Investigations on prostatic adenocarcinomas in rats

Cyclooxygenase-2 (COX-2) inhibition for prostate cancer chemoprevention: double-blind randomised study of pre-prostatectomy celecoxib or placebo

OBJECTIVE

To evaluate the biological effects of selective cyclooxygenase-2 inhibition on prostate tissue in patients undergoing radical prostatectomy (RP).

PATIENTS AND METHODS

Patients with localised prostate cancer were randomised to receive either celecoxib 400 mg twice daily or placebo for 4 weeks before RP. Specimens were analysed for levels of apoptosis, prostaglandins, and androgen receptor (AR). Effects on serum prostate-specific antigen (PSA) and postoperative opioid use were also measured.

RESULTS

In all, 28 of 44 anticipated patients enrolled and completed treatment. One patient in the celecoxib arm had a myocardial infarction postoperatively. For this reason, and safety concerns in other studies, enrolment was halted. The apoptosis index (AI) in tumour cells was 0.29% [95% confidence interval (CI) 0.11-0.47%] vs 0.39% (95% CI 0.00-0.84%) in the celecoxib and placebo arms, respectively (P = 0.68). The AI in benign cells was 0.18% (95% CI 0.03-0.32%) vs 0.13% (95% CI 0.00-0.28%) in the celecoxib and placebo arms, respectively (P = 0.67). Prostaglandin E₂ and AR levels were similar in cancerous and benign tissues when comparing the two arms. The median baseline PSA level was 6.0 and 6.2 ng/mL for the celecoxib and placebo groups, respectively, and did not significantly change after celecoxib treatment. There was no difference in postoperative opiate usage between arms.

CONCLUSION

Celecoxib had no effect on apoptosis, prostaglandins or AR levels in cancerous or benign prostate tissues. These findings coupled with drug safety concerns should serve to limit interest in these selective drugs as chemopreventive agents.

A Systematic Review of the Modifying Effect of Anaesthetic Drugs on Metastasis in Animal Models for Cancer

Background

Distant metastasis or local recurrence after primary tumour resection remain a major clinical problem. The anaesthetic technique used during oncologic surgery is suggested to influence the metastatic process. While awaiting the results of ongoing randomised controlled trials (RCTs), we have analyzed the evidence regarding the influence of anaesthetic drugs on experimental tumour metastasis in animal studies.

Methods

PubMed and Embase were searched until April 21^st, 2015. Studies were included in the systematic review when they 1) assessed the effect of an anaesthetic drug used in clinical practice on the number or incidence of metastasis in animal models with experimental cancer, 2) included an appropriate control group, and 3) presented unique data.

Results

20 studies met the inclusion criteria (published between 1958–2010). Data on number of metastases could be retrieved from 17 studies. These studies described 41 independent comparisons, 33 of which could be included in the meta-analysis (MA). The incidence of metastases was studied in 3 unique papers. From these 3 papers, data on 7 independent comparisons could be extracted and included in the MA. Locally administered local anaesthetics appear to decrease the number of metastases (SMD -6.15 [-8.42; -3.88]), whereas general anaesthetics (RD: 0.136 [0.045, 0.226]), and more specifically volatile anaesthetics (SMD 0.54 [0.24; 0.84]), appear to increase the number and risk of metastases in animal models for cancer.

Conclusions

Anaesthetics influence the number and incidence of metastases in experimental cancer models. Although more high quality experimental research is necessary, based on the currently available evidence from animal studies, there is no indication to suggest that locally administered local anaesthetics are harmful during surgery in cancer patients. Volatile anaesthetics, however, might increase metastasis in animal models and clinical trials investigating this possibly harmful effect should receive priority. The results of our systematic review in animal studies are broadly consistent with clinical reports that anaesthetic technique does seem to affect the tumour metastasis process.

Carprofen induction of p75NTR-dependent apoptosis via the p38 mitogen-activated protein kinase pathway in prostate cancer cells

The p75 neurotrophin receptor (p75(NTR)) functions as a tumor suppressor in prostate epithelial cells, where its expression declines with progression to malignant cancer. Previously, we showed that treatment with R-flurbiprofen or ibuprofen induced p75(NTR) expression in several prostate cancer cell lines leading to p75(NTR)-mediated decreased survival. Using the 2-phenyl propionic acid moiety of these profens as a pharmacophore, we screened an in silico database of 30 million compounds and identified carprofen as having an order of magnitude greater activity for induction of p75(NTR) levels and inhibition of cell survival. Prostate (PC-3 and DU-145) and bladder (T24) cancer cells were more sensitive to carprofen induction of p75(NTR)-associated loss of survival than breast (MCF-7) and fibroblast (3T3) cells. Transfection of prostate cell lines with a dominant-negative form of p75(NTR) before carprofen treatment partially rescued cell survival, showing a cause-and-effect relationship between carprofen induction of p75(NTR) levels and inhibition of survival. Carprofen induced apoptotic nuclear fragmentation in prostate but not in MCF-7 and 3T3 cells. Furthermore, small interfering RNA knockdown of the p38 mitogen-activated protein kinase (MAPK) protein prevented induction of p75(NTR) by carprofen in both prostate cell lines. Carprofen treatment induced phosphorylation of p38 MAPK as early as within 1 min. Expression of a dominant-negative form of MK2, the kinase downstream of p38 MAPK frequently associated with signaling cascades leading to apoptosis, prevented carprofen induction of the p75(NTR) protein. Collectively, we identify carprofen as a highly potent profen capable of inducing p75(NTR)-dependent apoptosis via the p38 MAPK pathway in prostate cancer cells.

COX-2 inhibitors and other nonsteroidal anti-inflammatory drugs in genitourinary cancer

Selective cyclooxygenase (COX)-2-inhibiting and other nonsteroidal anti-inflammatory drugs (NSAIDs) show promise for preventing and treating bladder and prostate cancers. In contrast to the strong NSAID epidemiology in colorectal cancer, the epidemiologic data on NSAIDs and genitourinary (GU) cancers are limited and mixed. However, a substantial body of preclinical in vitro and in vivo animal model data shows consistent NSAID activity in treating, and in some cases preventing, GU cancers and begins to address the mechanisms behind this activity (eg, involving Akt and ERK2 in the prostate). Many preclinical and clinical NSAID studies currently under way are helping to resolve the best type (selective or nonselective COX inhibitors or non-COX inhibitors), dose and duration of NSAID treatment for prevention in the GU setting. Future studies likely will focus on clarifying the NSAID mechanisms behind and developing NSAID combinations for both treating and preventing GU cancers.

Contrasting effects of aspirin on prostate cancer cells: suppression of proliferation and induction of drug resistance

BACKGROUND

Aspirin is widely used as a preventive measure against occlusive vascular diseases. Since the age group in which aspirin use has become prevalent is similar to the one presenting with prostate cancer, we decided to examine the potential effects of aspirin on prostate cancer.

METHODS

We studied the effects of plasma-attainable concentrations of aspirin (0.5-2 mM) on the human prostate cancer cell lines LNCaP, PC-3, and DU 145, employing cytotoxicity assays and flow cytometric analyses.

RESULTS

Incubation with aspirin for 3 days reduced cellular proliferation by up to 35-55% in each cell line studied, but induced a tripling of the percentage of cells expressing P-glycoprotein (an efflux pump conferring multidrug resistance) only in the LNCaP cells. Both effects were dose-dependent. The effect on P-glycoprotein expression was reflected in the induction of resistance against adriamycin cytotoxicity. Furthermore, this protective effect of aspirin was reversed by a specific P-glycoprotein inhibitor, PSC833. The cellular expression of P-glycoprotein returned to normal within 3 days following the removal of aspirin. Aspirin did not affect the cell cycle distribution of LNCaP cells.

CONCLUSIONS

This study suggests that aspirin enhances the ability of androgen-responsive prostate cancer cells to resist chemotherapeutic drugs. These findings could potentially have significant clinical ramifications for prostate cancer patients taking aspirin shortly before or during chemotherapeutic sessions.

Androgen receptor expression in primary prostate cancers of Lobund-Wistar rats and in tumor-derived cell lines

Prostate tumors were induced in Lobund-Wistar rats by treatment with N-methyl-N-nitrosourea (MNU) and testosterone propionate (TP). Androgen receptor (AR) expression was confirmed in 16 (100%) of the primary prostate cancers, with strong uniform staining in well-differentiated tumors and more variable AR immunoreactivity in poorly differentiated tumors. Epithelial cell lines were established from nine of the tumors. At early passages, four of the tumor cell lines tested were strongly immunoreactive for AR; however, only two of the cell lines, E2(A) and F2, have remained AR-positive. These cell lines specifically bind 5H-DHT at 40 and 19 fmol/mg protein, respectively, and express a 110 kDa AR immunoreactive protein. Proliferation in in vitro culture of both E2(A) and F2 cells was increased in the presence of 5alpha-dihydrotestosterone (DHT). The antiandrogen, hydroxyflutamide was able to prevent the DHT-induced growth of E2(A) but not F2 cells. Furthermore, hydroxyflutamide alone increased proliferation of F2 cells, suggesting that the androgen signalling pathway in this cell line may be abnormal. Tumorigenicity of the AR-expressing and nonexpressing cell lines was confirmed by xenograft formation following subcutaneous inoculation into intact male nude mice. In summary, carcinogen-induced prostate tumors of Lobund-Wistar rats express AR and two of nine cell lines derived from the tumors express AR. Further evaluation of AR structure in primary prostate tumors forming spontaneously or following MNU and TP induction will determine whether, as in human prostate cancers, disease progression in Lobund-Wistar rats is associated with mutations in the AR gene.

Enhancement of metastasis of prostate adenocarcinoma cells by immune-suppressive cyclosporine A

The rate and extent of metastasis by prostate adenocarcinoma-III cells was enhanced in Lobund-Wistar rats by administration of immune-suppressive cyclosporine A. PA-III cells spread from the subcutaneous PA-III-derived tumor, through ipsilateral lymph nodes, to the lungs in which they developed secondary tumors. Swollen lymph nodes, compacted with PA-III cells, indicate that the 'normal' host-engendered level of intravascular non-specific restraints to metastasis were abrogated by CSA.

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).

Suppression of x-ray induced transformation by Valium and aspirin in mouse C3H10T1/2 cells

Two commonly used drugs, Valium (diazepam) and Aspirin (acetylsalicyclic acid), were shown to suppress X-ray induced transformation in mouse C3H/10T1/2 cells. Valium was studied in an ethanol solution. Aspirin, which is soluble in both water and ethanol, was active only in the ethanol solution. Both drugs were effective only when present throughout the entire assay period.

The beneficial effects of diphosphonate and piroxicam on the osteolytic and metastatic spread of rat prostate carcinoma cells

Transplantable rat prostate adenocarcinoma III cells produce local tumors and osteolytic and osteoplastic lesions and they metastasize through defined lymphatic channels to the lungs in which they produce expanding focal tumors. The bone lesions were prevented by treatments with dichloromethane diphosphonate (Cl2MDP). Treatment of rats with piroxicam, a nonsteroidal antiinflammatory drug, suppressed to some extent tumor growth, bone destruction, and metastasis. However, simultaneous treatments of rats with both drugs (Cl2MDP and piroxicam) prevented bone damage and suppressed tumor growth and metastatic spread very significantly without evidence of toxicity.

Metastatic spread of the PAIII prostatic adenocarcinoma after implantation in the tail of the rat

The spontaneous metastatic spread of a suspension of PAIII prostatic adenocarcinoma cells from the tail site of implantation was analyzed over a period of 5 weeks in male Lobund-Wistar (LW) rats. Following subcutaneous injection of the PAIII cells, the tumor metastasized through the primary lymphatic drainage. PAIII microfoci were evident in the gluteal and iliac lymph nodes prior to colonization of the lungs. Growth of the primary tumor was evidenced by significant weight differences of the tails of PAIII-bearing and control rats 1 week after tumor implantation. Time-dependent sequential spread of the adenocarcinoma was quantitated. Significant differences were noted between PAIII-bearing and control animals with respect to the gluteal lymph node weights (+2 weeks), iliac lymph node weights (+3 weeks), dry lung weights, and lung colony numbers (+4 weeks) after tumor implantation. During the course of these studies, the whole blood prothrombin, activated partial thromboplastin, and recalcification times for the PAIII-bearing animals were similar to those of the control group. These findings indicate that there were no gross changes in systemic blood coagulation accompanying the metastasis of PAIII cells from the primary tumor. The tumor in LW rats produced a consistent pattern of growth and metastasis that is suitable for quantitation. The PAIII prostatic adenocarcinoma is a sensitive and reproducible system that may be useful to evaluate potential antimetastatic and cytotoxic agents for the treatment of hormone-insensitive prostatic cancer.

Effect of piroxicam on primary intestinal tumors induced in rats by N-methylnitrosourea

Piroxicam, a non-steroidal anti-inflammatory agent, was administered in the feed to rats which had been inoculated intra-rectally with N-methylnitrosourea (MNU). When examined 5 months later, the piroxicam-treated rats had a significant reduction of intestinal tumors compared to tumor incidences and tumor numbers in rats which were fed drug-free diet. There was no evidence of toxicity associated with the consumption of piroxicam.

Animal models and treatment of prostate cancer

Model systems for prostate cancer in rats have been developed and used for investigations on tumor biology and therapy. The "Pollard tumors" provide a combination of in vitro and in vivo attributes by which investigations can be directed at local tumor development and spontaneous metastasis. The evolution and early applications of this model system are reviewed, and the therapeutic benefits of delayed release of cyclophosphamide are presented.

In vitro responses of human prostate tumour cell lines to a range of antitumour agents

Four human prostate tumour continuous cell lines were employed for in vitro drug sensitivity testing of nine cytotoxic drugs, X-irradiation and two hormonal preparations. Responses were assessed by measuring cell survival as judged by colony formation in agarose. A marked heterogeneity of responses was noted to many of the agents studied, including X-irradiation. However, in terms of ID70 values for 24-h drug exposures, comparable responses in all the cell lines tested, with values falling within a 1.4- to 2.9-fold range, were noted with actinomycin D, adriamycin, m-AMSA, dibromodulcitol, 5-fluorouracil, hydroxyurea and ICRF-159. In contrast, mixed responses to cis-platinum and methotrexate were particularly marked, with ID70 values differing by factors of 3.8 and 7.5 respectively. In addition, when higher drug concentrations of m-AMSA, cis-platinum, dibromodulcitol and ICRF-159 were employed, significant deviations in the four survival curves became apparent. Continuous exposure to diethylstilboestrol and medroxyprogesterone acetate caused negligible cell kill. Due to these variable responses it was not possible to predict that any agent tested might have specific value in the treatment of prostate cancer. However, preliminary in vitro screening with such a panel of cell lines may complement in vivo studies with models of prostatic cancer and prove useful in investigations of mechanisms of drug resistance.

A new prostatic cancer model: systemic induction of prostatic cancer in rats by a nitrosamine

Weekly intragastric application of N-nitrosobis(2-oxopropyl) amine (BOP) at a dose of 10 mg/kg body wt induced prostatic cancer in 5 out of 15 MRC rats. Hyperplasia and metaplasia of the prostatic gland were found in 13 rats with or without cancer. All tumors had developed in the dorsal lobe, had reached a size of up to 20 mm and were invasive. Distant metastases were not observed. Although hyperplastic lesion were of a glandular type, all carcinomas had squamous cell character. All cases of prostatic cancer were associated with papillomas or carcinomas of the urethral epithelium, which had initially developed in the colliculus seminalis. The induction of prostatic cancer for the first time by a systemic application by a nitrosamine provides a promising model for understanding basic principals of prostatic cancer.

Interference with in vivo growth and metastasis of prostate adenocarcinoma (PA-III) by ICRF-159

Rat prostate adenocarcinoma III (PA III) cells metastasize spontaneously from extravascular implant sites through ipsilateral lymphatic channels to the lungs in which they develop as distinct expanding foci of tumors. ICRF-159 (30 + 60 mg/kg body weight) was administered to rats with PA-III cells at daily intervals from day 0 to 2 weeks (5 days/week). When the rats were examined after 35 and 40 days, the drug treatment caused a significant suppression of the primary tumor and of metastatic dissemination. When the treatment schedule with ICRF-159 was delayed to day 18 in rats with metastasizing PA III cells, the progress of metastasis was thereafter interrupted or retarded significantly. Rats with PA II cells which metastasize in fulminant pattern through lymphatic and blood channels to multiple target organs were administered ICRF-159 (60 mg/kg body weight) from day 0 for over 2 weeks. They did with disseminated tumors within days after cessation of treatments.

Animal models for prostate cancer

Four model systems for prostate adenocarcinomas have been developed in rats: they are designated Dunning, Noble, ACI, and Pollard tumors. They have attributes that make them valuable sources of information, of relevance to the disease in man. The development and use of the Pollard tumors as in vitro and in vivo model systems are reviewed, especially on the phenomenon of metastasis. Specific agents either accelerate or retard the rate and extent of metastatic spread of the prostate tumor cells from extravascular sites to specific target organs. Specific enzymes may be involved in the phenomenon of metastasis.

The effect of 5-fluorouracil and adriamycin on heterotransplantation of Noble rat prostatic tumors in congenitally athymic (nude) mice

The Nb rat prostatic adenocarcinoma is a well-characterized, hormonally induced family of tumors that are all readily transplantable into congenitally athymic (nude) mice. Because of this versatile heterotransplantation model, multiple replicate copies of individual tumors can be studied "in rodent." We have extended this by studying the chemotherapeutic response of such tumors and believe that this provides a useful avenue for evaluation of cytotoxic agents. Indeed, this combination of both animal model systems may provide a useful experimental tool to evaluate tumor growth, histopathologic changes and responsiveness to appropriate therapy. We report herein that two Nb rat prostatic carcinomas (2 Pr-129-D-11A and Pr-90) and thie responsiveness to Adriamycin and 5-fluorouracil are objective by studying both growth rates and tumor histology.

Testosterone metabolism by the prostate of the aging canine

Examination of testosterone metabolism in the dorsal, lateral, and ventral regions of the beagle prostate showed an absence of regional heterogeneity for testosterone metabolite production and metabolic capacity. Testosterone metabolism by the hyperplastic prostate of aged beagles (11.1 years old) was distinguished from that of young mature (2.5-year-old) and mature adult (4.5-year-old) beagle prostate by increased reductive metabolism. The change was principally the consequence of increased production of 5 alpha-dihydrotestosterone and decreased production of 4-androstenedione. These alterations in testosterone metabolism occurred progressively and may be weakly linked to other changes in canine prostate which occur during aging. 5 alpha-Androstane-3 alpha, 17 beta-diol production was maximal for prostate from 4.5-year-old beagles and the amount of this metabolite produced appeared to be unrelated to prostate size. Co-incubation of prostate from any of the beagles with testosterone and estradiol showed that estradiol had no in vitro effect upon testosterone metabolism. Mean plasma testosterone content of aged beagles (11.1 years old) was not significantly different from that of younger individuals; however, the heterogeneity of the values for the subject groups was notable. The data demonstrate that the consequences of aging upon testosterone metabolism by canine prostate, which principally develops benign prostatic hyperplasia, are opposite to those characteristic of senescent rat prostate, which does not develop bening prostatic hyperplasia and has a high incidence of spontaneous adenocarcinoma.