Pharmacologic basis for the enhanced efficacy of dutasteride against prostatic cancers
ABSTRACT Prostatic dihydrotestosterone (DHT) concentration is regulated by precursors from systemic circulation and prostatic enzymes of androgen metabolism, particularly 5alpha-reductases (i.e., SRD5A1 and SRD5A2). Therefore, the levels of expression SRD5A1 and SRD5A2 and the antiprostatic cancer growth response to finasteride, a selective SRD5A2 inhibitor, versus the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, were compared.
Real-time PCR and enzymatic assays were used to determine the levels of SRD5A1 and SRD5A2 in normal versus malignant rat and human prostatic tissues. Rats bearing the Dunning R-3327H rat prostate cancer and nude mice bearing LNCaP or PC-3 human prostate cancer xenografts were used as model systems. Tissue levels of testosterone and DHT were determined using liquid chromatography-mass spectrometry.
Prostate cancer cells express undetectable to low levels of SRD5A2 but elevated levels of SRD5A1 activity compared with nonmalignant prostatic tissue. Daily oral treatment of rats with the SRD5A2 selective inhibitor, finasteride, reduces prostate weight and DHT content but did not inhibit R-3327H rat prostate cancer growth or DHT content in intact (i.e., noncastrated) male rats. In contrast, daily oral treatment with even a low 1 mg/kg/d dose of the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, reduces both normal prostate and H tumor DHT content and weight in intact rats while elevating tissue testosterone. Daily oral treatment with finasteride significantly (P < 0.05) inhibits growth of LNCaP human prostate cancer xenografts in intact male nude mice, but this inhibition is not as great as that by equimolar oral dosing with dutasteride. This anticancer efficacy is not equivalent, however, to that produced by castration. Only combination of dutasteride and castration produces a greater tumor inhibition (P < 0.05) than castration monotherapy against androgen-responsive LNCaP cancers. In contrast, no response was induced by dutasteride in nude mice bearing androgen-independent PC-3 human prostatic cancer xenografts.
These results document that testosterone is not as potent as DHT but does stimulate prostate cancer growth, thus combining castration with dutasteride enhances therapeutic efficacy.
- SourceAvailable from: Junichi Inokuchi
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- "Our findings suggested that inhibition of 5a-reductase may prevent the progression to CRPC in metastatic prostate cancer. The dual 5a-reductase inhibitor dutasteride effectively prevented prostate cancer tumour growth combined with castration in a mouse xenograft model . In addition, dutasteride combined with the novel anti-androgen enzalutamide could suppress cancer proliferation in hormone-naı¨ve cancer as well as CRPC "
ABSTRACT: De novo androgen synthesis is thought to be involved in the progression to castration-resistant prostate cancer (CRPC) during androgen-deprivation therapy (ADT). During androgen synthesis, 5α-reductase encoded by SRD5A catalyses testosterone into more active dihydrotestosterone and may be involved in the progression to CRPC. Then, this study aimed to reveal the association between genetic variations in SRD5A and the prognosis in metastatic prostate cancer. We studied the polymorphisms rs518673 and rs166050 in SRD5A1, and rs12470143, rs523349, rs676033 and rs2208532 in SRD5A2 as well as the time to CRPC progression and overall survival in 104 patients with metastatic prostate cancer that had undergone primary ADT. The association between the polymorphisms and the progression to CRPC as well as overall survival was examined. Patients carrying the more active GG genotype in SRD5A2 rs523349 exhibited a higher risk of the progression (hazard ration [95% confidence interval], 1.93 [1.14-3.14], p=0.016) and death (hazard ration [95% confidence interval], 2.14 [1.16-3.76], p=0.016), compared with less active GC/CC genotypes in SRD5A2 rs523349. High 5α-reductase activity due to the polymorphism in SRD5A2 may contribute to resistance to ADT. Furthermore, SRD5A2 rs523349 polymorphism may be a promising biomarker for metastatic prostate cancer patients treated with primary ADT and a molecular target for advanced prostate cancer. Copyright © 2015 Elsevier Ltd. All rights reserved.European journal of cancer (Oxford, England: 1990) 07/2015; DOI:10.1016/j.ejca.2015.06.122 · 4.82 Impact Factor
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- "The lack of DA neuroprotection observed here with Finasteride could also be due to its short serum half-life compared to Dutasteride . In rats, serum half-life of Dutasteride is reported to be 31 h and 2 h for Finasteride (Xu et al., 2006). Hence, compared to Finasteride, Dutasteride injected once daily, given its affinity and long half-life, would exhibit a more sustained protection to counteract MPTP toxicity. "
ABSTRACT: Finasteride and Dutasteride are 5α-reductase inhibitors used in the clinic to treat endocrine conditions and were recently found to modulate brain dopamine (DA) neurotransmission and motor behaviour. We investigated if Finasteride and Dutasteride have a neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) male mice as a model of Parkinson's disease (PD). Experimental groups included saline treated controls and mice treated with saline, Finasteride (5 and 12.5 mg/kg) or Dutasteride (5 and 12.5 mg/kg) for 5 days before and 5 days after MPTP administration (4 MPTP injections, 6.5 mg/kg on day 5 inducing a moderate DA depletion) and then they were euthanized. MPTP administration decreased striatal DA contents measured by HPLC while serotonin contents remained unchanged. MPTP mice treated with Dutasteride 5 and 12.5 mg/kg had higher striatal DA and metabolites (DOPAC and HVA) contents with a decrease of metabolites/DA ratios compared to saline-treated MPTP mice. Finasteride had no protective effect on striatal DA contents. Tyrosine hydroxylase (TH) mRNA levels measured by in situ hybridization in the substantia nigra pars compacta were unchanged. Dutasteride at 12.5 mg/kg reduced the effect of MPTP on specific binding to striatal DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) measured by autoradiography. MPTP reduced compared to controls plasma testosterone (T) and dihydrotestosterone (DHT) concentrations measured by liquid chromatography-tandem mass spectrometry; Dutasteride and Finasteride increased plasma T levels while DHT levels remained low. In summary, our results showed that a 5α-reductase inhibitor, Dutasteride has neuroptotective activity preventing in male mice the MPTP-induced loss of several dopaminergic markers. Copyright © 2015. Published by Elsevier Ltd.Neuropharmacology 05/2015; 97. DOI:10.1016/j.neuropharm.2015.05.015 · 4.82 Impact Factor
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- "Our findings are similar to results in other animal models that found finasteride failed to inhibit prostate cancer progression  or tumor growth [18,19] and dutasteride decreased prostate tumor growth . We found the weakest response to dutasteride in the ventral lobe. "
ABSTRACT: The prostate cancer prevention trial (PCPT) and Reduction by dutasteride of Prostate Cancer Events (REDUCE) trial found that 5α-reductase (5αR) inhibitors finasteride and dutasteride respectively, decreased prostate cancer prevalence but also increased the incidence of high-grade tumors. 5αR2 is the main isoenzyme in normal prostate tissue; however, most prostate tumors have high 5αR1 and low 5αR2 expression. Because finasteride inhibits only 5αR2, we hypothesized that it would not be as efficacious in preventing prostate cancer development and/or progression in C57BL/6 TRAMP x FVB mice as dutasteride, which inhibits both 5αR1 and 5αR2. Six-week-old C57BL/6 TRAMP x FVB male mice were randomized to AIN93G control or pre- and post- finasteride and dutasteride diet (83.3 mg drug/kg diet) groups (n =30-33) that began at 6 and 12 weeks of age, respectively, and were terminated at 20 weeks of age. The pre- and post- finasteride and dutasteride groups were designed to test the preventive and therapeutic efficacy of the drugs, respectively. Final body weights, genitourinary tract weights, and genitourinary tract weights as percentage of body weights were significantly decreased in the Pre- and Post-dutasteride groups compared with the control. The Post-dutasteride group showed the greatest inhibition of prostatic intraepithelial neoplasia progression and prostate cancer development. Surprisingly, the Post-dutasteride group showed improved outcomes compared with the Pre-dutasteride group, which had increased incidence of high-grade carcinoma as the most common and most severe lesions in a majority of prostate lobes. Consistent with our hypothesis, we found little benefit from the finasteride diets, and they increased the incidence of high-grade carcinoma. Our findings have commonalities with previously reported PCPT, REDUCE, and the Reduction by dutasteride of Clinical Progression Events in Expectant Management (REDEEM) trial results. Our results may support the therapeutic use of dutasteride, but not finasteride, for therapeutic or preventive use.PLoS ONE 10/2013; 8(10):e77738. DOI:10.1371/journal.pone.0077738 · 3.23 Impact Factor