Expression of Ki-67--a proliferation-associated antigen--in prostatic cancer

The expression of the proliferation-associated antigen Ki-67 was studied in human prostatic cancer. The antigen was analyzed with an immuno-histochemical technique in TUR specimens. A correlation was seen between Ki-67 positivity and differentiation grade. All TUR specimens (15/15) with poorly differentiated carcinomas expressed the antigen. Moderately differentiated carcinomas constituted an intermediate group and slightly less than half of the cancers (12/27) were positive for the antigen. Only one of the highly differentiated carcinomas (1/12) expressed the antigen. All TUR specimens from patients with benign prostatic hyperplasia (8/8) were negative. The effect on Ki-67 positivity was also investigated in a human prostatic cancer heterotransplanted to nude mice and subjected to ionizing irradiation with or without concomitant estramustine treatment. The antigen expression was compared with that seen in tumour tissues from untreated mice and from mice treated with estramustine alone. A pronounced effect was seen in the combination treatment group with an approximately 50% reduction of the Ki-67 positive cells. The results are discussed in relation to prognosis and follow-up after radiation therapy and the possible use of estramustine in combination with radiation therapy.