c‐erbB‐2 oncoprotein in relation to DNA ploidy and prognosis in colorectal adenocarcinoma

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Abstract
Overexpression of the c‐erbB‐2 onocogene has been demonstrated in a variety of tumours, including colorectal tumours. In breast carcinoma, c‐erbB‐2 overexpression is associated with DNA ploidy, some other prognostic indicators, and unfavourable survival prospects. However, there is little such information available regarding colorectal tumours. In this study, c‐erbB‐2 was analysed retrospectively by immunohistochemistry in 293 primary colorectal adenocarcinomas to assess its relation to DNA ploidy, S‐phase fraction, other prognostic factors, and patient survival. Using the monoclonal antibody NCL‐CB11, we found that 23% of the tumours were strongly c‐erbB‐2 positive, while 36% showed weak expression. The highest frequency of c‐erbB‐2 expression was 81% in DNA tetraploid tumours, compared to 63% in aneuploid and, 53% in diploid tumours (test for heterogeneity, p=0.031). Overexpression of c‐erbB‐2 indicated a favourable prognosis in patients with DNA aneuploid tumours (p=0.0088), but not in those with diploid or tetraploid tumours. The prognostic value of c‐erbB‐2 in DNA aneuploid tumours remained even after adjustment for Dukes' stage (p=0.027). The results suggest that a combination of c‐erbB‐2 expression and DNA ploidy may improve the identification of patients' risk of cancer death.