Biopathologic characteristics of DNA content in crypt cells of transitional mucosa adjacent to carcinomas of the rectum and rectosigmoid

Frequent p53 mutation in brain (fetal)-type glycogen phosphorylase positive foci adjacent to human 'de novo' colorectal carcinomas

'de novo' carcinogenesis has been advocated besides 'adenoma carcinoma sequence' as another dominant pathway leading to colorectal carcinoma. Our recent study has demonstrated that the distribution of brain (fetal)-type glycogen phosphorylase (BGP) positive foci (BGP foci) has a close relationship with the location of 'de novo' carcinoma. The aims of the present study are to investigate genetic alteration in the BGP foci and to characterize them in the 'de novo' carcinogenesis. 17 colorectal carcinomas without any adenoma component expressing both immunoreactive p53 and BGP protein were selected from 96 resected specimens from our previous study. Further investigations to examine the proliferating cell nuclear antigen (PCNA)-labelling index, and the p53 and the codon 12 of K-ras mutation using the polymerase chain reaction-single strand conformation polymorphism were performed in the BGP foci, BGP negative mucosa and carcinoma. The BGP foci were observed sporadically in the transitional mucosa adjacent to the carcinoma in all cases. The PCNA labelling index in the BGP foci was significantly higher than that in the BGP negative mucosa (P< 0.001). p53 mutations were observed in 8 carcinomas, but no K-ras mutation was detected. Interestingly, although none of the overexpressions of p53 protein was detected immunohistochemically in the BGP positive foci, the p53 gene frequently (41.2% of the BGP foci tested) mutated in spite of no K-ras mutation. The present study demonstrates potentially premalignant foci in the colorectal transitional mucosa with frequent p53 gene mutation. It is suggested that BGP foci are promising candidates for the further investigation of 'de novo' colorectal carcinogenesis.

Cell proliferation kinetics are abnormal in transitional mucosa adjacent to colorectal carcinoma

The transitional mucosa adjacent to colorectal carcinoma shows characteristic morphological and histochemical abnormalities that may be indicative of premalignant changes. Sixteen colorectal carcinomas were studied to analyse the proliferative activity and its distribution pattern in tissue samples from transitional mucosa located within 2 cm of the cancer and from uninvolved mucosa 10 cm from the cancer. Proliferative activity was assessed using a monoclonal antibody to proliferating cell nuclear antigen (PCNA). The total labelling index (percentage of labelled cells in a column) of transitional mucosa was not significantly different from that of uninvolved mucosa and normal control mucosa but it was significantly higher in cancer tissue (P < 0.001). An upward shift of the compartment of proliferating epithelial cells towards the bowel lumen was seen in transitional mucosa. The labelling index of the middle compartment (compartment 3) of the crypt in transitional mucosa was significantly higher than that in uninvolved mucosa and control mucosa (P < 0.001). Unstable cytokinetic change may already have started in apparently normal transitional mucosa. Assessment of cell proliferation kinetics by PCNA immunostaining may be useful in screening for heightened risk of the development of colorectal cancer.

Chromogranin positive cells in colorectal carcinoma and transitional mucosa

AIMS

Immunostaining of chromogranin identifies gastrointestinal mucosal endocrine cells. The detailed distribution and significance of chromogranin positive cells in colorectal carcinomas and in transitional mucosa remain unclear. The aim of this study was to clarify these aspects.

METHODS

The distribution of chromogranin positive cells was studied by immunohistochemical methods in normal epithelium remote from carcinoma, in transitional mucosa, and in carcinomas of the colorectum. In selected cases northern or western blot analyses were performed.

RESULTS

Chromogranin positive cells were seen in the lower third of the normal crypts and less frequently in transitional mucosa. Thirty five per cent (n = 38) of colorectal carcinomas showed immunohistochemically positive carcinoma cells in the tumour tissue. Northern and western blot analyses showed similar results. There was no difference in clinicopathological factors, including prognosis, between chromogranin positive cases of colorectal carcinoma (n = 38) and chromogranin negative cases (n = 70).

CONCLUSIONS

Neuroendocrine cell differentiation is controlled in transitional mucosa and the presence of chromogranin positive cells in carcinoma tissue does not influence the patient's prognosis.