ras p21 expression in relation to DNA ploidy, S-phase fraction and prognosis in colorectal adenocarcinoma

Overexpression of wild-type p21Ras plays a prominent role in colorectal cancer

Colorectal cancer (CRC) is the most common gastrointestinal type of cancer. The overexpression of Ras proteins, particularly p21Ras, are involved in the development of CRC. However, the subtypes of the p21Ras proteins that are overexpressed and the mutation status remain unknown restricting the development of therapeutic antibodies targeting p21Ras proteins. The present study aimed to investigate the mutation status of ras genes associated with Ras proteins that are overexpressed in CRC and explore whether or not wild-type p21Ras could be a target for CRC therapy. p21Ras expression was examined immunohistochemically in normal colorectal epithelium, benign lesions and malignant colorectal tumor tissues by monoclonal antibody (Mab) KGH-R1 which is able to react with three types of p21Ras proteins: H-p21Ras, N-p21Ras and K-p21Ras. Then, the expression levels of p21Ras subtypes were determined in CRC by a specific Mab for each p21Ras subtype. Mutation status of ras genes in p21Ras-overexpressing CRC was detected by DNA sequencing. There was rare p21Ras expression in normal colorectal epithelium but a high level of p21Ras expression in CRC, with a significant increase from normal colorectal epithelium to inflammatory polyps, low-grade intraepithelial neoplasia, high-grade intraepithelial neoplasia and invasive colorectal adenocarcinoma, respectively. Overexpression of K-p21Ras was found in all CRC tissues tested, overexpression of N-p21Ras was found in 85.7% of the CRC tissues, while H-p21Ras expression was not found in any CRC tissue. DNA sequencing showed that there were no K-ras mutations in 60% of the K-p21Ras-overexpressing CRC, while 40% of the CRC tissues harbored K-ras mutations. N-ras mutations were not found in any N-p21Ras-overexpressing CRC. Our findings indicate that overexpression of wild-type p21Ras may play a prominent role in the development of CRC in addition to ras mutations and could be a promising target for CRC therapy.

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.

K-ras mutations in colorectal adenocarcinomas and neighbouring transitional mucosa

The K-ras gene in codons 12 and 13 was investigated using allele-specific polymerase chain reaction in matched normal mucosa (n = 106), transitional mucosa (n = 69) and tumours (n = 149) from 149 patients with colorectal adenocarcinomas. K-ras mutations in codon 12 were detected in 41/149 (28%) of tumours and 4/69 (6%) of transitional mucosa samples, but not in the normal mucosa. Further, mutation rates were increased in younger patients (P = 0.001) and in mucinous carcinomas (50%) compared with well differentiated (17%), moderately differentiated (26%) or poorly differentiated (24%) tumours. Our findings indicate that mucinous carcinoma may represent a distinct genetic entity.

Ki-ras mutations and prognosis in colorectal cancer

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

Flow cytometric DNA ploidy and S-phase fraction correlate with histopathologic indicators of tumor behavior in colorectal carcinoma

BACKGROUND

The clinical behavior of colorectal carcinoma is highly variable without reliable predictive biomarkers. Previous reports have shown that flow cytometric DNA analysis may provide valuable prognostic information in these tumors.

PURPOSE AND METHODS

This study evaluates the DNA ploidy and the S-phase fraction (SPF) on frozen samples obtained from 61 patients with colorectal carcinoma by using flow cytometry, and it correlates the data with histopathologic features known to affect disease prognosis. Tumors were classified using the World Health Organization's histologic criteria and were staged according the American Joint Committee on Cancer's classification system. Grade of the neoplasm, vascular invasion, and perineural tumor spread were evaluated in every case.

RESULTS

Fifty-nine percent of tumors were aneuploid and showed statistically significant higher S-phase values than diploid tumors (22.5 vs. 11.2 percent; P < 0.00001). Mean SPF of the whole series was 17.9 (range, 4.2-44.2) percent. A statistically significant association was found between SPF values and histologic grade (P < 0.0016), nodal status (P < 0.0007), distant metastasis (P < 0.0001), tumor stage (P < 0.0001), venous invasion (P < 0.0002), and lymphatic permeation (P < 0.01) but not with perineural growth and infiltration of the neoplasm through the bowel wall (T). DNA ploidy correlated positively with tumor stage (P < 0.03), and the association between aneuploidy and advanced stages of the disease was statistically significant.

CONCLUSIONS

These findings showed that flow cytometric DNA ploidy and SPF, evaluated in fresh samples, are potentially useful parameters to estimate colorectal carcinoma biopathology. Aneuploidy and high replicative neoplastic activity correlated with histopathologic features that are commonly associated with the prognosis of colorectal carcinoma, being SPF-related to disease dissemination and, therefore, an indicator of clinical relevance.

Oncoproteins and tumor progression in papillary thyroid carcinoma: presence of epidermal growth factor receptor, c-erbB-2 protein, estrogen receptor related protein, p21-ras protein, and proliferation indicators in relation to tumor recurrences and patient survival

BACKGROUND

The prognostic relevance of activated oncogenes and oncoproteins has not been well studied in papillary thyroid cancer, which is slow-growing, with only regional spread in most cases. Therefore, the influence of some protein markers and tumor cell proliferation on disease progress in a series of patients with surgically treated papillary thyroid carcinoma was studied.

METHODS

One hundred twenty-seven patients with papillary thyroid carcinoma larger than 10 mm in greatest dimension were studied retrospectively, and the majority were treated with total or near-total thyroidectomy. Immunohistochemical and flow cytometric analyses of paraffin embedded tumor material were performed and the results were related to time to recurrence and thyroid cancer deaths using the univariate product-limit survival analysis and the multivariate Cox' regression method.

RESULTS

Immunohistochemical expression of c-erbB-2 protein, estrogen receptor-related protein (p29), which may be regarded as an indicator of hormone-dependent growth, S-phase, G2M-phase, sex, age, histologic grade, and primary tumor extent were all of significant prognostic importance in univariate analyses of patient survival. In the final Cox' model, however, only male sex (P = 0.017), older age, (P < 0.00005) and high grade histologic features (P = 0.006) were associated independently with decreased survival. Among females, decreased expression of c-erbB-2 protein was independently related to decreased patient survival (P = 0.019). In multivariate analysis of time to recurrence, lymph node status (P = 0.0001), epidermal growth factor (EGF) receptor expression (P = 0.013) and estrogen receptor-related protein (P = 0.007) were independent risk indicators, and S-phase fraction (P = 0.074) showed a borderline significance.

CONCLUSION

In this study, sex, age, and histologic grade were independent indicators of deaths from thyroid cancer. Lymph node metastases, EGF-receptor expression, and decreased estrogen receptor-related protein staining persisted as prognostic variables in the final multivariate analysis of recurrence free survival. Alterations in these oncogenes thus seem to play some role in disease progression in papillary thyroid carcinoma, although conventional variables are still important as prognostic indicators.

Variables related to risk of recurrence in rectal cancer without lymph node metastasis

BACKGROUND

There has been recent interest in the use of local excision for rectal cancer under consideration of patient's quality of life. However, local excision of the primary tumor does not remove the areas of lymphatic spread. Therefore, the decision to use this procedure must be considered carefully.

METHODS

The authors retrospectively analyzed 142 patients who underwent radical resection of rectal cancer without lymph node metastasis in order to define the risk factors for recurrence. The macroscopic and microscopic pathological characteristics, immunohistochemical staining for p53, and DNA ploidy pattern of the primary tumor were examined as potential predictors of recurrence.

RESULTS

The rates for 5-year disease-free survival, local control, freedom from distant metastasis, and overall survival in these 142 patients were 87%, 93%, 93%, and 91%, respectively. Factors related to recurrence and prognosis included the depth of tumor invasion, vascular/lymphatic involvement, tumor differentiation, and tumor size. However, p53 staining and DNA ploidy pattern were not useful indicators.

CONCLUSIONS

Our findings suggest that adjunctive radiotherapy and chemotherapy should be considered for patients who have rectal cancer without lymph node metastasis in the following situations: tumor invasion of the serosa, vascular/lymphatic involvement, moderately differentiated adenocarcinoma, and lesions > 2 cm in diameter. Local excision should not be used in these situations, even if there are no lymph node metastases.

Immunodetection of the p21-ras products in human normal and preneoplastic tissues and solid tumors: a review

Immunohistochemical detection of p21-ras to identify and characterize preneoplastic or neoplastic lesions in human tissues is reviewed. Information concerning the commercially available antibodies is presented. Antibodies DWP, Ras-10, Y13-259, YA6-172, NCC-001, and NCC-004 are fully documented with respect to their behavior in appropriate specificity tests and appear to be reliable reagents. After reviewing the data we have identified three groups of tissues or organs with respect to positive immunostaining for p21-ras as the significant criterion of malignancy. These three groups comprise (1) tissues for which no definite conclusion could be drawn (colon, lung, bladder, ovary, and neural and odontogenic tissues) despite occasional claims to the contrary, (2) tissues for which conclusions were negative (pancreas and stomach), and (3) tissues for which p21-ras staining positively discriminated malignant from normal tissues (liver, uterus, and salivary gland). Immunohistochemically detectable levels of products from a mutated ras gene could be demonstrated in a fraction of the samples from colon, lung, and bladder carcinomas, as well as in some histologically normal tissues adjacent to a colon carcinoma. The possibility that a higher relative intensity of the immunostaining reaction for p21-ras might discriminate malignant tissues from normal tissues or benign lesions in breast, pancreas, stomach, lung, uterus, or thyroid samples is suggested. Further studies now appear warranted and a strategy is proposed to validate the conclusions reached thus far.

Prognostic significance of p53 expression in relation to DNA ploidy in colorectal adenocarcinoma

p53 expression, DNA ploidy and S-phase fraction were analysed retrospectively in colorectal adenocarcinomas from 293 patients in whom the long-term outcome was known. The frequency of nuclear p53 staining was increased in non-diploid tumours (42%) when compared with diploid tumours (33%). Cytoplasmic p53 positive tumours were more common in the proximal colon (32%) than in the distal sites (21%). In univariate survival analysis, nuclear p53 and cytoplasmic staining were significantly associated with poor prognosis in patients with Dukes' A-C tumours. The patients showing both nuclear and cytoplasmic p53 staining had the poorest survival and the patients with tumours negative in both the nucleus and cytoplasm showed the best prognosis. The patients with tumours positive in the nucleus alone or in the cytoplasm alone presented an intermediate survival. In multivariate survival analyses, nuclear p53 expression, cytoplasmic p53 expression and DNA ploidy were prognostic indicators independent of Dukes' stage and each other. Further analysis suggested that the prognostic importance of cytoplasmic p53 expression was greater in diploid than in non-diploid tumours. We conclude that nuclear p53 expression, cytoplasmic p53 expression and DNA ploidy provide important prognostic information in colorectal adenocarcinomas.