Acid phosphatase-producing androgen-independent subline of rat prostatic adenocarcinoma (Dunning R3327 tumor) in cell culture

Inhibition of growth and increase of acid phosphatase by testosterone on androgen-independent murine prostatic cancer cells transfected with androgen receptor cDNA

Most androgen-unresponsive prostatic cancer cells are found to lack androgen receptor (AR). To clarify the role of AR in the process of the progression from androgen-dependent to androgen-unresponsive tumor, the AR gene was transfected into an AR-negative rat prostatic cancer cell line CUB-II. AR-transfectant cells expressed AR mRNA and showed binding to R1881. AR was found in nuclei of AR-transfectant cells by histochemical examination. Therefore, AR-transfectant cells were considered to contain functional AR. The growth of AR-transfectant cells was markedly inhibited in culture in the presence of testosterone, and the effect of testosterone was reduced by simultaneous addition of flutamide. Moreover, tumors inoculated with AR-transfectant cells in male mice showed much slower growth than those in females. The tumors of AR-transfectant cells in mice consisted of slightly larger spindle-shaped cells when compared to those of CUB-II cells. Moreover, AR-transfectant cells contained a few polynuclear giant cells. Since CUB-II cells contained acid phosphatase (AcP) activity, the addition of testosterone in culture increased AcP activity of AR-transfectant cells. It is concluded that resumption of androgen-dependent processes reduces the growth rate accompanying changes of phenotype.

A comparative study on expression of prostatic inhibin peptide, prostate acid phosphatase and prostate specific antigen in androgen independent human and rat prostate carcinoma cell lines

Prostatic inhibin peptide (PIP), consisting of 94 amino-acid residues is synthesized and secreted by the prostate gland. Previous studies on immunohistochemical localization of PIP in primary prostatic tumor and their metastasis, have documented the value of this peptide as a tumor marker for diagnosis of prostate cancer (PCa). The present study was undertaken to compare the expression of PIP with that of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) in androgen independent human PCa cell lines (PC-3, DU-145 and TSU-Prl) by immunoperoxidase technique. The results of the study indicated that the staining for PIP was more intense than that of PSA and PAP. The PSA staining was either weakly positive (PC-3) or totally absent (TSU-Prl and DU-145) while PAP staining was intense in PC-3 and moderate in the other two human cell lines. The intense staining observed for PIP in all of the androgen independent cell lines suggests that the synthesis and secretion of PIP is not primarily dependent on androgens. Furthermore, expression of these markers in Dunning rat cultured adenocarcinoma cell lines and tumors were studied. Positive staining for all three human tumor associated antigens (PIP, PSA and PAP) cross-reacting with the Dunning rat PCa cell lines and the tumors, suggest the suitability of this model for preclinical screening of various therapeutic agents.

Nonrandom involvement of chromosome 4 in the progression of rat prostatic cancer

Owing to progression of the original spontaneous Dunning R-3327 rat prostatic cancer, a large series of transplantable prostatic tumors have been isolated that differ widely in their histological degree of differentiation, growth rate, androgen sensitivity, and metastatic ability. Using these parameters as criteria, the full spectrum of disease progression is represented within this Dunning system of rat prostatic cancers, ranging from slow-growing, well-differentiated, androgen-sensitive, nonmetastatic forms to fast-growing, anaplastic, androgen-independent, highly metastatic forms. Cytogenetic analysis of the two least progressionally advanced Dunning cancers (i.e., histologically well-differentiated, slow-growing, nonmetastatic variants) demonstrated no structural or numerical chromosomal aberration, suggesting that the initial development of prostatic cancer may not require detectable cytogenetic changes. In contrast, all 16 of the progressionally more advanced Dunning variants analyzed had a series of characteristic structural and/or numerical chromosomal aberrations that minimally involved chromosome 4. This nonrandom involvement of chromosome 4 was consistently observed regardless of whether the karyotype of the cancer was near-diploid or hyperaneuploid, suggesting that chromosome 4 aberrations are specifically involved in the progression of rat prostatic cancer. In addition, all four variants that were highly metastatic had, besides aberration of chromosome 4, structural aberrations involving chromosomes 1, 2, and 11. Of the 14 variants that did not have a high metastatic ability, only two had a similar aberrations involving chromosomes 1, 2, 4, and 11, suggesting that these specific chromosomal aberrations may be necessary, albeit not sufficient, for a high metastatic ability of rat prostatic cancers.