p53 expression and DNA ploidy pattern in Egyptian colorectal carcinoma.
OBJECTIVE
p53 gene mutation occurs in about 50-60% of colorectal carcinoma cases. This mostly occurs as a late event in the adenoma-carcinoma sequence. These late stages are associated with more aneuploidy compared to adenomas and early carcinomas. However there is a controversy regarding the relation between p53 overexpression and DNA index. This study was designed to investigate the relationship between p53 status and DNA ploidy pattern.


METHODS
Nuclear DNA content of paraffin-embedded material from 83 colectomy specimens for colorectal carcinoma was measured by flow cytometry. Also, p53 was detected by immunohistochemistry in 73 out of the 83 tumor cases using a monoclonal antibody that detects both wild and mutant p53 proteins (Biogenex 1801).


RESULTS
Aneuploidy was identified in 37 cases (46.25%). Tumors with rectal location were significantly more aneuploid in comparison to other sites (P = 0.009), p53 staining showed three patterns: diffuse staining (29 cases), focal (13 cases), and negative (31 cases). Diffuse p53 staining was associated with aneuploidy (P = 0.04). The majority of DNA indices fell within the range 1.1-2.2 (32 out of 37). Twenty-one of these had DNA index = 1.1-1.8 (aneuploidy short of tetraploidy) significantly associated with diffuse p53 staining compared with peritetraploid cases (DNA index 1.8-2.2) (P = 0.034).


CONCLUSIONS
p53 immunohistochemistry demonstrates two distinct patterns in colorectal carcinoma. Diffuse p53 staining, which is associated with aneuploidy short of tetraploidy (DNA index 1.1-1.8), a finding which is different from previously published work. Focal p53 staining pattern, in contrast, is related to high G2M and more abnormal tetraploid peaks but less aneuploidy.
Zalata
Khaled R
KR
Department of Pathology, Faculty of Medicine, Mansoura University, Egypt.
Leech
Stephen H
SH
Ming
Si-Chun
SC
Nasif
Wesam A
WA
Nada
Nadia A
NA
Mohamed
Ibrahim E
IE
Atallah
Abdelfattah M
AM
Gad-el-Hak
Nabil A
NA
D000230:Adenocarcinoma / Q000235:genetics*; D002288:Adenocarcinoma, Mucinous / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000235:genetics*; D004534:Egypt; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D016158:Genes, p53 / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011003:Ploidies