Background: The cancerogenic process of colorectal cancer depends on a series of events involving oncogenes and inactivation of suppressor genes. This study concerns changes in DNA content, p53 and PCNA expression in human colon in dysplastic, precancerous and cancerous tissues.
Materials and methods: These characteristics were analyzed in a series of hyperplastic polyps (HP), adenomas (AD), adenocarcinomas evolved within adenomas (AC-AD) and adenocarcinomas (AC) of the large bowel. DNA ploidy was analyzed by flow cytometry and PCNA and p53 expression was evaluated by immunohistochemistry using monoclonal antibodies PC10 and PAb 1801.
Results: Aneuploidy was found in 43/67 (64%) of AC and only occasionally in other subgroups (AC vs all other groups: 64% vs 99%; p = 0.00002). PCNA positivity gradually increased in the sequence from HP to AC and were significantly higher in AC compared to HP (90% vs 44%; p = 0.00007). p53 positive cells were found in 67% of AC while only occasionally in other groups (HP vs AC: p = 0.0002, AD (low dysplasia) vs AC: p = 0.001; AD (moderate dysplasia) vs AC: p = 0.001).
Conclusions: These results demonstrated a progressive immunoreactivity for PCNA in the HP to AC sequence, while p53 positivity and aneuploidy seemed specific for colon carcinoma.