Abnormal expression of the retinoblastoma protein (pRb) and cyclin D1
have been reported in a variety of malignancies, but the frequencies o
f these deregulations and their relation to prognosis in colorectal ca
ncer has not been clarified. We characterised 90 colorectal cancers wi
th respect to immunohistochemical expression of cyclin D1, pRb and Ki-
67. Two of 90 (2%) tumours lacked nuclear pRb staining, indicating ina
ctivation of the protein, while 10 (11%) expressed high levels of pRb.
Abnormal expression of pRb was significantly correlated to low levels
of nuclear cyclin D1 observed in 32% of the tumours. Strong nuclear c
yclin D1 expression was detected in 12% of the tumours. Cytoplasmic st
aining of cyclin D1 was observed in 17% of the tumours, showing an inv
erse relationship (P = 0.006) to the Ki-67 labelling index. Eight of 1
1 tumours with high nuclear overexpression of cyclin D1 and both tumou
rs with pRb defects were located in the right colon in comparison with
zero of 25 in the rectum (P = 0.009). Regarding prognosis, neither pR
b nor cyclin D1 expression correlated with patient survival. (C) 1998
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