Tyrosine protein kinase activity of human hyperplastic prostate and carcinoma cell lines PC3 and DU145.

Using the substrate poly[Glu80Na,Tyr20] [poly(GT)] and the autoradiographic detection of alkali-resistant phosphoproteins after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, tyrosine protein kinase (TPK) has been evidenced in human hyperplastic prostates (BPH) and the prostatic carcinoma cell lines PC3 and DU145. The enzyme was mainly found in the soluble fractions from hyperplastic tissues and in Triton extracts from the cell lines. However, its specific activity in tissues was 1.5- to 4.5-fold times higher in particulate than in soluble fractions and it was of the same order of magnitude as that of neoplastic cells. Under these conditions, no activity was detected in human seminal plasma and in sera from normal adult males or patients with BPH and/or prostatic carcinoma. On the other hand, some TPK activity was associated with human spermatozoa, with a specific activity 4- to 6-fold lower than in BPH tissue fractions and a total activity, per 10(6) cells, 5- to 20-fold lower than that in prostatic carcinoma cells. The activity of prostatic TPK was dependent upon the presence of the divalent cations Mn2+ or Mg2+ and it was completely abolished by heat denaturation. Angiotensin II, casein, and histone H2B were poor substrates compared to poly(GT). The TPK activities towards poly(GT) as well as endogenous proteins were not stimulated by epidermal growth factor and insulin or by dihydrotestosterone and estradiol. The autoradiography of alkali-resistant phosphoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed several bands in both BPH tissues and neoplastic cells (molecular weight ranging from 17,000 to 200,000). Preliminary characterization of TPK by gel filtration on Sephacryl S-300 showed that the soluble enzyme from BPH tissues had a molecular weight of 50,000, while the particulate-associated TPK, when assayed on poly(GT), eluted with proteins of Mr 210,000. When these peak fractions were used for endogenous phosphorylation, several major alkali-resistant phosphoproteins in the range of Mr 40,000-60,000 were evidenced, together with a Mr 110,000 band phosphorylated by the particulate TPK of Mr 210,000. In similar conditions, the TPK solubilized from rat liver membranes and partially purified by gel filtration was associated with a Mr 170,000 alkali-resistant phosphoprotein. Thus, TPKs are expressed in BPH tissues and carcinoma cell lines. In BPH tissues, two forms of TPK are expressed and the predominant enzyme is soluble and of low molecular weight (Mr 40,000-60,000).