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Biomedical subjects

G Wilding

Publications and source records attributed to G Wilding.

At least 73 records · Page 4Linked to original sources
PubMed1993

Effects of suramin on the proliferation of primary epithelial cell cultures derived from normal, benign hyperplastic and cancerous human prostates.

Primary epithelial cultures (PECs) derived from normal, benign hyperplastic (BPH), and cancerous human prostate tissue were treated with increasing doses of suramin, and assayed for cell proliferation over a period of days. The suramin IC50 (inhibitory concentration 50%) value was 0.5 to 1.0 x 10(-4) M, whereas doses between 2.5 x 10(-4) and 5 x 10(-4) M resulted in total growth inhibition. This inhibition was reversible by exchange with suramin-free medium up to day 6. Concentrations > or = 5 x 10(-4) M resulted in increased cytotoxicity as exposure time increased. No differential response to suramin could be demonstrated among the prostate PECs derived from different tissues. The established cell lines, PC-3 and DU 145, grown in serum containing medium exhibited IC50s comparable to the PECs grown in serum free medium. EGF, bFGF, alpha, or beta ECGF at the concentrations tested did not reverse suramin inhibition. Increasing concentrations of bovine pituitary extract (BPE) increased cell growth in both the treated and the control cells. However, the percent growth inhibition by suramin at each concentration of BPE remained constant. Flow cytometry examination of cells treated for 7 days with suramin (0-10(-3) M) failed to detect any significant cell cycle alterations compared to control. At high concentrations of suramin (> or = 10(-4) M), large numbers of viable and dead cells were detectable in the medium. The increase in unattached viable cells was most prevalent (80%) in cultures treated with suramin at the time of plating, but also occurred with cells (25-30%) plated hours prior to the addition of suramin. Treatment for several days with low concentrations of suramin (10(-7) to 10(-5) M) transiently enhanced cell growth compared to controls.

Cell Adhesion↗
PubMed1993

Evidence of an absorption phase after short intravenous suramin infusions.

Suramin was given as an intravenous infusion to 16 cancer patients in a phase I trial. Individual pharmacokinetic parameters were calculated from a test dose given 1 week prior to the administration of a full-dose (350-700 mg/m2) regimen of 1-h loading and maintenance infusions. A distribution phase of 3.8 h was found. Plasma suramin concentrations were noted to increase following cessation of the intravenous test infusion in eight subjects. A model is proposed in which high-capacity, low-affinity binding of suramin to a shallow compartment adjacent to the intravascular space occurs rapidly during infusion, followed by absorption back into the measured blood pool with binding to plasma albumin. Despite the observable presence of this postinfusion peak shortly after the cessation of the brief suramin infusion, the pharmacokinetics of suramin were best characterized by a traditional two-compartment model. The dose-adjusted area under the concentration-time curve (AUC) increased with dose, supporting a hypothesis of sustained absorption of suramin to vascular endothelium but also raising the possibility of dose-dependent clearance.

Absorption↗
PubMed1993

Characteristics of the glutathione/glutathione-S-transferase detoxification system in melphalan resistant human prostate cancer cells.

Glutathione (GSH) and glutathione-S-transferases (GST) have been implicated in resistance of tumor cells to certain alkylating agents, including melphalan. Glutathione levels and GST activities were determined in melphalan-resistant sublines of the human prostate carcinoma cell lines DU 145, PC-3 and LNCaP produced by serial treatment with melphalan at progressively increasing concentrations. The resistant sublines M4.5DU145, M5DU145, M6DU145, M6PC-3 and M6LNCaP were 27-, 7-, 3-, 6- and 2-fold more resistant to melphalan than the parental lines. The melphalan-resistant DU 145 and PC-3 lines showed cross-resistance to cisplatin and tetraplatin, but retained sensitivity to vinblastine, colchicine and etoposide. Interestingly, both sublines were also resistant to methotrexate and adriamycin. The melphalan-resistant LNCaP line showed slight resistance to cisplatin and adriamycin, but remained sensitive to tetraplatin and methotrexate. This line also retained sensitivity to vinblastine while developing resistance to colchicine. Intracellular GSH levels were increased 2.8 fold for M5DU145, 1.7 fold for M6PC-3 and 2.1 fold for M6LNCaP compared to the parental lines, whereas GST activity using chlorodinitro-benzene as a substrate was comparable for all lines. When cumene hydroperoxide was used as a substrate, an increase in GST activity was noted only in the M6PC-3 line as compared with the parent line. Western blot analysis showed no change in GST isozyme profile between parent and resistant DU 145 lines; however a mu class isoenzyme was detected in the resistant, but not in the parent PC-3 line, using a Yb1 antibody. M5DU145 cells maintained in the absence of melphalan for seven months maintained their resistance to melphalan. Depletion of GSH, with buthionine sulfoximine, to control levels reversed melphalan resistance to control levels.

Antineoplastic Agents↗
PubMed1993

A comparison of knowledge and communication skill evaluations by written essay and oral examinations in preclinical medical students.

While both oral and written communication skills are important in the daily work of physicians, medical school evaluation methods focus on content of written essays or often answers to multiple choice questions. To determine the feasibility and value of oral examinations for preclinical medical students, we gave a written short essay examination and an oral examination on the same question to 106 second-year medical students in a required neoplastic diseases course. Examination performance by each method was evaluated according to the same specific content and, separately, based on four communication skills criteria. We found high levels of inter-rater reliability with two oral examiners for both content and skills. Content and skills performance on both written and oral evaluations could be separately determined. Content performance was greater on the written evaluation.

Achievement↗
PubMed1992

Disruption of mitochondrial function by suramin measured by rhodamine 123 retention and oxygen consumption in intact DU145 prostate carcinoma cells.

Suramin, an antiparasitic drug, has shown antitumor activity in humans. This may occur in part through disruption of energy balance, which is believed to be part of its antiparasitic action. Suramin disrupts mitochondrial function in intact DU145 prostate carcinoma cell monolayers as seen by its causing the release of rhodamine 123 from prestained cells beginning at about 10 microM in 96-well microtiter plates measured with a fluorescent plate scanner. This effect was similar to the ionophore carbonyl cyanide m-chlorophenylhydrazone, dissolved in ethanol at 0.01 N and indicates that suramin acts as a respiratory poison or an ionophore. This effect was confirmed by studies of oxygen consumption with a Clark oxygen electrode and cellular ATP content which demonstrated uncoupling of oxidative phosphorylation by 100 microM suramin, a clinically achievable plasma drug level.

Adenosine Triphosphate↗
PubMed1992

Increase in gamma-glutamylcysteine synthetase activity and steady-state messenger RNA levels in melphalan-resistant DU-145 human prostate carcinoma cells expressing elevated glutathione levels.

The biochemical and molecular basis for the elevation of glutathione (GSH) levels commonly detected in many drug-resistant cells has not been elucidated. In a series of L-phenylalanine mustard-resistant human prostate carcinoma cell lines (DU-145), resistance was associated with elevated GSH levels, increased activity of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH biosynthesis, and a marked increase in the steady-state levels of GCS-specific transcripts (4.0 and 3.2 kilobases). Loss of the resistant phenotype was accompanied by a reduction in GSH and a return of GCS activity and transcript levels to values comparable to those detected in the drug-sensitive parent cells. These data strongly implicate up-regulation of GCS activity as an important mechanism in the evolution of drug resistance associated with increased levels of intracellular GSH. The results further suggest that the ability to synthesize GSH may be more indicative of resistance than steady-state GSH levels per se.

Drug Resistance↗
PubMed1992

A pilot trial of chemohormonal therapy for metastatic prostate carcinoma.

Fifteen patients with previously untreated metastatic prostate cancer were treated on a pilot trial with a combination of maximal androgen blockade plus intermittent cytotoxic therapy after androgen priming to stimulate cell division. Androgen blockage was carried out using a gonadotropin-releasing hormone analog (leuprolide) plus a nonsteroidal antiandrogen (flutamide). Carboplatin (CBDCA) (800 mg/m2) was given intravenously every 28 days, preceded for 3 days and followed for 3 days by androgen treatment with fluoxymesterone (5 mg orally twice a day), during which time flutamide was discontinued. Three patients (20%) achieved a complete response (CR), and eight patients (53.3%) achieved a partial response (PR). Four patients (26.7%) had stable disease (SD). The median progression-free survival (PFS) time was 31 months. Nine of 15 patients (60%) remain alive with a median follow-up time of 42+ months (range, 22 to 54 months). Grade 4 thrombocytopenia and Grades 3 or 4 leukopenia were experienced in 87% and 80% of patients, respectively, requiring dose reductions of CBDCA in 85% of the cycles. Six of 15 patients experienced a flare in bone pain with androgen priming. There were no associated spinal cord compressions; however, exclusion of impending spinal cord compression was required before entrance on study.

Adenocarcinoma↗
PubMed1992

A phase I trial of 5-fluorouracil, leucovorin, and dipyridamole given by concurrent 120-h continuous infusions.

A phase I trial of 5-fluorouracil (FUra) and leucovorin (LV) given with and without dipyridamole (DP) by concurrent 120-h continuous infusion was performed in 27 patients with advanced solid malignancies, 8 of whom had previously received FUra. The LV and DP doses were fixed at 500 mg/m2 daily and 7.7 mg/kg daily, respectively, whereas the FUra dose was escalated. Level 3 (450 mg/m2 FUra daily) represented the maximum tolerated dose for both FUra/LV+DP and FUra/LV. Dose-limiting stomatitis (greater than or equal to grade 3 or grade 2 occurring during the infusion) was encountered in 75% of the first courses given at level 4 (600 mg/m2 daily). Stomatitis was observed in 44/78 (56%) courses. Diarrhea was infrequent and mild. DP infusions were complicated by mild to moderate headache, which was controlled with narcotic analgesics, and mild to moderate nausea/vomiting. FUra-related toxicity was not enhanced by DP administration. Limited pharmacokinetic sampling at levels 3 and 4 revealed mean steady-state FUra concentrations of around 1.0 microM with infusions of FUra/LV+DP. Among three paired courses given with and without DP, no statistically significant difference was found in the total body clearance of FUra (P = 0.44). One partial response was seen in a patient with metastatic gastric carcinoma. For phase II trials, we recommend that concurrent 120-h continuous infusions of FUra (450 mg/m2 daily) and LV (500 mg/m2 daily) be given with and without DP (7.7 mg/kg daily) every 21 days.

Adult↗
PubMed1992

Phase I evaluation of 773U82-HCl in a two-hour infusion repeated daily for three days.

One of a novel series of compounds (AMAPS or arylmethylaminopropanediols), 773U82-HCl has shown significant antitumor activity in in vitro and in in vivo tumor systems, but has less animal CNS toxicity than the lead compound in the same series (crisnatol). This study was designed to evaluate the pharmacokinetics, qualitative and quantitative toxicities of 773U82-HCl and to determine the recommended phase II dose (MTD) of 773U82-HCl given as a short infusion daily for 3 days every 3 weeks. Twenty-nine patients with refractory malignancies received 79 courses over 9 dose levels during this study. Doses ranged from 50 to 1060 mg/m2/d x 3 days. Due to the possibility of local hemolysis with concentrations > 1.5 mg/ml, drug was administered in solutions containing < or = 1.5 mg/ml. Because large volumes were needed at the higher dose levels, the infusion duration was increased from 2 hours to 4 hours. Mild to moderate nausea, vomiting, fatigue, dizziness and headaches were observed. Myelosuppression was the dose limiting toxicity. The recommended phase II dose and schedule was determined to be 800 mg/m2/d x 3d every 3 weeks. 773U82-HCl plasma concentration-time data were analyzed using a two-compartment pharmacokinetic model. The t1/2 beta averaged 6 hours and the total body clearance was 75.9 L/hr/m2. The volume of distribution (Vdss) was large, averaging 470 L/m2.

Adult↗
PubMed1992

The importance of steroid hormones in prostate cancer.

Steroid hormones have an important role in prostate biology. Androgens are crucial for the normal development of the prostate gland and in maintaining its functional state in the adult. It seems that the prolonged presence of androgens might also be an important factor in the development of prostate cancer. In addition, androgens and oestrogens appear to play some part in the development of benign prostatic hyperplasia, although the exact nature of their role has not been clearly defined. Stimulation of prostate cancer growth by androgens is well established, with androgen withdrawal therapy constituting the most effective therapy in men with prostate cancer. Additive steroid therapy of metastatic prostate cancer with oestrogens or progestins has also proven effective. The effects of androgens on prostate cancer cell growth might be mediated through modulation of growth factor expression and alteration of growth factor receptor levels. Androgen response can be modulated by the expression of mutated oncogenes such as ras. Androgen independence can occur through a loss of AR expression or mutation of the AR; however, the patterns of AR expression in normal prostatic tissue from development to adulthood and in cancer are now just beginning to be described. Other steroids, such as the retinoids, show promise as preventive agents, possibly through the modulation of growth factors.

Androgens↗
PubMed1991

Disruption of cellular energy balance by suramin in intact human prostatic carcinoma cells, a likely antiproliferative mechanism.

The antiparasitic drug, suramin, has antiproliferative effects in human carcinoma cells. It has been suggested that this occurs through blockade of growth factor-receptor interactions. Three types of evidence that suramin rapidly inhibits cellular respiration or disrupts cellular energy balance in intact cells of the human prostate carcinoma cell line, DU145, are presented. Beginning at approximately 10(-4) M, suramin rapidly causes dose-dependent inhibition of tetrazolium conversion by mitochondrial dehydrogenases in intact cells, demonstrating an inhibition of respiration. This effect is reversed by exchange with suramin-free media but not by pretreatment with serum, epidermal growth factor, insulin-like growth factor I, acidic and basic fibroblast growth factors, or calcium. Rhodamine 123 (10 micrograms/ml) uptake by mitochondria in intact DU145 cells is inhibited in the presence of 10(-3) M suramin. Treatment with 10(-4)-10(-3) M suramin causes the loss of rhodamine 123 from cells with mitochondria prestained with rhodamine 123, indicating that suramin is acting as an ionophore or respiratory poison. Also shown by electron microscopy are progressive toxic changes in mitochondria of DU145 cells within 1 h after treatment with 10(-4) M suramin. These data indicate that in intact DU145 cells 10(-4) M suramin rapidly disrupts cellular energy balance or respiration as seen by three studies of mitochondrial state. Disruption of energy balance or respiration represents a likely antiproliferative mechanism, as is thought to be a primary mechanism for the action of suramin in parasitic diseases. This proposed mechanism of action for suramin can explain the most prominent observed clinical toxicities of nephrotoxicity, adrenal toxicity, coagulopathy, and demyelinating neuropathy.

Biological Transport↗
PubMed1991

Transforming growth factor beta 1 induces cachexia and systemic fibrosis without an antitumor effect in nude mice.

While stimulating the growth of fibroblasts, transforming growth factor beta 1 (TGF-beta 1) inhibits the growth of various normal and malignant cell lines in vitro. We studied the effects of TGF-beta 1 in vivo. The level of TGF-beta 1 in serum was maximally elevated 2 h after injecting 1 muCi of 125I-TGF-beta 1 into the peritoneal cavity of nude mice. Five h after the i.p. administration of 10 micrograms of unlabeled TGF-beta 1, 20 ng/ml of TGF-beta-like material in serum were detected by a radioreceptor assay on A549 lung carcinoma cells. Trichloracetic acid-precipitable 125I-TGF-beta 1 was taken up by liver, spleen, lungs, kidneys, and tumor tissue but not by the brain. At doses exceeding 2 micrograms/day, TGF-beta 1 induced a generalized interstitial fibrosis and a cachexia, which was not mediated by elevated serum levels of tumor necrosis factor alpha as determined by Western blot analysis and enzyme-linked immunosorbent assay. A total of 200,000 cells of the estrogen receptor-negative human breast cancer line MDA-MB-231, which had been shown to be maximally growth inhibited in vitro by 40 pM TGF-beta 1 and to have high-affinity receptors (9, 11, 12), were injected into the mammary fat pad of each nude mouse. The duration of treatment was 16 days with ten animals in the control group and five animals in the treated groups. The dose ranged from 1 to 4 micrograms per animal daily. The treatment was started 24 h after the injection of the tumor cells. Tumor growth was not significantly affected at either nontoxic or toxic doses of TGF-beta 1. Thus, we have demonstrated that TGF-beta 1, apart from being a local growth factor, has systemic effects, such as cachexia and multiple fibrosis. Its role as an antitumor agent may be limited.

Animals↗
PubMed1991

Phase I clinical trial of fazarabine as a twenty-four-hour continuous infusion.

A phase I trial of fazarabine (ara-AC, 1-beta-D-arabinofuranosyl-5-azacytosine, NSC 281272) administered as a 24-h continuous infusion was performed in 24 adults with solid tumor malignancies. The majority of patients had received prior marrow-suppressive therapy. Level 7 (54.5 mg/m2/h for 24 h) was the maximum tolerated dose since during 6 evaluable first courses, 2 episodes of grade 4 granulocytopenia and 3 episodes of grade 3 occurred. Moderate thrombocytopenia also occurred at level 7 with 3 episodes of grade 1 and 1 episode of grade 4 thrombocytopenia during 6 first course treatments. Minimal myelosuppression, principally leukopenia, was seen prior to level 7. The nadir WBC through 47 courses had a linear relationship with plasma steady-state concentrations of ara-AC. The only other toxicity noted was moderate nausea/vomiting, which did not appear to be dose related. Plasma steady-state concentrations of ara-AC were reached in all patients within 4-6 h and ranged from 1.1 microM (11 mg/m2/h for 24 h) to 7.5 microM (54.5 mg/m2/h for 24 h). The mean total body clearance of ara-AC for 47 courses, levels 1-7, was 592 +/- 147 (SD) ml/min/m2 which is similar to prior pharmacokinetic data from the 24-h and 72-h infusion trials of the Pediatric and Medicine Branches, respectively. There were no objective disease responses during the trial. The recommended adult phase II dose for a 24-h infusion of ara-AC is 45-50 mg/m2/h.

Adult↗
PubMed1991

A phase I study of SR-2508 and cyclophosphamide administered by intravenous injection.

SR-2508, a less lipophilic ane neurotoxic analogue of the nitroimidazole, misonidazole, has exhibited significant chemosensitization properties in preclinical studies with alkylating agents. A phase I trial was carried out to assess toxicity and possible pharmacological interactions of the combination of short infusions of SR-2508 and cyclophosphamide (CP). Patients were randomly assigned to receive either CP alone followed in 3 wk by CP + SR-2508, or CP + SR-2508 followed by CP alone. All additional courses were CP + SR-2508. The maximum tolerated dose of the combination was determined by dose escalation of SR-2508 while the dose of CP remained fixed, initially 1.0 g/m2, and then a second maximum tolerated dose was determined with CP at 1.6 g/m2. One hundred seventeen evaluated courses were administered to 39 patients, the majority of whom had received prior treatment. Somewhat unexpectedly, reversible grade 4 granulocytopenia was the dose-limiting toxicity occurring in four of five evaluable first combination courses at level 6 (SR-2508, 11.3 g/m2; CP, 1.0 g/m2), the initial maximum tolerated dose. SR-2508 enhanced CP-induced myelosuppression as exhibited by the significant difference (p less than 0.001) between the 27 paired courses (CP versus CP + SR-2508) for WBC nadirs over levels 1 to 6. The neurotoxicity encountered was similar to that seen in past clinical trials, being reversible, mild, and usually peripheral in nature. There was one treatment-related death (neutropenic sepsis) on study. No other significant toxicity was seen. SR-2508 exhibited linear pharmacokinetics over the dose range studied. The SR-2508 area under the concentration-time curve increased linearly with dose (r = 0.858; p less than 0.001). No other parameters were dose related. Neither drug appeared to affect the pharmacokinetics of the other, and CP pharmacokinetic values were consistent with those from prior studies. Due to the interaction noted between the two agents and the preclinical data suggesting preferential enhancement of antitumor efficacy under this combination, phase II study appears warranted.

Adult↗
PubMed1991

Effects of interferon beta ser and transforming growth factor beta on prostatic cell lines.

The effect of interferon beta ser (IFN beta ser) on the growth of three prostatic cancer cell lines DU-145, PC-3 and LNCaP was studied. IFN beta ser inhibited growth of anchorage dependent semiconfluent monolayers and anchorage dependent colony formation of both DU-145 and PC-3 in a dose dependent manner but had no effect on LNCaP. Transforming growth factor beta (TGF beta 1) inhibited proliferation of DU-145 and PC-3 cells in 1% but not 8% fetal calf serum. The combination of TGF beta 1 and IFN beta ser was additive in its effects on growth. Neither epidermal growth factor (EGF) nor transforming growth factor alpha (TGF alpha) reduced the antiproliferative effect of IFN beta ser on these cells. These antiproliferative effects were reproduced in studies on primary epithelial cell cultures derived from prostate specimens with various pathologies. The potential use of IFN beta ser in combination with hormonal therapy to delay the development of hormone refractory tumors is discussed.

Cell Count↗
PubMed1991

v-rasH expression confers hormone-independent in vitro growth to LNCaP prostate carcinoma cells.

The LNCaP human prostate cancer cell line is dependent on androgen for in vitro growth. To discover genes that may be responsible for progression of prostate cancer from hormone dependence to hormone independence, we transfected LNCaP cells with expression vectors that contained either the v-rasH or c-rasH gene under the control of the cadmium (Cd2+)-inducible human metallothionein-IIA promoter. Numerous derivative cell lines were isolated which manifested inducible expression of rasH p21 protein when the cells were treated with Cd2+. None of the cell lines transfected with c-rasH were found to have an altered growth phenotype. Several derivative cell lines expressing inducible v-rasH manifested hormone-independent growth in culture when treated with 10(-7) M Cd2+ . Cd2+ induction of v-rasH p21 was also shown to increase anchorage-independent colony formation of the v-rasH-expressing cell lines tested. Expression of a dominant mutated oncogene can change the hormone-dependent growth phenotype of prostate cancer cells.

Animals↗
PubMed1991

Response of prostate cancer cells to peptide growth factors: transforming growth factor-beta.

The growth of human prostate cancer and its relationship to the surrounding stroma are controlled by complex mechanisms that are incompletely understood. Clearly, peptide growth factors appear to have crucial roles in these processes. One of these factors, TGF-beta, and its family members are notable for their wide spectrum of biological effects. In terms of growth, TGF-beta inhibits the growth of prostate cancer cells in a cytostatic fashion while stimulating the growth of critical stromal cells, such as fibroblasts. Since the inhibitory effects of TGF-beta on prostate cancer cells appear to diminish as the process of transformation progresses towards less differentiated states, the net effect on prostate tumour growth may be positive. Recent evidence suggests that the inhibitory effects of TGF-beta on growth, at least, might be mediated through the RB tumour suppressor gene product and the proto-oncogene c-myc. Beyond its direct growth effects, TGF-beta also alters the response of prostate cancer cells to positive mitogenic factors, such as members of the EGF and FGF families, suggesting that growth control is a delicate balance between positive and negative influences. Non-mitogenic responses to TGF-beta by prostate cancer cells, the immune system, the stroma and the vascular system provide evidence that TGF-beta might also be important in the processes of carcinogenesis, tumour establishment and metastases. In addition, TGF-beta appears to influence metabolic pathways important to drug metabolism and steroidogenesis. In vivo, limited evidence suggests that TGF-beta can alter the growth and differentiation of some tumour types but appears to be very toxic when administered in high doses. A better understanding of the response of prostate cancer cells to members of the TGF-beta family may open new avenues of treating and controlling this disease.

Animals↗