The early monoclonal antibodies (MAbs) to p53 are considered reliable only on frozen sections. We examined the immunohistochemical expression of p53 in 40 paraffin-embedded samples obtained from colon carcinomas using the two new MAbs DO-1 and DO-7. Thirty-one frozen samples were obtained from the same surgical specimens and were stained using MAb PAb 1801 which has a high specificity to p53. Fifty-five percent of 40 paraffin-embedded samples was positively stained with both MAbs DO series and showed a 100% concordance rate while 52% of 31 frozen samples was positively stained with MAb PAb 1801. The concordance rate between the reactivity of MAbs DO series and that of MAb PAb 1801 was 98%. Therefore, the reactivity of MAbs DO Series in paraffin-embedded material is similar and reflects accurately the overexpression of p53 when compared with the reactivity of MAb PAb 1801. Further investigations, moreover, can be performed using the MAbs DO series on archival material for a full understanding of the p53 involvement in human cancer.

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