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

Metalloproteinase-1, Metalloproteinase-7, and p53 Immunoexpression and their Correlation with Clinicopathological Prognostic Factors in Colorectal Adenocarcinoma

Aim

The aim of this study was to analyze the immunoexpression of metalloproteinase-1, metalloproteinase-7, and p53 in colorectal adenocarcinoma, and to correlate this with clinicopathological prognostic factors.

Material and methods

Formalin-fixed paraffin-embedded tumor tissue from 82 patients was analyzed by means of immunohistochemistry, using the streptavidin-biotin method and the tissue microarray technique. Protein tissue expression was correlated with the variables of the degree of cell differentiation, stage, relapse-free survival, recurrence, survival, and specific mortality.

Results

All of the tumors were positive for metalloproteinase-1, while 50 (61%) were positive for metalloproteinase-7, and 32 (39%) were negative for the latter. For p53, 70 (85.4%) of the tumors were positive and 12 (14.6%) were negative. Correlation of the marker expressions separately and in conjunction did not produce any statistically significant data.

Conclusion

The immunoexpression of metalloproteinase-1, metalloproteinase-7, and p53 did not correlate with recurrence, mortality, relapse-free survival, survival, degree of cell differentiation, or staging of colorectal cancer.

Prognostic role of KRAS mutations in Sardinian patients with colorectal carcinoma

The presence of mutations in the KRAS gene is a predictor of a poor clinical response to EGFR-targeted agents in patients affected by colorectal cancer (CRC), but its significance as a global prognostic factor remains unclear. The aim of the present study was to evaluate the impact of the KRAS mutational status on time to first metastasis (TTM) and overall survival (OS) in a cohort of Sardinian CRC patients. A total of 551 patients with metastatic CRC at the time of enrolment were included. Clinical and pathological features of the disease, including follow-up information, were obtained from medical records and cancer registry data. For mutational analysis formalin-fixed paraffin-embedded tissue samples were processed using a standard protocol. The coding sequence and splice junctions of exons 2 and 3 of the KRAS gene were screened for mutations by direct automated sequencing. Overall, 186 KRAS mutations were detected in 183/551 (33%) patients: 125 (67%) were located in codon 12, 36 (19%) in codon 13, and 18 (10%) in codon 61. The remaining mutations (7; 4%) were detected in uncommonly-affected codons. No significant correlation between KRAS mutations and gender, age, anatomical location and stage of the disease at the time of diagnosis was identified. Furthermore, no prognostic value of KRAS mutations was found considering either TTM or OS. When patients were stratified by KRAS mutational status and gender, males were significantly associated with a longer TTM. The results of the present study indicate that KRAS mutation correlated with a slower metastatic progression in males with CRC from Sardinia, irrespective of the age at diagnosis and the codon of the mutation.

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.

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.

Replication error phenotype, clinicopathological variables, and patient outcome in Dukes' B stage II (T3,N0,M0) colorectal cancer

AIMS

To examine the relation between the replication error (RER) phenotype and other genetic events, clinical features, and long term survival in patients with Dukes' B stage II (T3,N0,M0) colorectal cancer.

METHODS

RER phenotype was investigated in 159 patients by PCR amplification of microsatellite marker loci on chromosomes 5q, 17p, 17q, and 18q from tumour DNA extracted from archival tissue. Data on activating c-Ki-ras mutations were available from a previous study. Immunohistochemical detection of p53 and c-erbB-2 expression was performed on paraffin wax embedded tissue.

RESULTS

Of 159 colorectal cancers studied, 22 (14%) were RER+ while 137 (86%) were RER- for two or more loci. RER+ tumours were more commonly located in the right colon, tended to be larger than RER- tumours, and were more often poorly differentiated than RER- cancers. No significant associations were seen between RER status and the presence of a mutant c-Ki-ras gene, or between RER status and p53, c-erbB-2, or c-myc gene expression. Univariate survival analysis showed that outcome was similar in RER+ and RER- cases. Multivariate survival analysis showed that the relative risk of death for patients with RER+ cancers was 0.95 that of patients with RER- cancers.

CONCLUSIONS

The results suggest that, while the RER phenotype may be associated with some differences in tumour pathology (site, size, differentiation), it is not associated with the genetic alterations studied or with significant differences in long term survival.

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.

K-ras mutations in patients with early colorectal cancers

BACKGROUND

Published data are contradictory about the importance of K-ras mutations in advanced tumours and are not available for early cancers.

AIMS

To establish whether specific K-ras mutations are prognostic markers in early stage colorectal adenocarcinoma.

METHODS

The presence of K-ras exon 1 mutations were correlated with tumour recurrence in two groups of patients: group 1 was a consecutive series of patients with resected colorectal adenocarcinoma at low risk of recurrence; group 2 were patients referred for chemotherapy after relapse of previously resected early stage tumours. K-ras mutations were detected by direct sequencing of whole tissue samples in all patients and in some, the leading edge and centre of the tumour were also microdissected out individually and sequenced.

RESULTS

Mutations were present in 26 (26.5%) of 98 patients in group 1; 14 patients developed a recurrence, four (28.5%) of whom had a K-ras mutation. Seventy nine patients have not developed tumour recurrence, 22 (28%) of whom had a mutation (p = 0.84). K-ras mutations were present in five of 14 patients in group 2. Microdissection did not increase the number of mutations detected.

CONCLUSIONS

Individual K-ras genotypes are distributed homogeneously throughout early stage colorectal adenocarcinomas, but detection of a mutation has no apparent prognostic value.