Prostatic Adenocarcinoma Model Research Articles

Inhibitory Effect of Warfarin on the Metastasis of the PAIII Prostatic Adenocarcinoma in the Rat

The PAIII rodent metastatic prostatic adenocarcinoma model was employed to evaluate the effects of dietary warfarin, a prototypic antagonist of thrombin generation, on the lymphatic and pulmonary metastases of the tumor from the tail site of subcutaneous transplantation in male Lobund Wistar (LW) rats. In addition, the anticoagulant effects of warfarin were determined in the same animals. Warfarin, administered in the diet at concentrations equivalent to 0.063, 0.125 or 0.250mg./kg. b.w. for 30 days had no effect on final body weight, gluteal or iliac lymph node weights. Significant (p < 0.05) dose-dependent extensions of whole blood prothrombin (WBPT), activated partial thromboplastin (WBAPTT) and clotting times (WBCT) over control values were observed with warfarin treatment. Preliminary studies demonstrated that the 0.500mg./kg. dose produced 50 per cent mortality at +14 days. Warfarin produced significant (p < 0.05) dose-dependent decreases in the number of PAIII pulmonary metastases as indicated by reductions in dry lung weights and lung colony numbers when compared to untreated tumor-bearing controls. While the therapeutic index of warfarin is a limiting factor in clinical use as an antimetastatic agent, these results suggest that compounds capable of altering hemostatic mechanisms may be potential inhibitors of tumor metastasis. The PAIII prostatic adenocarcinoma model may be a useful system to quantitatively evaluate potential antimetastatic and cytotoxic agents.

Nb Rat Prostate Adenocarcinoma Model: Evaluation of the Subrenal Capsular Assay System

During the course of the last 6 years, this laboratory unit has evaluated the Nb rat prostate adenocarcinoma model with respect to various chemotherapies. Heretofore, tumors were treated after they had been implanted in the subcutaneous space. The most active chemotherapeutic agents have been cyclophosphamide, adriamycin, and cis-platinum. Herein, we report our initial experience utilizing the subrenal capsular assay. The advantage of this system is that one is able to determine the effect of chemotherapy in a very short period of time, ie, 7 days. This may be a method to save considerable expense and may serve as a useful predictor for potential future chemotherapeutic trials. In our assay systems, cyclophosphamide, adriamycin, cis-platinum, and methotrexate did result in a significant decrease in the change in tumor volume. This change paralleled the results that we have seen in the past with the use of chemotherapy of the subcutaneous tumor nodules. Further exploration of this method is warranted from a time efficiency standpoint as well as a cost standpoint.

Investigation of the Combination of the Agonist D-Trp-6-LH-RH and the Antiandrogen Flutamide in the Treatment of Dunning R-3327H Prostate Cancer Model

The therapy for the treatment of prostate cancer and other sex-steroid-dependent tumors based on agonists of LH-RH has been made more practical and efficacious by the development of a long-acting formulation of microcapsules of D-Trp-6-LH-RH for controlled release. Antiandrogens, which neutralize the effect of endogenous androgens, have been used also in the management of prostate cancer in man. The effects of a simultaneous administration of the antiandrogen flutamide and microcapsules of the agonist D-Trp-6-LH-RH were studied in the Dunning R-3327H rat prostate adenocarcinoma model to determine whether the combination of these two drugs might inhibit tumor growth more effectively than single agents. Microcapsules of D-Trp-6-LH-RH, calculated to release a controlled dose of 25 micrograms/day for a period of 30 days were injected intramuscularly once a month. Flutamide was administered SC at a daily dose of 25 mg/kg. The therapy was started 100 days after the tumor transplantation and continued for 60 days. Tumor weights and volumes were significantly reduced in rats treated with microcapsules or flutamide alone, but the former drug inhibited tumor growth more than the latter. The combined treatment of flutamide and microcapsules significantly decreased tumor weight and volume, but did not exert a synergistic effect on tumor growth, the reduction being smaller for the combination than for the microcapsules alone. There was a significant elevation of serum testosterone, LH, and prolactin in rats treated with flutamide. On the other hand, in rats given microcapsules of D-Trp-6-LH-RH, testosterone fell to castration levels within 7 days and remained at nondetectable values, serum LH and prolactin levels being also suppressed in this group. The combined administration of microcapsules and flutamide also significantly decreased serum testosterone to nondetectable levels by day 7 and suppressed serum LH and prolactin. Our findings raise doubts of whether the daily administration of the combination of LH-RH agonist with an antiandrogen offers an advantage over the use of microcapsules of an agonist like D-Trp-6-LH-RH alone in the treatment of prostatic carcinoma.

Nb rat prostate adenocarcinoma model: evaluation of the subrenal capsular assay system.

During the course of the last 6 years, this laboratory unit has evaluated the Nb rat prostate adenocarcinoma model with respect to various chemotherapies. Heretofore, tumors were treated after they had been implanted in the subcutaneous space. The most active chemotherapeutic agents have been cyclophosphamide, adriamycin, and cis-platinum. Herein, we report our initial experience utilizing the subrenal capsular assay. The advantage of this system is that one is able to determine the effect of chemotherapy in a very short period of time, ie, 7 days. This may be a method to save considerable expense and may serve as a useful predictor for potential future chemotherapeutic trials. In our assay systems, cyclophosphamide, adriamycin, cis-platinum, and methotrexate did result in a significant decrease in the change in tumor volume. This change paralleled the results that we have seen in the past with the use of chemotherapy of the subcutaneous tumor nodules. Further exploration of this method is warranted from a time efficiency standpoint as well as a cost standpoint.

Metastasis in the androgen-insensitive Nb rat prostatic carcinoma system.

This unit has in the past evaluated the Nb rat prostatic adenocarcinoma model with respect to chemotherapies. Recently, this unit has been evaluating agents that may have a role in decreasing metastatic rate. The three androgen-insensitive tumors, Nb Pr A.I. I, II, III, have been evaluated herein. Agents that have been used include indomethacin, heparin, heparin plus cortisone, and heparan sulfate (SP54). It has been shown that these agents do play a role in reducing the metastasis. In evaluation of Nb Pr A.I, I, control animals had a metastatic rate of 57%. In treatment with indocin, only 21% of the animals, three of 14 animals treated, had a metastasis, and treatment with heparin and cortisone resulted in one of 14 animals having metastasis. Similar observations were seen when treatment with SP54 and heparin was evaluated in the Nb Pr A.I. III; 18 and 27% of treatment group animals had metastasis, whereas 55% of control groups had metastasis. Similarly, in the Nb Pr A.I. II evaluation, control animals having a metastatic rate of 43% had heparin plus cortisone and heparin alone, and this particular tumor model revealed complete resolution with no animals having metastatic disease. The majority of these agents have not effected tumor volume in terms of reduction as much as the best chemotherapeutic agents in this model system include cyclophosphamide and cis-platinum.

Retardation of Prostate Tumor Progression in the Noble Rat by 4-Methyl-4-aza-steroidal Inhibitors of 5α-Reductase&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

The effect of 4-methyl-4-aza-steroidal inhibitors of 5 alpha-reductase has been evaluated on tumor growth in the Noble rat model of prostatic adenocarcinoma. The growth characteristics of the tumor line 2Pr-121D(1) were consistent with heterogeneity of cell types, composed of androgen-sensitive and androgen-insensitive malignant cells. Both sodium 4-methyl-3-oxo-4-aza-5 alpha-pregnane-20 (s)-carboxylate and 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 and 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one significantly retarded tumor progression. Each agent increased tumor volume doubling time by approximately 62%. On the basis of their similarities to female rats and male castrate group, in terms of growth rate, tumor doubling time, and histologic characteristics, the treatments with the 4-methyl-4-aza-steroids appeared to produce effects common to both castration and estrogenization (chronic administration of pharmacologic doses of estrogen). The failure of 5 alpha-reductase inhibitors to be active as antiprostatic agents in vivo has hitherto detracted from their use of therapeutic agents. Present studies demonstrate that the 4-methyl-4-aza-steroidal inhibitors of 5 alpha-reductase may represent an alternative to orchiectomy and chronic estrogen therapy for the management of the hormone-dependent phase of prostate cancer.

Investigation of the combination of the agonist D-Trp-6-LH-RH and the antiandrogen flutamide in the treatment of Dunning R-3327H prostate cancer model.

The therapy for the treatment of prostate cancer and other sex-steroid-dependent tumors based on agonists of LH-RH has been made more practical and efficacious by the development of a long-acting formulation of microcapsules of D-Trp-6-LH-RH for controlled release. Antiandrogens, which neutralize the effect of endogenous androgens, have been used also in the management of prostate cancer in man. The effects of a simultaneous administration of the antiandrogen flutamide and microcapsules of the agonist D-Trp-6-LH-RH were studied in the Dunning R-3327H rat prostate adenocarcinoma model to determine whether the combination of these two drugs might inhibit tumor growth more effectively than single agents. Microcapsules of D-Trp-6-LH-RH, calculated to release a controlled dose of 25 micrograms/day for a period of 30 days were injected intramuscularly once a month. Flutamide was administered SC at a daily dose of 25 mg/kg. The therapy was started 100 days after the tumor transplantation and continued for 60 days. Tumor weights and volumes were significantly reduced in rats treated with microcapsules or flutamide alone, but the former drug inhibited tumor growth more than the latter. The combined treatment of flutamide and microcapsules significantly decreased tumor weight and volume, but did not exert a synergistic effect on tumor growth, the reduction being smaller for the combination than for the microcapsules alone. There was a significant elevation of serum testosterone, LH, and prolactin in rats treated with flutamide. On the other hand, in rats given microcapsules of D-Trp-6-LH-RH, testosterone fell to castration levels within 7 days and remained at nondetectable values, serum LH and prolactin levels being also suppressed in this group. The combined administration of microcapsules and flutamide also significantly decreased serum testosterone to nondetectable levels by day 7 and suppressed serum LH and prolactin. Our findings raise doubts of whether the daily administration of the combination of LH-RH agonist with an antiandrogen offers an advantage over the use of microcapsules of an agonist like D-Trp-6-LH-RH alone in the treatment of prostatic carcinoma.

The Relationship of Androgen Receptor Levels to Androgen Responsiveness in the Dunning R3327 Rat Prostate Tumor Sublines

The objective of this study was to determine whether androgen receptor levels in a transplantable animal model of prostatic adenocarcinoma correlated with androgen responsiveness of the tumor. This is the first comparative study of androgen receptor levels in 3 subcellular compartments (cytosol, nuclear salt-extractable and nuclear salt-resistant fractions) of 4 Dunning R3327 rat prostatic adenocarcinoma sublines that vary in their response to androgen ablation. Tumors were harvested from intact adult male rats in order to best approximate the human clinical setting in which receptor levels are quantitated prior to androgen ablative therapy. Only the nuclear salt-resistant (nuclear matrix) and total nuclear androgen receptor contents were significantly different among all tumor sublines. The properties of the tumors studied and their nuclear salt-resistant androgen receptor levels were as follows: H tumor—well-differentiated, slow growing, androgen-dependent, 63 ± 11 fmol./mg. DNA; HI tumor—well-differentiated, slow growing, androgen-insensitive, 19 ± 8 fmol./mg. DNA; G tumor—poorly-differentiated, fast growing, androgen-sensitive, 195 ± 42 fmol./mg. DNA; and AT-2 tumor—anaplastic, fast growing, androgen-insensitive, no detectable receptors. There was no apparent quantitative relationship between androgen receptor content and tumor growth rates, which varied considerably irrespective of the androgen responsiveness of the tumor. However, there was a qualitative relationship between nuclear salt-resistant or total nuclear receptor content and androgen responsiveness. Higher levels of receptor (H and G tumor sublines) were associated with responsiveness to androgen ablation (cessation or slowing of growth, respectively), whereas lower levels of receptor (HI and AT-2 sublines) were associated with androgen insensitivity. These observations, based on relatively homogeneous tumors, may have important implications for human prostatic cancers which appear to be composed of heterogeneous cell populations.

The noble rat bladder cancer model. FANFT-induced tumors

This laboratory unit has been working with the Nb rat prostate adenocarcinoma model for the last several years and has recently used this model system to study efficacy of various chemotherapeutic agents in FANFT-induced bladder carcinomas in this rat strain. The purpose of this project is to identify factors and chemotherapeutic agents that might be useful for treatment of human bladder carcinoma. It is proposed that the use of the Nb rat be utilized to develop a data base to advance understanding of the management of bladder carcinoma induced by FANFT ingestion in Nb rats. Conventional cytotoxic agents and new combination chemotherapy will be utilized intravesically and systemically.

Therapy for Nb rat tumor transplanted in athymic mice.

Two Nb rat prostatic adenocarcinomas, 13 Pr-12, an autonomous tumor, and 2 Pr-128, an androgen-dependent tumor, were transplanted into groups of congenitally athymic nude mice. The agents used for treatment of these tumors are agents characteristically not used in treatment of prostatic adenocarcinoma in humans. However, these have been efficacious in treating other solid malignancies. Both agents, BCNU and Actinomycin-D, were efficacious in producing tumor regression and in causing at least a temporary decrease in tumor growth. The combination of the Nb rat prostatic adenocarcinoma model and nude mouse is presented as an appropriate system to screen therapeutic agents that have proved efficacious in treatment of other solid malignancies but have not been used in treating prostatic adenocarcinoma.

Combination chemotherapy in a prostate tumor model: Nb rat prostatic adenocarcinoma model.

This report presents the experience with single and combination chemotherapy in the Noble rat prostatic adenocarcinoma model. The best single agent in treatment of these tumors is cyclophosphamide, the best combination was triple drug therapy cyclophosphamide, cis-platinum, and adriamycin. This report examines the effect of the various chemotherapeutic regimens on tumor volume, number of metastasis, and complete tumor regression.

Chemotherapy and radiation of Nb rat prostatic adenocarcinoma: Nb Pr-A.I.-1

The Nb rat prostatic adenocarcinoma model has been evaluated utilizing the autonomous tumor Nb Pr A.I.-1. Chemotherapeutic evaluation as well as radiation treatment of tumors was employed. Chemotherapy was evaluated in Nb rats as well as congenitally athymic (nude) mice. Adriamycin, cyclophosphamide, and N,N-bis(2-chloroethyl)- N-nitrosourea were all significant ( P < 0.01); however, the methotrexate-treated animals as well as animals receiving the low dose of adriamycin were not affected by these modalities. Similar results were observed in both Nb rats as well as nude mice in respect to the affect of chemotherapy. Also, this model has been used to evaluate the affect of irradiating the 2-mm 3 wedges of tumor tissue with the following doses of radiation: 250, 500, 1000, and 1500 rad. Tumor growth retardation was observed in animals receiving greater than 1000 rad.

Chemotherapy of Nb rat adenocarcinoma of the prostate heterotransplanted into congenitally athymic (nude) mice: Report of 5-fluorouracil and cyclophosphamide

The desirability of an animal model of human prostatic adenocarcinoma is based on major theoretical and practical considerations. The Nb rat prostatic adenocarcinoma is induced by implantation of hormones, testosterone, and estrogen in young rats and mimics the human condition with respect to hormone dependence, histology, and obstruction of the urinary tract. These Nb rat prostatic adenocarcinomas have been heterotransplanted into athymic (nude) mice and provide a useful model to evaluate chemotherapy. Herein is reported preliminary experience with the use of cyclosphosphamide, adriamycin, and 5-fluorouracil on these tumors.

Testosterone, prostate gland and hormone action

Although the androgens, testosterone (T) and its highly active metabolite dihydrotestosterone (DHT) play a role in the development and progression of prostate cancer, the mechanism(s) are unclear. Furthermore, 5α-reductase which catalyze the conversion of T to DHT, has been a target of manipulation in the treatment of prostatic cancer, hence synthetic 5α-reductase activity inhibitors have shown therapeutic promise. To demonstrate that nutrients derived from dietary sources can exert similar therapeutic promise, this study was designed using benign hyperplastic cells (BHC) and malignant tumorigenic cells (MTC) derived from Lobund–Wistar (L–W) rat model of prostatic adenocarcinoma to test the effects of gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and their 15-lipoxygenase metabolites on cellular 5α-reductase activity. Our data revealed: (i) that incubation of MTC with [3H]-T resulted in marked conversion to [3H]-DHT when compared to similar incubation with BHC; (ii) that DHT-enhanced activity of 5α-reductase was inhibited 80% by 15S-hydroxyeicosatrienoic acid, the 15-lipoxygenase metabolite of GLA, when compared to 55% by 15S-hydroxyeicosapentaenoic acid, the 15-lipoxygenase metabolite of EPA; and (iii) that their precursor fatty acids, respectively, exerted moderate inhibition. Taken together, the study underscores the biological importance of 15-lipoxygenase metabolites of polyunsaturated fatty acids (PUFAs) in androgen metabolism.