC development for the Pro allele with chronic liver disease and family history of HCC in first-degree relatives. Compared with subjects without the Pro allele and chronic liver disease, the increase in HCC risk associated with chronic liver disease among those without the Pro allele was only threefold. Subjects with both chronic liver disease and the Pro allele were at an increased risk of 7.60 (95% CI = 2.28-25.31). When subjects without family history of HCC and the Pro allele were considered as the reference group, there was no apparent increased risk of HCC for those without the Pro allele who had family history of HCC. Among those with both factors, there was a significantly increased risk of 3.29 (95% CI = 1.10-9.85). Both cigarette smoking and glutathione S-transferase M1 genotype modified the risk of HCC associated with the p53 polymorphism. Significantly increased risk associated with the p53 genotype was observed only among smokers who were glutathione S-transferase-null (Pro/Pro vs. Arg/Arg: odds ratio = 6.46; 95% CI = 1.55-26.94). The p53 polymorphism also interacted with the cytochrome P450 1A1 and carotenoid levels in smoking-related hepatocarcinogenesis.

Evaluation of the usefulness of testing for p53 mutations in colorectal cancer surveillance for ulcerative colitis

OBJECTIVE

Immunohistochemical staining for p53 suppressor gene mutations is sensitive and, therefore, has potential for use as a complementary test for dysplasia to improve ulcerative colitis (UC) cancer surveillance program performance.

METHODS

A cohort of 95 patients with long standing pan-UC enrolled in a surveillance program was studied. Archival colonic biopsy specimens were stained for p53 mutations and clinical information was obtained from medical records.

RESULTS

The 37 patients who developed p53 mutations were significantly more likely to develop dysplasia or cancer (relative risk [RR] 4.53, 95% confidence interval [CI] 2.16-9.48). The p53 mutations developed approximately 8 months before low grade dysplasia, 26 months before high grade dysplasia, and 38 months before cancer. Three of seven cancer patients with p53 mutations had Dukes' stage C or D, whereas only one of five cancer patients without p53 mutations had Dukes' C or D; all three patients who died from metastatic cancer had p53 mutations (three of 37 vs 0 of 58, p < 0.03). Folic acid supplementation had a small, significant protective effect for p53 mutations (RR 0.97, CI 0.94-1.00).

CONCLUSION

p53 Mutations 1) are associated with, and likely precede, dysplasia and cancer, 2) are associated with cancer-related mortality, and 3) may possibly be prevented by folic acid supplementation.

Prognostic value of p53 genetic changes in colorectal cancer

PURPOSE

To explore whether there is a linkage between different mutations in the p53 gene in primary colorectal cancer and the risk of death from colorectal cancer in a large group of patients with long follow-up. We also compared a complementary DNA-based sequencing method and an immunohistochemical (IHC) method for detecting p53 protein overexpression in colorectal cancer.

MATERIALS AND METHODS

The entire coding region of the p53 gene was sequenced in 191 frozen tumor samples collected from January 1988 to November 1992. RNA was extracted and synthesized to cDNA. p53 was amplified by the polymerase chain reaction, and the DO-7 monoclonal antibody was used in the IHC assessments.

RESULTS

Mutations were detected in 99 samples (52%) from 189 patients. There was a significant relationship between the p53 mutational status and the cancer-specific survival time, with shorter survival time for patients who had p53 mutations than for those who did not (P = .01, log-rank test). Mutations outside the evolutionarily conserved regions were associated with the worst prognosis. Multivariate analysis showed that the presence of p53 mutations was an independent prognostic factor (relative hazard, 1.7, P = .03). There was no significant relationship between overexpression of p53 protein, as determined by IHC analysis, and cancer-specific survival.

CONCLUSION

Mutational analyses of the p53 gene, using cDNA sequencing in colorectal cancer, provide useful prognostic information. In addition, cDNA sequencing gives better prognostic information than IHC assessment of p53 protein overexpression.

The p53 tumour suppressor gene

BACKGROUND

Abnormalities of the p53 tumour suppressor gene are thought to be central to the development of a high proportion of human tumours. This article reviews current understanding of its function and potential clinical significance.

METHODS

Material was identified from previous review articles, references cited in original papers, a Medline search of the literature over the 12 months to January 1998, and by scanning the latest issues of relevant journals.

RESULTS AND CONCLUSION

p53 is considered to be a stress response gene, its product (the p53 protein) acting to induce cell cycle arrest or apoptosis in response to DNA damage, thereby maintaining genetic stability in the organism. These functions are executed by a complex and incompletely understood series of steps known as the 'p53 pathway', part of which involves induction of the expression of a number of other genes. As p53 is the most commonly mutated gene in human cancer, it has attracted a great deal of interest as a prognostic factor, diagnostic tool and therapeutic target. However, despite many promising studies, its potential in practical cancer management has still to be realized.

Expression of cartilage extracellular matrix and potential regulatory genes in a new human chondrosarcoma cell line

A human chondrosarcoma cell line has been established from an aggressive chondrosarcoma. The cells grow in a monolayer culture (doubling time: 2 days) and form aggregates. The aggregates consist of a rim of cells surrounding a hollow core. The cell line exhibits a unique pattern of mRNA expression with several molecules characteristic of the chondrocyte phenotype. Consistent with the chondrocyte phenotype, mRNAs encoding types IX and XI collagens were present along with an abundant expression of mRNAs encoding the core protein of the cartilage proteoglycans biglycan and aggrecan. No expression of mRNAs encoding types I or II fibrillar collagens or the proteoglycan decorin was observed. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of [35S]sulfate-radiolabeled material confirmed the translation of proteoglycans containing glycosaminoglycan chains. The expression of molecules that contribute to cartilage development and tumorigenesis was examined. The cell line produces abundant mRNA that encodes transforming growth factor-beta1, a member of a family of cartilage and bone inductive proteins. The expression of mRNA encoding two proteins associated specifically with chondrogenesis was detected: Cart-1, a homeobox protein involved in cartilage differentiation, and CD-RAP, a secreted molecule restricted under normal conditions to differentiating chondrocytes and cartilage. Overexpression of p53, a tumor-suppressor gene, was detected. DNA analysis revealed a loss of heterozygosity at the chromosomal locus encoding p53, with the deletion of one p53 allele and the mutation of the remaining allele in both the parent tumor and the cell line. The malignant chondrosarcoma phenotype may be related to the unique gene expression pattern that is characteristic in many ways of differentiating chondroblasts, as well as to the inactivation of the p53 function that could contribute to the proliferative capacity of the cell line. This cell line may serve as a biological model for further investigation of the etiology of human chondrosarcomas and for the synthesis and regulation of cartilage-specific genes.

Increased serum p53 antibody levels indicate poor prognosis in patients with colorectal cancer

Serum p53 antibody levels were analysed using an enzyme-linked immunosorbent assay in serum samples obtained before surgery from 184 consecutive patients with primary colorectal cancer. Possible associations with tumour stage and tumour differentiation and the relation to patient survival time after a median follow-up of 6 years were studied. Analysis of serum p53 antibodies in the entire material demonstrated prognostic value in univariate analysis (P = 0.02); a finding that did not remain (P = 0.07) when the Dukes' stage was included in a multivariate analysis model. When the survival analysis was restricted to the potentially cured patients in Dukes' stages A-C, the serum p53 antibody levels retained independent prognostic value (P = 0.03). No clear association with tumour differentiation was found. We conclude that analysis of serum p53 antibodies may be of value for the identification of patients with different prognoses. This may be of relevance for selection of patients for adjuvant treatment.

Nuclear p53 protein expression in resected hepatic metastases from colorectal cancer: an independent prognostic factor of survival

An association has been reported between nuclear p53 protein expression in tumour cells and a poor outcome in patients with colorectal cancer (CRC). In this study we investigated the prognostic significance of nuclear p53 protein expression in CRC liver metastases after curative hepatic resection. The study population consisted of 69 consecutive patients who underwent curative hepatic resection for metastases from CRC at our Institution between February 1987 and October 1993. Immunohistochemical expression of p53 protein was evaluated in formalin-fixed paraffin-embedded sections of CRC liver metastases using the monoclonal antibodies (MAbs) D01 and Pab 1801. The Cox proportional hazards model was used in forward stepwise regression to assess the relative influence of different prognostic factors. Forty-four (63.8%) CRC liver metastases were p53-positive. Kaplan-Meier survival curves demonstrated that patients with p53-positive metastases had a median survival of 27 months versus 93 months for patients with p53-negative metastases (P < 0.01). The 3 and 5 years survival rates were 31.5 and 21.0% in patients with p53-positive metastases and 71.8 and 53.1% in patients with p53-negative metastases. At multivariate analysis p53 protein status was the single best predictor of survival (P = 0.0079); the odds ratio of death among patients with p53-positive tumours was 2.53. Nuclear p53 protein expression in hepatic metastases from CRC is an independent prognostic factor of survival following liver resection. These findings may be of clinical importance in the selection of patients more likely to benefit from liver resection and could be used as criteria for stratification in trials on adjuvant therapy.

The prognostic significance of p53 expression for survival and local control in rectal carcinoma treated with surgery and postoperative radiotherapy

PURPOSE

To investigate whether p53 immunoreactivity is a prognostic factor for survival and pelvic control in rectal carcinoma treated with surgery and postoperative radiotherapy.

METHODS AND MATERIALS

From 1981 through 1989, 146 patients with rectal carcinoma received postoperative radiotherapy and were followed for at least 5 years or until death. The specimens of 123 of these 146 patients could be retrieved and examined immunohistochemically for p53 expression. The prognostic value for survival and pelvic control of p53 expression and other patient and treatment factors was examined by univariate and multivariate analyses.

RESULTS

p53 expression has no prognostic significance for overall survival in this group of 123 patients. The only prognostic factor for survival in this material is tumor stage (p < 0.01). The actuarial pelvic recurrence rates of p53- and p53+ cases are different in favor of the p53- ones. In the univariate analysis this difference is significant (p = 0.05). However, in the multivariate analysis the influence of p53 expression, additional to stage, becomes nonsignificant (p = 0.10). This indicates that p53 expression is not a strong independent prognostic factor for pelvic recurrence. In the multivariate analysis stage turns out to be the only predictor of pelvic recurrence (p = 0.03). When only recurrences inside the radiation field are considered, there is no difference between p53+ and p53-cases.

CONCLUSION

Based on this material, we have found no convincing evidence that p53 expression is an important predictor of survival or local control in rectal cancer treated with surgery and postoperative radiotherapy. We have found no evidence that possible differences in radiosensitivity between p53+ and p53- tumors have clinical significance for this group of patients.

Screening for APC mutations based on detection of truncated APC proteins

Mutation of the adenomatous polyposis coli (APC) gene is frequently found in colorectal tumors from both familial adenomatous polyposis (FAP) and non-FAP patients. Analysis of APC mutation is time-consuming and costly due to the large size of the APC gene. As the majority of APC mutations result in the truncation of gene products, the detection of truncated APC proteins may be used as a screening method for APC mutations. The aim of this study is to establish a practical method of detecting truncated APC proteins for the screening of APC mutations. APC proteins in human colorectal cancer cell lines were analyzed by western blotting. Truncated APC proteins were expressed in all of the colorectal cancer cell lines studied. Two species of truncated APC proteins were expressed in two cell lines. Western blotting is a rapid, reliable screening method for APC mutations and provides information on both alleles.

p53 expression in human carcinomas: could flow cytometry be an alternative to immunohistochemistry?

Several studies have shown that p53 expression has important clinical implications as an indicator of prognosis and response to chemotherapy or radiotherapy in different human tumor types. Determination of p53 expression by immunohistochemistry (IHC) has been incorporated into routine practice and its reliability has been consolidated. However, flow cytometric (FCM) analysis might represent an important objective and rapid approach. In the present study we determined p53 expression by IHC and FCM on a series of 118 human solid tumors. IHC determination was performed on histological sections and FCM analysis on cell suspensions. Low correlation coefficients (rs from 0.22 to 0.57) were observed between IHC and FCM data from individual tumors. By considering the IHC approach as the gold standard, high sensitivity and low specificity were found for FCM in detecting p53 expression. The FCM analysis of p53 expression and DNA content showed p53-positive cells in all cell cycle phases. Moreover, in most breast, lung, and colon aneuploid tumors (77%), p53-positive cells were detected only in the subpopulations with abnormal DNA content. In conclusion, FCM-p53 expression cannot be used alternatively to IHC determination, and its clinical relevance remains to be validated. Nevertheless, FCM may provide important information about p53 protein expression in the different subpopulations and cell cycle phases. (J Histochem Cytochem 46:41-47, 1998)

Role of p53 and p21/WAF1 detection in patient selection for preoperative radiotherapy in rectal cancer patients

BACKGROUND

Recent studies showed that p53 and p21 may play major roles in determining tumor radiosensitivity through the apoptosis pathway. The aim of this study was to investigate the predicting value of radiosensitivity in human rectal carcinoma.

METHODS

p53 and p21/WAF1 expressions in formalin fixed, paraffin-embedded, preradiation biopsy samples from 49 patients with primary rectal carcinoma were analyzed immunohistochemically. p53 and p21 expressions and their relationships with histopathologic changes after radiation and other clinical features were evaluated.

RESULTS

Expressions of p53 and p21/WAF1 were 49 and 28.6 percent, respectively. In 36.7 percent of total tumors, significant histopathologic effect can be observed. There was a significant inverse expression of p53 and p21. Most of the p53(+) or p21(-) tumors were radioresistant, and the majority of p53(-) or p21(+) tumors were radiosensitive. Tumors size in the radiosensitive, p53(-), or p21(+) group decreased more significantly than in radioresistant, p53(+), or p21(-) group (P < 0.01), and patients with radioresistant, p53(+), or p21(-) tumors had more local recurrence, more distant metastasis, and a shorter five-year survival rate than those with radiosensitive, p53(-), or p21(+) tumors, but without statistic significance. No statistically significant correlation can be observed between other tumor clinical features and radiosensitivity, p53, or p21 expressions.

CONCLUSION

Immunohistochemistry detection of p53 and p21 expressions may be useful parameters for more radiosensitive patients selected for preoperative radiotherapy.

Expression of the HGF/SF receptor, c-met, and its ligand in human colorectal cancers

The c-met proto-oncogene product is a receptor tyrosine kinase that mediates the effects of the multifunctional cytokine hepatocyte growth factor/scatter factor (HGF/SF). We have studied the expression of both the c-met receptor and HGF/SF at both the protein and message level in colorectal cancer tissues of varying disease stage. All of the tumors displayed an overexpression of the c-met mRNA compared to their normal tissue counterparts while 16 of 21 tissues (75%) displayed up-regulation of c-met protein. No HGF/SF mRNA or protein could be detected in either tissue type. Viable tumor cells extracted from cancer tissue exhibited increased motility in response to HGF/SF stimulation demonstrating that c-met was functionally active. No correlation between expression of c-met and tumor stage or degree of differentiation was observed. HGF/SF is known to be a potent stimulator of tumor cell motility and invasion, two cellular properties essential for the metastatic development of cancers. The overexpression of the HGF/SF receptor in colorectal cancers may result in an increased sensitivity to HGF/SF, which may confer an enhanced metastatic potential to the cancer cells within the tumor body.

Genetic prognostic markers in colorectal cancer

The contribution of molecular genetics to colorectal cancer has been restricted largely to relatively rare inherited tumours and to the detection of germline mutations predisposing to these cancers. However, much is now also known about somatic events leading to colorectal cancer. A number of studies has been undertaken examining possible relations between genetic features and prognostic indices. While many of these studies are small and inconclusive, it is clear that a number of different pathways exist for the development of this cancer and some molecular characteristics correlate with clinicopathological features. With the advent of methods for the rapid genotyping of large numbers of colorectal cancers, it should be possible to evaluate fully the clinical usefulness of colorectal cancer genotypes through multivariate analyses.

Molecular biology of colorectal cancer

Colorectal cancer is a significant cause of morbidity and mortality in Western populations. This cancer develops as a result of the pathologic transformation of normal colonic epithelium to an adenomatous polyp and ultimately an invasive cancer. The multistep progression requires years and possibly decades and is accompanied by a number of recently characterized genetic alterations. Mutations in two classes of genes, tumor-suppressor genes and proto-oncogenes, are thought to impart a proliferative advantage to cells and contribute to development of the malignant phenotype. Inactivating mutations of both copies (alleles) of the adenomatous polyposis coli (APC) gene--a tumor-suppressor gene on chromosome 5q--mark one of the earliest events in colorectal carcinogenesis. Germline mutation of the APC gene and subsequent somatic mutation of the second APC allele cause the inherited familial adenomatous polyposis syndrome. This syndrome is characterized by the presence of hundreds to thousands of colonic adenomatous polyps. If these polyps are left untreated, colorectal cancer develops. Mutation leading to dysregulation of the K-ras protooncogene is also thought to be an early event in colon cancer formation. Conversely, loss of heterozygosity on the long arm of chromosome 18 (18q) occurs later in the sequence of development from adenoma to carcinoma, and this mutation may predict poor prognosis. Loss of the 18q region is thought to contribute to inactivation of the DCC tumor-suppressor gene. More recent evidence suggests that other tumor-suppressor genes--DPC4 and MADR2 of the transforming growth factor beta (TGF-beta) pathway--also may be inactivated by allelic loss on chromosome 18q. In addition, mutation of the tumor-suppressor gene p53 on chromosome 17p appears to be a late phenomenon in colorectal carcinogenesis. This mutation may allow the growing tumor with multiple genetic alterations to evade cell cycle arrest and apoptosis. Neoplastic progression is probably accompanied by additional, undiscovered genetic events, which are indicated by allelic loss on chromosomes 1q, 4p, 6p, 8p, 9q, and 22q in 25% to 50% of colorectal cancers. Recently, a third class of genes, DNA repair genes, has been implicated in tumorigenesis of colorectal cancer. Study findings suggest that DNA mismatch repair deficiency, due to germline mutation of the hMSH2, hMLH1, hPMS1, or hPMS2 genes, contributes to development of hereditary nonpolyposis colorectal cancer. The majority of tumors in patients with this disease and 10% to 15% of sporadic colon cancers display microsatellite instability, also know as the replication error positive (RER+) phenotype. This molecular marker of DNA mismatch repair deficiency may predict improved patient survival. Mismatch repair deficiency is thought to lead to mutation and inactivation of the genes for type II TGF-beta receptor and insulin-like growth-factor II receptor. Individuals from families at high risk for colorectal cancer (hereditary nonpolyposis colorectal cancer or familial adenomatous polyposis) should be offered genetic counseling, predictive molecular testing, and when indicated, endoscopic surveillance at appropriate intervals. Recent studies have examined colorectal carcinogenesis in the light of other genetic processes. Telomerase activity is present in almost all cancers, including colorectal cancer, but rarely in benign lesions such as adenomatous polyps or normal tissues. Furthermore, genetic alterations that allow transformed colorectal epithelial cells to escape cell cycle arrest or apoptosis also have been recognized. In addition, hypomethylation or hypermethylation of DNA sequences may alter gene expression without nucleic acid mutation.

Molecular pathogenesis of colorectal cancer

The enormous progress made in the identification of genes that are involved in colon carcinogenesis has provided the foundation for further understanding the biology of both normal and cancer cells and for targeted therapeutic strategies. In one sense, the genes described in this review are only the building blocks of a larger puzzle that constitutes the integrated metabolic function of a cell. The current challenge is to understand the functional role of these genes in normal cellular physiology and make the connections between pathways that knit together integrated cellular homeostasis. A complete understanding of the regulatory pathways, and the synthesis and modifications of the proteins involved, will provide novel targets for therapeutic agents.