Influence of isoflavones in soy protein isolates on development of induced prostate-related cancers in L-W rats.

Lobund-Wistar (L-W) rats are inherently susceptible to spontaneous and induced metastasizing adenocarcinomas in the prostate-seminal vesicle (P-SV) complex. L-W rats were fed soy protein isolates containing high isoflavones (genistein and daidzein) or low isoflavones to determine their effects on development of induced P-SV tumors in two stages of the tumorigenic process. In rats fed the high-isoflavone-supplemented soy diet before initiation by methylnitrosourea (MNU), the incidence of induced prostate-related cancer was reduced and the disease-free period was prolonged by 27% compared with rats fed the same diet but low in isoflavones. Rats fed the same diets, started after MNU, manifested suggestive but less consistent results than those noted above. The incidence rates were of marginal significance, suggesting that the high intensity of the active induced disease may not represent the character of the slower-growing spontaneous (natural) disease. The delay of disease onset is of clinical significance.

Phenobarbital promotes multistage pulmonary carcinogenesis in MNU-inoculated L-W rats.

Lobund-Wistar (L-W) rats develop adenocarcinomas spontaneously in the accessory sex glands (prostate-seminal vesicles) (P-SV) in the livers and in the lungs-all after long periods of latency. This report addresses (a) the multistage pattern of induced lung carcinomas in L-W rats and (b) the role(s) of two putative promotional agents (testosterone propionate (TP) and phenobarbital (PB) in the development of carcinomas in the lungs of L-W rats. Lung cancer is a rare slow-growing spontaneous neoplasm in L-W rats. Their incidence increased from 4.4% in avg 25.6 months (spontaneously) to 23.8% in avg 19 months following a single IV inoculation of methylnitrosourea (MNU), and further increased to 57% in avg 15 months by adding phenobarbital to the diet of MNU-inoculated rats. Three stages of lung tumorigenesis were manifested in L-W rats following treatments with MNU, or MNU + PB: hyperplasia, adenoma, and carcinoma.

Increased phospholipid fatty acid remodeling in human and rat prostatic adenocarcinoma tissues.

PURPOSE: To study the mechanism of diminished arachidonic acid levels in malignant prostatic tissues. MATERIALS AND METHODS: Benign and malignant prostate tissues were obtained from human radical prostatectomy specimens and from rats using Pollard's Lobund/Wistar rat prostate cancer model. Fatty acid composition and a variety of enzyme activities involved in maintaining phospholipid fatty acid composition were compared in malignant and benign prostatic tissues. RESULTS: Decreased arachidonic acid levels, previously reported in human prostate cancer, were present in malignant rat as well as in human tissues. There were 21% and 26% decreases of arachidonic acid levels in the rat and human malignant tissues compared with benign tissues. Fatty acid desaturase activity was undetectable. Fatty acyl-CoA hydrolase and synthetase activities were not altered in the malignant tissues. However, there was a 2-fold increase in phospholipase A2 activity and a 4- to 12-fold increase in fatty acyl-CoA lysophosphatidylcholine acyltransferase activity in malignant rat and human prostatic tissues. CONCLUSIONS: These data indicate that, in malignant prostate tissues, the fatty acid remodeling mechanism is activated through the deacylation-reacylation cycle. This process may be a result of increased use of arachidonic acid for the formation of prostaglandins that may be crucial for the further development and growth of the malignant tissues.

Phenobarbital promotes the development of adenocarcinomas in the accessory sex glands of MNU-inoculated L-W rats.

Aged Lobund-Wistar (L-W) rats develop: (i) spontaneous and induced metastasizing adenocarcinomas in the prostate and seminal vesicle (P-SV) complex; and (ii) spontaneous hepatomas and hepatocarcinomas. Within the time-frame of 14 months, similar adenocarcinomas were induced in the P-SV complex in 70-90% of younger L-W rats by a single i.v. inoculation of methylnitrosourea (MNU) which was followed by slow release s.c. implants of testosterone propionate (TP). Within the same time-frame, neither MNU nor TP alone induced significant incidences of P-SV tumors; and untreated control L-W rats were disease-free. Methylnitrosourea or TP and combinations thereof did not induce liver tumors. However, when MNU-inoculated L-W rats were fed phenobarbital (PB), they developed (i) metastasizing adenocarcinomas in the P-SV complex and (ii) altered cellular foci and nodules in the livers. Methylnitrosourea induced a high incidence of benign lung adenomas which progressed to lung cancers in numbers which were of marginal significance. Thus, dormant MNU-initiated cells in the P-SV complex were activated by phenobarbital, to produce adenocarcinomas in that complex.

Immunotherapy by BCG against prostate adenocarcinomas in anatomical compartments.

The prostate adenocarcinoma-III (PA-III) cell line manifests a high rate of metastasis from the SC tumor site through lymphatic channels to the lungs in which they produce visible focal tumors. i.v. inoculation of BCG interfered with the passage of PA-III cells to the lungs; but not if the BCG was inoculated IP. IP inoculation of BCG suppressed propagation of PA-III cells in the peritoneal cavity, but there was no effect on metastasis of PA-III cells from a SC PA-III tumor to the lungs. Inoculation of BCG did not induce a systemic anticancer effect unless PA-III cells and BCG occupied the same anatomical compartment. Two compartments are described: intravascular and intraperitoneal.

Activation of dormant cancer cells in the prostates and seminal vesicles of Lobund-Wistar rats.

Lobund-Wistar (L-W) rats are unique in their susceptibility to spontaneous and induced metastasizing adenocarcinomas in the prostate-seminal vesicle (P-SV) complex. Tumors were induced in 70-100% of rats by a combination of i.v. inoculated methylnitrosourea (MNU) followed by a series of subcutaneous slow-release implants of testosterone propionate (TP). Adenocarcinoma cells initiated by MNU in 3-month-old L-W rats were activated significantly by implants of the promoter, TP, after intervening periods of 3, 6 and 12 months following their exposures to MNU. The longer the time between MNU and TP, the shorter the subsequent latent period. Control rats inoculated with MNU (without TP) did not develop tumors during the observation period of 12 months, and their dormant tumor cells were activated by a single implant of TP, thereby eliciting P-SV tumors.

The antimetastatic effect of IV-inoculated BCG on adenocarcinomas in the prostate-seminal vesicle complex of L-W rats.

Adenocarcinomas were induced in the prostate-seminal vesicle complex of Lobund-Wister (L-W) rats by a single IV inoculation of N-methyl-N-nitrosourea. This was followed by three slow-release S.C. implants of testosterone propionate, each at intervals of 2 months. Small (0.5 cm diameter) palpable tumors developed which enlarged during the following month to 3-4 cm diameter. At the latter stage, tumor cells spread via lymphatics to the lungs and/or by direct extension into the peritoneal cavity. Rats with small palpable tumors were inoculated IV with viable Bacillus Calmette-Guerin (BCG). One month later, the rats were killed and examined. Untreated rats with large tumors served as controls. Comparison of the two groups revealed that body weights and tumor sizes were similar and most of them had developed metastatic tumors in the peritoneal cavity. However, lung metastases were rare in the BCG-inoculated rats compared to controls. Spleen and liver weights were significantly heavier in the BCG-treated rats. It is speculated that an intra-vascular mechanism(s), engendered by BCG, immobilized the circulating tumor cells, but not those tumor cells that spread by direct extension from the primary tumor into the peritoneal cavity.

The anti-metastatic effect of intravenously-inoculated BCG on prostate tumor cells.

The complication of metastasis from the primary tumor site to the distant organ is difficult to control. Tumor cells usually spread through the vascular system: lymphatics and/or blood; or by direct extension into adjacent sites. Transplantable prostate adenocarcinoma (PA-III) cells in L-W rats produces a tumor in the implant site and then spreads via the ipsilateral lymphatic route to the lungs in which new visible tumors develop. Viable bacillus Calmette-Guerin (BCG) was inoculated SC or IV into rats which were then inoculated either SC or IV with PA-III cells. They were examined thereafter for primary and for lung tumors. IV-inoculated BCG generated a strong intravascular intervention mechanism on metastatic PA-III cells in L-W rats. This immobilization mechanism was not demonstrable in rats that had been inoculated SC with BCG.

Early manifestations of induced prostate tumors in Lobund-Wistar rats.

Lobund-Wistar (L-W) rats are susceptible to spontaneous and induced metastasizing prostate cancer. In the search for the initial site of tumor development in the induced disease, rats at risk were examined periodically to acquire this information. In the course of 12 months after the onset of the induction of prostate cancer in L-W rats, 14 of 40 rats (35%) developed visible tumors in the anterior and in the dorso-lateral lobes of the gland. The prostate tumors appeared at 7 months and thereafter. Two of the tumor-bearing rats had developed, in addition, a visible neoplasm in the seminal vesicle. None of the rats with small early tumors had developed visible metastatic tumors, which were manifested in rats with large tumors.

The inhibitory effect of 4-hydroxyphenyl retinamide (4-HPR) on metastasis of prostate adenocarcinoma-III cells in Lobund-Wistar rats.

Tumor cells of transplanted prostate adenocarcinoma-III (PA-III) spread with very high frequency from the extravascular implant site through ipsilateral lymphatic channels to the lungs in which they produce visible focal tumors. The latter enlarge, coalesce and eventually kill the host. This system was used to demonstrate the effect of a retinoid on metastasis. Lobund-Wistar (L-W) rats were administered 1 mmol 4-HPR/kg diet L-485, and control rats received the same diet without 4-HPR. After an interval, all rats were inoculated subcutaneously with PA-III cells. When examined at autopsy, all rats had developed an anticipated tumor at the implant site. However, the numbers of focal PA-III tumors in the lungs were significantly reduced among the 4-HPR-treated rats compared to the control rats (P = 0.002).

Prevention of primary prostate cancer in Lobund-Wistar rats by N-(4-hydroxyphenyl)retinamide.

We report for the first time that a synthetic retinoid, N-(4-hydroxyphenyl)retinamide, can prevent the development of both primary and metastatic tumors in an animal model of metastasizing primary prostate cancer. Prostatic adenocarcinomas were induced in high incidence in Lobund-Wistar rats by initiation with methylnitrosourea i.v. and promotion with testosterone. Feeding of N-(4-hydroxyphenyl)retinamide to these rats during the latency period markedly diminished the final incidence of both primary and metastatic prostate carcinomas.

In vivo model systems for assessing an anti-cancer drug: responses of autochthonous and transplanted prostate tumors to cyclophosphamide.

Therapeutic effects of cyclophosphamide (CPA) were compared in L-W rats with (a) transplanted prostate adenocarcinomas (PAs), and (b) with induced autochthonous PAs. All rats, except controls, were treated by IP-administered CPA in slow-release silastic membranes (a) at time 0 after inoculation of transplanted PA cells; or (b) after development of palpable transplanted PAs thereof; or (c) after detection of palpable autochthonous PAs. The treated rats did not manifest evidence of CPA-related toxicity. The transplanted PAs and lung metastases thereof were suppressed by CPA; but, the same treatment schedule with CPA failed to modify continued growth of the autochthonous PAs. This report serves to emphasize the need for test systems of autochthonous model tumors of the counterpart disease in humans.

Prevention and treatment of primary intestinal tumors in rats by piroxicam.

Over 90% of methylazoxymethanol acetate-treated male Lobund Sprague-Dawley rats developed intestinal tumors within 20 weeks; the incidence and numbers of tumors remained basically the same at 40 weeks. However, at week 40 the numbers of large tumors (greater than 0.5 cm in diameter) were increased. At week 40, tumors in methylazoxymethanol acetate-inoculated rats that had been treated with piroxicam (approximately 2.3 mg/day) from week 1 or from week 20 (after tumors had developed) were significantly reduced in numbers, but many large tumors persisted. Rats treated with piroxicam up to 40 weeks carried 0.6 tumor/rat compared with 2.7 tumors/rat among untreated controls (P less than 0.0001). Rats at week 20 had developed 2.8 tumors/rat and rats treated with piroxicam from week 20 to week 40 carried 1.4 tumors/rat (P less than 0.007). Most of the tumors in the piroxicam-treated rats showed evidence of histological differentiation.

Prevention of prostate cancer and liver tumors in L-W rats by moderate dietary restriction.

Aging conventional (CV) and germfree Lobund-Wistar (L-W) rats developed spontaneous tumors, predominantly in the prostate, liver, and adrenal glands. In CV L-W rats a 30% reduction of daily intake (natural ingredient diet L-485) had the following effects: (1) reduction of the incidence of metastatic prostate adenocarcinomas (PA) from 25.7% to 6.3% and extension of the average latent periods from 26.6 to 36.7 months; and (2) reduction of the incidence of hepatomas from 59% to 26% and extension of the average latent periods from 31.3 to 34 months. Adrenal medullary tumors developed in approximately 60% of rats older than 19 months, regardless of dietary intake and microbial status. Stromal hyperplasia developed among 36 of 78 (46%) rats older than age 30 months. Rats with PA were free of stromal hyperplasia, and the reverse was also true. Germfree L-W rats developed all of the above tumors, but the diet-related differences were not as significant as those among the conventional counterpart rats. The incidence of prostatis was reduced from 22% to 6% among the diet-restricted rats, but this lesion did not develop among the germfree rats.

The promotional effect of testosterone on induction of prostate-cancer in MNU-sensitized L-W rats.

Large metastasizing prostate adenocarcinomas (PAs) were induced in L-W rats by a single intravenous (i.v.) inoculation of methylnitrosourea (MNU) and then single subcutaneous implants of testosterone propionate (TP) at intervals of 2 months. This procedure induced PAs in approximately 90% of rats in an average of 11 months. PAs did not develop spontaneously in L-W rats under age 20 months. With this model system, it was demonstrated that within a 14-month observation period, significant numbers of PAs were elicited by TP implants in L-W rats after intervals of 1 week, 1 month and 2 months following the inoculation of MNU. A direct relationship was also demonstrated between amount of TP administered to L-W rats and the resulting incidence of PAs. TP is characterized as a prostate-directed promoter of PA, following a single inoculation of MNU which served as the tumor initiator.

Prevention and treatment of experimental prostate cancer in Lobund-Wistar rats. I. Effects of estradiol, dihydrotestosterone, and castration.

The Lobund-Wistar (L-W) rat is unique in its susceptibility to spontaneous and induced metastasizing prostate adenocarcinomas (PAs). A single IV inoculation of methylnitrosourea (MNU) produced PAs in 20% of L-W rats in 12 months. The combination of MNU plus two to seven slow-release implants of testosterone propionate (TP) induced PAs in 50-90% of rats respectively in an average of 11.5 months. The induction of PAs was prevented by early treatments of rats at risk with estradiol and less so with dihydrotestosterone (DHT). However, on a technical basis, the results were not significant. Treatments of MNU-inoculated rats with estradiol, with DHT, or by castration, at intermediate points in the projected latency time of tumor development, reduced significantly the incidences of PA development. Rats in which overt PAs had already developed in response to 12 months of exposure to implants of TP did not respond to treatment by estradiol, DHT, or castration. Thus there are early stage(s) in induced prostate tumorigenesis in L-W rats that are sensitive to modulating agents.

Effects of diphosphonate and x-rays on bone lesions induced in rats by prostate cancer cells.

Prostate adenocarcinoma-III (PA-III) cells deposited over the scapula of Lobund-Wistar (L-W) rats induced osteolytic and osteoplastic changes in that bone. The osteolytic process was prevented and interrupted by administrations of dichloromethylene diphosphonate (Cl2MDP); but the osteoplastic process, once initiated, continued. The latter process was interrupted by ionizing radiation. Treatments of PA-III-affected bones with Cl2MDP and x-rays immobilized both osteolytic and osteoplastic processes.

Characterization of xenogeneic mouse-to-rat bone marrow chimeras. I. Examination of hematologic and immunologic function.

Eighteen xenogeneic chimeric rats (survival: greater than 100 days) were established by transplanting bone marrow cells from femurs of 10 gnotobiotic CFW mice into each germfree Sprague-Dawley or Wistar rat. The erythrocytes circulating in the rats were of mouse origin as determined by hemagglutination. Hemoglobin electrophoresis, radial immunodiffusion for IgG, and assay of granulocytic neutrophils for leukocyte alkaline phosphatase verified that true chimerism was achieved. The extent of hematological and immunological reconstitution varied. In general, hematocrit levels were low to normal, white blood cell counts and differentials were within normal limits, and serum protein levels were normal. Levels of circulating IgG of each species were comparable to those of germfree rat and mouse controls. Natural killer (NK) activity was depressed, a phenomenon that may be attributable to the radiation treatment of recipients, or to failure to transfer NK cells or precursors. Mitogenic stimulation reactions were varied, but most chimeric rats demonstrated moderately depressed responses. Reactions as a whole suggested that gnotobiotic rats with xenogeneic bone marrow are incompletely reconstituted, both hematologically and immunologically. No acute graft-versus-host reaction was seen.

Autochthonous prostate adenocarcinomas in Lobund-Wistar rats: a model system.

An experimental model system for autochthonous prostate adenocarcinoma (PA) has been developed in Lobund-Wistar (L-W) rats. Large primary PAs were induced in 31 of 40 (77.5%) L-W rats within an average of 10.7 months after a single dose of methylnitrosourea (MNU) and subcutaneous implants of testosterone. Metastatic tumors had developed in over 60% of the tumor-bearing rats. In addition, localized in situ PAs had developed in 5 of the 40 test rats. At 14 months 50 untreated L-W rats were free of demonstrable PAs. Two of 20 (10%) L-W rats developed PA at 14 months after inoculation of MNU alone. Six of 42 (14%) L-W rats developed PAs within 14 months after s.c. administration of testosterone implants. Thus, testosterone acted as a tumor promoter of PA for cells that had been initiated by MNU. The manifestations of the PAs in the L-W rats resembled many aspects of the counterpart disease in man.