Dunning R-3327 Rat Prostatic Adenocarcinoma Research Articles

Intratumoral Delivery of Paclitaxel for Treatment of Orthotopic Prostate Cancer

Locally recurrent prostate cancer can lead to significant morbidity, metastasis, and even death. The objective of this study was to evaluate the efficacy of an injectable polymeric paste formulation containing paclitaxel against orthotopic prostate tumor in rats. The Dunning R-3327 rat prostate adenocarcinoma is experimental tumor model used to study tumor progression. The polymer loaded with paclitaxel was injected into the tumor bearing prostate glands of the rats 3 days after tumor cell inoculation. In control untreated rats, tumor volume reached 14cm3 after 25 days, while in rats treated with intratumoral injection of polymer/paclitaxel formulation the prostate volume with the tumor was only 0.9cm3, 35 days posttumor cells inoculation. In the group treated with intratumoral injection of paclitaxel suspension, the tumor volume was 6.6cm3, and in the group treated with intraperitonial (IP) paclitaxel formulation, the tumor volume reached 13.9cm3 25 days posttumor cells inoculation. No metastases were found in rats treated intratumorally with 200µL of polymer/paclitaxel formulation, while rats in other treatment groups developed metastases in the lungs and lymph nodes. The results of this study indicated that a site-directed, injectable, controlled release formulation of paclitaxel is effective against localized prostate tumors and metastasis.

Efficacy of a synthetic lytic peptide in the treatment of prostate cancer

In the last several years, significant effort has been applied to identifying novel agents with effectiveness against prostate cancer. These studies were designed to determine the efficacy of one of these novel compounds, D2A21, in the treatment of an animal model of prostate cancer. Using the Mat-Ly-Lu(MLL) line of the Dunning R-3327 rat prostate adenocarcinoma model, the optimal dose, schedule and route of administration of D2A21 were established. A study involving the G line was used to further support these findings. In addition, hemotoxylin and eosin stained tissue samples were examined to investigate the extent of inhibition of lung metastases in animals injected with MLL cells. When D2A21 was injected intraperitoneally or subcutaneously, MLL and G cell tumor growth was inhibited 50-72% as demonstrated by both tumor volumes and weights. The optimal dosage of 0.179 mg/injection was established and it was determined to be most efficacious when administered five times per week. At this concentration, D2A21 appears to have no significant toxicity. Additionally, D2A21 increased the survival rate from only 25% to 70-75% in animals that were challenged with a large number of tumor cells. The peptide D2A21 is able to significantly inhibit tumor growth in rat models of prostate cancer. In addition, it can inhibit metastases and decrease deaths resulting from metastases in these animals.

Effects of tobacco smoke on tumor growth and radiation response of dunning R3327 prostate adenocarcinoma in rats.

The influence of tobacco smoke has been investigated on the growth rate and histology of prostate cancer, both in untreated tumors and in those subjected to fractionated irradiation. Twenty-five rats were implanted bilaterally with Dunning R3327 tumor fragments at 10 weeks of age. Approximately 3 months later, they were randomly allocated to two groups, one of which was exposed to tobacco smoke for an hour each day, 5 days a week. Three weeks later the groups were further subdivided into two groups which acted as controls or were subjected to 5 daily doses of 6 Gy. The tumors were measured weekly to construct growth curves. At a fixed time, 9 weeks or 20 weeks later, the animals were sacrificed and the tumors were removed for histological evaluation of the tissue composition. Sections from each tumor were scored in a morphometric analysis of the fraction of the area of tumor that was occupied by (epithelial) tumor cells, by stroma, or by luminal spaces. In addition, the density of mast cells was assessed in adjacent sections stained with toluidine blue. Smoking caused only minor changes in the growth rates of both the control and the irradiated tumors. At the cellular level, smoking caused a small but significant increase in the fraction of tumor cells relative to controls. Irradiation also caused a small but significant decrease in tumor cell fraction compared to controls, even after 20 weeks of regrowth. This difference was reduced in the smoking and irradiation group. The main difference observed was in the mast cell numbers. Smoking caused a 4-fold increase in mast-cell density. Irradiation caused an even greater increase (25-fold). The combination of smoking and irradiation resulted in an intermediate increase (10-fold). Long-term smoke exposure can slightly alter the growth rate and morphology of Dunning R3327 rat prostatic adenocarcinoma, but our study does not show a negative effect on the outcome of radiation treatment of this tumor model. We have also demonstrated a highly elevated number of mast cells in the irradiated group, and have shown that smoke exposure significantly depressed the radiation-induced enhancement of the number of mast cells.

The response of Dunning R3327 prostatic adenocarcinoma to IL-2, histamine and radiation.

A syngeneic, androgen-sensitive Dunning R3327 rat prostatic adenocarcinoma was transplanted bilaterally in the flanks of male Copenhagen Fisher rats. Approximately 3 months after implantation, when the tumours had a median volume of 150 mm3, one group of rats was treated with histamine alone (4 mg kg(-1) subcutaneously on week days), another group with human recombinant interleukin 2 (IL-2) alone (425 IU kg(-1) continuous infusion) and a third group with both histamine and IL-2 during 6 weeks. Tumours on one flank were irradiated (6 Gy once daily for 3 days to a total dose of 18 Gy) beginning 1 week after the onset of treatment with histamine and/or IL-2. The contralateral tumour served as the intra-animal control. The tumour volumes were determined weekly. The growth curves showed that all three drug treatments were effective in delaying growth, but when used individually did not cause tumour shrinkage. Radiation was the most effective single agent, but when used alone the shrinkage did not occur until 2 weeks after irradiation. When combined with the drugs, more rapid and extensive growth delay and/or shrinkage was seen. The growth curves showed clear differences between the different treatments. The combination of the three agents was the most effective of all. The most striking difference between radiation alone and radiation plus biotherapy was the time at which a tumour response was detectable. Thus, active biotherapy alone and especially in a combination with histamine and radiotherapy warrants further investigation as a potential therapeutic approach to prostate cancer.

Bioenergetics of rat prostate cancer cell migration

Increased cell motility and increased glycolysis are two well-known hallmarks of cancer. We undertook these studies to determine whether increased glycolysis is required for prostate cancer cell locomotion. We studied the highly metastatic MatLu cell line, which is a variant of the Dunning R-3327 rat prostate adenocarcinoma model. Using videomicroscopy and computer image analysis, we compared the speed of migration of cells grown in serum-free medium in either the presence or absence of glucose. We found that cells grown in glucose-free, conditioned medium maintained speeds of migration and intracellular ATP levels for 24 hr which were equivalent to those of cells grown in conditioned medium containing glucose. In contrast, migration was significantly inhibited by growth in glucose-free, unconditioned medium. We also tested the effect of antimycin A and rotenone, two inhibitors of mitochondrial electron transport, on cell migration and ATP levels. Antimycin A had no significant effect on either feature, while rotenone slightly inhibited cell migration without affecting ATP levels. 1) Glycolysis is not necessary for rat prostate cancer cell locomotion in the presence of conditioned medium. 2) MatLu cells grown in the absence of both serum and conditioned medium require glucose to maintain cellular ATP levels and cell migration. 3) MatLu cells in conditioned medium adapt to inhibition of glycolysis or mitochondrial respiration by increasing the activity of the uninhibited pathway.

Heterogeneous Expression of Invasive and Metastatic Properties in a Prostate Tumor Model.

Cellular heterogeneity of neoplasia is well demonstrated in the Dunning R-3327 rat prostate adenocarcinoma. In this study, we measured the differential expression of invasive and metastatic properties of this prostate model by cloning from a heterogeneous parental cell line. Four cell clones were derived and characterized by morphological studies, E-cadherin expression, and invasive and metastatic potential. Three of the clones (clones 5A, 5C, and 5D) demonstrated a fibroblastic morphology and were anchored to the substrate by loose microvillous processes. The fourth clone (clone 5B) grew in tight clusters and displayed many closely spaced microvilli, long overlapping cytoplasmic regions with well-defined junctional complexes. The parental line (R3327-5) demonstrated a combination of both these growth patterns. E-cadherin expression was absent in clones 5A, 5C, and 5D and very prominent in clone 5B, when compared to the parental line. The absence of E-cadherin expression correlated with increased invasiveness, as measured in an in vitro invasion assay. Subcutaneous injections of clones 5A, 5C, and 5D yielded lung metastases and no primary tumors at the site of inoculation while clone 5B was tumorigenic and produced fewer lung metastases in vivo. These clones, therefore, provide a potential for studying a variety of molecules involved in prostate cancer invasion and metastasis, especially for the direct testing of the significance of E-cadherin expresssion in prostate cancer progression.

Prostate cancer cells lose their sensitivity to TGFβI growth inhibition with tumor progression

The observation that advanced prostate cancer has reduced sensitivity to transforming growth factor βI (TGFβI) growth inhibition suggests that the acquisition of TGFβI resistance may play a role in prostate tumor progression. Using the Dunning R3327 rat prostate adenocarcinoma model, it was determined that prostate carcinoma cells became less responsive to TGFβI growth inhibition with differentiated tumors more resistant to TGFβI. A TGFβ receptor defect was not found in advanced prostate carcinoma cells because both the type I and II TGFβ receptors were present and functional. Moreover, TGFα/epidermal growth factor receptor (EGFR) and basic fibroblast growth factor (bFGF)/fibroblast growth factor receptor (FGFR) autocrine stimulatory pathways, which may potentially counter-regulate the inhibitory effects of TGFβI, were not present with prostate cancer progression. However, the likelihood that other prereceptor stimulatory pathways or TGFβ postreceptor signaling alterations are responsible for reduced sensitivity to TGFβI growth inhibition remains to be elucidated.

Biometric assessment of prostate cancer's metastatic potential.

Currently, no protocol exists that can assess the metastatic potential of prostate adenocarcinoma. The reason for this is partly due to the lack of information on cellular changes that result in a tumor cell's becoming metastatic. In this investigation, attempts were made to devise a method that correlated with the metastatic potential of AT-1, Mat-Lu, and Mat-LyLu cell lines of the Dunning R-3327 rat prostatic adenocarcinoma system. To accomplish this, we applied BioQuant biometric parameters, i.e., area, shape factor, and cell motility. AT-1 had a lower shape factor and a greater area as compared with the more highly metastatic Mat-Lu subline. No significant difference in area or shape factor was detected between the AT-1 cell line and the highly metastatic Mat-LyLu line. However, the lowly metastatic AT-1 line had less motility as compared with the Mat-Lu and Mat-LyLu lines. This study revealed that metastatic potential could be partially predicted via area and shape factor and accurately predicted via cell motility.

12(S)-HETE enhancement of prostate tumor cell invasion: selective role of PKC alpha.

Prostate carcinoma has become the second most fatal cancer in American men. In Dunning R3327 rat prostate adenocarcinoma cells, elevated invasiveness positively correlates with metastatic potential. However, the mechanism(s) responsible for regulation of tumor cell motility and invasion is poorly understood. We have reported that a lipoxygenase metabolite of arachidonic acid, 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], augments tumor cell metastatic potential through activation of protein kinase C (PKC). We proposed to determine the effect of 12(S)-HETE on the motility and invasion of low-metastatic rat prostate AT2.1 tumor cells and the effect of 12(S)-HETE activation of specific PKC isoform(s) in these processes. The motility of AT2.1 cells was determined by the colloidal gold phagokinetic track assay and the invasiveness measured as their ability to invade through basement membrane Matrigel-coated filters. Expression of PKC isoforms was determined by Western blotting of the whole cell lysate with isoform-specific anti-PKC antibodies. Cytosol and membrane fractions were prepared and the subcellular distribution of PKC was analyzed by Western blotting and activity assay. The effect of 12(S)-HETE on cell proliferation was examined. Data were analyzed for significance of difference with the two-sampled, two-sided Student's t test. 12(S)-HETE increased the motility and invasion of AT2.1 cells, and this 12(S)-HETE-increased motility and invasion were inhibited by a selective PKC inhibitor, calphostin C, as well as a Ca2 chelator, bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/tetra(acetoxy-methyl)ester. AT2.1 cells expressed the PKC isoforms alpha and delta, and 12(S)-HETE increased the membrane association of PKC alpha but not delta. Further, the motility and invasion of AT2.1 cells were increased by thymelea toxin, a selective activator of PKC alpha over PKC delta. 12(S)-HETE augments the invasiveness of AT2.1 cells via selective activation of PKC alpha. 12(S)-HETE modulation of PKC alpha invasiveness may be an important mechanism of action for the regulation of the invasive potential of rat prostate carcinoma cells, and the 12-lipoxygenase enzyme and/or PKC alpha may serve as key targets for the development of anti-invasive agents useful for combating the spread of prostate cancer.

Flow cytometric assay of pinocytosis: Correlation with membrane ruffling and metastatic potential in the dunning R‐3327 rat prostatic adenocarcinoma model

Membrane ruffling has been associated with neoplastic transformation, Harvey ras expression, and metastatic capability. In the Dunning R-3327 rat prostatic adenocarcinoma model, membrane ruffling graded visually upon live cultured cells filmed by time-lapse video-microscopy has distinguished sublines of high and low metastatic potential. Fluid-phase pinocytosis is a constitutive, noninducible internalization of medium by cell membrane. Fluid phase pinocytosis may be measured flow cytometrically by cellular uptake of fluorescein-labelled medium constituents. The optimum conditions for a flow cytometric assay of pinocytosis were determined using AT-2 subline that has an intermediate degree of membrane ruffling. The optimum dextran concentration was selected from the midpoint of the linear portion of the dose-response (0.01-10.00 mg/ml) curve, whereas the optimum incubation time was determined from a time-course (1-405 min.) curve study. Cultured cells from 6 Dunning sublines incubated with 1.0 mg/ml of fluorescein-labelled dextran for 90 min were washed, fixed, and the fluorescence of 10,000 cells studied by flow cytometry. For each subline, dextran fluorescence was measured in four independent experiments. Pinocytosis failed to distinguish sublines of high (AT-3 63.5 +/- standard error 4.1 mean channel number, MAT-LyLu 63.2 +/- 6.3, MAT-Lu 64.3 +/- 5.6) and low (G 33.5 +/- 1.2, AT-1 63.5 +/- 4.1, AT-2 58.4 +/- 3.6) (rank p = 0.38) metastatic potential but correlated strongly with visually graded membrane ruffling (r = 0.95, p = 0.003). Pinocytosis assayed by flow cytometry reflects membrane ruffling observed visually and thus flow cytometric assays may facilitate study of membrane activity.

Prediction of Metastatic Potential of Aspirated Cells from the Dunning R-3327 Prostatic Adenocarcinoma Model

Pathological grading systems have failed to assess accurately the prognosis of patients with prostatic carcinoma. A visual grading system of cancer cell motility has described successfully the metastatic potential of sublines of the Dunning R-3327 rat prostatic adenocarcinoma model maintained in vitro and in vivo. Clinical application of this technique would be facilitated if it could be performed upon aspirated cells. We compared the motility of cells obtained by biopsy and fine needle aspiration from in vivo Dunning tumors and determined if the motility of aspirated cells could predict metastatic potential. Specimens from the same tumor were obtained by fine needle aspiration and incisional biopsy from three sublines of low (<10%) and three sublines of high (>90%) metastatic potential. Membrane ruffling, pseudopodal extension and cellular translation of 100 cells were graded using time-lapse videomicroscopy. Cells obtained by biopsy and aspiration had similar average (analysis of variance, p >0.7) and variation (coefficient of variation, aspirated = 18.6%, biopsy = 17.7%) of motility. Aspirated cells from three low metastatic sublines (membrane ruffling 5.20 ± SEM 0.41, pseudopodal extension 4.10 ± 0.57 and cellular translation 3.07 ± 0.45) were distinguished from cells of three high metastatic sublines (membrane ruffling 7.10 ± 0.15, pseudopodal extension 6.93 ± 0.22 and cellular translation 5.47 ± 0.25). Cellular translation, the best discriminator, correctly classified the metastatic potential of the subline of origin in 82% of 60 individual cells. A grading system based upon the motility of aspirated cancer cells should be studied in human prostatic carcinoma.

Dose/response study of the effects of oestrogens on tumour growth and morphology in the Dunning R3327 prostatic adenocarcinoma

The present study was undertaken to investigate to what extent the oestrogen-induced effects on growth and morphology of the Dunning R3327 rat prostatic adenocarcinoma are dose-dependent. Castrated and testosterone-supplemented rats were used in order to study effects of increasing doses of oestrogens on the tumour. It was found that the lowest dose of oestradiol-17 beta that reduced the overall growth, the volume density of the epithelium and epithelial cell area in Dunning R3327 prostatic tumours is 10 micrograms given as daily injections. Higher oestrogen doses (50 micrograms, 200 micrograms, and 500 micrograms), in addition to reducing the volume of tumour epithelium, also induced an increase of the volume density of tumour stroma. The area of stroma cell nuclei was increased by 50 micrograms and 200 micrograms oestradiol-17 beta. These observation, may indicate that the lowest effective oestrogen dose is different in the epithelium and stroma of Dunning tumours and that large doses of oestrogen stimulate the stromal compartment. This stimulatory effect did not influence the inhibitory effects seen on the overall growth of the tumour and on the tumor epithelium.

An autocrine motility factor secreted by the dunning R‐3327 rat prostatic adenocarcinoma cell subtype AT2.1

Tumor cell locomotion is an integral part of the metastatic process. We present a new autocrine motility factor (AMF) derived from the serum-free conditioned medium of the Dunning R-3327 rat prostate adenocarcinoma AT2.1 tumor cell subline AT2.1-AMF, prepared by concentration of components less than or equal to 30 kDa- in size and washed free of low-molecular-weight growth factors, stimulated motility of AT2.1 cells in modified Boyden chamber migration assays. This stimulated migration was dose-dependent, and by checkerboard analysis was both chemotactic and chemokinetic. AT2.1-AMF activity was labile to heat, acid, base, reduction, oxidation, and proteases. Lyophilization and treatment with 6M urea caused a mild decrease (less than 20%) in migration-stimulating capability. Tumor-cell specificity was demonstrated for AMF of AT2.1 and AT3.1 Dunning sublines, and the A2058 human melanoma cell lines. AT2.1 cell migration to AT2.1-AMF was inhibited by 2 hr pre-treatment with cholera toxin (0.1 microgram/ml) or forskolin (100 microM), but not altered by 2 hr pre-treatment with pertussis toxin (1.0 microgram/ml). This indicates that guanine nucleotide binding protein-mediated regulation of cAMP is involved in modulating the AT2.1 cell response to its AMF. The AT2.1-AMF belongs to a related family of tumor autocrine motility factors and represents a new model for understanding the role of tumor-cell migration in the metastatic process of human prostate cancer.

Estramustine binding protein (EMBP) in rat R3327 dunning tumors: Partial characterization and effect of hormonal withdrawal, hormonal replacement, and cytotoxic treatment on its expression

Expression of estramustine-binding protein (EMBP) was determined in eight variants of the Dunning R3327 rat prostate adenocarcinoma. This secretory protein was previously isolated from the normal rat prostate and binds estramustine and estromustine, the metabolites exerting anti-mitotic and anti-proliferative activity of the anticancer agent estramustine phosphate (EstracytR). EMBP was found in relatively high amounts only in the androgen-responsive G and H tumors from intact hosts, whereas low (AT-1, HI-F) or nondetectable levels (HI-S, AT-3, MAT-LyLu, MAT-Lu) were obtained in the androgen-independent tumors. Castration decreased EMBP expression in both G and H tumors, as did estradiol and estramustine when given separately to intact rats. Supplementation of castrates with exogenous androgen stimulated EMBP expression above the pre-castration level and was further enhanced when combined with estradiol and in particular estramustine. Partial physicochemical characterization of EMBP in G and H tumors was performed by using ligand-based and immunoblotting techniques. [3H]Estromustine was bound to cytosols and salt extracts from tumors with the same affinity and displayed similar surface-charge distribution, sedimentation behavior, and subunit composition as found for ventral and dorsolateral prostatic tissue from tumor-bearing rats. This study indicates that the synthesis of EMBP is under androgenic control and that its expression may be correlated to androgen responsiveness, metastatic potential, and androgen receptor content but not to growth rate and morphology of the tumors. EMBP may therefore provide a mechanism for concentration of cytotoxic activity at the target site in EMBP-positive tumors and help in the evaluation of antitumor effects obtained when administering estramustine.

Estrogen treatment combined with castration inhibits tumor growth more effectively than castration alone in the dunning R3327 rat prostatic adenocarcinoma

This study was designed to investigate whether the combination of castration with estrogen treatment for 6 weeks (combined treatment) further inhibits growth of the Dunning R3327 rat prostatic adenocarcinoma as compared with castration alone. Combined treatment arrested tumor growth more effectively than castration. Combined treatment also induced morphological changes in both tumor stroma and epithelium that were not found in tumors from castrated animals. The volume density of the tumor epithelium was reduced and the volume density of the tumor stroma was increased by the combined treatment as compared with castration alone. The number of tumor epithelial cells was calculated by morphological methods: combined treatment lowered the number as compared with castration alone. The number of tumor epithelial cells was similar in castrated and intact rats. Both combined treatment and castration alone reduced tumor epithelium cell size as compared with tumors from intact rats. These findings suggest that estrogen may have direct effects on total number and function of prostatic tumor cells.

Receptors for luteinizing hormone‐releasing hormone, somatostatin, prolactin, and epidermal growth factor in rat and human prostate cancers and in benign prostate hyperplasia

Using sensitive multipoint micromethods, we estimated membrane receptors for [D-Trp6]-luteinizing hormone-releasing hormone ([ D-Trp6]-LH-RH), somatostatin (SS-14), human prolactin (hPRL), and epidermal growth factor (EGF) in experimental Dunning rat prostate cancers and in samples of normal human prostate, benign prostatic hyperplasia (BPH), and human prostate cancer (PC) obtained from biopsy, after prostatectomy, or at autopsy. In the Dunning R-3327 rat prostate adenocarcinoma specimens, the receptors were characterized in untreated animals and following in vivo treatment with microcapsules of the agonist [D-Trp6]-LH-RH and the somatostatin analog RC-160. Two populations of binding sites were found for [D-Trp6]-LH-RH, one with high affinity and low capacity and another with low affinity and high capacity. Treatment with [D-Trp6]-LH-RH and RC-160 alone or with the combination of these analogs increased the binding capacity (Bmax) of the low-affinity binding sites for [D-Trp6]-LH-RH and decreased Bmax for hPRL and EGF. Therapy with [D-Trp6]-LH-RH also reduced Bmax of SS-14 binding and dissociation binding constant of high-affinity binding sites for [D-Trp6]-LH-RH, whereas administration of RC-160 or the combination treatment with both analogs increased Bmax of SS-14 binding. These findings are compatible with the view that analogs of LH-RH and SS-14 might exert some direct inhibitory effects on the Dunning prostate cancer. Among 13 human BPH samples examined, only one had receptors for [D-Trp6]-LH-RH, and seven specimens exhibited binding for prolactin. [D-Trp6]-LH-RH receptors were found in all seven samples of human PC but not in any of the eight specimens of normal human prostate. All samples of normal human prostate, BPH, and human PC exhibited binding sites for EGF but not for SS-14. Our findings on the membrane receptors in the human and rat prostate cancers raise the intriguing possibility that LH-RH, acting as a growth factor, along with EGF and prolactin, might be involved in complex interactions that contribute to the promotion of prostate cancer in man.

Cell Surface Charge in Predicting Metastatic Potential of Aspirated Cells From the Dunning Rat Prostatic Adenocarcinoma Model

The transplantable Dunning R-3327 rat prostatic adenocarcinoma model has provided a series of tumor variants with broad ranges of metastatic potential. We tested whether cell surface charge might be related to metastatic potential by measuring the electrophoretic mobility of live tumor cells obtained by needle aspiration. Cells were aspirated from tumors with low metastatic potential (following subcutaneous inoculation of 106 tumor cells the H, G and AT-1 variants had <5% metastases; AT-2 had 5-20%) and were compared to the electrophoretic mobility of cells aspirated from highly metastatic tumors (MAT-LyLu, MAT-Lu, AT-3 had >90% metastases). Electrophoretic mobility expressed in μ/sec/volt/cm. was measured on 100 cells from each tumor subline, and the cell surface charge expressed as a zeta potential was calculated from electrophoretic mobility using the Helmholtz-Smoluchowski equation. The average zeta potential (± S.E.M.) for the four sublines with low metastatic potential was (-17.4 ± 0.4 mV) compared to the three sublines with high metastatic potential (-26.5 ± 0.7 mV), and the differences were significant (p C.01) using the Mann-Whitney Wilcoxon test. Using a zeta potential of -20.5 mV as the cutoff between high and low metastatic potential, the sensitivity and specificity of zeta potential in predicting metastatic potential in 140 determinations on seven tumor lines were 92% and 82.5%, respectively. The predictive value of a positive test (value >-20.5 mV) was 80% and the predictive value of a negative test (value <-20.5 mV) was 93%. The results support a difference in the cell surface charge between these metastatic and nonmetastatic tumors with increasing negativity at the cell surface correlating with increased metastatic potential, but not with tumor growth rates.

Oncogene expression in prostate cancer: Dunning R3327 rat dorsal prostatic adenocarcinoma system.

Steady-state levels of myc, fos, p53, sis, and neu mRNAs were measured in eight variants derived from the Dunning R3327 rat prostate adenocarcinoma and compared to levels in normal dorsal prostate. Expression of the myb and erbB oncogenes in the Dunning tumors was below the limits of detection. Myc, p53, and sis mRNA levels in all tumors were at or above control levels. Fos mRNA levels were below control levels in four of five anaplastic tumors and were above control levels in the remaining tumors. A comparison of mRNA levels along the two Dunning lineages revealed that increased expression of these oncogenes did not correlate with tumor progression.

Expression of ras proto-oncogenes in the Dunning R3327 rat prostatic adenocarcinoma system.

Steady-state levels of c-Ha-ras mRNA were measured in eight sublines of the Dunning R3327 rat prostatic adenocarcinoma. As a control, normal dorsal prostate tissue was studied. Increased expression of c-Ha-ras is associated with tumor progression in one lineage of the Dunning R3327 system (H to AT1 to MAT-Lu and MAT-Ly-Lu). Here ras mRNA increases as the tumor advances from androgen dependence and a high degree of differentiation to an anaplastic aneuploid phenotype with high metastatic potential. However, in the other Dunning lineage (H to HI to HI-F to AT3), expression of c-Ha-ras is variable and does not correlate with tumor progression. Immunocytochemistry showed that levels of the c-Ha-ras p21 protein paralleled steady-state mRNA levels in variants. Transfection assays, using NIH/3T3 cells, suggested that the ras loci were not activated in the R3327 tumors. Levels of c-Ki-ras mRNA were also measured in the Dunning tumors; these did not correlate with tumor progression in either lineage. Expression of N-ras mRNA was not detected in the Dunning tumors.

Effects of olfactory bulbectomy, melatonin, and/or pinealectomy on three sublines of the Dunning R3327 rat prostatic adenocarcinoma.

Conventional antiandrogen therapy for prostatic cancer generally results in the death of androgen-dependent cells, resulting in shrinkage of the tumor, followed by regrowth of the tumor as androgen-insensitive cells take over. Because of reported antigonadotropic and antineoplastic effects of the pineal hormone melatonin (MEL), we hypothesized that this indole might provide an effective therapy for prostate cancer, as it would be effective against both populations of tumor cells. We used three sublines of the Dunning R3327 rat prostatic adenocarcinoma to determine whether MEL could suppress the growth of these tumors and, if so, by what mechanisms this occurs. In one experiments, we compared the growth of a well-differentiated slow-growing Dunning tumor in rats given MEL combined with the potentiating procedure olfactory bulbectomy (BULBX), with that in rats pinealectomized (PINX) or untreated. Tumor growth in BULBX-MEL rats was significantly suppressed over that in the other two groups, as were the weights of the gonads and accessory sex glands. Tumor morphology, DNA concentration, and androgen receptor concentration and distribution were identical in untreated controls and in BULBX-MEL rats, suggesting that the treatment affected all populations of tumor cells equally. With another strain of well-differentiated slow-growing Dunning tumor, we examined the effects of MEL in rats with and without BULBX. Reproductive parameters were not suppressed in BULBX-MEL rats and, while there was a trend toward slower tumor growth in this group, this was not significant. Intact rats given MEL grew larger tumors than did control rats but, again, differences were not significant. In a third experiment, we examined a fast-growing androgen-insensitive anaplastic Dunning tumor. PINX was without effect on this tumor, but BULBX-MEL resulted in a significant suppression of one of the constants in the logistic equation fitted to the growth curves. This indicates that there were some direct antitumor effects of BULBX-MEL on this tumor strain. We conclude that MEL suppresses growth of some Dunning tumor strains.