DETECTION OF P21(WAF1 CIP1) IN BRAIN METASTASES/

The p21(WAF1/Cip1) (p21) protein, a negative regulator of G(1) checkpo int control, was overexpressed in the majority of human gliomas. To in vestigate whether p21 expression in brain metastases from various syst emic origins is similar to that in gliomas and whether p21 expression is regulated differently in brain metastases and in corresponding prim ary tumors, we used immunohistochemical staining to examine the expres sion of p21 in paraffin-embedded sections prepared from primary colon and breast carcinomas and from metastatic brain tumors that originated from colon, breast, lung, and kidney cancers and from melanoma. Our r esults showed that 56% (28 of 50) of the brain metastases samples have more than 1% p21-positive staining cells compared with 87% of primary gliomas reported previously. Among the samples analyzed, p21 expressi on in brain metastases from breast carcinomas was much higher than in primary breast carcinomas. In contrast, p21 expression in brain metast ases from colon carcinomas was less than primary colon carcinomas. The results from this pilot study suggest that p21 expression is regulate d differently in metastatic and primary tumors.