The role of combined allelic imbalance and mutations of p53 in tumor progression and survival following surgery for colorectal carcinoma

The role of p53 mutations in disease progression and survival of colorectal cancer is unclear, since numerous studies have reported different conclusions. However, few reports, if any, have evaluated disease progression and survival in relationship to 'functional' and 'non-functional' p53 status defined by genetic and molecular indications. Malignant colorectal tumors, from 72 unselected patients who underwent primary and potentially curative elective tumor resections, were either classified as p53 functional (p53 +/+ , p53 +/- ) or non-functional (p53 -/- ) based on DNA sequence analysis of all p53 exons, including determination of allelic imbalance of p53 (LOH), according to four DNA markers; 2 within the coding gene and two markers in the immediate flanking regions of p53. Tumor frequency of microsatellite instability was also analyzed according to Dukes' A-D stages. Dukes' staging predicted survival as expected, while the conceptual p53 status, functional p53 vs non-functional p53, did not clearcut predict disease specific survival. p53 mutations alone or allelic imbalance inside the reading frame of the gene were unpredictive of survival, while allelic imbalance down-stream of p53 predicted reduced survival (p<0.05). The present study demonstrates that base mutations in combination with allelic imbalance within the reading frame of p53 do not predict survival or progression of colorectal cancer, while allelic imbalance upstream coding parts of the gene predicted disease-specific survival in univariate analysis. Thus, structural alterations within the gene seem less important than alterations in regions with potential control elements.