Comparative experimental study of the serum prostate specific antigen and prostatic acid phosphatase in serially transplantable human prostatic carcinoma lines in nude mice.

Three different human lines of prostate carcinoma were successively transplanted on Balb/c nude mice and the serum values of the prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) were determined simultaneously. In a group of the tumor-bearing animals the influence of endocrine manipulation (castration, estradiol) on the serum concentration of these tumor markers was studied. As far as untreated tumor-bearing mice are concerned, the serum values of both PAP and PSA proved to be strictly dependent on the tumor volume measured. In the exponential growth phase of the grafted tumors, linear growth was linked with a correspondingly increasing PAP and PSA serum level of the test animals. A close correlation was found to exist between the two tumor markers; however, the indicator value of PSA was 20 to 50 times higher than that of PAP under the test conditions. PSA determination yielded no false-negative results, if PAP was elevated. PAP determination was false-negative in 21 per cent of cases with measurable tumors, although the serum level of PSA already showed marked elevation. In treated animals both markers were found to decrease. Arrested growth and tumor regression was associated with falling PAP and PSA serum levels or with levels within normal range. The results of this experimental study support the conclusion that prostate specific antigen represents a substantially more sensitive tumor marker than prostatic acid phosphatase.