Effect of alpha1-adrenoceptor antagonist exposure on prostate cancer incidence: an observational cohort study

Pharmacological characterization of zinc and copper interaction with the human alpha(1A)-adrenoceptor

Metal ions have a major role in human health, and interact with many classes of receptors including the G-protein coupled receptors. In the peripheral system, zinc mainly accumulates in the soft prostate organ and, with copper, influences prostate disease progression, from normal to hypertrophic or cancerous states. The development of these pathologies may be influenced by the α(1A)-adrenoceptor, the principal regulator of prostate tonicity. There is currently no information on possible interactions between metals and the α(1A)-adrenoceptor. We therefore studied the effects of several mono- and divalent ions on this receptor subtype using binding and functional experiments performed on expressed cloned human α(1A)-adrenoceptor. Regardless of the counter anion used, Zn(2+) and Cu(2+) interact with α(1A)-adrenoceptor with apparent affinities in the low micromolar range. In addition, using specific binding experiments, we established that these ions acted as negative allosteric ligands on prazosin/α(1A)-adrenoceptor interaction, but in a different manner from the allosteric modulator 5-(N-ethyl-N-isopropyl)-amiloride, suggesting distinct mode of interaction. In addition, the presence of Cu(2+) weakly decreased epinephrine affinity, whereas the addition of Zn(2+) shifted to the left the epinephrine binding curve, revealing a positive allosteric effect but only on half of the binding site. Finally, cell-based functional experiments demonstrated that Zn(2+) and Cu(2+) antagonized epinephrine activation in an insurmountable manner, by reducing agonist efficacy without any shift in the epinephrine activation curves. This study shows the interactions between metal ions and the α(1A)-adrenoceptor with affinities compatible with physiological concentrations and suggests that zinc and copper may have a biological role in prostate function.

Significance of talin in cancer progression and metastasis

Upon detachment from the extracellular matrix, tumor epithelial cells and tumor-associated endothelial cells are capable of overcoming anoikis, gain survival benefits, and hence contribute to the process of metastasis. The focal-adhesion complex formation recruits the association of key adaptor proteins such as FAK (focal-adhesion kinase). Vimentin, paxillin, and talin are responsible for mediating the interaction between the actin cytoskeleton and integrins. Talin is an early-recruited focal-adhesion player that is of structural and functional significance in mediating interactions with integrin cytoplasmic tails leading to destabilization of the transmembrane complex and resulting in rearrangements in the extracellular integrin compartments that mediate integrin activation. Talin-mediated integrin activation plays a definitive role in integrin-mediated signaling and induction of downstream survival pathways leading to protection from anoikis and consequently resulting in cancer progression to metastasis. We recently reported that talin expression is significantly increased in prostate cancer compared with benign and normal prostate tissue and that this overexpression correlates with progression to metastatic disease implicating a prognostic value for talin during tumor progression. At the molecular level, talin is functionally associated with enhanced survival and proliferation pathways and confers anoikis resistance and metastatic spread of primary tumor cells via activation of the Akt survival pathway. In this review, we discuss the growing evidence surrounding the value of talin as a prognostic marker of cancer progression to metastasis and as therapeutic target in advanced prostate cancer, as well as the current understanding of mechanisms regulating its signaling activity in cancer.

Beta-blocker drug therapy reduces secondary cancer formation in breast cancer and improves cancer specific survival

Laboratory models show that the beta-blocker, propranolol, can inhibit norepinephrine-induced breast cancer cell migration. We hypothesised that breast cancer patients receiving beta-blockers for hypertension would show reduced metastasis and improved clinical outcome. Three patient subgroups were identified from the medical records of 466 consecutive female patients (median age 57, range 28-71) with operable breast cancer and follow-up (>10 years). Two subgroups comprised 43 and 49 hypertensive patients treated with beta-blockers or other antihypertensives respectively, prior to cancer diagnosis. 374 patients formed a non-hypertensive control group. Metastasis development, disease free interval, tumour recurrence and hazards risk were statistically compared between groups. Kaplan-Meier plots were used to model survival and DM. Beta-blocker treated patients showed a significant reduction in metastasis development (p=0.026), tumour recurrence (p=0.001), and longer disease free interval (p=0.01). In addition, there was a 57% reduced risk of metastasis (Hazards ratio=0.430; 95% CI=0.200-0.926, p=0.031), and a 71% reduction in breast cancer mortality after 10 years (Hazards ratio=0.291; 95% CI=0.119-0.715, p=0.007). This proof-of-principle study showed beta-blocker therapy significantly reduces distant metastases, cancer recurrence, and cancer-specific mortality in breast cancer patients suggesting a novel role for beta-blocker therapy. A larger epidemiological study leading to randomised clinical trials is needed for breast and other cancer types including colon, prostate and ovary.

Identification of novel p53 pathway activating small-molecule compounds reveals unexpected similarities with known therapeutic agents

Manipulation of the activity of the p53 tumor suppressor pathway has demonstrated potential benefit in preclinical mouse tumor models and has entered human clinical trials. We describe here an improved, extensive small-molecule chemical compound library screen for p53 pathway activation in a human cancer cell line devised to identify hits with potent antitumor activity. We uncover six novel small-molecule lead compounds, which activate p53 and repress the growth of human cancer cells. Two tested compounds suppress in vivo tumor growth in an orthotopic mouse model of human B-cell lymphoma. All compounds interact with DNA, and two activate p53 pathway in a DNA damage signaling-dependent manner. A further screen of a drug library of approved drugs for medicinal uses and analysis of gene-expression signatures of the novel compounds revealed similarities to known DNA intercalating and topoisomerase interfering agents and unexpected connectivities to known drugs without previously demonstrated anticancer activities. These included several neuroleptics, glycosides, antihistamines and adrenoreceptor antagonists. This unbiased screen pinpoints interference with the DNA topology as the predominant mean of pharmacological activation of the p53 pathway and identifies potential novel antitumor agents.

Pathophysiology of oral cancer in experimental animal models: a review with focus on the role of sympathetic nerves

Global increase in incidence and mortality as well as poor prognosis of oral cancer (OC) has intensified efforts towards early detection and prevention of this disfiguring disease. Several studies have been conducted using experimental animal models to understand the pathophysiology and molecular events involved in OC. Lack of identification of specific biomarkers during the multifaceted steps of oral carcinogenesis has hindered its diagnosis and treatment. Solid stress generated by growing tumors as well as abnormalities in tumor vasculature lead to increased interstitial fluid pressure, which could obstruct therapeutic drug delivery to tumors. Furthermore, the sympathetic nervous system is known to affect angiogenesis, vessel permeability, immune responses and carcinogenesis. Recent findings indicate that, in addition to angiogenic and lymphangiogenic factors, tumor cells release neurotrophic factors that initiate innervation. Interactions between cytokines and sympathetic neurotransmitters, and their respective receptors expressed by the nerve, immune and tumor cells appear to influence tumor growth. Thus, understanding the complex signaling processes and interrelationships between vascular, nervous and immune systems during oral carcinogenesis may prove vital for successful prevention and treatment of OC. This review aims at outlining the available knowledge on pathophysiology of OC in experimental animal models including evidence from our own findings.

Testing whether drugs that weaken norepinephrine signaling prevent or treat various types of cancer

Recently, I put forth the hypothesis that the signaling molecule, norepinephrine (NE), is an etiological factor in a number of types of cancer. In this brief commentary, I summarize evidence that NE plays a role in cancer and describe details involved in testing the hypothesis in humans through epidemiological investigation of existing medical records of persons who have taken pharmaceutical drugs that affect NE. If NE plays an etiological role in cancers of a number of organs, then taking a single pharmaceutical drug (such as clonidine, prazosin, or propranolol) that weakens NE signaling systemically, may simultaneously prevent or treat many different types of cancer, and this may represent a breakthrough in pharmaceutical prevention and possibly treatment of cancer.

Apoptosis induction by doxazosin and other quinazoline alpha1-adrenoceptor antagonists: a new mechanism for cancer treatment?

Doxazosin and related, quinazoline-based alpha(1)-adrenoceptor antagonists can induce apoptosis in prostate and various other normal, benign, smooth muscle, endothelial and malignant cells. Such apoptosis-inducing effects occur independently of alpha(1)-adrenoceptor antagonism and typically require much high concentrations than those required for receptor occupancy. Several studies have invested efforts towards the elucidation of the molecular mechanisms underlying doxazosin-induced apoptosis. These include various tumor cells, cardiomyocytes, endothelial cells and bladder smooth muscle cells. While the high concentrations of doxazosin required to induce apoptosis challenge the use of this and related drugs for clinical optimization of apoptosis induction, such quinazoline structure may represent chemical starting points to develop more potent apoptosis-inducing agents free of alpha(1)-adrenoceptor antagonistic action and suitable for cancer treatment with minimal and well-tolerated side effects.

Prostate cancer incidence among finasteride and alpha-blocker users in the Finnish Prostate Cancer Screening Trial

Background:

The Prostate Cancer Prevention Trial has shown a protective effect of finasteride on prostate cancer in low-risk men. It is uncertain whether similar results can be expected when finasteride is used to treat benign prostatic hyperplasia.

Methods:

We performed an observational cohort study within the Finnish Prostate Cancer Screening Trial. Using a comprehensive prescription database on medication reimbursements during 1995–2004 of men using finasteride or alpha-blockers for benign prostatic hyperplasia, we evaluated prostate cancer incidence among 23 320 men screened during 1996–2004.

Results:

Compared to medication non-users, overall prostate cancer incidence was not significantly affected in finasteride users (hazard ratio 0.87; 95% CI 0.63–1.19). Incidence of Gleason 2–6 tumours, however, was decreased among finasteride users (HR 0.59; 95% CI 0.38–0.91), whereas incidence of Gleason 7–10 tumours was unchanged (HR 1.33; 95% CI 0.77–2.30). The protective effect concerned mainly screen-detected tumours. Overall prostate cancer risk was not significantly reduced among alpha-blocker users relative to non-users, but decreased incidence of high-grade tumours was observed (0.55; 95% CI 0.31–0.96).

Conclusions:

The detection of low-grade, early-stage tumours is decreased among men who use finasteride for symptomatic BPH. The protective effect of finasteride can also be expected in men with benign prostatic hyperplasia.

Neurotransmission and cancer: implications for prevention and therapy

Published evidence compiled in this review supports the hypothesis that the development, progression, and responsiveness to prevention and therapy of the most common human cancers is strongly influenced, if not entirely orchestrated, by an imbalance in stimulatory and inhibitory neurotransmission. The neurotransmitters acetylcholine, adrenaline, and noradrenaline of the autonomic nervous system act as powerful upstream regulators that orchestrate numerous cell and tissue functions, by releasing growth factors, angiogenesis factors and metastasis factors, arachidonic acid, proinflammatory cytokines, and local neurotransmitters from cancer cells and their microenvironment. In addition, they modulate proliferation, apoptosis, angiogenesis, and metastasis of cancer directly by intracellular signaling downstream of neurotransmitter receptors. Nicotine and the tobacco-specific nitrosamines have the documented ability to hyperstimulate neurotransmission by both branches of the autonomic nervous system. The expression and function of these neurotransmitter pathways are cell type specific. Lifestyle, diet, diseases, stress, and pharmacological treatments modulate the expression and responsiveness of neurotransmitter pathways. Current preclinical testing systems fail to incorporate the modulating effects of neurotransmission on the responsiveness to anticancer agents and should be amended accordingly. The neurotransmitter gamma-aminobutyric acid has a strong inhibitory function on sympathicus-driven cancers whereas stimulators of cyclic adenosine monophosphate/protein kinase A signaling have strong inhibitory function on parasympathicus-driven cancers. Marker-guided restoration of the physiological balance in stimulatory and inhibitory neurotransmission represents a promising and hitherto neglected strategy for the prevention and therapy of neurotransmitter-responsive cancers.

Involvement of transcription factor activator protein-2alpha in doxazosin-induced HeLa cell apoptosis

AIM

To investigate the pro-apoptotic effects of alpha1-adrenergic inhibitor doxazosin in HeLa cells and the potential involvement of transcription factor activator protein-2alpha (AP-2alpha) in doxazosin-induced apoptosis.

METHODS

The HeLa cells were exposed to various concentrations of doxazosin for 16 h. Apoptosis was detected using a DNA fragmentation assay, Hoechst 33258 staining, and flow cytometric analysis. The expression of AP-2alpha and caspase-3 was detected by relative quantitative RT-PCR and Western blot assays, respectively. After the respective transfections of the HeLa cells with AP-2alpha overexpressing constructs and an antisense oligonucleotide against AP-2alpha, apoptosis was assessed by flow cytometric analysis, and the expression of AP-2alpha and caspase-3 was detected by relative quantitative RT-PCR and Western blot assays. The colorimetric assay was performed to detect the caspase-3 activity.

RESULTS

Treatment with various concentrations of doxazosin for 16 h increased the apoptotic rate and total cell death rate of the HeLa cells in a dose-dependent manner and upregulated the expression of AP-2alpha and caspase-3 in a dose-dependent manner. A dose-dependent increase was observed in the caspase-3 activity. Overexpressing AP-2alpha led to the increased rate of doxazosin-induced apoptosis and the total cell death, whereas doxazosin-induced apoptosis and the total cell death in HeLa cells decreased by antisense AP-2alpha. Furthermore, overexpressing AP-2alpha increased the expression and activity of caspase-3, whereas antisense AP-2alpha in part abolished the increased effects of doxazosin on caspase-3 expression and activity.

CONCLUSION

Doxazosin induces apoptosis in HeLa cells in a dose-dependent manner, and transcription factor AP-2alpha is functionally involved in doxazosin-induced HeLa cell apoptosis.

Novel quinazoline-based compounds impair prostate tumorigenesis by targeting tumor vascularity

Previous evidence showed the ability of the quinazoline-based alpha(1)-adrenoreceptor antagonist doxazosin to suppress prostate tumor growth via apoptosis. In this study, we carried out structural optimization of the chemical nucleus of doxazosin and a subsequent structure-function analysis toward the development of a novel class of apoptosis-inducing and angiogenesis-targeting agents. Our lead compound, DZ-50, was effective at reducing endothelial cell viability via a nonapoptotic mechanism. Treatment with DZ-50 effectively prevented in vitro tube formation and in vivo chorioallantoic membrane vessel development. Confocal microscopy revealed a significantly reduced ability of tumor cells to attach to extracellular matrix and migrate through endothelial cells in the presence of DZ-50. In vivo tumorigenicty studies using two androgen-independent human prostate cancer xenografts, PC-3 and DU-145, showed that DZ-50 treatment leads to significant suppression of tumorigenic growth. Exposure to the drug at the time of tumor cell inoculation led to prevention of prostate cancer initiation. Furthermore, DZ-50 resulted in a reduced formation of prostate-tumor derived metastatic lesions to the lungs in an in vivo spontaneous metastasis assay. Thus, our drug discovery approach led to the development of a class of lead (quinazoline-based) compounds with higher potency than doxazosin in suppressing prostate growth by targeting tissue vascularity. This new class of quinazoline-based compounds provides considerable promise as antitumor drugs for the treatment of advanced prostate cancer.

Decreased risk of bladder cancer in men treated with quinazoline-based α1-adrenoceptor antagonists

Previous studies documented that human bladder cancer cells are sensitive to the apoptotic effects of quinazoline-derived α1-adrenoreceptor antagonists and bladder tumors exhibit reduced tissue vascularity in response to terazosin. More recent evidence suggests that exposure to quinazoline α1-adrenorecptor antagonists leads to a significant reduction in prostate cancer incidence. This retrospective observational cohort study was conducted to determine whether male patients treated with quinazoline α1-adrenoceptor antagonists for either benign prostate hyperplasia (BPH) or hypertension have a decreased risk of developing bladder cancer. Review of the medical records of all male patients enrolled at the Lexington Veterans Administration (VA) Medical Center identified men exposed to quinazoline-based α1-adrenoceptor antagonists (Jan 1, 1998-Dec 31, 2002) for either hypertension and/or benign prostate obstructive symptoms. The whole group of 27,138 male patients was linked to the Markey Cancer Center's Kentucky Cancer Registry (KCR), part of the NCI's Surveillance, Epidemiology, and End Results (SEER) Program, to identify all incident bladder cancer cases diagnosed in this population. Measures of disease incidence, relative risk, and attributable risk were calculated to compare the risk of developing bladder cancer for α1-blocker-exposed versus unexposed men. A two-by-two contingency table of α1-antagonist exposure versus bladder cancer diagnoses was constructed and the relative risk was calculated. Our analysis revealed a cumulative bladder cancer incidence of 0.24% among the α1-blocker-exposed men compared to 0.42% in the unexposed group. Thus, there was a risk difference of -0.0018, which indicates that 1.8 fewer bladder cancer cases developed per 1000 exposed men. Alternatively stated, 556 men would need to be treated with quinazoline α1-blockers to prevent one case of bladder cancer. Exposure to quinazoline α1-blockers thus may have prevented 7 to 8 bladder cancer cases among the 4173 treated men during the study period. The data yield an unadjusted risk ratio of 0.57 (95% CI: 0.30, 1.08) and therefore, men treated with α1-adrenoreceptor antagonists have a 43% lower relative risk of developing bladder cancer than unexposed men (p=0.083). Our inability to determine person-years at risk of developing bladder cancer for each unexposed control patient, was a limitation for calculating an incidence ratio and rate difference. These results offer an initial indication that exposure to doxazosin and terazosin decreases the incidence of bladder cancer. This is the first epidemiological evidence that the anti-tumor action of quinazoline-based α1-antagonists may potentially translate into a protective effect from bladder cancer development.