Prognostic value of p53 overexpression and c-Ki-ras gene mutations in colorectal cancer

Alterations of p53 gene and Ha-ras gene are independent events in solar keratosis and squamous cell carcinoma

In order to clarity the multiple-step progression from solar keratosis to squamous cell carcinoma, aberrations of the p53 gene (exons 2-11) and ras genes (exons 1 and 2) in solar keratosis and squamous cell carcinoma were investigated by polymerase chain reaction and single-strand conformation polymorphism analysis. In a series of Japanese patients, eight of 27 (30%) samples of solar keratosis and three of six (50%) samples of squamous cell carcinoma showed structural abnormalities in the p53 gene. Only one solar keratosis (4%) showed a point mutation in the Ha-ras gene but not in the p53 gene. Among these cases, no mutation of ras genes could be detected in squamous cell carcinoma. Simultaneous mutation of ras genes and the p53 gene was not detected in any cases of either solar keratosis or squamous cell carcinoma. It is concluded that aberrations of the p53 gene and ras genes are induced through independent processes of ultraviolet irradiation in the course of carcinogenic change from solar keratosis to squamous cell carcinoma.

Prognostic markers in rectal carcinoma

Guidelines from two major organizations have recently supported the use of only the serological marker carcinoembryonic antigen (CEA) for the prognostication and monitoring of patients with colorectal carcinoma. However, in view of the exciting advances made recently in elucidating the molecular and cellular biology of adenocarcinoma of the rectum, the molecules that transform the well-ordered normal rectal epithelium into an invasive adenocarcinoma may yield information about the ultimate behavior of that cancer. Consequently, assessing the expression of molecules within a primary cancer may predict the probability of regional and distant metastasis, response to therapy, and outcome. This review analyzes the current state of intratumoral expression of several molecular markers for the management of rectal cancer and evaluates their potential for defining which patients may undergo rectal sphincter preservation and need adjuvant therapy.

Presence of activated ras correlates with increased cysteine proteinase activities in human colorectal carcinomas

The metastatic potential of ras-transfected cells has been attributed in part to significant ras induction of proteinase expression. To determine whether primary cancers also demonstrate higher cysteine proteinase activities in the presence of activated ras genes or altered ras protein expression, we have analyzed 60 primary human colorectal carcinomas for ras gene or protein changes together with the expression of cathepsins B and L. Cancers containing K-ras mutations (47% of 60 carcinomas) demonstrated greater increases in cathepsin L activity than cancers without K-ras mutations (p = 0.029), with particularly significant correlations for earlier stage cancers (Dukes' A and B carcinomas, p = 0.006). Western blots used to characterize ras protein patterns in the same cancer/normal pairs have demonstrated that N-ras protein is more highly expressed in colon tissues than H- or K-ras proteins and that N-ras overexpression occurs in almost 70% of colorectal cancers, with or without a concurrent change in electrophoretic mobility of N-ras protein. Our current study has now shown that N-ras protein overexpression alone does not significantly induce cathepsin B or L activity levels in colon cancers. However, carcinomas demonstrating altered N-ras protein forms, in the absence of any K- or N-ras mutations, expressed significantly higher levels of cathepsin B and L activities compared with carcinomas with normal N-ras protein banding patterns. Our data suggest that colorectal carcinomas with either K-ras mutations or altered forms of N-ras protein may increase their tumorigenic potential via the induction of cathepsin L or B expression levels. Our results also confirm that ras oncogene up-regulation of cathepsin B and L activities, previously reported in cultured cells, is a frequent event in primary human colorectal carcinomas.

Prognostic factors in colorectal cancer. Literature review for clinical application

PURPOSE

Identification of prognostic factors is a primary basis for planning the treatment and predicting the outcome of patients with colorectal cancer. Reviewing studies from the literature performed using univariate and multivariate analyses and their own study, the authors critically discuss the prognostic value of the clinicopathologic parameters of the tumor.

METHODS

Among 853 patients with colorectal tumors seen at the Department of Clinical Surgery of the Catholic University of Rome, Italy, 690 cases that were curatively resected the study. Overall survival rate, related to the clinicopathologic variables, was calculated, and univariate and multivariate analyses were performed.

RESULTS

Five-year and ten-year overall survival rates were 70 and 55 percent, respectively. Univariate and multivariate analyses showed that node involvement, distant metastases, bowel obstruction, and patient gender are factors independently related to outcome.

CONCLUSIONS

Data from the literature and the present study suggest that only a few clinical parameters, particularly bowel obstruction, and some pathologic factors (tumor stage, vessels invasion, and tumor ploidy) are related to patient survival rate and are the most reliable prognostic criteria. In prospective clinical studies, any other new pathologic or molecular factors should be matched with these parameters to confirm their value in outcome prediction.

Association of p53 accumulation with TP53 mutations, loss of heterozygosity at 17p13, and DNA ploidy status in 273 colorectal carcinomas

The aim of this study was to establish an experimentally based cutoff level for assessing p53 immunoreactivity in colorectal tumors. The accumulation of p53 protein in 273 colorectal tumors was correlated with previously obtained data on TP53 mutation and loss of heterozygosity at two 17p13 loci in the same tumors. The monoclonal antibody PAb 1801 was used for p53 staining, and the results obtained by immunohistochemistry and immunoblotting were similar. Mutation analyses of exons 5-8 were performed using constant denaturant gel electrophoresis followed by sequencing. There were no statistically significant differences for any measured TP53 gene alteration between the group of tumors without p53-positive nuclei (n = 83) and the group with <5% positive nuclei (n = 58). The majority of mutations within these groups were deletions/insertions and nonsense mutations without p53 accumulation. Therefore, we assume that 5% p53-positive nuclei is the relevant cutoff level to assess TP53 damage in colorectal tumors. A prerequisite for this recommendation is optimal conditions for p53 protein detection. The parameters for p53 dysfunction were correlated to DNA aneuploidy measured by flow cytometry. TP53 mutations were significantly associated with DNA aneuploidy (P < 0.00001), and a nonrandom distribution of TP53 gene alterations among diploid (DI = 1), hyperdiploid (1.0 < DI < 1.3), and highly aneuploid (DI > 1.3) tumors indicates that DNA hyperdiploid tumors constitute a separate developmental entity different from tumors with gross aneuploidy.

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.

The association between telomerase, p53, and clinical staging in colorectal cancer

BACKGROUND

A proposed etiology of tumor activation involves p53 mutations while telomerase may serve as a key enzyme for maintenance of tumor cell proliferation.

METHODS

Telomerase activity levels were measured in colorectal adenocarcinomas and corresponding normal tissue using a modified telomeric repeat amplification protocol, and p53 mutations were identified using immunohistochemical staining. Results were compared with staging data using regression analysis.

RESULTS

Telomerase activity was present in 23 of 23 (100%) of the tumors and only 2 (9%) of normal specimens (P <0.0001). The p53 mutations were present in 18 of 23 (78%) of the tumors. No significant correlation between p53 mutations, telomerase activity levels, and staging was found.

CONCLUSIONS

Telomerase activity in 100% of the tumors suggests telomerase activation is a universal event in colorectal tumor progression; however, telomerase activity appears to be independent of p53 mutations and clinical staging.

The detection of K-ras mutations in colorectal cancer using the amplification-refractory mutation system

A total of 301 colorectal carcinoma (CRC) archival samples were analysed using the amplification-refractory mutation system (ARMS). Each sample was examined to determine the mutation status of codons 12 and 13 of the K-ras oncogene. The results from direct DNA sequence analysis carried out on 30 of the samples differed from the ARMS result in almost 50% of the cases as a result of the relative excess of wild-type to mutated DNA sequences. To assess the validity of the ARMS data, the polymerase chain reaction (PCR) was used to generate an amplicon from K-ras exon 1 from 23 of the samples. The PCR amplicons were cloned and sequenced, and the DNA sequence analysis of the cloned material was in agreement with the ARMS results in all but one case. This case represented a tumour that exhibited a five-nucleotide reversed inversion. The cloned sequence data confirm the sensitivity and specificity of the individual ARMS reactions and that it is possible in certain cases to detect additional, more complex, sequence variations.

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.

The type of K-ras mutation determines prognosis in colorectal cancer

BACKGROUND

Mutations involving the oncogene K-ras in colorectal cancer may be related to tumor aggressiveness. However, the value of K-ras gene determination as a prognostic marker has not been clearly established.

PATIENTS AND METHODS

The results from 98 patients recruited in a prospective study analyzing the effect of a K-ras mutation as a prognostic factor in colorectal cancer are reported.

RESULTS

Disease-free (P = 0.02) and overall survival (P = 0.03) were significantly reduced for patients harboring a K-ras mutation. Two specific mutations demonstrated a significantly increased risk of disease recurrence, namely, 12-TGT (P = 0.04) and 13-GAC substitutions (P = 0.002). Patients with either of these substitutions had a 2-year disease-free survival rate of 37% compared with that of 67% for the group of patients harboring any other mutation type or a wild-type status (P = 0.01).

CONCLUSIONS

The results herein presented suggest that K-ras acts as a prognostic factor in colorectal cancer and that this effect is probably related to a limited number of defined mutations.

Ki-ras mutations and prognosis in colorectal cancer

A total of 191 colorectal adenocarcinomas, obtained from consecutive patients with a median follow-up of 6 years, were studied in order to evaluate the possible association of Ki-ras mutations with tumour stage, tumour differentiation and survival time. Resected full-cross tumour samples were screened for Ki-ras mutations in codons 12 and 13 using temporal temperature gradient gel electrophoresis (TTGE). Ki-ras mutations were detected in 62 (32%) of the samples. The most frequent mutation, observed in 21 samples, was from GGT to GAT changing glycine to aspartic acid in codon 12. The study did not show any association between Ki-ras mutations and Dukes' stage or tumour differentiation. Patients with Ki-ras mutations had a marginally shorter survival time (median 50 months) compared with patients without (median 59 months), but the difference was not statistically significant. The results indicate that Ki-ras gene mutations have no relevant prognostic importance in this cohort of colorectal cancer patients.

Diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer

PURPOSE

The study contained herein was undertaken to review and summarize the current literature on diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer.

RESULTS

Limitations of traditional imaging techniques have encouraged development of targeted imaging strategies using radiolabeled monoclonal antibodies. Diagnostic immunoscintigraphy can detect lesions not identified by conventional imaging modalities, although it has not proven useful in the management of primary colorectal cancers and in hepatic metastases. Immunoscintigraphy shows promise in cases of local recurrence and rising carcinoembryonic antigen values; however, the impact of immunoscintigraphy on clinical outcomes and cost-effectiveness remains unproven. Radioimmunoguided surgery has been advocated as a method of more accurately detecting tumor extension and accomplishing radical resection. The technique remains controversial, and its use is not widespread. With respect to therapeutic applications, immunotherapy has most often been investigated in the setting of advanced stage disease. Results in this setting have been poor. In contrast, adjuvant immunotherapy after resection of Dukes C carcinoma has achieved convincing results, with improvements in survival comparable with that of adjuvant chemotherapy. Adjuvant trials are now under way to examine the effectiveness of monoclonal antibodies in the postoperative treatment of early-stage (II) tumors and the combination of monoclonal antibodies and chemotherapy in advanced-stage (III) tumors. Bispecific antibodies, or immunoconjugates with cytokines or toxins, represent additional areas of interest and future investigations.

CONCLUSIONS

At present, immunoscintigraphy is not sufficient to determine, by itself, resectability of colorectal tumor and has limited usefulness in select cases of recurrent cancer and possibly in cases of rising carcinoembryonic antigen values. Immunotherapy with monoclonal antibodies as a postoperative adjuvant treatment shows promise and is currently being investigated in national trials.

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 advances in the etiology and treatment of colorectal cancer

The diagnosis and treatment of colorectal cancer remains a formidable health care problem. Colorectal cancer is the second most frequently diagnosed cancer in both men and women in Western countries and accounts for over 55,000 deaths annually in the United States alone. Cancer of the colon and rectum is eminently curable by surgical resection if identified early; however, despite our best efforts, patient survival from this disease has changed little over the past 50 years. With the advent of molecular and genetic techniques, a number of novel discoveries have been made in the last decade which have greatly expanded our understanding of the etiology and cellular mechanisms contributing to the development and subsequent progression of colorectal cancer. This review summarizes the recent molecular advances in the understanding of both familial (HNPCC and FAP) and sporadic colorectal cancers. The numerous scientific advances described in this review offer the promise of the development of novel chemotherapeutic agents, more accurate prognostic indicators and better screening techniques.

Prognostic value of immunohistochemistry for p53 in primary soft-tissue sarcomas: a multivariate analysis of five antibodies

Most changes of tumor suppressor p53 and its pathway involve a protein with prolonged half-life that permits immunohistochemical detection. The goal of this study was to compare the prognostic relevance of five different p53 antibodies in primary soft-tissue sarcomas (STS) with known p53 mutation status, using a multivariate Cox regression model (adjusted to tumor grading, staging, localization, tumor type, and therapy). A group of 198 primary STS of six types were investigated for p53 overexpression, using p53 antibodies DO-1, DO-7, Pab1801, Pab240, and CM-1. A positive marker frequency between 36.2% and 62.6% was detected. Out of 65 patients whose primary tumor reacted positively to all five antibodies, 52 (80%) died within the study period. Only the N-terminal-binding monoclonal antibodies DO-1, DO-7 and Pab1801 showed a multivariate correlation with survival (P = 0.0014, 0.0048 and 0.02). CM-1 and Pab240 had a univariate, but not a multivariate correlation, with a confounding effect of grading. The prognostic relevance for the five p53 antibodies was: DO-1 > Pab1801 > DO-7 > CM-1 > Pab240. This is the first study that investigates multivariately the prognostic relevance of p53 immunostaining in STS. If monoclonal antibodies with an epitope in the N-terminal region of the p53 protein (DO-1, Pab1801, DO-7) are applied, p53 immunohistochemistry provides an independent prognostic marker in STS.

K-RAS-2 gene mutations as predictors of metachronous colorectal adenomas

BACKGROUND

Mutations of K-RAS-2 gene and tumour suppressor genes have been found in both colorectal adenomas and carcinomas. The aim of this study was to investigate the prognostic value of K-RAS-2 gene mutations found in initial colorectal adenomas for predicting the risk of metachronous adenomas.

METHODS

Genomic DNA was extracted from formalin-fixed and paraffin-embedded adenomas larger than 5 mm in diameter removed at the initial total colonoscopy between 1980 and 1982. All patients underwent colonoscopic follow-up for at least 10 years. The sequence of exon 1 of the K-RAS-2 oncogene was amplified with the polymerase chain reaction technique and screened for mutation by single-strand conformation polymorphism analysis. All suspected mutations were confirmed by direct DNA sequencing. The predictive value of K-RAS-2 gene mutations for the risk of metachronous adenomas was assessed by chi-square testing and logistic regression analysis.

RESULTS

Of 54 patients 39 (72%) were male and 15 (28%) female. At the time the initial adenoma was removed, 31 (57%) patients were younger than 60, whereas 23 (43%) were 60 years or older. Point mutations of the K-RAS-2 oncogene were found in the index adenomas of 15 (27.7%) patients. Mutations were found more frequently in large (> or = 20 mm) adenomas and in adenomas with severe dysplasia (P = 0.0011 and P = 0.0310, respectively). There were no significant associations between K-RAS-2 mutations and anatomic location, histologic type, or number of synchronous initial lesions. Mutations were found predominantly at codon 12 with transversions from GGT to GTT (57%), from GGT to GAT (36%), and from GGT to TTT (one patient). The single mutation found at codon 13 showed a transversion from GGC to GAC. There were significant associations between size (> or = 20 mm) and K-RAS-2 mutation of the initial adenomas and the size (> 5 mm) of metachronous adenomas (P = 0.0259 and P = 0.0265, respectively). However, multivariate analysis showed that K-RAS-2 mutations did not provide a significant additional contribution to the prognostic value of the size of the initial adenoma (odds ratio, 7.62; 95% confidence interval (CI), 1.68-34.48) and the amount of villous structure (odds ratio, 0.22; 95% CI, 0.05-0.90) it contained.

CONCLUSIONS

Patients with large (> or = 20 mm) adenomas and adenomas with K-RAS-2 mutations found at the initial examination have a significantly higher risk of developing large (> 5 mm) metachronous adenomas during surveillance. Multivariate analysis of initial adenoma characteristics showed that the risk of metachronous colorectal adenomas can be adequately estimated by the size and the histologic type of the largest initial adenoma and that K-RAS-2 mutations are of secondary importance only. Further studies based on a larger series will have to identify the adenoma characteristics that will help to improve follow-up strategies.

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.

Comparison of p53 expression in proximal and distal gastric cancer: histopathologic correlation and prognostic significance

BACKGROUND

The overexpression of p53 has been found to be correlated with prognosis of some carcinomas, including gastric cancer, but no studies have reported on its relationship to the location of gastric cancer. In the present study, we compared the p53 expression of proximal and distal gastric cancer concerning histopathology and prognosis.

METHODS

A total of 170 tumors in the patients with proximal (80 cases) and distal (90 cases) gastric cancer were studied by immunohistochemical methods.

RESULTS

p53 immunopositivity was detected in 28.8% of all tumors. The p53-positive expression in proximal gastric cancer was higher than in distal gastric cancer (38.8% vs. 20.0%, p < 0.05). A 5-year survival analysis showed that there is no significant difference between tumors that are p53 positive and p53 negative. No correlation was found between p53 expression and histopathology of gastric cancer.

CONCLUSION

p53 nuclear staining is not useful as a prognostic indicator or as a parameter in gastric cancer.

Prognostic significance of Bcl-2 expression and p53 nuclear accumulation in colorectal adenocarcinoma

The products of bcl-2 and p53 genes are involved in the regulation of apoptosis and proliferation and have been associated with prognosis in several malignancies, including colorectal adenocarcinoma. Although 2 European studies have reported a prognostic significance of Bcl-2 expression in colorectal adenocarcinomas, a study from the United States did not observe such an association. Therefore, we used immunohistochemistry to evaluate the prognostic significance of Bcl-2 expression, p53 nuclear accumulation and their concomitant expression in 134 US patients with colorectal adenocarcinoma. Antigen retrieval was required for adequate detection of Bcl-2 expression. Fifty percent of the colorectal tumors were classified as expressing Bcl-2, and Bcl-2 expression was associated with longer patient survival. Antigen retrieval was not necessary for detecting nuclear accumulation of p53 by immunohistochemistry. Nuclear accumulation of p53 was detected in 44% of colorectal adenocarcinomas and was associated with decreased patient survival. Tumors that did not express detectable levels of Bcl-2 but exhibited nuclear accumulation of p53 were associated with the shortest patient survival (log rank, p = 0.001). Multivariate Cox regression analysis demonstrated that Bcl-2 expression (p = 0.018), p53 nuclear accumulation (p = 0.024) and regional lymph-node metastasis (p = 0.005) were independent prognostic factors. Although a trend toward an inverse correlation between Bcl-2 and p53 expression was observed, the prognostic value of Bcl-2 expression was independent of p53 status. Thus, assessment of both Bcl-2 and p53 status may be valuable in predicting the prognosis of patients with colorectal adenocarcinomas.

K-ras mutation and loss of heterozygosity of chromosome 17p and survival in colorectal cancer

BACKGROUND

The development of colorectal cancer (CRC) is thought to be a multistage process involving alterations to several types of genes, including oncogenes and tumour suppressor genes. This study examined the associations between allelic deletions of chromosome 17p in the region of the p53 gene and K-ras gene mutation and survival among CRC patients.

METHODS

Resected specimens from 233 patients were examined. Point mutation of codon 12 of K-ras was assessed using a modified polymerase chain reaction method. Allelic deletion of 17p was demonstrated by loss of heterozygosity (LOH) with the marker Mfd144.

RESULTS

Fifty-seven tumours (24%) showed somatic point mutation of codon 12 of K-ras and 86 tumours (37%) showed LOH of Mfd144. There were 107 tumours (46%) with either K-ras mutation or LOH and 18 tumours (8%) with both. Compared with patients with neither alteration, significantly poorer survival was experienced only by those with both alterations (P = 0.015). However, when this variable was introduced into a multivariate analysis controlling for the patient's age and tumour stage, it failed to show a statistically significant independent effect on survival.

CONCLUSIONS

Point mutation of K-ras and LOH of Mfd144 in CRC does not add to the prognostic information already available from clinicopathological staging.

p53 protein immunoexpression in esophageal squamous cell carcinoma and adjacent epithelium

BACKGROUND

Immunoreactivity for p53 tumor suppressor gene product is commonly found in human malignancies and some premalignant lesions, but its role in cancer development and its value as a marker of tumor biologic behavior is still unclear.

OBJECTIVES

This study was undertaken to assess p53 immunoexpression in esophageal squamous cell carcinoma and attempts to determine its correlation with morphological features associated with tumor behavior.

METHODS

Immunohistochemical study was performed on archival paraffin-embedded tissue of 37 esophageal squamous cell carcinomas and respective adjacent mucosa.

RESULTS

Twenty-one tumors (56.8%) demonstrated specific staining for p53. Sixteen areas of dysplasia were present in 14 out of the 35 cases. p53 positivity was found in one low-grade dysplasia and in six high-grade dysplasias. By univariate analysis, p53 immunoexpression correlated positively with local invasion (P = 0.01) and perineural spread (P = 0.04). Multivariate analysis with logistic regression showed that tumor invasion was the only factor that discriminated between p53 positive and p53 negative cases (OR: 15.6, P < 0.02). No relationship was found between p53 expression and tumor grade, DNA nuclear ploidy, and S-phase fraction.

CONCLUSIONS

These data suggest that p53 dysfunction may be implicated in early, preinvasive, stages of esophageal cancer as well as in the tumor progression related to a more invasive phenotype.

Topographic genotyping of colorectal carcinoma: from a molecular carcinogenesis model to clinical relevance

BACKGROUND

In recent years, as a result of refinement in molecular biology techniques, significant progress has been made in the understanding of colorectal carcinogenesis. Particular attention has been drawn to identification of genetic mutation that may predispose to colorectal carcinoma (familial syndromes) and may affect tumor behavior and prognosis (sporadic cases).

CONCLUSIONS

Our method of topographic genotyping of human colonic carcinomas has shown a correlation between K-ras-2 and p53 mutations and stage at diagnosis as well as long-term survival. Data from other investigators in this field confirm the importance of genetic analysis of human colorectal tumors. These findings are likely to impact management by allowing a more individualized therapeutic approach.

Genetic heterogeneity in sporadic colorectal adenomas

The majority of colorectal cancers develop from adenomatous polyps under the influence of factors that are still poorly understood. Tumourigenesis is generally considered a multistep process in which multiple genetic alterations occur, eventually reflected in abnormalities of the cellular DNA content. Macroscopical features such as tumour size and tumour architecture (tubular, tubulovillous, or villous) are correlated wit the chance of malignancy in the lesion. Grade of dysplasia can be considered an indicator for the level of progression of the adenoma towards invasive carcinoma. These characteristics were correlated with the presence or absence of K-ras mutations and the DNA ploidy in a prospective study performed on 46 large sporadic colorectal adenomas resected by endoscopy. DNA ploidy and K-ras mutations were analysed in two samples taken at distant sites in the adenomas. Aneuploidy was present in 12 adenomas (26 per cent) and K-ras mutations occurred in 26 (57 per cent). A highly significant correlation was found between aneuploidy and adenoma size, architecture, and grade of dysplasia. The presence of K-ras mutations was significantly correlated only with the size of the adenomas. The proportion of adenomas with aneuploidy and/or a K-ras mutation increased when two samples were analysed instead of one. This observation suggests that the prevalence of genetic mutations and of aneuploidy is probably underestimated, as generally only one sample is investigated. No correlation was observed between K-ras mutations and ploidy. This study demonstrates the presence of genetic heterogeneity in colorectal adenomas and supports the notion that K-ras mutation is an early event, while aneuploidy is a late event in the adenoma-carcinoma sequence.

Association between sucrase-isomaltase and p53 expression in colorectal cancer

BACKGROUND

Sucrase-isomaltase (SI) is a tissue-based phenotypic marker that is an independent prognostic factor in colorectal cancer (CRC). DF3 and galectin 3 are two other tissue-based markers that are upregulated during neoplastic transformation. Because p53 mutations are acquired during neoplastic progression, we reasoned that alterations in SI and p53 may be associated despite an apparent lack of biological interaction.

METHODS

Paraffin sections from 183 patients who underwent surgery at New England Deaconess Hospital (NEDH) between 1965 and 1977 were analyzed first by immunohistochemistry (IHC) for the expression of the markers SI, DF3, and galectin 3, which were scored as absent or present. Paraffin sections from a second group of 59 patients who underwent surgery at NEDH between 1985 and 1992 were analyzed by IHC for the expression of p53 as well as SI, DF3, and galectin 3. p53 nuclear staining was scored as absent or present. Previous work has shown that p53 is mutated in all cells with nuclear staining and in 10% of tumors that are unstained.

RESULTS

SI expression was not associated with the expression of either DF3 or galectin 3, and neither DF3 nor galectin 3 were prognostic factors in CRC. None of the phenotypic markers were associated with any of the clinicopathologic variables. However, 21 of 24 p53-positive cases (88%) expressed SI, whereas 15 of 35 p53-negative cases (43%) were also SI negative (p = 0.02, Fisher exact test). p53 expression was not associated with expression of DF3 or galectin 3.

CONCLUSIONS

SI expression and p53 mutation are associated significantly in CRC. Although the mechanism underlying such an association in presently unknown, the association may define a subset of patients with a worse prognosis.

Immunohistochemical detection of p53 and c-erbB-2 in oesophageal carcinoma; no correlation with prognosis

TNM staging of oesophageal cancer provides significant prognostic information but its clinical impact is limited as many patients present with advanced disease (i.e. T3N1). Additional prognostic markers may help separate those with 'good' and 'bad' prognosis tumours and so help with decisions such as selection for adjuvant therapy. p53 and c-erbB-2 overexpression may correlate with poor prognosis in oesophageal cancer, but this is uncertain. This study aimed to investigate the value of these biomarkers as prognostic indicators in resected oesophageal cancer. Two hundred and five oesophageal tumours (127 adenocarcinoma, 78 squamous) resected by a single surgeon between June 1979 and January 1991 were investigated for p53 and c-erbB-2 overexpression using DO-7 and CB-11 immunohistochemistry. Patient survival was analysed by Kaplan-Meir life tables. Median survival was 61 weeks (range: 5-747) and survival diminished significantly with increasing UICC stage (P < 0.0001). Sixty-eight per cent of squamous tumours and 66% of adenocarcinomas overexpressed p53 but there was no statistically significant correlation with prognosis. Twenty-six per cent of squamous tumours and 23% of adenocarcinomas overexpressed c-erbB-2, but again this did not correlate with survival. p53 and c-erbB-2 are commonly overexpressed in oesophageal cancer but do not appear to be related to prognosis in this large series of resected oesophageal cancers and other candidate biomarkers must be sought.

K-ras mutations and prognosis in large-bowel carcinomas

BACKGROUND

Colorectal carcinogenesis is regarded as a multistep process involving several genetic alterations, with mutation in the K-ras gene in about half of the tumours. We aimed at clarifying the role of this genetic alteration related to survival and clinicopathologic variables.

METHODS

One hundred large-bowel carcinomas operated on between 1978 and 1982 were studied for the presence of point mutations in codons 12 and 13 of the K-ras gene, using enriched polymerase chain reaction amplification, restriction fragment length polymorphism analysis, and direct sequencing.

RESULTS

Forty mutations were found (40%): 31 in codon 12 and 9 in codon 13, 7 different types. There was no relationship between tumours with and without K-ras mutations with regard to Dukes' stages, age or sex of the patient, tumour localization, histologic grade, DNA ploidy pattern, HLA-DR staining pattern, or survival. Samples from 5 different localizations in 7 carcinomas showed identical K-ras mutation pattern, as did 19 recurrences/ metastases originating from 11 carcinomas.

CONCLUSIONS

When present, the primary tumour shows homogeneous distribution of K-ras mutation, and the mutation follows the carcinoma in the secondary deposit, regardless of lymphogenous or hematogenous spread. The presence of K-ras mutation does not seem to have prognostic significance for the patient, and the precise nucleotide change is furthermore not predictive of tumour behaviour.

p53 and Rb1 protein expression: are they prognostically useful in colorectal cancer?

The expression of the p53 and Rb1 proteins was examined in an unselected consecutive series of 250 primary operable colorectal carcinomas with a mean follow-up of 4.3 years (range 43-77 months). The overall cancer-specific mortality was 34.8%, with 87 cancer deaths and 35 deaths as the result of other causes. Expression of p53 protein was identified in 152 of 250 (60.8%) cases, with expression of Rb1 protein in 207 of 250 (82.8%) cases. There was no association of p53 or Rb protein expression with patient age, sex, tumour site, tumour size, tumour type, tumour grade, peritumoral fibrosis, tumour lymphocytic infiltrate, nature of the tumour margin, extramural vascular invasion, number of lymph nodes or high apical lymph node involved or local peritoneal infiltration by tumour, Dukes' stage or Jass group. There was no difference in overall survival or recurrence-free survival for those cases that showed p53 expression or Rb1 protein expression compared with those cases showing absence of p53 or Rb1 protein expression, although patients with tumours showing aberrant (reduced) Rb1 protein expression demonstrated shorter recurrence-free survival and overall survival. The effect of 'aberrant' Rb1 protein expression and shorter recurrence-free and overall survival did not, however, achieve independent statistical significance. The results from this study would suggest that expression of p53 and Rb1 proteins does not appear be useful in determining the prognosis of operable colorectal cancer.

A detailed analysis of the role of K-ras gene mutation in the progression of colorectal adenoma

To elucidate the role of ras gene mutations during the early stage of colorectal tumour progression, K-ras gene mutations were analysed in 32 benign adenomas and 36 adenomas with focal carcinoma in the colorectum by microscraping of histologically pure regions from tissue sections, polymerase chain reaction-restriction fragment length polymorphism and in part by direct sequencing. Several regions were scraped out and analysed when an adenoma contained areas with different grades of dysplasia. The frequencies of K-ras gene mutation in mild dysplasia, moderate dysplasia and focal carcinoma were 19% (7/36), 51% (25/49) and 39% (14/36) respectively. The K-ras gene status was heterogeneous in 4 of the 11 benign adenomas from which multiple samples were obtained, and mutations were always found in the regions with more advanced dysplasia in these adenomas. Thirteen of the 36 adenomas with focal carcinoma showed heterogeneity of mutations between the adenoma region and the focal carcinoma. Seven of which had mutations only in the adenoma region. These findings indicated that the K-ras gene mutations occur during the late stage of adenoma progression and may confer a more advanced morphological phenotype of adenoma, but these mutations are not mainly involved in malignant transformation from adenoma to carcinoma.

Prognostic significance of p53 abnormalities in colorectal carcinoma detected by PCR-SSCP and immunohistochemical analysis

Abnormalities in the p53 tumour suppressor gene and in the expression of its protein are common in colorectal carcinoma. The prognostic significance of these p53 abnormalities was studied in 66 patients with colorectal cancer, followed for more than 10 years. Single-strand conformation polymorphism (SSCP) analysis was used to detect alterations in exons 5-8 of the p53 gene. Paraffin sections were examined immunohistochemically for p53 overexpression with the monoclonal antibody DO-7 (Dako) both with and without microwave antigen retrieval. Abnormalities of the p53 gene were found in 41 per cent of cases by SSCP analysis. Outcome was unrelated to SSCP abnormalities (P = 0.19), except for the Dukes' A and B subgroup, where decreased survival was found in cases with abnormal SSCP (P = 0.01). Overexpression of p53 protein was seen by immunohistochemistry in 47 per cent of cases without, and in 52 per cent of cases with microwave antigen retrieval. Immunohistochemical overexpression of p53 protein either with or without microwave antigen retrieval was an independent prognostic indicator of poor survival. These results suggest that for routine purposes, immunohistochemical detection of the p53 protein product may be more useful than SSCP analysis of the encoding p53 gene in identifying those at high risk of colorectal cancer recurrence and death.

p53 expression in carcinoma of the cervix

AIM

To assess overexpression of the proposed tumour suppressor gene product p53 using the mouse monoclonal antibody DO-7 in the three main subtypes of carcinoma of the uterine cervix and to evaluate its value as a prognostic indicator.

METHODS

Eighty two cases of FIGO Stage IB/IIA uterine cervical carcinoma were studied retrospectively. The tumours had been previously typed into adenocarcinomas, squamous carcinomas and adenosquamous carcinomas after the tissue had been fixed in formalin and embedded in paraffin wax. p53 protein expression was assessed using a standard immunohistochemical technique and the findings were correlated with tumour type, lymph node status and clinical outcome.

RESULTS

In total, the p53 gene product was overexpressed in 17.1% (14/82) of all carcinomas and also in areas of cervical intraepithelial neoplasia grade III adjacent to invasive squamous carcinoma. Where present, the normal epithelium was uniformly negative. No association was found between p53 overexpression and tumour subtype, lymph node status or clinical outcome.

CONCLUSIONS

It seems unlikely that p53 analysis will be of value in determining prognosis in carcinoma of the uterine cervix.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in colonic adenomas-adenocarcinomas

Colonic adenocarcinomas evolve through a multistep process from tubular adenomas to invasive adenocarcinomas. Matrix metalloproteinases (MMPs) have been implicated in proteolysis of basement membrane for initiation of metastatic cascade.

METHODS

By immunocytochemical staining, hyperplastic polyps, tubular adenomas, tubovillous adenomas, villous adenomas to adenocarcinomas were systematically examined for the presence of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) and tissue inhibitor of MMP (TIMP)-1 and TIMP-2, respectively.

RESULTS

MMP-2 and MMP-9, and TIMP-1 and TIMP-2 were immunolocalized in scattered stromal cells, whereas epithelial cells of normal mucosa and hyperplastic polyps were weakly stained. From tubular adenomas to villous adenomas, immunolocalization of gelatinases and TIMPs showed increasing gradually, and in situ carcinomas showed a definite positive, immunolocalization of gelatinases and TIMPs.

CONCLUSION

Increasing immunolocalization of gelatinases and TIMPs from tubular adenomas to adenocarcinomas coincides with a multistep process of colonic tumorigenesis.

Prognostic significance of p53 nuclear and cytoplasmic overexpression in right and left colorectal adenocarcinomas

The prognostic significance of nuclear and cytoplasmic p53 protein, detected immunocytochemically using CM1 and PAb 1801 antibodies, was evaluated in right-sided and left-sided colorectal adenocarcinomas from 293 patients. CM1 nuclear and cytoplasmic p53 accumulation occurred in 38 and 25% of cases, respectively. PAb 1801 nuclear staining occurred in 18%, with no cytoplasmic staining. CM1 expression either in the nucleus or in the cytoplasm was positively related to PAb 1801 expression (P < 0.001 and P = 0.009, respectively). The incidence of CM1 nuclear and cytoplasmic expression was more frequent in right-sided tumours (P = 0.023 and P = 0.034, respectively), while PAb 1801 nuclear staining was more common in left-sided tumours (P = 0.011). In survival analyses, CM1 nuclear overexpression in the right-sided tumours (P = 0.016) and CM1 cytoplasmic overexpression in left-sided tumours (P = 0.04) were prognostic indicators, independent of Dukes' stage, DNA ploidy, PAb 1801 expression and each other. Further analysis showed that the prognostic value of CM1 nuclear expression was greater in right-sided tumours than in left-sided tumours (P = 0.018). The nuclear and cytoplasmic p53 protein detected with CM1 and PAb 1801 may play different roles in tumour progression and provide prognostic indicators for right- and left-sided colorectal tumours.

Concordance between p53 protein overexpression and gene mutation in a large series of common human carcinomas

Immunohistochemical (IHC) detection of p53 protein was compared with the presence of p53 gene mutation in many colorectal (n = 100), breast (n = 92), endometrial (n = 122), and gastric (n = 116) carcinomas. Two commercially available antibodies, DO7 and CM1, were used for IHC analysis of paraffin-embedded tissue sections. Screening for gene mutations in frozen and paraffin-embedded tumor samples was carried out using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP). The frequency of nuclear staining with DO7 or CM1 for each tumor type, respectively, was colorectal (36%, 23%); breast (15%, 19%); endometrial (21%, 33%); and gastric (23%,-). Overall correlation between the two antibodies for nuclear staining was 90% for the 314 tumors analyzed. Cytoplasmic staining was observed with DO7 in 7% of breast and 5% of gastric carcinomas and with CM1 in 17% of breast and 54% of endometrial carcinomas. p53 gene mutation was found in 39% of colorectal, 28% of breast, 13% of endometrial, and 25% of gastric cancers. The concordance between p53 nuclear overexpression and gene mutation (both positive or both negative) was 68% for colorectal, 79% for breast, 76% for endometrial, and 73% for gastric carcinomas. This study provides further evidence that IHC detection of p53 protein accumulation does not always indicate the presence of a gene mutation and vice versa. Discordant results were observed in approximately 20% to 30% of the tumors studied, highlighting the need for careful characterization of both p53 gene and protein alterations when assessing the relationship between p53 status and tumor behavior.

Clinical and pathological associations with p53 tumour-suppressor gene mutations and expression of p21WAF1/Cip1 in colorectal carcinoma

Inactivation of the p53 tumour-suppressor gene is common in a wide variety of human neoplasms. In the majority of cases, single point mutations in the protein-encoding sequence of p53 lead to positive immunohistochemistry (IHC) for the p53 protein, and are accompanied by loss of the wild-type allele. Recently, the WAF1/Cip1 gene was identified as one of the genes induced by wild-type p53, and increased expression of p21WAF1/Cip1 has been found to reflect the status of the p53 tumour-suppressor pathway. We investigated the inactivation of p53 in a relatively small, but well-characterised, group of 46 colorectal carcinomas that were previously studied for allelic alterations, ras oncogene mutations and DNA aneuploidy. Alterations in p53 were identified by IHC, loss of 17p and DNA sequence analysis of exons 5-8, whereas p21WAF1/Cip1 protein expression was determined by IHC. p53 mutations were identified in 19 of the 46 tumours (41%), whereas positive IHC for p53 was found in 21 of the 46 tumours (46%). Positive IHC for p21WAF1/Cip1 was detected in 16 of 42 cases (38%). We found no relationship between p21WAF1/Cip1 staining and p53 protein expression or p53 mutational status. Inactivating mutations in the p53 gene correlated with LOH at 17p but not with LOH at 5q or 18q, Dukes' stage, tumour grade or DNA ploidy. There was a higher survival rate independent of Dukes' stage in the group with no alterations in p53 compared with those with evidence of dysfunction of p53, but the difference was not statistically significant. We conclude that inactivation of p53 and altered expression of p21WAF1/Cip1 are common in colorectal carcinoma but do not correlate with each other or with the clinical or pathological parameters investigated.

Prognostic significance of p53 overexpression and mutation in colorectal adenocarcinomas

The p53 tumour-suppressor gene is found altered in the majority of colorectal cancers. Lesions include allelic loss, mutation of the gene and overexpression of the p53 protein. All of these lesions have been analysed for prognostic significance, and whereas both mutation and allelic loss have been shown to be reasonably useful markers of prognosis, the utility of overexpression of the p53 protein is more ambiguous. Given that many authors use p53 overexpression as a marker for point mutation this issue is of some importance. We have therefore examined 100 colorectal carcinomas for mutation of the p53 gene, as well as overexpression of the p53 protein. Results show that whereas mutation of the p53 gene is associated with p53 overexpression, the degree of association depends, at least in part, upon the particular antibody used. Moreover, although mutation of the p53 gene does provide prognostic information, overexpression of the p53 protein, as detected with two antibodies, does not. These results suggest that immunohistochemistry is not a suitable alternative to direct detection of mutation in assessing prognosis in colorectal cancer patients.

Prognostic significance of cytoplasmic p53 overexpression in colorectal cancer. An immunohistochemical analysis

p53 overexpression was studied by immunohistochemistry in 96 consecutive colorectal cancer patients, subdividing positive specimens according to two staining patterns: cytoplasmic or nuclear. Forty-seven per cent of the cases were p53 positive, a significant correlation being found with Dukes' stage (P = 0.0036). A prevalence of nuclear staining was observed in Dukes' B and cytoplasmic in Dukes' D stages. After 36 months, 23% of the patients had a recurrence, and 45% were p53 positive, all Dukes' C-D stage with cytoplasmic staining. The Kaplan-Meier curve showed a significant correlation between p53 cytoplasmic staining and disease-free survival period (P = 0.002). With respect to disease-free survival, the Cox proportional hazard regression test, comparing p53 positivity with Dukes' stage, showed the latter to be the most significant variable. In our series of patients, advanced Dukes' stage tumours were localised in the right colon, where a higher percentage of p53 positivity (67% versus 40% of the left side), as well as a higher frequency of cytoplasmic staining was observed. In conclusion, from the data obtained, a strong correlation between p53 cytoplasmic staining and patient prognosis is clearly indicated.

p53 accumulation in colorectal cancer with hepatic metastasis

The prevalence of immunoreactive p53 and argyrophilic nucleolar organizer region (AgNOR) numbers were compared between colorectal cancers with (n=44) and without (n=51) hepatic metastasis for at least 5 years. At the same time, the distribution of p53-positive cells in primary, metastatic, and xenografted tumors from the same individuals were studied. Overall, p53 positivity was found more frequently in the cases with hepatic metastasis than in non-metastatic controls, regardless of the distribution pattern (P<0.05), whereas AgNOR counts were not different between the two groups. Significant heterogeneity in the distribution of p53 immunoreactivity was noted in both the primary and metastatic lesions. The intratumor distribution patterns of p53 immunoreactive cells in the primary (n=33), metastatic (n=33), and xenografted (n=7) tumors of the same individuals were consistent in the majority of cases. There were a few cases in which the p53 immunoreactive cells were more dominant in the metastatic tumor cells. Our observations suggest that p53 accumulation in colorectal cancer is associated with increased risk for hepatic metastasis, while cell proliferation as represented by AgNOR numbers is not. In addition, heterogeneity of abnormal p53 accumulation in the tumor is maintained during the course of metastasis and even after implantation in nude mouse. p53-Immunoreactive cells in the population of colorectal cancer cells do not necessarily have higher metastasizing potential.

C-KI-RAS activation and the biological behaviour of proximal and distal colonic adenocarcinomas

One hundred and forty colonic adenocarcinomas originating on the left side of the colorectum and 70 colorectal carcinomas originating on right side of the colorectum were examined for activating mutations of codons 12 and 13 of the C-KI-RAS proto-oncogene. Rates of mutation were significantly different (right colon 43%, 30/70 versus left colon 23%, 32/140; P = 0.0025). Adenocarcinomas from the left side of the colorectum showed a significant association between C-KI-RAS activation and tumour progression, including the presence of distant organ metastasis at the time of surgery (P = 0.0039), and during patient follow-up (P = 0.00027), whereas those from the right of the colorectum did not (P = 0.4 and P = 0.5, respectively). Mutation of the C-KI-RAS proto-oncogene was found to be associated with a significantly poorer patient prognosis on the left of the colorectum (P = 0.0001 by log rank analysis of Kaplan-Meier plots) but not on the right (P = 0.7). These results demonstrate that, not only is the timing and frequency of C-KI-RAS activation different between carcinomas originating on the left or right of the colorectum, but also that the biological consequences of such mutations may differ.

Growth factors: potential for the management of solid epithelial tumours

At present we are on the threshold of an enormous change in clinical practice. The application of molecular medicine has already started and the area of growth factor biology is particularly relevant to this endeavor (Figure 6) (Jankowski and Polak 1996). Perhaps the major limitation to this process is the rate at which the clinician can comprehend and then undertake carefully designed molecular studies in gastroenterology. In time monographs that specifically address the issue of molecular medicine in clinical gene analysis and manipulation may perhaps replace standard text books (see Jankowski and Polak, 1996).

Synchronous colon carcinomas: molecular-genetic evidence for multicentricity

BACKGROUND

The synchronous presentation of multiple colonic adenocarcinomas is an unusual, but well-recognized event accounting for approximately 2-11% of these neoplasms. Synchronous tumors may have a different biology and prognosis than solitary tumors. Evidence based on measurement of DNA ploidy suggests that a significant percentage of synchronous tumors have a common clonal origin, probably resulting from translumenal metastasis.

METHODS

Fifteen synchronous colorectal cancers (30 tumors) were examined for histologic differences as well as genetic mutations. p53 gene abnormalities were detected by polymerase chain reaction (PCR) followed by single-strand conformation polymorphism analysis. Ki-ras mutations were detected by PCR followed by oligonucleotide-specific hybridization.

RESULTS

p53 gene mutations were detected in 12 of 30 tumors. In only one case was the same p53 mutation present in both tumors from one patient. Similarly, Ki-ras mutations were observed in 9 of 30 tumors. Concordant Ki-ras mutations were observed in only one case, which was also concordant for p53 mutation.

CONCLUSION

Because p53 and Ki-ras mutations tend to occur fairly early in tumor development, it seems likely that cases discordant for p53 and Ki-ras mutations represent independently developing tumor foci. Taken together, these findings strongly suggest that the great majority of synchronous colonic adenocarcinomas arise as independent neoplasms and their worsened prognosis is not a result of unusually early metastatic spread.

Expression of p53 protein as a prognostic factor in patients with gastric cancer

The prognostic value of overexpression of the p53-encoded protein was evaluated in 242 patients with gastric cancer. Formalin-fixed paraffin-embedded specimens of gastric adenocarcinomas were stained with the monoclonal antibody DO-7. 95 patients (39%) showed a high level of immunoreactivity (> or = 20% of cell nuclei staining positively), suggesting the presence of a mutation in the TP53 coding sequence. Overexpression of the p53 protein correlated significantly with stage of disease (P = 0.01), the presence of distant metastases (P = 0.04) and with the intestinal type of cancer (P = 0.04). No correlation between p53 overexpression and age, gender or the presence of the lymph node metastases was found. In univariate analysis, p53 immunoreactivity correlated significantly with survival (P = 0.0005). The median survival in the p53 high-level group was 19 months compared with 65 months in the p53 low-level group. In multivariate analyses, stage of disease and the presence of distant metastases emerged as independent prognostic factors, whereas p53 immunoreactivity did not (P = 0.08). The present results indicate that overexpression of the p53 protein is not an independent prognostic factor in patients with gastric cancer.