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Biomedical subjects

M Gleave

Publications and source records attributed to M Gleave.

At least 19 recordsLinked to original sources
PubMed2006

The effects of the dual 5alpha-reductase inhibitor dutasteride on localized prostate cancer--results from a 4-month pre-radical prostatectomy study.

BACKGROUND: As dihydrotestosterone (DHT) is the most potent androgen in the prostate, inhibition of the 5alpha-reductase isoenzymes, which convert testosterone to DHT, could be an appropriate target for the treatment of prostate cancer. METHODS: Eighty-one men with clinically localized prostate cancer received daily dutasteride 3.5 or 0.5 mg, or no therapy for 4 months before radical prostatectomy. Histopathological assessments were conducted on prostatectomy specimens. RESULTS: Treatment with dutasteride was associated with reductions in serum and intraprostatic DHT of >or=90%, and a decrease in total prostate and tumor volumes. No effect of dutasteride was noted on Gleason grade. Histopathological effects on benign tissue were similar but less prominent than those seen with androgen ablation, whereas there was no significant difference in cancer histology among the groups. CONCLUSIONS: Dutasteride treatment results in similar but less marked changes compared with androgen ablation.

5-alpha Reductase Inhibitors↗
PubMed2006

Targeting and killing of prostate cancer cells using lentiviral constructs containing a sequence recognized by translation factor eIF4E and a prostate-specific promoter.

To develop a gene therapy that would selectively kill prostate cancer cells while sparing normal cells, we have constructed lentiviral vectors that contain a therapeutic gene with a short DNA sequence in the 5'-untranslated region (UTR) that is recognized by the translation initiation factor, eIF4E, which is often overexpressed in malignant cells. Infection of cancer (LNCaP, PC-3M, DU145, and MCF-7 cells) and noncancer cell lines (BPH-1, 267-B1, Plat-E, and Huvec-c cells) with lentivirus having a CMV-promoter and EGFP reporter resulted in high levels of EGFP expression in all cells, whereas, inclusion of the eIF4E UTR recognition sequence restricted high expression to cancer cells and Plat-E cells, which also express substantial levels of eIF4E. Infection of the cells with lentiviral vectors having this UTR in front of the HSV thymidine kinase suicide gene resulted in differential sensitivity to the killing effects of ganciclovir, with at least 100-fold more drug required to kill noncancer cells than cancer cells. Furthermore, in experiments where the CMV promoter was replaced by the prostate-specific ARR(2)PB promoter, the killing effects of ganciclovir were restricted to prostate cancer cells and not seen in nonprostate cancer cells. Our results indicate that combined translational regulation, by incorporation of an eIF4E-UTR recognition sequence into a therapeutic gene, together with transcriptional regulation with a prostate-specific promoter, may provide a means to selectively destroy prostate cancer cells while sparing normal prostate cells.

Cell Death↗
PubMed2004

Effect of time of castration and tumour volume on time to androgen-independent recurrence in Shionogi tumours.

OBJECTIVE: To use the androgen-dependent Shionogi tumour model in mice to help define the effects of the timing of androgen ablation on the development of androgen resistance in prostate cancer, as the timing of androgen ablation remains controversial. MATERIALS AND METHODS: Groups of nine mice were castrated at 1, 3, 6, 10 and 14 days after tumour inoculation, with a similar-sized group of mice castrated before tumour inoculation serving as a control. The time of first palpable tumour recurrence and tumour volume was monitored after castration. RESULTS: All mice were observed for > or = 80 days after castration. Only mice castrated at 10 and 14 days had palpable tumour at the time of castration. Mice castrated at 14 days had the highest rate of early tumour recurrence (all nine) while mice castrated before inoculation or at 1 and 3 days afterward had a significantly lower rate of tumour recurrence (four of nine; P < 0.01). Mice castrated at 14 and 10 days had tumour recurrence significantly earlier than mice in the other groups. When calcium-channel blockers were administered to inhibit apoptosis, all mice had a similar time to recurrence and time to death regardless of the time of castration. CONCLUSIONS: Large tumour volume and corresponding delay in castration reduced the time to androgen-independent tumour recurrence and survival. Earlier androgen ablation, at the time of subclinical (impalpable) disease, significantly delayed the rate and time to androgen-independent recurrence compared with delayed therapy when the tumour burden was high.

Androgens↗
PubMed2002

Going malignant: the hypoxia-cancer connection in the prostate.

The metabolic organization of both normal and malignant prostate cellular phenotypes involves some unusual and surprising features. In particular, both conditions exhibit ratios of NADH/NAD+ and NADPH/NADP+ characteristic of high oxidative states despite a chronic shortage of O2 in both conditions. In this paper, we observe that, in prostate cancer cells, the oxidizing power of the fatty acid synthesis (FAS) pathway is so large that redox is stabilized more favorably (more oxidized) than in normal prostate cells. This FAS-facilitated redox improvement occurs despite the fact that malignant cells are more O2 limited and therefore express more hypoxia inducible factor 1 (HIF1) and express hypoxia-regulated genes more robustly. This unusual metabolic situation clearly separates direct regulatory effects of redox balance from secondary effects of hypoxia per se. The physiological significance of the FAS pathway is thus the harnessing of its oxidizing power for improving redox balance despite conditions of more extreme hypoxia. Similar hypoxia defense strategies are found in animal species that are unusually tolerant to oxygen lack. Our hypothesis is that the metabolic organization in the "low zinc, low citrate" phenotype reflects an hypoxia-defense adaptation geared toward redox balance, with prostate cancer cells being relatively more oxidized, even if more hypoxic, than normal prostate cells. Recognition and understanding of these redox balancing and hypoxia defense functions may lead to new intervention strategies by developing new intracellular targets for prostate cancer therapy.

Humans↗
PubMed2000

Placebo-associated remissions in a multicentre, randomized, double-blind trial of interferon gamma-1b for the treatment of metastatic renal cell carcinoma. The Canadian Urologic Oncology Group.

OBJECTIVE: To determine the validity of using an historical maximum spontaneous regression rate (reportedly 0-1.1% in those with lung metastases after nephrectomy) in clinical trials of treatments for patients with metastatic renal cell carcinoma (RCC), as the eligibility criteria for most studies will select patients with better performance status (and thus excluding those who are unlikely to respond) and more modern staging methods would potentially reduce the number of false-positives. PATIENTS AND METHODS: A multicentre randomized,placebo-controlled, double-blind trial was recently completed in which 197 patients with metastatic RCC from 17 study centres across Canada were randomized to receive placebo or recombinant interferon gamma-1b (60 microg/m2) subcutaneously once every 7 days until disease progression. All tumour responses were validated by an independent response committee unaware of the treatment. RESULTS: The median (95% confidence interval) overall response rate (complete, CR, and partial, PR) for those on interferon-gamma was 4 (1.4-11.5)% and for those on placebo was 6 (2. 5-13.2)% (P = 0.75). In the six patients who were receiving placebo the CR and PR (three each) was considered to represent spontaneous remission. Of these six patients (aged 44-64 years) five had undergone nephrectomy, one a tumour embolization, four had clear cell carcinoma and one an adenocarcinoma, and all had regression of lung and/or lymph node metastases. CONCLUSION: The lack of efficacy of interferon-gamma in this trial underlines the importance of continued research to identify alternative therapeutic agents or combinations of agents in phase II studies. However, the threshold response rate for initiating phase III trials should be increased to 18% in the phase II trials, i.e. three times the response rate on placebo.

Adult↗
PubMed2000

A randomized phase 3 study of intraoperative cavernous nerve stimulation with penile tumescence monitoring to improve nerve sparing during radical prostatectomy.

PURPOSE: We determine if mapping of the cavernous nerve during radical prostatectomy using intraoperative cavernous nerve stimulation with tumescence monitoring results in improved erectile potency compared to conventional nerve sparing. MATERIALS AND METHODS: A prospective, randomized, single blinded study was performed on 61 patients at 6 centers. Patients had elected to undergo nerve sparing prostatectomy and had normal preoperative erectile function documented by the Sexual Function Inventory Questionnaire (SFIQ) and RigiScan parallel testing. Patients were randomized between conventional nerve sparing and nerve sparing assisted by the CaverMap Surgical Aid. paragraph sign In all patients neural continuity was assessed immediately after prostate removal by proximal cavernous nerve stimulation. All patients were blinded according to their allocation cohort. RESULTS: At 1 year there was substantial improvement in erectile function in the CaverMap group as measured by RigiScan. This group had a mean of 15. 9 minutes of greater than 60% nocturnal tumescence compared to 2.1 minutes in the conventional nerve sparing group (p <0.024). By SFIQ there was a nonsignificant trend to improved potency in the CaverMap group (71% versus 62%, p = 0.17). Of patients who had bilateral, unilateral and no response to stimulation after resection erectile function assessed by SFIQ recovered in 68%, 27% and 0%, respectively (p = 0.016). CONCLUSIONS: CaverMap assisted prostatectomy led to improved erectile function as assessed by RigiScan testing with no associated adverse events. A response to stimulation immediately after removal of the prostate accurately predicted return of erectile function.

Adult↗
PubMed2000

Neoadjuvant hormone therapy: the Canadian trials.

The Canadian Urologic Oncology Group has carried out three studies of neoadjuvant hormonal therapy (NHT) in prostate cancer. The first, a study of 3 months of cyproterone acetate (CPA) 100 mg TID in patients undergoing external-beam radiation therapy, showed a benefit with respect to time to biochemical progression. There are no survival or clinical progression data available from this study. The second study involved 3 months of CPA prior to radical prostatectomy compared with radical prostatectomy alone and enrolled 200 patients. The probability of biochemical progression at 36 months was similar in the two groups (CPA 40%; surgery alone 30%; P = 0.3233). More recently, we have carried out a randomized trial of 3 v 8 months of leuprolide plus flutamide prior to radical prostatectomy in 547 patients. Patients were stratified by clinical stage, Gleason grade, and serum prostate specific antigen (PSA) concentration. In the 3- and 8-month groups, presurgery PSA concentrations were <0.1 ng/mL in 35% v 73%, and >0.3 ng/mL in 37% v 10%, respectively. In the 3- and 8-month groups, the positive margin rates were 17% and 5% and the organ-confined rates 71% and 91% (P < 0.01). One-year follow-up is now available on the entire cohort. Data regarding time to biochemical and clinical progression and overall and disease-specific survival will be required to determine whether this change in the pathologic findings translates into a patient benefit.

Androgen Antagonists↗
PubMed1999

Progression to androgen independence is delayed by adjuvant treatment with antisense Bcl-2 oligodeoxynucleotides after castration in the LNCaP prostate tumor model.

Bcl-2 has emerged as a critical regulator of apoptosis in a variety of cell systems and is up-regulated during progression to androgen independence in prostate cancer cells. The objectives of this study were to characterize changes in Bcl-2 after androgen withdrawal and during progression to androgen independence in the human prostate LNCaP tumor model and determine whether adjuvant use of antisense Bcl-2 oligodeoxynucleotides (ODNs) with androgen ablation delays progression to androgen independence. Bcl-2 expression in LNCaP cells is down-regulated to undetectable levels by androgen in vitro and up-regulated after castration in vivo. Antisense Bcl-2 ODN treatment reduced LNCaP cell Bcl-2 messenger RNA and protein levels by >90% in a sequence-specific and dose-dependent manner at concentrations >50 nM. Bcl-2 mRNA levels returned to pretreatment levels by 48 h after discontinuing treatment. Athymic male mice bearing SQ LNCaP tumors were castrated and injected i.p. with 12.5 mg/kg/day with two-base mismatch ODN control, reverse polarity ODN control, or antisense Bcl-2 ODN. Tumor volume in control mice gradually increased 5-fold (range, 3-6) by 12 weeks after castration compared to a 10-50% decrease in precastrate tumor volume in mice treated with antisense Bcl-2 ODN. Changes in serum PSA paralleled changes in tumor volume, increasing 4-fold faster above nadir in controls than in mice treated with antisense Bcl-2 ODN. After decreasing 70% by 1 week after castration, PSA increased 1.6-fold above precastrate levels by 11 weeks in controls while staying 30% below precastrate levels in antisense-treated mice. In a second group of experiments, LNCaP tumor growth and serum PSA levels were 90% lower (P<0.01) in mice treated with antisense Bcl-2 ODN compared with mismatch or reverse polarity ODN controls. These results support the hypothesis that Bcl-2 helps mediate progression to androgen independence and is an appropriate target for antisense therapy.

Androgens↗
PubMed1998

Differential transactivation by the androgen receptor in prostate cancer cells.

BACKGROUND: The purpose of this study was to determine the contribution of different transactivating regions of the androgen receptor (AR) to the induction of androgen-regulated promoters in poorly (PC3 cells) and well-differentiated (LNCaP cells) prostate cancer cell lines. METHODS: PC3 and LNCaP cells were co-transfected with plasmids expressing full-length AR or deletion mutants together with luciferase reporters linked to the probasin (PB) and PSA promoters; as well as to ARR3tk, a PB-derived recombinant promoter. RESULTS: Androgen induction of the ARR3tk promoter in the presence of AR was 8- to 10-fold higher than that seen with the PB promoter. Activation of ARR3tk was greatest with an androgen-independent construct in which the first 231 amino acids and the ligand binding domain had been removed, indicating that this promoter is more responsive to activating functions in the N-terminal domain than in the ligand binding domain. By comparison, induction of the PB promoter was greatest with the full-length AR, which suggests that the ligand binding domain also makes a major contribution to the activation of this promoter. In similar analyses with the PSA promoter, AR regions required for promoter induction was dependent on the host cell type. In PC3 cells, the predominant AR transactivation function was androgen-independent and resided in the N-terminal domain, whereas in LNCaP cells, the highest level of induction was androgen dependent and also required participation of the ligand binding domain. CONCLUSIONS: Our results indicate that the relative utilization of transactivating functions in N-terminal and ligand binding domains of the AR is promoter and cell specific.

Androgen-Binding Protein↗
PubMed1998

Intermittent androgen suppression for prostate cancer: rationale and clinical experience.

Research on hormonal treatments of prostate cancer over the past 20 y have focused on maximizing androgen ablation through combination therapy. Maximal androgen ablation increases treatment-related side-effects and expense and fails to prolong time to androgen-independent (AI) progression. The rationale behind intermittent androgen suppression (IAS) is based on: (1) observations that androgen ablation is palliative, not curative in most patients where quality of life must be considered; (2) assumption that immediate androgen ablation is superior to delayed therapy in improving survival of patients with prostate cancer; and (3) the hypothesis that if tumor cells which survive androgen withdrawal are forced into a normal pathway of differentiation by androgen replacement, then apoptotic potential might be restored and progression to androgen independence may be delayed. Observations from animal model studies suggest that progression to androgen-independence involves adaptive responses to androgen deprivation which are, in turn, modulated by intermittent androgen replacement. Supported by these animal model observations, several centers have now tested the feasibility of IAS therapy in non-randomized groups of patients with prostate cancer using serum PSA as trigger points. Experimental and clinical data suggest that prostate cancer is amenable to control by IAS. IAS may offer clinicians an opportunity to improve quality of life in patients with prostate cancer by balancing the benefits of immediate androgen ablation (delayed progression and prolonged survival) while reducing treatment-related side effects and expense. Whether time to progression and survival is affected in a beneficial or adverse way is being studied in randomized, prospective protocols. The purpose of this article is to review the rationale behind IAS, compare observations from published series, and discuss potential indications and treatment strategies using IAS.

Journal Article↗
PubMed1998

Intermittent androgen suppression for prostate cancer: rationale and clinical experience.

The rationale behind intermittent androgen suppression (IAS) is based on: (1) observations that androgen ablation is palliative, not curative, in most patients with prostate cancer, and that quality of life must be considered; (2) the assumption that immediate androgen ablation is superior to delayed therapy in improving survival; (3) the hypothesis that if tumour cells surviving androgen withdrawal are forced into a normal pathway of differentiation by androgen replacement, then apoptotic potential might be restored and progression to androgen independence delayed. Several centres have now tested the feasibility of IAS therapy in non-randomized groups of prostate cancer patients using serum of prostate-specific antigen levels as trigger points. Clinical data suggest that prostate cancer is amenable to control by IAS and offers clinicians an opportunity to improve patients' quality of life by balancing the benefits of immediate androgen ablation (delayed progression and prolonged survival) while reducing treatment-related side effects and expense. Whether time to progression and survival is affected in a beneficial or adverse way is being studied in randomized, prospective protocols.

Androgen Antagonists↗
PubMed1996

Control of tumor progression by maintenance of apoptosis.

The ability to induce multiple apoptotic regressions of an androgen-dependent tumor cell population by repeated cycles of androgen withdrawal and replacement may be advantageous in therapeutic strategies aimed at delaying or preventing tumor progression. With greater insight into factors that either initiate or limit apoptosis, more efficient application of intermittent therapy might be achieved, especially if methods could be devised to increase the length or number of treatment cycles. Both calreticulin and clusterin represent proteins with a potential role in the regulation of apoptosis. Calreticulin may inhibit target gene transcription by interacting with steroid hormone receptors, thereby masking their DNA-binding sites and triggering the onset of the apoptotic process. Clusterin, on the other hand, is a membrane-stabilizing protein that appears to be involved in limiting the autophagic lysis of epithelial cells during apoptosis. Also, the increasing tendency for nuclear localization of clusterin after androgen withdrawal may preserve the nuclear environment, limiting the lethal effect of treatment. Thus, tumor progression, characterized by the loss of apoptotic potential, appears to be linked in part to the inappropriate activation of TRPM-2 gene, which accounts for the constitutive expression of clusterin.

Amino Acid Sequence↗