The common molecular genetic alterations in Dukes' B and C colorectal carcinomas are not short-term prognostic indicators of survival

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.

Adverse prognostic effect of methylation in colorectal cancer is reversed by microsatellite instability

PURPOSE

DNA methylation is an important biologic event in colorectal cancer and in some cases is associated with the development of microsatellite instability (MSI). In this study, we sought to determine the prognostic significance of DNA methylation, both in univariate analysis and in concert with other clinicopathologic factors known to influence outcome.

PATIENTS AND METHODS

Fresh tissue (625 cancers) was obtained from 605 individuals (age range, 29 to 99 years) undergoing curative surgery for colorectal cancer at one institution during a period of 8 years. Clinicopathologic details were recorded for all tumors, including stage, grade, type, vascular space invasion, and clinical follow-up to 5 years. Microsatellite status was assessed using standard markers. Methylation of p16 and hMLH1 promoters was determined by methylation-specific polymerase chain reaction (PCR), whereas methylation at methylated-in-tumor loci (MINT)1, MINT2, MINT12, and MINT31 loci were assessed by bisulfite-PCR.

RESULTS

Patients with microsatellite unstable tumors (12%) had better disease-specific survival than those with microsatellite stable (MSS) tumors (univariate analysis: hazard ratio [HR], 0.53; 95% CI, 0.27 to 1.0). Overall survival of individuals with MSS tumors was influenced by three independently significant factors: tumor stage (HR, 7.3; 95% CI, 5.1 to 10.4), heavy tumor methylation (HR, 2.1; 95% CI, 1.1 to 4.0), and vascular space invasion (HR, 1.9; 95% CI, 1.3 to 2.9). In MSS tumors, methylation at any single site was not independently predictive of survival. Neither methylation nor microsatellite status predicted a favorable response to chemotherapy.

CONCLUSION

DNA methylation is associated with a worse outcome in colorectal cancer, but this adverse prognostic influence is lost in those methylated tumors showing MSI. The mechanisms of these events warrant additional investigation.

Prognostic molecular markers for planning adjuvant chemotherapy trials in Dukes' B colorectal cancer patients: how much evidence is enough?

The benefit of postoperative adjuvant chemotherapy in patients with Dukes' B colorectal cancer is still uncertain and its routine use is not recommended. Prognostic biomarkers may be useful for identifying high-risk patients with resected, node-negative disease, and this stratification may represent an innovative strategy for designing adjuvant chemotherapy trials. Featured prognostic molecular markers can be divided into the following categories: cell proliferation indices (Ki-67, Mib-1, proliferating cell nuclear antigen); oncogenes/tumor suppressor genes [p53, K-ras, Deleted in Colorectal Cancer (DCC), Bcl-2, c-erbB2]; DNA repair (microsatellite instability); markers of angiogenesis (vascular count, vascular endothelial growth factor); markers of invasion/metastasis (plasminogen-related molecules, matrix metalloproteinases); and biochemical markers (thymidylate synthase). Studies that have investigated their prognostic role in Dukes' B colorectal cancer patients are reviewed here. Current data do not provide sufficient evidence for the incorporation of available prognostic biomarkers into clinical practice. However, a biomarker-based approach could be an effective strategy for improving results of postoperative adjuvant treatments in high-risk Dukes' B colorectal cancer patients. Markers of altered DCC function have shown promising prognostic role and sufficient prevalence in retrospective investigations and they deserve further assessment in prospective studies.

Genetic tumor markers with prognostic impact in Dukes' stages B and C colorectal cancer patients

PURPOSE

To examine several genetic changes in primary colorectal carcinomas (CRCs) from patients with 10 years of follow-up and associate the findings with clinicopathologic variables.

MATERIAL AND METHODS

DNA from 220 CRCs were analyzed for allelic imbalances at 12 loci on chromosome arms 1p, 14q, 17p, 18q, and 20q, and the microsatellite instability (MSI) status was determined. The clinical significance of the tumor protein 53 (TP53) mutations was re-evaluated.

RESULTS

Patients with tumors containing 17p or 18q deletions had shorter survival than those without these alterations (P =.021, P =.008, respectively). This was also significant for the Dukes' B group (P =.025, P =.010, respectively). Furthermore, patients with tumors showing losses of both chromosome arms revealed an even poorer disease outcome than those with either 17p or 18q loss. Patients with low increase in 20q copy number in their tumors had longer survival compared with those without changes (P =.009) or those with a high increase of copy number (P =.037). This was also evident for the Dukes' C group (P =.018, P =.030, respectively). MSI was seemingly a beneficial marker for survival (P =.071). A significant association between mutations affecting the L3 zinc-binding domain of TP53 and survival was confirmed in this cohort after 10 years of follow-up, and also was found to apply for patients in the Dukes' B group. Several associations were found among genetic and pathologic data.

CONCLUSION

The present study indicates that 17p, 18q, and 20q genotypes, and TP53 mutation status add information in the subclassification of Dukes' B and C patients and may have impact on the choice of treatment.

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.

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.

Inverse relationship between microsatellite instability and K-ras and p53 gene alterations in colon cancer

Some studies have shown an inverse relationship between microsatellite instability in colon cancer and mutations in p53 and K-ras, whereas others have not. We therefore evaluated these features in a population-based sample of 496 individuals with colon cancer. Microsatellite instability was determined by a panel of 10 tetranucleotide repeats, the Bethesda consensus panel of mono- and dinucleotide repeats, and coding mononucleotide repeats in transforming growth factor-beta receptor type II, hMSH3, BAX, hMSH6, and insulin-like growth factor receptor type II. Mutations in codons 12 and 13 in K-ras were evaluated by sequencing. p53 overexpression (as detected by immunohistochemistry) was used as an indicator of p53 mutation; this was evaluated in 275 of the tumors. K-ras mutations were present in 33.2% of tumors, p53 overexpression in 51.5%, and microsatellite instability (as determined by the Bethesda consensus panel) in 12.5%. K-ras mutations were significantly less common in unstable tumors than stable tumors (11.8% versus 36.9%, P: < 0.001). p53 overexpression was significantly less common in unstable tumors than stable tumors (20.0% versus 55.7%, P: < 0.001). These inverse relationships between microsatellite instability and ras gene mutations and p53 overexpression were shown to be independent of tumor site in logistic regression analyses. All other measures of instability also showed statistically significant inverse relationships independent of tumor site with alterations in ras and p53, and instability results determined by the panel of 10 tetranucleotide repeats were highly significantly related to those determined by the Bethesda consensus panel. Coding mononucleotide repeat mutations were significantly more common in unstable tumors than stable tumors (85.7% versus 1.0%, P: < 0.001). We conclude that there is an inverse relationship between microsatellite instability and mutations in p53 and K-ras, and that the molecular profile of colon cancers with microsatellite instability is characterized by relatively infrequent mutations in K-ras and p53 and relatively frequent mutations in coding mononucleotide repeats.

Death from early colorectal cancer is predicted by the presence of transcripts of the REG gene family

An intrinsic component of colorectal carcinogenesis may be the capacity to activate regenerative responses simultaneously with inhibition of apoptosis. Since apoptosis is known to be inhibited in colorectal cancer, this study sought evidence for the activation of the REG family of genes which are considered to be activated during regeneration of intestinal mucosa. Transcripts for the REG gene were found in 53% of colorectal cancers and for the PAP gene in 60% of colorectal cancers, by RT-PCR. Using in situ hybridization, the REG transcripts were found to be present in the tumour cells themselves rather than inflammatory or stromal cells. There were no significant correlations between the expression of these two genes and tumour stage, age or sex of the patient population or tumour site. However, in patients with non-metastatic disease who underwent ostensibly curative surgery, the expression of REG alone and co-expression of REG with PAP had a highly significantly adverse effect on survival. These data provide support for the concept that, in some tumours, carcinogenesis involves a regenerative process which co-exists with apoptotic inhibition and may provide a valuable selective indicator of the need for adjuvant therapy in those patients with early-stage colorectal cancer whose disease is destined to recur after curative surgery.

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.

American Joint Committee on Cancer Prognostic Factors Consensus Conference: Colorectal Working Group

BACKGROUND

The American Joint Committee on Cancer (AJCC), which regularly reviews TNM staging systems, established a working party to develop recommendations for colorectal carcinoma.

METHODS

A multidisciplinary consensus conference using published literature developed an arbitrary classification system of prognostic marker value (Category I, IIA, IIB, III, and IV), which forms the framework for this report.

RESULTS

The working party concluded that several T categories should be subdivided: pTis into intraepithelial carcinoma (pTie) and intramucosal carcinoma (pTim); pT1 into pT1a and pT1b corresponding to the absence or presence of blood or lymphatic vessel invasion, respectively; and pT4 into pT4a and pT4b according to the absence or presence of tumor involving the surface of the specimen, respectively. The working party also recommended that TNM groups be stratified based on the presence or absence of elevated serum levels of carcinoembryonic antigen (CEA) (>/= 5 ng/mL) on preoperative clinical examination. In addition, the working party also concluded that carcinoma of the appendix should be excluded from the colorectal carcinoma staging system because of fundamental differences in natural history.

CONCLUSIONS

The TNM categories and stage groupings for colorectal carcinoma published in the current AJCC manual have clinical and academic value. However, a few categories require subdivision to provide increasing discrimination for individual patients. The serum marker CEA should be added to the staging system, whereas multiple other factors should be recorded as part of good clinical practice. Although many molecular and oncogenic markers show promise to supplement or modify the current staging systems eventually, to the authors' knowledge none have yet been evaluated sufficiently to recommend their inclusion in the TNM system.

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.

Genomic instability and alterations in Apc, Mcc and Dcc in Hong Kong patients with colorectal carcinoma

Our aim was to reveal the significance of tumor-suppressor genes and genomic instability in 99 Hong Kong Chinese colorectal carcinoma (CRC) patients by PCR-LOH analysis and PCR-PTT assay. The frequencies of allelic loss of Apc, Mcc and Dcc and of APC truncation were 31.3% (15/48), 11.6% (5/43), 44.4% (20/45) and 46/93 (49.5%), respectively. The frequency of Apc LOH was similar to, the Mcc LOH was lower than, and the Dcc LOH was higher than that reported for Caucasians and Japanese. In Hong Kong CRC patients, the replication error-positive (RER(+)) phenotype occurred with a frequency of 10% (10/99), which was similar to other results using microsatellite markers where RER(+) frequencies ranged from 11% to 28%. The rates of genetic alteration in RER(+) tumors were lower in tumors harboring p53, Mcc and Dcc alterations; similar in Apc; and higher in Ki-ras tumors compared with RER(-) tumors, though these differences did not achieve statistical significance. None of the biomarkers examined were predictive of survival independently, but strong trends confirming earlier observations of associations between RER(+) phenotypes with proximal tumor location and poorly differentiated tumor status were noted. The RER(+) phenotype was correlated significantly to the less aggressive Duke's stage B and improved prognosis. Additionally, tumors with RER(+) phenotypes were positively correlated with young age and sex. Our results support the observation that a subset of younger male CRC patients in Hong Kong may develop CRC via the RER pathway and show differences in RER status and sex. A significantly higher percentage of older Hong Kong Chinese CRC patients had APC truncations. Int. J. Cancer (Pred. Oncol.) 84:404-409, 1999.

Microsatellite instability and 8p allelic imbalance in stage B2 and C colorectal cancers

BACKGROUND

Microsatellite instability (MSI) and allelic imbalance involving chromosome arms 5q, 8p, 17p, and 18q are genetic alterations commonly found in colorectal cancer. We investigated whether the presence or absence of these genetic alterations would allow stratification of patients with Astler-Coller stage B2 or C colorectal cancer into favorable and unfavorable prognostic groups.

METHODS

Tumors from 508 patients were evaluated for MSI and allelic imbalance by use of 11 microsatellite markers located on chromosome arms 5q, 8p, 15q, 17p, and 18q. Genetic alterations involving each of these markers were examined for associations with survival and disease recurrence. All P values are two-sided.

RESULTS

In univariate analyses, high MSI (MSI-H), i.e., MSI at 30% or more of the loci examined, was associated with improved survival (P =.02) and time to recurrence (P =.01). The group of patients whose tumors exhibited allelic imbalance at chromosome 8p had decreased survival (P =.02) and time to recurrence (P =.004). No statistically significant associations with survival or time to recurrence were observed for markers on chromosome arms 5q, 15q, 17p, or 18q. In multivariate analyses, MSI-H was an independent predictor of improved survival (hazard ratio [HR] = 0.51; 95% confidence interval [CI] = 0.31-0.82; P =.006) and time to recurrence (HR = 0.42; 95% CI = 0.24-0.74; P =.003), and 8p allelic imbalance was an independent predictor of decreased survival (HR = 1.89; 95% CI = 1.25-2.83; P =. 002) and time to recurrence (HR = 2.07; 95% CI = 1.32-3.25; P =.002).

CONCLUSIONS

Patients whose tumors exhibited MSI-H had a favorable prognosis, whereas those with 8p allelic imbalance had a poor prognosis; both alterations served as independent prognostic factors. To our knowledge, this is the first report of an association between 8p allelic imbalance and survival in patients with colorectal cancer.

Expression of the deleted in colorectal cancer gene is related to prognosis in DNA diploid and low proliferative colorectal adenocarcinoma

PURPOSE

Whether or not the deleted in colorectal cancer (DCC) gene is implicated in metastases or in predicting prognosis in patients with colorectal cancer has not previously been substantiated. Our aims were to investigate DCC expression in primary colorectal cancers and in metastases to identify any prognostic significance.

PATIENTS AND METHODS

DCC expression was examined immunohistochemically in 195 primary colorectal adenocarcinomas and in 23 paired primary tumors and lymph node metastases. DNA content and S-phase fraction were measured by flow cytometry.

RESULTS

The absence of DCC expression was observed in 55 primary tumors (28%). DCC negativity was significantly related to poor prognosis in patients with DNA diploid tumors (P =.03) and those with a low S-phase fraction (< 5%, P =.02) but not in patients with nondiploid tumors or those with a higher S-phase fraction. Furthermore, DCC expression retained its prognostic significance in the diploid subgroup after adjusting for sex, age, site, stage, growth pattern, and differentiation (P =.01). DCC expression was similar in primary tumors and their metastases.

CONCLUSION

The absence of DCC predicted a poor outcome in the patients with diploid tumors and those tumors with a low S-phase fraction. Immunohistochemistry may be considered as a practical test to assess prognosis in this subgroup of patients.

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 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.

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.

Kirsten ras mutations in patients with colorectal cancer: the multicenter "RASCAL" study

BACKGROUND

Kirsten ras (Ki-ras) gene mutations occur early in the progression of colorectal adenoma to carcinoma. The aim of this collaborative study was to clarify the association between Ki-ras mutations, patient outcome, and tumor characteristics by use of data from colorectal cancer patients worldwide.

METHODS

Investigators who had published data on Ki-ras and colorectal cancer were invited to complete a questionnaire for each patient entered into a database. Two-sided statistical tests were used to analyze data.

RESULTS

Patients (n = 2721) were recruited from 22 groups in 13 countries. Mutations of Ki-ras codon 12 (wild type = GGT = glycine) or codon 13 (wild type = GGC = glycine) were detected in 37.7% of the tumors; 80.8% (584 of 723) of all the specified mutations occurred in codon 12, and 78.1% (565 of 723) of all the specified mutations were at the second base of either codon. Mutations were not associated with sex, age, tumor site, or Dukes' stage. Mutation rates seen in patients with sporadic tumors were comparable to those observed in patients with a predisposing cause for their cancer. Poorly differentiated tumors were less frequently mutated (P = .002). Multivariate analysis suggested that the presence of a mutation increased risk of recurrence (P<.001) and death (P = .004). In particular, any mutation of guanine (G) to thymine (T) but not to adenine (A) or to cytosine (C) increased the risk of recurrence (P = .006) and death (P<.001). When individual, specific mutations were evaluated, only valine codon 12 was found to convey an independent, increased risk of recurrence (P = .007) and death (P = .004).

CONCLUSIONS

Ki-ras mutations are associated with increased risk of relapse and death, but some mutations are more aggressive than others.

Mutation of the transforming growth factor-beta type II receptor gene in right-sided colorectal cancer: relationship to clinicopathological features and genetic alterations

The presence of inactivating mutations in the transforming growth factor-beta (TGF-beta) type II receptor (RII) gene in the colon cancer suggests that it may behave like a tumour suppressor gene. RII is mutated in the majority of colon tumours exhibiting widespread microsatellite instability, a characteristic generally referred to as the replication error phenotype (RER+). We investigated the association between RII mutations and various clinicopathological variables and genetic alterations in a large series of sporadic adenocarcinomas arising in the proximal colon. RII mutations were found in 17 per cent (36/210) of right-sided tumours and in 86 per cent (32/37) of those displaying RER+. They were associated with the absence of lymph node invasion (P = 0.04), poor histological differentiation (P = 0.006), and with a trend for improved patient survival. Tumours with an RII mutation also showed non-significant trends for a lower incidence of p53 protein overexpression and of p53, K-ras, and APC gene mutation compared with tumours with normal RII. These results indicate that right-sided colorectal tumours containing RII mutations resemble those with the RER+ phenotype in terms of their clinicopathological features and genetic alterations.

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 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.

[Colonic cancer: from molecular diagnosis to diagnostic and therapeutic procedure]

Studies of tumour cell genetic alterations have demonstrated the existence of two distinct groups of colorectal cancers. The first one is characterised by the existence of hyperploid tumour cells and frequent loss of heterozygosity. These colorectal cancers are the most common. The second one is characterised by the presence of microsatellite instability. Among the most frequent genetic alterations, the loss of heterozygosity on the short arm of chromosome 17 and the long arm of chromosome 18 seems to be indicators of a pejorative prognosis. In the same way the existence of a p53 mutation in tumour cells has been demonstrated as an independent prognostic factor in colorectal cancer. The indication of an adjuvant chemotherapy on the basis of such genetic alterations remains to be demonstrated by randomised trials.

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.

Prognostic markers for colorectal cancer: expression of P53 and BCL2

P53 is a tumor suppressor gene that has been implicated in the pathogenesis of a wide range of tumor types including colorectal cancers. bcl2 is a proto-oncogene that inhibits apoptosis. Immunostaining for P53 and BLC2 protein product was performed in a retrospective series of 80 colorectal carcinomas with a minimum follow-up of 5 years. The aim of the study was to evaluate the prognostic significance of P53 and BCL2 protein expression and their correlation with clinicopathologic variables such as pathologic disease stage (Dukes system), histologic grade, and vascular invasion. The patients were 41 to 76 years of age, and the follow-up ranged between 5 and 10 years. Among the 80 cases, 30 were Dukes stage A and 50 stage B. We found vascular invasion in 21.2%. P53 and BCL2 expression was detected, respectively, in 30.0% and 8.8%. We concluded that the P53 and BCL2 expression detected by immunohistochemistry in routinely processed, paraffin-embedded tissues: (1) has no prognostic significance; and (2) was not correlated with pathologic disease stage, histologic grade, or vascular invasion. Nevertheless, the number of patients in our study was small, and we believe that investigation of a larger series of patients is indicated.

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.

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.

p53 accumulation and mutation are prognostic indicators of poor survival in human gastric carcinoma

The aim of our study was to examine the prognostic significance of p53 protein accumulation and gene mutation in a series of 116 gastric carcinomas from a low incidence population. Formalin-fixed, paraffin-embedded tumour sections were used to investigate p53 protein accumulation by immunostaining with monoclonal antibody (MAb) DO-7 and p53 gene mutation by single-strand conformation polymorphism analysis of exons 5-8. Nuclear p53 accumulation was detected in 23% of tumours and mutation in 28%. Concordance between the 2 alterations was observed in 73% of cases. p53 protein accumulation was more frequent in tumours with lymph node metastasis, while p53 mutations were more frequent in tumours from older patients. The histopathological parameters of depth of invasion, grade and histological type showed no significant associations with either p53 alteration. In univariate analysis, both alterations were associated with significantly shortened patient survival. The 5-year survival rate for patients with a p53 mutation was 9% compared to 42% for those without a mutation. In multivariate analysis adjusted for the other histopathological parameters, p53 gene mutation but not immunohistochemically-detected p53 protein accumulation was an independent prognostic indicator of poor survival in gastric carcinoma.