Functional categories of TP53 mutation in colorectal cancer: results of an International Collaborative Study.

BACKGROUND: Loss of TP53 function through gene mutation is a critical event in the development and progression of many tumour types including colorectal cancer (CRC). In vitro studies have found considerable heterogeneity amongst different TP53 mutants in terms of their transactivating abilities. The aim of this work was to evaluate whether TP53 mutations classified as functionally inactive (< or=20% of wildtype transactivation ability) had different prognostic and predictive values in CRC compared with mutations that retained significant activity. MATERIALS AND METHODS: TP53 mutations within a large, international database of CRC (n = 3583) were classified according to functional status for transactivation. RESULTS: Inactive TP53 mutations were found in 29% of all CRCs and were more frequent in rectal (32%) than proximal colon (22%) tumours (P < 0.001). Higher frequencies of inactive TP53 mutations were also seen in advanced stage tumours (P = 0.0003) and in tumours with the poor prognostic features of vascular (P = 0.006) and lymphatic invasion (P = 0.002). Inactive TP53 mutations were associated with significantly worse outcome only in patients with Dukes' stage D tumours (RR = 1.71, 95%CI 1.25-2.33, P < 0.001). Patients with Dukes' C stage tumours appeared to gain a survival benefit from 5-fluorouracil-based chemotherapy regardless of TP53 functional status for transactivation ability. CONCLUSIONS: Mutations that inactivate the transactivational ability of TP53 are more frequent in advanced CRC and are associated with worse prognosis in this stage of disease.

bcl-2 protein expression is associated with better prognosis in colorectal cancer.

AIMS: To investigate the expression of bcl-2 in colorectal carcinoma and to examine its association with mediators of apoptosis (p53 and mdm-2), clinicopathological features and long-term outcome. METHODS AND RESULTS: We determined by immunohistochemistry the expression of bcl-2 in 102 colorectal carcinomas with 10-year follow-up. In 66 of these cases in which we had previously assessed p53 status, no correlation was seen between bcl-2 and p53. The mdm-2 protein was not detected in any of the 66 cases. Cytoplasmic staining of the bcl-2 gene product was seen in the tumour cells of 22 cases (22%). Using a polymerase chain reaction technique we showed that overexpression of bcl-2 was not due to rearrangement of the bcl-2 gene. Expression of bcl-2 protein was related to tumour grade but was unrelated to patient age, sex, tumour site, tumour size or Dukes' stage. There was a trend towards increased survival in those whose tumours expressed bcl-2 protein (P = 0.055). When entered into a multivariate analysis, this survival difference was independent of tumour stage (P = 0.05). CONCLUSIONS: These results suggest that bcl-2 expression in colorectal carcinoma is associated with a better long-term prognosis.

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

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

Purification and structural study of two albumin variants in an Irish population.

Two types of variant albumins were detected during routine electrophoresis on cellulose acetate on 34,000 sera from patients in a relatively stable Irish population. The fast type (IRE1) (relative mobility 1.05) had a heterozygote frequency of 1/3,780, and the slow type (IRE2) (relative mobility of 0.94) had a heterozygote frequency of 1/8,500. A method for purification of the two types of variants is described. Structural study of the fast variant established a single amino acid substitution 313 lysine----asparagine (313 Lys----Asn); this variant has been reported in several European populations and also in New Guinea indigenes. However, the slow variant has a new substitution, 479 glutamic acid----lysine (479 Glu----Lys). Because it appears to be uniquely Irish, the slow variant (formerly called IRE2) has been renamed albumin Dublin. Three other albumin variants most often reported in European populations (cumulative frequency only about 1/3,500) were not detected in this study. Because of the significance of albumin genetic variants for the study of protein evolution and as an aid in identification of drug-binding sites, clinical chemists are asked to be on the alert for cases of bisalbuminemia.

A second albumin variant in an Irish population.

Three patients with bisalbuminemia of the slow type (relative mobility 0.94) were detected and the properties of the variant albumin investigated. Three additional patients possessing a fast type variant (relative mobility 1.05) have been detected since a previous report of 4 such cases and studies on these patients are also reported.

A simple method for the separation and quantification of urinary porphyrins.

A simple routine method for the separation and quantification of urinary coproporphyrin and uroporphyrin using anion-exchange resin columns is described. The coproporphyrin is first removed from the urine by ether extraction. The anion exchange resin column is then used to isolate the uroporphyrin from the aqueous residue. The proposed method is compared with an existing method developed by Rimington in terms of recovery and reproducibility. Results from 15 urine specimens analysed by both methods are compared. The proposed method yielded lower values for coproporphyrin and higher values for uroporphyrin than the established method, but there was a good correlation between the two methods. This and its relative simplicity make it suitable for routine use.

Four cases of fast-type bisalbuminemia in an Irish population.

Four cases of bisalbuminemia detected routine electrophoresis on cellulose acetate have been investigated. Available members of the families have also been studied. The variant albumins which are all of the fast type were found to possess the same properties in terms of electrophoretic mobility, dye-binding, thyroxine binding, temperature stability and immunochemical reactivity.