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

Mutant KRAS, chromosomal instability and prognosis in colorectal cancer

The RAS gene family provides a global effect on gene expression by encoding small GTP-binding proteins which act as molecular switches connecting extracellular signals with nuclear transcription factors. While wild type RAS proteins are switched off shortly after activation, mutant RAS proteins remain constitutively activated leading to complex interactions among their downstream effectors. For some human tumor types, these interactions were shown to contribute to cancer genesis and progression by inducing changes in cell survival, apoptosis, angiogenesis, invasion and metastasis. This review addresses the controversial link of KRAS mutations in colorectal cancer with chromosomal instability and patient prognosis.

Association of k-ras, b-raf, and p53 status with the treatment effect of bevacizumab

BACKGROUND

A recent phase III trial showed that the addition of bevacizumab, a monoclonal antibody to vascular endothelial growth factor-A, to first-line irinotecan, 5-fluorouracil, and leucovorin (IFL) prolonged median survival in patients with metastatic colorectal cancer. We carried out a retrospective analysis of patients in the trial to evaluate whether mutation status of k-ras, b-raf, or p53 or P53 expression could predict which patients were more likely to respond to bevacizumab.

METHODS

Microdissected tumors from 295 patients (274 primary tumors, 21 metastases) were subject to DNA sequence analysis to identify mutations in k-ras, b-raf, and p53. Nuclear P53 expression was determined by immunohistochemistry. Hazard ratios and 95% confidence intervals (CI) for overall survival were estimated using Cox regression analysis.

RESULTS

In all biomarker subgroups, estimated hazard ratios for risk of death were less than 1 for bevacizumab-treated patients as compared with those for placebo-treated patients. Mutations in k-ras and/or b-raf were observed in 88 of 213 patients (41%). Hazard ratios for death among patients with tumors with wild-type k-ras/b-raf status, as compared with those of patients with mutations in one or both genes, were 0.51 (95% CI = 0.28 to 0.95) among those treated with IFL plus bevacizumab and 0.66 (95% CI = 0.37 to 1.18) among those treated with IFL plus placebo. Mutations in p53 were found in 139 of 205 patients (68%), and P53 was overexpressed in 191 of 266 patients (72%); neither p53 mutation nor P53 overexpression was statistically significantly associated with survival.

CONCLUSIONS

We did not find a statistically significant relationship between mutations of k-ras, b-raf, or p53 and the increase in median survival associated with the addition of bevacizumab to IFL in metastatic colorectal cancer.

Colon cancer

Colon cancer is one of the leading tumours in the world and is considered among the big killers, together with lung, prostate and breast cancer. In the recent years very important advances occurred in the field of treatment of this frequent disease: adjuvant chemotherapy was demonstrated to be effective, chiefly in stage III patients, and surgery was optimized in order to achieve the best results with a low morbidity. Several new target-oriented drugs are under evaluation and some of them (cetuximab and bevacizumab) have already exhibited a good activity/efficacy, mainly in combination with chemotherapy. The development of updated recommendations for the best management of these patients is crucial in order to obtain the best results, not only in clinical research but also in everyday practice. This report summarizes the most important achievements in this field and provides the readers useful suggestions for their professional practice.

Connective tissue growth factor inhibits metastasis and acts as an independent prognostic marker in colorectal cancer

BACKGROUND & AIMS

Connective tissue growth factor (CTGF) has been shown to be implicated in tumor development and progression. The aim of this study was to investigate the role of CTGF in progression of colorectal cancer (CRC).

METHODS

Immunohistochemical staining of specimens from 119 patients with CRC was performed. Liposome-mediated transfection was used to introduce a CTGF expression vector into CRC cell lines. Transfectants were tested in invasive ability and experimental hepatic metastasis in BALB/c mice. Furthermore, a FOPflash/TOPflash reporter assay was performed to investigate CTGF on the beta-catenin/T-cell factor signaling pathway.

RESULTS

Patients with stage II and stage III CRC whose tumors displayed high CTGF expression had a significantly higher overall survival and a disease-free advantage over patients with CRC with low CTGF expression. Alterations in the CTGF level in CRC cell lines modulated their invasive ability with an inverse correlation. In addition, a reduction in the CTGF level of CT26 cells after stable transfection with antisense CTGF resulted in increased liver metastasis in BALB/c mice. The activity of the beta-catenin/T-cell factor signaling pathway and its downstream effector gene matrix metalloproteinase 7 in these CTGF-transfected cells was strongly attenuated. Blockage of matrix metalloproteinase 7 with its neutralizing antibodies inhibited increased invasiveness in antisense CTGF-transfected CT26 cells.

CONCLUSIONS

Our results implicate CTGF as a key regulator of CRC invasion and metastasis, and it appears to be a useful and better prognosis factor for patients with stage II and stage III CRC.

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.

Rectal cancer

Rectal cancer is an important tumour from an epidemiological point of view and represents the benchmark for an optimal use of integrated treatments (surgery, radiotherapy and chemotherapy) in the oncological practice. Performing radio-chemotherapy (best if preoperatively), medical and radiation oncologists are now able to increase survival, to decrease the occurrence of pelvic recurrence and to ameliorate the quality of life of patients. Updated recommendations for the management of these patients are here reported.

Simultaneous mutations in K-ras and TP53 are indicative of poor prognosis in sporadic colorectal cancer

Despite the fact that the mutations in K-ras codon 12 and TP53 are common abnormalities in colorectal cancer, the determination of K-ras mutation combined with TP53 gene mutation, with diagnostic and prognostic purposes is still controversial. We have analyzed K-ras and TP53 mutations in 77 sporadic colorectal adenocarcinomas by means of polymerase chain reaction and sequencing. We observed a negative correlation between both K-ras and TP53 mutations. Patients with mutations in K-ras but not in TP53 exhibited worse survival rates than those with mutations in TP53 and not in K-ras. Moreover, we found the worst outcome in patients with mutations in both K-ras and TP53. These results may relate to the previously published data about primary human and rodent cells, in which transformation by Ras require either a cooperating oncogene or the inactivation of tumor suppressors such as p53 or p16. In conclusion, simultaneous mutations in K-ras and TP53 are indicative of a worse prognosis in sporadic colorectal cancer.

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.

Molecular prognostics in colorectal cancer

Conventional staging of colorectal cancer does not account for the marked variability in outcome that exists within each stage. Certain populations of patients with early recurrence, resistance to chemotherapy and decreased survival cannot be predicted utilizing common histopathologic criteria. As the molecular mechanisms underlying colorectal carcinogenesis are elucidated, putative molecular prognostic factors are identified. A comprehensive review of various molecular markers and their roles as prognostic factors in colorectal cancer is presented.

Colon cancer: prevalence, screening, gene expression and mutation, and risk factors and assessment

Colon cancer detection at an early stage and identifying susceptible individuals can result in reduced mortality from this prevalent cancer. Genetic events leading to the development of this cancer involve a multistage progression of adenoma polyps to invasive metastatic carcinomas. Currently, there is no satisfactory screening method that is highly specific, sensitive, or reliable. Dietary patterns associated with the greatest increase in colon cancer risk are the ones that typify a diet rich in fat and calories, and low in vegetable, fruits, and fibers. Genetic susceptibility to environmental carcinogenesis must be factored into the risk assessment for this cancer. Many genes have been shown to be associated with increased expression and mutations in colorectal cancer patients. These genes have been reviewed; it is hoped that by carefully selecting a number of them, a molecular approach that is suitable for arriving at a tumorigenic expression index is developed, which will reliably detect this cancer at an early stage (i.e., before it metastasizes), especially in exfoliated samples (e.g., stool and blood), so that appropriate intervention strategies can be implemented. Illustrated herein is the utility of employing real-time reverse transcriptase polymerase chain reaction (RT-PCR) to quantitatively measure gene expression, and develop an index that is specific for this cancer, which if perfected may result in a reliable and sensitive screening technique for colorectal cancer detection.

Prognostic significance of Bcl-2 and p53 expression in gastric cancer

BACKGROUND AND AIMS

Apoptosis regulates cell death and influences cell proliferation and therefore may play an important role in development or growth of various malignant tumors. The Bcl-2 and p53 are closely linked in the regulation of apoptosis. We investigated the prognostic significance of Bcl-2 and p53 expression in patients with gastric cancer.

PATIENTS AND METHODS

Immunohistochemistry was used to study Bcl-2 and p53 expression in 308 consecutive patients with gastric cancer.

RESULTS

Bcl-2 expression was positive in 39 patients (12.7%) and showed a significant negative correlation with depth of invasion and lymph node metastasis. p53 expression was observed in 105 patients (34.1%) and was significantly associated with depth of invasion, lymph node metastasis, distant metastasis, and intestinal type. Patients with Bcl-2(+) tumors showed a trend to better 5-year survival rate (81%) than those with Bcl-2(-) negative tumors (71%). The 5-year survival rate in p53 positive cases (60%) was significantly lower than that in p53-negative cases (78%). In addition, p53 expression showed a significantly poorer prognosis in both diffuse and intestinal types. In multivariate analysis restricted to patients with R0 resection p53 expression was an independent prognostic factor (relative risk: 2.063). In combined assessment of p53 and Bcl-2 expression the group with p53(+)/Bcl-2(-) tumors showed significantly worse 5-year survival (57%) than the other groups, while best survival was seen in the group with p53(+)/Bcl-2(+) tumors (100%).

CONCLUSION

p53 expression is an unfavorable prognostic factor in gastric cancer. Bcl-2 expression may have possible prognostic value when combined with p53 expression.

Modern management of colorectal cancer--a pathologist's view

Colorectal cancer is an increasingly significant cause of both mortality and morbidity due to wider adoption of the Western lifestyle and a progressively ageing population. Recently steps forward have been made both in surgical and chemoradiotherapeutic management of this disease. Well performed total mesorectal excision surgery has now become the gold standard for rectal cancer resection. Several prognostic markers, both clinicopathological and molecular, have been identified allowing better patient counselling and targeting of treatment. The rationale for patient selection, timing and dose of radiotherapy has been further elucidated. New chemotherapy agents are under trial and predictive factors allowing selection of those patients most likely to respond to them have been identified. Many of these factors will increase in importance as colorectal cancer becomes a chronic disease with lengthening survival times. As we will discuss the pathologist has important roles in all of these developments and at all stages of colorectal cancer management.

TP53 mutation in colorectal cancer

Approximately half of all colorectal cancers show p53 (TP53) gene mutations, with higher frequencies observed in distal colon and rectal tumors and lower frequencies in proximal tumors and those with the microsatellite instability or methylator phenotypes. Alterations to this gene appear to have little or no prognostic value for colorectal cancer patients treated by surgery alone, but are associated with worse survival for patients treated with chemotherapy. There is some evidence that different p53 mutations are associated with different clinical features including prognosis and response to therapy, although further large studies are required to confirm this. Several in vitro, animal and clinical studies have shown that normal p53 is required for the response of colorectal cancers to 5-fluorouracil-based chemotherapy. This should be confirmed by additional retrospective cohort studies and by the incorporation of P53 status in ongoing and future clinical trials. The evaluation of p53 overexpression, using a standardized immunohistochemical (IHC) procedure, could be a clinically useful marker for the identification of colorectal cancer patients likely to benefit from the standard chemotherapy regime currently used for this disease.

p53, DCC and thymidylate synthase as predictors of survival after resection of hepatic metastases from colorectal cancer

BACKGROUND

Hepatic metastasis from colorectal cancer is a common problem. Hepatic resection offers the only chance of cure. Prognosis of patients following hepatic resection is currently based on clinicopathological factors (of both the primary cancer and the hepatic metastasis), which do not accurately predict the subsequent behaviour of the tumour. The aim of this study was to evaluate three molecular genetic markers - p53, DCC (deleted in colonic cancer) and thymidylate synthase - in both the primary colorectal tumour and the resected hepatic metastases, and to determine their correlation, if any, with survival in patients with resected hepatic metastases from colorectal cancer.

METHODS

Sixty-three patients with hepatic metastases and 40 corresponding colorectal primary tumours were studied using immunohistochemical staining for p53, DCC and thymidylate synthase, as well as p53 gene mutations using polymerase chain reaction-single-stranded conformational polymorphism (PCR-SSCP) analysis. The results were correlated with survival.

RESULTS

There was no correlation between p53, DCC or thymidylate synthase immunohistochemical staining, or between p53 PCR-SSCP analysis, and survival for either hepatic metastases or the colorectal primary tumour.

CONCLUSION

Prediction of prognosis in patients having resection of hepatic metastases from colorectal cancer continues to be problematic. Other genetic markers or combination of markers need to be evaluated.

High incidence of protein-truncating mutations of the p53 gene in liver metastases of colorectal carcinomas

To clarify the significance of p53 mutations in liver metastasis of colorectal carcinogenesis, the characteristics of p53 mutations from 51 liver metastases and 76 primary invasive carcinomas without liver metastasis (Dukes' A, B and C) were compared. The frequency of tumors with p53 mutations was 61% (31 out of 51) in the liver metastases, and 51% (39 out of 76) in the primary carcinomas without liver metastasis. Approximately 90% of the informative cases having p53 mutation showed 17pLOH. Mutations detected within exons 4-10 of the p53 gene included missense, nonsense, frameshift, inframe deletion, and inframe insertion mutations. Out of the tumors with p53 mutations, we found that the percentage of tumors with protein-truncating mutations (nonsense and frameshift mutations) was extremely higher in liver metastases (16 out of 31, 52%) than in primary carcinomas without liver metastasis (5 out of 39, 13%) (P=0.0005). The present results suggest that protein-truncating mutations of the p53 gene are more relevant than missense mutations as one of the prognostic factors in liver metastasis of colorectal carcinomas.

Specific codon 13 K-ras mutations are predictive of clinical outcome in colorectal cancer patients, whereas codon 12 K-ras mutations are associated with mucinous histotype

BACKGROUND

K-ras mutations, one of the earliest events observed in colorectal carcinogenesis, are mostly found in codons 12 and 13, and less frequently in codon 61, all three of which are estimated to be critical for the biological activity of the protein. Nevertheless the prognostic significance of such mutations remains controversial. Our purpose was to assess whether any or specific K-ras mutations in primary colorectal cancer had prognostic significance and were linked to clinico-pathological parameters.

PATIENTS AND METHODS

Paired tumor and normal tissue samples from a consecutive series of 160 untreated patients (median of follow up 71 months), undergoing resective surgery for primary colorectal carcinoma, were prospectively studied for K-ras mutations by PCR/single strand conformation polymorphism sequencing.

RESULTS

Seventy-four of the 160 (46%) primary colorectal carcinomas presented mutations in K-ras: 54% in codon 12, 42% in codon 13 (particularly G-->A transition) and 4% in both. Codon 12 K-ras mutations were associated with mucinous histotype (P <0.01), while codon 13 K-ras mutations were associated with advanced Dukes' stage (P <0.05), lymph-node metastasis (P <0.05) and high S-phase fraction (P <0.05). Multivariate analysis showed that codon 13 K-ras mutations, but not any mutation, were independently related to risk of relapse or death.

CONCLUSIONS

Our results suggest that codon 12 K-ras mutations may have a role in the mucinous differentiation pathway, while codon 13 mutations have biological relevance in terms of colorectal cancer clinical outcome.

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.

Molecular markers in prognosis of colorectal cancer and prediction of response to treatment

Colorectal cancer is the third most common human malignancy. Direct observation and biopsy sampling by colonoscopy have provided unique opportunities to study the natural history of the disease. As a consequence, advances in the understanding of colorectal cancer pathogenesis have evolved more rapidly than with most other solid tumours. Numerous molecular events arising during the development of colorectal cancer have been sorted out over the past two decades. Despite these advances, predicting outcome and response to therapy is still a major challenge in the management of patients with colorectal cancer. Molecular and biochemical markers of colorectal cancer are greatly needed for diagnosis and prognosis as well as for the selection and monitoring of treatments. The purpose of this chapter is to provide a critical assessment of the usefulness of markers in the prognosis and prediction of response to treatment in colorectal cancer.

Pathology--a molecular prognostic approach

Colorectal cancer affects 29,000 people and kills approximately 15,000 in England and Wales each year, most of these deaths resulting from the effects of local or distant recurrence. There is a need to give these patients accurate prognoses and individualised treatment regimens. At present, the best prognostic markers are clinicopathological. Post-genomic science and the new high throughput technologies offer unrivalled opportunities to understand the biology and molecular pathology of colorectal cancer. These technologies should be used in the context of large randomised controlled trials to identify new molecular prognostic and predictive markers and also new targets for therapy.

Expression of p185 and p53 in benign and malignant colorectal lesions

The c-erbB2 gene has been found to be amplified in a number of human adenocarcinomas, leading to elevated levels of expression of its encoded product, p185. Mutations in the p53 gene are also common in colorectal carcinomas, brain tumours, leukaemia and lymphomas. In this study, p185 and p53 overexpression was analyzed in colorectal adenomas (22 tubular adenomas and 2 tubulo-villous adenomas) and moderately differentiated adenocarcinomas (n = 22) in order to determine whether there was a relationship between these two proteins. The proteins are encoded by two genes located in the same chromosome. p185 and p53 expression was determined on tissue sections by immunohistochemical staining procedure. Expression of p185 was significantly higher (p < 0.01) in preneoplastic lesions (95.8% of cases) than colorectal cancer (63.6% of cases). p53 showed an inverse pattern to p185, being expressed in 58.3% of benign lesions and 72.7% of adenocarcinomas. These results confirm that p185 overexpression is associated with the early stages of colorectal cancer, whereas p53 is associated with more advanced stages. Although there was no correlation between p185 and p53 expression in premalignant lesions and adenocarcinomas, these two proteins have an important role in the adenoma-carcinoma sequence.

P27kip1 expression is associated with tumor response to preoperative chemoradiotherapy in rectal cancer

BACKGROUND

Our aim was to ascertain whether or not the response to preoperative chemoradiotherapy for rectal cancer is associated with p27kip1 and p53 protein expression.

METHODS

Thirty-eight patients (27 male, 11 female) with a mean age of 59 years (age range 33-87) and stage II-III rectal cancer received preoperative chemoradiotherapy (45-50.4 Gy; 5-FU 350 mg/m2/day and leucovorin 10 mg/m2/day). Thirty-one underwent low anterior resection; seven underwent abdominoperineal excision. Endoscopic tumor biopsies, performed before adjuvant therapy, were evaluated for: histologic type, tumor differentiation, mitotic index, and p27kip1 and p53 protein expression which were immunohistochemically determined. p53 expression was graded as: a) absent or present in < or =10% of tumor cells; b) present in 11-25%; c) present in 26-75%; and d) present in >75% of tumor cells. p27kip1 expression was assessed using both light microscopy (percent of stained cells x10 HPF) and cytometry with an image analysis workstation. Tumor response, ascertained with histology, was classified using a scale from 0 (no response) to 6 (complete pathologic response).

RESULTS

The mitotic index for the endoscopic biopsies was low in 14 cases, moderate in 17 cases, and high in 7 cases. p53 protein expression was found in 21 (a), 3 (b), 3 (c), and 11 (d) cases. The mean percentage of cells expressing the p27kip1 protein was 34 (range 0-77.14%). A close correlation was found between cytometric and light microscopy findings for p27kip1 (r2 = 0.92, P = .0001). Tumor differentiation was good in 5 cases, poor in 2 cases, and moderate in the remaining 31 cases. While the response to adjuvant therapy was good/complete in 25 (65.78%) cases, it was absent/poor in 13 (34.21%) cases. Univariate analysis associated type of adjuvant therapy (chemoradiotherapy, P = .0428) and p27kip1 protein lower expression (P = .0148) with a poor response to adjuvant treatment. Stepwise linear regression found overexpression of p53 and p27kip1 and young age to be independent variables that were linked to a good response to adjuvant therapy.

CONCLUSIONS

Lack of p27kip1 and p53 protein expression in rectal cancer is associated with a poor response to preoperative adjuvant therapy.

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.

Determination of microsatellite instability, p53 and K-RAS mutations in hepatic metastases from patients with colorectal cancer: relationship with response to 5-fluorouracil and survival

In vitro and clinical studies have suggested that high-frequency microsatellite instability (MSI-H) phenotype, p53 and K-ras mutations might influence the response to chemotherapy in a variety of tumors, including primary colorectal cancers (CRC). Unresectable hepatic metastases from CRC are commonly treated with 5-fluorouracil (5FU) and folinic acid. Since several new active drugs are now used for treating CRC, molecular determinants predictive to response to 5FU would thus be crucial for optimizing indications of chemotherapy to those patients. MSI-H phenotype, p53 and K-ras status were characterized in a prospective study of 56 patients with CRC metastatic to the liver and treated with 5FU-based chemotherapy. The objective response rate after a 3-month treatment was 32.1%. The prevalence of p53 mutations, K-ras mutations and MSI-H phenotype was 62.5%, 30.3% and 1.8%, respectively. No significant association was found between response to chemotherapy and p53 mutations (78% mutated tumors in responders vs. 55% in nonresponders; p = 0.10) and K-ras mutations (39% mutated tumors in responders vs. 26% in nonresponders; p = 0.34). Survival was longer for patients with p53-mutated metastases than for patients with unresected wild-type p53 metastases (median survival 15 months vs. 17 months; p = 0.06). The determination of the MSI-H phenotype, p53 and K-ras status in hepatic metastases from CRC does not discriminate a group of patients that should preferentially benefit from 5FU-based chemotherapy. The prognosis of patients with treated liver metastases is better when p53 is mutated.

Prognostic value of K-ras mutations and allelic imbalance on chromosome 18q in patients with resected colorectal cancer

PURPOSE

We designed this study to assess the frequency of K-ras mutations in patients with resected colorectal tumors and their association with survival. A second objective was to analyze the prognostic value of different K-ras genotypes. In a subgroup of patients we also investigated the presence of allelic imbalance on chromosome 18q and its relationship to clinical outcome.

METHODS

One hundred fourteen colorectal tumors resected between 1983 and 1986 were analyzed to detect K-ras point mutations at codons 12, 13, and 61 by polymerase chain reaction followed by allele specific oligonucleotide hybridization. A subgroup of 77 tumors was further screened to detect loss of heterozygosity on chromosome 18q using three polymorphic microsatellite markers (D18S67, D18S474 and D18S58).

RESULTS

K-ras mutations were detected in 29 percent (33/114) of patients. K-ras mutations correlated with age and preoperative carcinoembryonic antigen levels, and there was some indication that they may be linked to poor survival, especially in Stage II tumors, where a subgroup of patients with aspartic and serine mutations showed significantly reduced survival (P = 0.03) compared with K-ras-negative patients. 18q loss of heterozygosity was present in 39 percent (25/63) of tumors. A multivariate analysis of Stage II tumors showed that 18q loss of heterozygosity was significantly associated with a worse prognosis (P = 0.006). A significant decrease in survival was identified in ten patients harboring both genetic alterations (K-i mutations and 18q loss of heterozygosity; P = 0.02).

CONCLUSIONS

In colorectal tumors, K-ras mutations and 18q loss of heterozygosity are two genetic markers which may identify patients with more aggressive behavior, mainly in Stage II tumors. These findings warrant further research, because they can be useful in customizing adjuvant chemotherapy.

Prognostic significance of K-ras and TP53 mutations in the role of adjuvant chemotherapy on survival in patients with Dukes C colon cancer

PURPOSE

Mutations in K-ras and TP53 genes are common in colorectal cancer. They affect biologic behavior and might influence chemotherapy susceptibility in these tumors. We investigated whether the survival of patients with Dukes C colon cancer treated with adjuvant chemotherapy is influenced by K-ras and TP53 mutations.

METHODS

Mutation screening of the hot spots of the K-ras gene and of the evolutionarily conserved regions of the TP53 gene was performed by denaturing gradient gel electrophoresis technique in formalin-fixed paraffin-embedded specimens of 55 consecutive patients with Dukes C colon cancer treated with adjuvant 5-fluorouracil-based chemotherapy. The median follow-up was 47 (range, 32-66) months.

RESULTS

Alterations in the mutation hot spots of K-ras were found at codon 12 (n = 11) and 13 (n = 4) in 15 of the 55 carcinomas (27 percent). No mutation was found at codon 61. Mutations of a probably causative nature in the evolutionarily conserved regions (exons 5-8) of the TP53 gene were found in 24 tumors (44 percent). K-ras and TP53 mutations were found equally in the group with recurrent disease (7/26 (26 percent) and 12/27 (44 percent), respectively) and in the group without recurrences (8/28 (24 percent) and 12/28 (43 percent), respectively). Cancer-specific survival did not differ significantly between patients with K-ras or TP53 or both mutated and nonmutated tumors, respectively (log-rank test: K-ras, P = 0.72 and TP53, P = 0.77; K-ras and TP53, P = 0.8). Also, potentially aggressive K-ras codon 12 and 13 mutations had the same survival as tumors without these mutations (log-rank test; P = 0.73).

CONCLUSIONS

Patients with K-ras or TP53 or both mutated Dukes C colon tumors have the same survival as nonmutated tumors when treated with adjuvant chemotherapy. These data suggest that mutations in K-ras or TP53 alone are not prognostic indicators in patients with Dukes C colon cancer receiving adjuvant 5-Fluorouracil-based therapy.

K-ras and p16 aberrations confer poor prognosis in human colorectal cancer

PURPOSE

Mutations in the K-ras gene are frequent in human cancer. ras activation in primary cells results in a cellular senescence phenotype that is precluded by inactivation of p16. At the clinical level, this may imply a differential behavior for tumors with alternative or cooperative activation of K-ras function and impairment of p16 pathways.

PATIENTS AND METHODS

We have determined the presence of mutations in the K-ras gene and the methylation status of p16 promoter in a series of 119 prospectively collected colorectal carcinomas. p53 mutations and p14 alternative reading frame methylation status were also assessed. Associations with survival were investigated.

RESULTS

K-ras mutations were present in 44 (38%) of 115 cases, and p16 methylation was present in 42 (37%) of 113 cases. p53 mutations were detected in 50% (56 of 115) and p14 methylation in 29% (32 of 112) of cases. K-ras and p16 alterations were independent genetic events. Presence of K-ras or p16 genetic alterations (analyzed independently) was associated with shorter survival, although differences were not statistically significant. Cox analysis of the two variables combined showed a diminished survival as the results of an interaction between p16 and K-ras. Alternative alteration of K-ras and p16 genes was an independent prognostic factor in human colorectal cancer in univariate and multivariate analysis. Differences were maintained when cases undergoing radical surgery and without distant metastases were considered.

CONCLUSION

These results suggest that the combined K-ras and p16 analyses may be of prognostic use in human colorectal cancer.

Specific c-K-ras gene mutations as a tumor-response marker in locally advanced rectal cancer treated with preoperative chemoradiotherapy

BACKGROUND

Forty percent of patients with colorectal cancer develop mutations in the K-ras gene.

OBJECTIVE

Our objective was to evaluate whether the presence of c-K-ras gene mutations is a useful tumor-response marker in patients with locally advanced rectal cancer treated with preoperative chemoradiotherapy.

MATERIAL AND METHODS

Thirty seven patients with locally advanced rectal cancer were treated with preoperative chemoradiotherapy. Four to six weeks later, surgery was performed. Specimens were classified according to the UICC-AJC classification. A segment of the tumor was obtained to analyze specific c-K-ras gene mutations. Restriction fragment length polymorphism (RFLP) and single strand confirmation polymorphism (SSCP) techniques were used with a set of probes to detect specific c-K-ras mutations in codons 12, 13, and 61. The 37 patients were divided into Group A (with mutations) and Group B (without mutations).

RESULTS

All 37 patients completed the scheduled treatment. Group A consisted of 12 patients, whose tumors were classified and specific c-K-ras mutations were located as follows: eight in codon 12, two in codon 13, and one in codon 61. Group B consisted of 25 patients. The tumors were classified and there were more early-stage tumors in Group A, whereas in Group B there were more advanced-stage tumors (P = .05, respectively). The mean follow-up was 36.2+/-18.3 months. All Group A patients survived, whereas 8 of the 25 patients in Group B died due to progressive metastatic disease. Survival in Group A was 100%, whereas in Group B it was 59% (P = .03).

CONCLUSIONS

The presence of specific c-K-ras mutations is an indicator of tumor response in patients with locally advanced rectal cancer treated with preoperative chemoradiotherapy and surgery. Therefore, responding patients may be more amenable to less radical surgical procedures based on c-K-ras mutations.

Impact of KRAS and TP53 mutations on survival in patients with left- and right-sided Dukes' C colon cancer

OBJECTIVE

It has been suggested that KRAS and TP53 mutated tumors might influence the phenotypic behavior of left- and right-sided colon tumors. We investigated the incidence of these mutations in left- and right-sided colon tumors and their possible influence on survival in a homogeneous group of patients with Dukes' C colon cancers.

METHODS

The primary tumors of 55 patients with a sporadic Dukes' C colon cancer, all treated with adjuvant chemotherapy were analyzed for the presence of KRAS and TP53 mutations. Mutation detection of the KRAS and TP53 genes was performed on paraffin-embedded tumor material, using denaturating gradient gel electrophoresis. The 5-yr survival rates of KRAS and TP53 mutated tumors were analyzed regarding right-sided tumors (defined as tumors up to the splenic flexure) and left-sided tumors (defined as tumors from the splenic flexure to the rectosigmoid peritoneal reflection).

RESULTS

KRAS mutations occurred more frequently in the right colon compared to the left colon (R = 38% (10/26); L = 10% (3/29); chi2 test: p = 0.014). KRAS mutations did not influence survival in patients with right-sided colon tumors. Patients with KRAS mutation-negative tumors in the right colon, however, had a significantly worse survival than patients with left-sided KRAS mutation-negative tumors (5-yr survival; R: 34% vs L: 65%, log-rank test: p = 0.007). TP53 mutations of a possible causative nature were found in 24 tumors (44%). Neither the incidence (R = 42% (11/26); L = 45% (13/29)) nor the survival of TP53 mutated tumors differed significantly between left- and right-sided tumors. Furthermore, survival of patients with TP53 mutation-negative tumors did not differ significantly between left- and right-sided tumors.

CONCLUSIONS

There seems to be no difference in survival rate between patients with KRAS mutated and KRAS negative Dukes' C colon tumors; however, KRAS mutations are more frequently found in the right colon compared to the left colon. TP53 mutations do not have predominance for either side of the colon, and there are no differences in survival in patients with left-sided versus right-sided tumors. Patients with KRAS-nonmutated tumors in the right colon did have a worse survival compared to those with such tumors in the left colon. This suggests that other genetic factors may play a role in tumor genesis in this subgroup of patients.

Prognostic factors in colorectal cancer. College of American Pathologists Consensus Statement 1999

BACKGROUND

Under the auspices of the College of American Pathologists, the current state of knowledge regarding pathologic prognostic factors (factors linked to outcome) and predictive factors (factors predicting response to therapy) in colorectal carcinoma was evaluated. A multidisciplinary group of clinical (including the disciplines of medical oncology, surgical oncology, and radiation oncology), pathologic, and statistical experts in colorectal cancer reviewed all relevant medical literature and stratified the reported prognostic factors into categories that reflected the strength of the published evidence demonstrating their prognostic value. Accordingly, the following categories of prognostic factors were defined. Category I includes factors definitively proven to be of prognostic import based on evidence from multiple statistically robust published trials and generally used in patient management. Category IIA includes factors extensively studied biologically and/or clinically and repeatedly shown to have prognostic value for outcome and/or predictive value for therapy that is of sufficient import to be included in the pathology report but that remains to be validated in statistically robust studies. Category IIB includes factors shown to be promising in multiple studies but lacking sufficient data for inclusion in category I or IIA. Category III includes factors not yet sufficiently studied to determine their prognostic value. Category IV includes factors well studied and shown to have no prognostic significance.

MATERIALS AND METHODS

The medical literature was critically reviewed, and the analysis revealed specific points of variability in approach that prevented direct comparisons among published studies and compromised the quality of the collective data. Categories of variability recognized included the following: (1) methods of analysis, (2) interpretation of findings, (3) reporting of data, and (4) statistical evaluation. Additional points of variability within these categories were defined from the collective experience of the group. Reasons for the assignment of an individual prognostic factor to category I, II, III, or IV (categories defined by the level of scientific validation) were outlined with reference to the specific types of variability associated with the supportive data. For each factor and category of variability related to that factor, detailed recommendations for improvement were made. The recommendations were based on the following aims: (1) to increase the uniformity and completeness of pathologic evaluation of tumor specimens, (2) to enhance the quality of the data needed for definitive evaluation of the prognostic value of individual prognostic factors, and (3) ultimately, to improve patient care.

RESULTS AND CONCLUSIONS

Factors that were determined to merit inclusion in category I were as follows: the local extent of tumor assessed pathologically (the pT category of the TNM staging system of the American Joint Committee on Cancer and the Union Internationale Contre le Cancer [AJCC/UICC]); regional lymph node metastasis (the pN category of the TNM staging system); blood or lymphatic vessel invasion; residual tumor following surgery with curative intent (the R classification of the AJCC/UICC staging system), especially as it relates to positive surgical margins; and preoperative elevation of carcinoembryonic antigen elevation (a factor established by laboratory medicine methods rather than anatomic pathology). Factors in category IIA included the following: tumor grade, radial margin status (for resection specimens with nonperitonealized surfaces), and residual tumor in the resection specimen following neoadjuvant therapy (the ypTNM category of the TNM staging system of the AJCC/UICC). (ABSTRACT TRUNCATED)

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.

p53 and Ki-ras as prognostic factors for Dukes' stage B colorectal cancer

Mutations of the TP53 and Ki-ras genes have been reported to be of prognostic importance in colorectal carcinomas. An increased intracellular concentration of the p53 protein, although not identical to, is sometimes seen in tumours with TP53 mutation and has been correlated with poor prognosis in some tumour types. Previous colorectal cancer studies, addressing the prognostic importance of Ki-ras mutation and TP53 aberrations, yielded contradictory results. The aim of this study was to determine in a clinically and therapeutically homogeneous group of 122 sporadic Dukes' B colorectal carcinomas with a median follow-up of 67 months (3-144 months) whether or not p53 protein expression, TP53 mutation and K-ras mutation correlated with prognosis. p53 staining was performed by immunohistochemistry, using the monoclonal antibody DO7 on paraffin-embedded tissue. Mutations in exons 5-8 of the TP53 gene and in codons 12 and 13 of the K-ras gene were assayed in paraffin-embedded tissue by the single-strand conformation polymorphism (SSCP) assay. Nuclear p53 staining was found in 57 (47%) tumours. Aberrant migration patterns indicating mutation of the TP53 gene were found in 39 (32%) tumours. Forty-six carcinomas (38%) showed a mutation of the Ki-ras codons 12 or 13. In a univariate analysis, patients with wild-type TP53 status showed a trend towards better survival, compared with those with mutated TP53 (log-rank test, P = 0.051). Likewise, tumours immunohistochemically positive for p53 showed a worse prognosis than p53-negative tumours (P = 0.010). The presence or absence of mutations in Ki-ras did not correlate with prognosis (P = 0.703). In multivariate analysis, only p53 immunoreactivity emerged as an independent marker for prognosis hazard ratio (HR) = 2.16, 95% confidence interval (CI) 1.12-4.11, P = 0.02). Assessment of p53 protein expression is more discriminative than TP53 mutation to predict the outcome of Dukes' stage B tumours and could be a useful tool to identify patients who might benefit from adjuvant therapy.

Colonic mucin-carbohydrate components in colorectal tumors and their possible relationship to MUC2, p53 and DCC immunoreactivities

To clarify changes in mucus components during colorectal tumorigenesis, we developed novel monoclonal antibodies (Abs) against carbohydrate chains of human colorectal mucin (HCM) obtained from normal sigmoid and rectal mucosae. A hundred and ninety-nine cases of colorectal carcinoma and 67 cases of tubular adenoma, along with 250 normal colonic tissue samples, were investigated immunohistochemically. The results were compared with clinical stage, survival and MUC2 (core protein of the intestinal type mucin) expression, as well as with the status of the p53 and DCC (deleted in colorectal carcinomas) genes. In the normal colonic epithelium, HCM14 Ab reacted with the cytoplasmic regions of the goblet cells and enterocytes, while HCM21 Ab bound to mucous droplets in the former, suggesting a more mature carbohydrate structure. Both HCM14 and 21 scores were significantly decreased in adenomas and carcinomas. This is in line with an altered PAS-Alcian blue staining, indicating accumulation of mucins with incomplete or abnormal glycosylation in tumors. Levels of HCM14 and 21 binding tended to show a positive correlation with expression of MUC2 and DCC, and a negative association with p53 protein accumulation in carcinomas, although there was no apparent link to Duke's stage or the prognostic outcome. These findings suggest a possible involvement of alterations in mucin carbohydrate in colorectal tumor development. The observed changes may be associated with loss of MUC2 and DCC expression, as well as with p53 protein accumulation.

Quercetin inhibits p21-RAS expression in human colon cancer cell lines and in primary colorectal tumors

Immunocytochemical studies have revealed that 10 microM quercetin reduced the steady state levels of p21-ras proteins in both colon cancer cell lines and primary colorectal tumors. These findings were confirmed by Western blot and flow cytometric analysis showing that the inhibition of p21-ras expression by quercetin was time- and concentration-dependent. Twenty-four-hour treatment with 10 microM quercetin reduced p21-ras levels to about 50% of control values. Quercetin was similarly effective in inhibiting the expression of K-, H-, and N-ras proteins. Moreover, the effect of quercetin on ras oncogene expression was not dependent on the cell cycle position of colon cancer cells and appeared to be specific and not merely a consequence of overall inhibition of protein synthesis. Northern blot analysis revealed that quercetin produced in colon cancer cells an early (30 min) reduction of the steady state levels of K-, H-, and N-ras mRNAs. This reduction was also present after 6 hr of flavonoid treatment. These effects of quercetin suggest a possible chemopreventive role for this compound in colorectal carcinogenesis.

p53 and K-ras gene mutations in carcinoma of the rectum among Finnish women

AIMS/BACKGROUND

The aim of this study was to identify p53 and K-ras gene mutations in carcinoma of the rectum among Finnish women. Mutation patterns might give clues to aetiological factors when comparisons are made with other human tumours.

METHODS

Of 134 women with carcinoma of the rectum, paraffin wax embedded specimens of the tumour tissue were obtained from 118 patients. Genomic DNA was extracted, and exons 4-8 of the p53 gene and codons 12/13 and 61 of the K-ras gene were amplified, and analysed for mutations by single strand conformation polymorphism and direct sequencing. The production of p53 and K-ras proteins was studied by immunohistochemistry.

RESULTS

The overall crude frequency for mutations in the p53 gene was 35% but the true frequency appears to be higher (up to 56%). In the K-ras gene, the mutation frequency (15%) was significantly lower than that reported for colon cancer. In the p53 gene, the mutation frequency increased significantly with patient age. In a high proportion of patients (14%) the rectal tumours contained small subclones of tumour cells that displayed extremely rare mutations at codons 110 and 232 of the p53 gene. Hot spot codon 175 mutations were significantly less common in rectal cancer than in cancer of the colon.

CONCLUSIONS

Rectal cancer among Finnish women has characteristics in the mutations of the p53 and K-ras genes that are uncommon in other human tumours, including cancer of the colon. A biological explanation of these findings is not clear at present, but might be associated with an unidentified genetic factor in Finland.

K-ras mutations, rectal crypt cells proliferation, and meat consumption in patients with left-sided colorectal carcinoma

It has been suggested that N-nitroso compounds derived from meat may increase the risk of K-ras mutations in the human colon. We sought evidence of associations between red meat consumption, frequency and type of K-ras mutations in resected tumours, and the rate of crypt cell proliferation (CCP) in the normal mucosa of patients with left-sided colorectal carcinoma. Meat consumption was assessed by food frequency questionnaire, and CCP was determined in rectal biopsies obtained prior to surgery. K-ras mutations in the resected tumours were determined using a PCR-based oligonucleotide hybridization assay. Fifteen K-ras mutations were detected in tumours from 43 patients; 13/15 in codon 12, 3/15 in codon 13, and 1/15 in both codons 12 and 13. All mutations were G-->A or G-->T transitions. There was no statistically significant difference between intakes of red meat in patients with a K-ras mutation (92.4 +/- 9.7 g/day) and those without (82.3 +/- 7.7 g/day). Rectal CCP was significantly higher in patients than in healthy controls, but there was no correlation with meat consumption or K-ras mutation. These data do not support the hypothesis that meat consumption is a risk factor for acquisition of K-ras mutations during colorectal carcinogenesis.

p27(kipl) protein expression: an independent prognostic factor in rectal carcinoma stages I-III

OBJECTIVE

To evaluate the impact of some molecular markers on lymph node metastases, overall (OS) and disease-free survival (DFS) in rectal cancer.

PATIENTS AND METHODS

We investigated p27(kip1) , p53, nm23, and vascular endothelial growth factor (VEGF) expression in 109 primary rectal cancer specimens (stage I, n=38; stage II, n=24; stage III, n=20; and stage IV, n=27) from patients operated on between 1990 and 1995 at Clinica Chirurgica II.

RESULTS

Tumour differentiation (P=0.0469), depth of rectal wall invasion (T status) (P=0.0000), distant metastases (P=0.0000), vascular invasion (P=0.0000), and p27(kip1) expression (P=0.0022) were associated with lymph node metastases (N status). During follow up (median duration 47 months), 48 patients died, and 25 patients (stages I-III) had recurrences. At multivariate analysis, T and N status, and intratumoural necrosis were independent risk factors for OS. The relative risk (RR) of death for patients with lymph node metastases, advanced T status and intratumoural necrosis was 3.3 (P=0.0002), 2.03 (P=0.0127), and 1.47 (P=0.1935), respectively. When analysis included only stage I-III patients, N status and p27(kip1) protein expression were found to be independent risk factors for OS. The RR of death for patients with lymph node metastases and those without p27(kip1) expression was 2.98 (P=0.0251), and 3.57 (P=0.0231), respectively. At multivariate analysis, N status, p27(kip1) expression, and intratumoural necrosis were independent risk factors for DFS. The RR of recurrence for patients with lymph node metastases, intratumoural necrosis and absence of p27(kip1) expression was 6.29 (P=0.0001), 3.04 (P=0.0168), and 3.25 (P=0.0387), respectively.

CONCLUSION

Absence of p27(kip1) expression is a useful marker of tumour aggressiveness in rectal carcinoma stages I-III, and an independent predictor for OS and DFS.

Expression of high p53 levels in colorectal cancer: a favourable prognostic factor

The expression of p53 protein was examined in a series of 111 colorectal cancer adenocarcinomas with a long follow-up. A quantitative luminometric immunoassay (LIA) was used for the measurement of wild-type and mutant p53 protein in extracts from colorectal tumour cytosols, p53 being detected in 42% of the samples (range 0.0-52 ng (mg-1)). Using an arbitrary cut-off value of 2.7 ng mg(-1), 25% of the tumours were classified as manifesting high p53 levels. There was no association of p53 expression with patient age, sex, serum preoperative carcinoembryonic antigen (CEA) levels, tumour site and size, nodal status or TNM stage. Significant and independent correlation was found to exist between high p53 levels and prolonged disease-free survival (P = 0.05) at a median follow-up of 60 months. This survival advantage was most apparent among stage III cancer patients. The results from this study would suggest that expression of high p53 levels appear to be useful in selecting a group of colorectal cancer patients with a better prognosis.

Expression of p53 and RB proteins in squamous cell carcinoma of the esophagus: their relationship with clinicopathologic characteristics

BACKGROUND

Cancer of the esophagus is one of the most malignant tumors and has a poor prognosis. The p53 and retinoblastoma (RB) genes are involved in the regulation of cell population by suppressing cell proliferative activity. Our goal was to clarify whether expression of p53 and RB genes could be prognostic factors in squamous cell carcinoma of the esophagus.

METHODS

Tumor samples taken from 73 patients undergoing subtotal esophagectomy were immunohistochemically stained for the p53 and RB genes. An image analyzer was used for quantitative assessment of the staining, and clinicopathologic characteristics of those patients were investigated.

RESULTS

Patients in whom p53 expression was high had greater tumor diameter, deeper tumor invasion, and worse prognosis compared with patients in whom p53 expression was low. Patients in whom RB expression was low had a higher incidence of lymph node metastasis and more advanced disease than did those in whom RB expression was high. The combination of p53 and RB expression revealed that the cases with high p53 and low RB expression had significantly worse survival rates and deeper tumor invasion compared with other groups. In various clinicopathologic parameters, (e.g., age, sex, tumor-diameter, tumor type, location, differentiation, TNM classification, TNM stage) tumor type, tumor size, depth of invasion, lymph node involvement, distant metastasis, and combined p53 and RB expression showed significant differences in survival by univariate analysis. Among those six variables, only lymph node involvement showed an independent prognostic factor for survival (P = .0055) by multivariate analysis.

CONCLUSIONS

The combination of p53 and RB expression is not a prognostic indicator in the surgical treatment of esophageal cancer.

p53 and K-ras gene mutations correlate with tumor aggressiveness but are not of routine prognostic value in colorectal cancer

PURPOSE

p53 gene and K-ras mutations are among the most common genetic alterations present in colorectal cancer. The prognostic utility of such mutations remains controversial. The purpose of this study was to prospectively evaluate the prognostic significance of p53 and K-ras gene mutations in colorectal cancer.

PATIENTS AND METHODS

One hundred forty patients were analyzed. Tumors belonging to the microsatellite mutator phenotype were excluded (n = 8). Mutations at the K-ras and p53 genes were detected and characterized by restriction fragment length polymorphism, single-strand conformation polymorphism, and sequencing, as appropriate.

RESULTS

p53 mutations were detected in 66 (50%) and K-ras mutations were detected in 54 (41%) of the 132 patients. In 26 cases (20%), ras and p53 mutations coexisted; in 38 cases (29%), neither mutation was found. Multivariate analysis of the whole population analyzed (n = 132) showed that survival was strongly correlated with the presence of p53 mutations alone or in combination with K-ras mutations (P = .002; log-rank test). When only patients undergoing a radical resection were considered (R0; n = 101), p53 mutations were no longer of prognostic significance.

CONCLUSION

p53 mutations alone or in combination with K-ras mutations are correlated with a worse outcome. However, the routine use of these mutations as prognostic markers in the clinical setting is not recommended.

Prognostic value of p53 protein expression for patients with gastric cancer--a multivariate analysis

Mutations in the p53 gene, one of the most common genetic alterations in human cancer, are implicated in tumorigenesis and tumour progression. Although p53 protein expression appears to be correlated to prognosis in patients with malignancy, its prognostic role in gastric cancer has remained controversial. We examined the clinical significance of p53 overexpression in 427 patients with gastric cancer, using multivariate analysis. Tumour sections of gastric cancer tissues from these 427 Japanese patients were stained immunohistochemically with monoclonal antibody PAb1801. The presence of p53 expression was statistically compared with clinicopathological features and post-operative survival, using univariate and multivariate analyses. p53 expression was detected in 38.6% (165 out of 427) of these gastric cancers and immunoreactivity was not observed in normal mucosa adjacent to the tumour. A higher rate of p53 detection was observed among large tumours and in those with a prominent depth of invasion, lymphatic and vascular invasion and lymph node involvement. Prognosis was significantly worse for patients with p53-positive-staining tumours. The 5-year survival rate was 62.5% for patients with p53-negative tumours and 43.3% for those with positive malignancies. p53 expression was a significant prognostic factor for node-positive gastric cancers in subjects undergoing treatment with curative resection, as assessed by Cox regression analysis. Thus, the expression of p53 was closely related to the potential for tumour advance and a poorer post-operative prognosis for patients with gastric cancer.

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.

Clinical relevance of transforming growth factor alpha, epidermal growth factor receptor, p53, and Ki67 in colorectal liver metastases and corresponding primary tumors

To determine whether the expression of transforming growth factor alpha (TGF-alpha), its receptor (epidermal growth factor receptor [EGFr]), p53 nuclear protein, and proliferation influences prognosis of patients with liver metastases, a study was performed in 45 liver metastases and 33 corresponding primary colorectal carcinomas in patients referred for liver surgery. The expression of TGF-alpha, EGFr, p53 nuclear protein, and proliferation rate was correlated with clinicopathological characteristics and survival after partial liver resection. In liver metastases, TGF-alpha expression was low in 42%, intermediate in 35%, and high in 23%. TGF-alpha expression was higher in liver metastases derived from lymph node-positive primary carcinomas, in synchronous and in irresectable liver metastases compared with those derived from lymph node-negative primary carcinomas, metachronous, and resectable liver metastases. Nuclear p53 expression was found in 83% of primary tumors and 71% of liver metastases. p53 expression did not correlate with the various clinicopathological characteristics. Ki67 expression was not associated with clinicopathological characteristics in primary and metastatic tumors. In the 38 patients in whom a partial liver resection was performed, median survival was 25 months in patients with a higher TGF-alpha expression in the metastasis than in the primary tumor and 60 months in patients with comparable or lower TGF-alpha expression in the metastasis than in the primary tumor (P = .036). Median survival after liver resection was 21 months in patients with p53-negative liver metastases and 58 months in patients with p53-positive metastases (P = .043). By multivariate analysis, p53 and EGFr expression on liver metastases were the best predictors of disease-free survival after partial liver resection, with relative risks of 2.38 and 3.33, respectively. In patients with colorectal liver metastases, referred for liver surgery, a higher TGF-alpha expression is associated with unfavorable tumor characteristics, whereas p53 and absence of EGFr expression is associated with a better survival after partial liver resection.

Genetic abnormalities and microsatellite instability in colorectal cancer

Our purpose was to investigate different genetic abnormalities, such as K-ras mutations, p53 alterations, and c-myc RNA overexpression, as well as microsatellite instability in 63 colorectal tumors obtained from patients that had undergone surgery. K-ras point mutations were analyzed by PCR-RFLP technique, followed by sequencing; p53 protein accumulation by immunohistochemistry; p53 gene mutations in exons 5-9 were studied by the SSCP and sequencing techniques, and c-myc overexpression by Northern blot. Microsatellite instability was performed at chromosomes 2p, 3p, and 11p by a PCR-based technique. Our data indicate a trend toward a poorer prognosis in patients who had K-ras transversions; besides, we have obtained a prevalence of c-myc RNA overexpression and p53 exon 7 mutations in the latest stages of tumor progression. In conclusion, our findings suggest that the recognition of molecular abnormalities might be used in colorectal cancer as a prognostic indicator or to determine the metastatic potential of colorectal adenocarcinomas.