Current status of primary pharmacotherapy and future perspectives toward upfront therapy for metastatic hormone-sensitive prostate cancer

Mineralocorticoid receptor signaling affects therapeutic effect of enzalutamide

BACKGROUND

Corticosteroids play important roles in prostate cancer therapeutics. However, their role when combined with enzalutamide remains obscure. Then, we aimed to elucidate the functional and clinical impact of corticosteroids on steroid receptors in androgen receptor (AR)-targeting therapy utilizing enzalutamide.

METHODS

The therapeutic effect was studied according to concomitant use of corticosteroids in 86 men treated with enzalutamide. The sensitivity to various agents was evaluated using cytotoxicity assays in prostate cancer cells. Gene expression levels were evaluated by quantitative real-time polymerase chain reaction in prostate cancer cells and tissues.

RESULTS

The therapeutic effect of enzalutamide was particularly lessened with concomitant treatment with dexamethasone. Consistently, dexamethasone increased cellular resistance to enzalutamide while prednisolone and aldosterone decreased cellular resistance to enzalutamide in prostate cancer cells. Inversely, mineralocorticoid receptor (MR) knockdown augmented the activity of AR signaling and the cellular resistance to enzalutamide.

CONCLUSIONS

MR plays a critical role in resistance to AR-targeting therapies, which may be overcome by activation of MR signaling.

Gene polymorphisms in antioxidant enzymes correlate with the efficacy of androgen-deprivation therapy for prostate cancer with implications of oxidative stress

Background

Oxidative stress mitigated by antioxidant enzymes is thought to be involved in the progression to castration-resistant prostate cancer (CRPC) during androgen-deprivation therapy (ADT). This study investigated the association between genetic variations in antioxidant enzymes and the efficacy of ADT as well as its biological background.

Patients and methods

The non-synonymous or promoter-locating polymorphisms of antioxidant enzymes were examined as well as the time to CRPC progression and overall survival in 104 and 92 patients treated with ADT for metastatic and non-metastatic prostate cancer, respectively. In addition, intracellular reactive oxygen species and expression levels of antioxidant enzymes were examined in castration-resistant and enzalutamide-resistant cells.

Results

In metastatic prostate cancer, the AG/GG allele in GSTM3 rs7483 and CT/TT allele in CAT rs564250 were associated with a significantly lower risk of progression to CRPC and all-cause death compared with homozygotes of the major AA allele (hazard ratio [HR]; [95% confidence interval (CI)], 0.55 [0.34-0.86], P = 0.0086) and CC allele (HR; [95% CI], 0.48 [0.24-0.88], P = 0.016), respectively. On multivariate analyses, only GSTM3 rs7483 was associated with significant progression risk (AG/GG versus AA; HR; [95% CI], 0.45 [0.25-0.79], P = 0.0047) even after Bonferroni adjustment. In non-metastatic prostate cancer, the AG/GG allele in GSTM3 rs7483 was associated with a significantly lower risk of progression to CRPC (HR; [95% CI], 0.35 [0.10-0.93], P = 0.034) and all-cause death (HR; [95% CI], 0.26 [0.041-0.96], P = 0.043) compared with the AA allele. Intracellular reactive oxygen species levels were increased, accompanied with augmented GSTM3 expression in both castration-resistant and enzalutamide-resistant cells.

Conclusions

Differential activity of antioxidant enzymes caused by the polymorphism in GSTM3 may contribute to resistance to hormonal therapy through oxidative stress. The GSTM3 rs7483 polymorphism may be a promising biomarker for prostate cancer patients treated with ADT.

Phosphodiesterase type 5 and cancers: progress and challenges

Cancers are an extraordinarily heterogeneous collection of diseases with distinct genetic profiles and biological features that directly influence response patterns to various treatment strategies as well as clinical outcomes. Nevertheless, our growing understanding of cancer cell biology and tumor progression is gradually leading towards rational, tailored medical treatments designed to destroy cancer cells by exploiting the unique cellular pathways that distinguish them from normal healthy counterparts. Recently, inhibition of the activity of phosphodiesterase type 5 (PDE5) is emerging as a promising approach to restore normal intracellular cyclic guanosine monophosphate (cGMP) signalling, and thereby resulting into the activation of various downstream molecules to inhibit proliferation, motility and invasion of certain cancer cells. In this review, we present an overview of the experimental and clinical evidences highlighting the role of PDE5 in the pathogenesis and prevention of various malignancies. Current data are still not sufficient to draw conclusive statements for cancer patient management, but could provide further rational for testing PDE5-targeting drugs as anticancer agents in clinical settings.

Adding abiraterone to androgen deprivation therapy in men with metastatic hormone-sensitive prostate cancer: A systematic review and meta-analysis

BACKGROUND

There is a need to synthesise the results of numerous randomised controlled trials evaluating the addition of therapies to androgen deprivation therapy (ADT) for men with metastatic hormone-sensitive prostate cancer (mHSPC). This systematic review aims to assess the effects of adding abiraterone acetate plus prednisone/prednisolone (AAP) to ADT.

METHODS

Using our framework for adaptive meta-analysis (FAME), we started the review process before trials had been reported and worked collaboratively with trial investigators to anticipate when eligible trial results would emerge. Thus, we could determine the earliest opportunity for reliable meta-analysis and take account of unavailable trials in interpreting results. We searched multiple sources for trials comparing AAP plus ADT versus ADT in men with mHSPC. We obtained results for the primary outcome of overall survival (OS), secondary outcomes of clinical/radiological progression-free survival (PFS) and grade III-IV and grade V toxicity direct from trial teams. Hazard ratios (HRs) for the effects of AAP plus ADT on OS and PFS, Peto Odds Ratios (Peto ORs) for the effects on acute toxicity and interaction HRs for the effects on OS by patient subgroups were combined across trials using fixed-effect meta-analysis.

FINDINGS

We identified three eligible trials, one of which was still recruiting (PEACE-1 (NCT01957436)). Results from the two remaining trials (LATITUDE (NCT01715285) and STAMPEDE (NCT00268476)), representing 82% of all men randomised to AAP plus ADT versus ADT (without docetaxel in either arm), showed a highly significant 38% reduction in the risk of death with AAP plus ADT (HR = 0.62, 95% confidence interval [CI] = 0.53-0.71, p = 0.55 × 10-10), that translates into a 14% absolute improvement in 3-year OS. Despite differences in PFS definitions across trials, we also observed a consistent and highly significant 55% reduction in the risk of clinical/radiological PFS (HR = 0.45, 95% CI = 0.40-0.51, p = 0.66 × 10-36) with the addition of AAP, that translates to a 28% absolute improvement at 3 years. There was no evidence of a difference in the OS benefit by Gleason sum score, performance status or nodal status, but the size of the benefit may vary by age. There were more grade III-IV acute cardiac, vascular and hepatic toxicities with AAP plus ADT but no excess of other toxicities or death.

INTERPRETATION

Adding AAP to ADT is a clinically effective treatment option for men with mHSPC, offering an alternative to docetaxel for men who are starting treatment for the first time. Future research will need to address which of these two agents or whether their combination is most effective, and for whom.

Targeting Taxanes to Castration-Resistant Prostate Cancer Cells by Nanobubbles and Extracorporeal Shock Waves

To target taxanes to castration-resistant prostate cancer cells, glycol-chitosan nanobubbles loaded with paclitaxel and docetaxel were constructed. The loaded nanobubbles were then combined with Extracorporeal Shock Waves, acoustic waves widely used in urology and orthopedics, with no side effects. Nanobubbles, with an average diameter of 353.3 ± 15.5 nm, entered two different castration-resistant prostate cancer cells (PC3 and DU145) as demonstrated by flow cytometry and immunofluorescence. The shock waves applied increased the amount of intracellular nanobubbles. Loading nanobubbles with paclitaxel and docetaxel and combining them with shock waves generated the highest cytotoxic effects, resulting in a paclitaxel GI₅₀ reduction of about 55% and in a docetaxel GI₅₀ reduction of about 45% respectively. Combined treatment also affected cell migration. Paclitaxel-loaded nanobubbles and shock waves reduced cell migration by more than 85% with respect to paclitaxel alone; whereas docetaxel-loaded nanobubbles and shock waves reduced cell migration by more than 82% with respect to docetaxel alone. The present data suggest that nanobubbles can act as a stable taxane reservoir in castration-resistant prostate cancer cells and shock waves can further increase drug release from nanobubbles leading to higher cytotoxic and anti-migration effect.

Synthesis and basic evaluation of 7α-(3-[18F]fluoropropyl)-testosterone and 7α-(3-[18F]fluoropropyl)-dihydrotestosterone

OBJECTIVE

7α-Substituted androgen derivatives may have the potential to visualize androgen receptors with positron emission tomography. In the present study, we synthesized fluoropropyl derivatives of 7α-(3-[¹⁸F]fluoropropyl)-testosterone ([¹⁸F]7) and 7α-(3-[¹⁸F]fluoropropyl)-dihydrotestosterone ([¹⁸F]15), and characterized their in vitro binding, in vivo biodistribution, and performed blocking studies in mature androgen deprived male rats.

METHODS

We synthesized [¹⁸F]7 and [¹⁸F]15. In vitro binding to recombinant rat AR ligand binding domain protein was determined using a competitive radiometric ligand-binding assay with the high-affinity synthetic androgen [17α-methyl-³H]-methyltrienolone ([³H]R1881). In vivo biodistribution was performed in mature male rats treated with diethylstilbestrol (chemical castration). A blocking study was performed by co-administration of dihydrotestosterone (36 µg/animal).

RESULTS

7α-(3-Fluoropropyl)-testosterone (7) and 7α-(3-fluoropropyl)-dihydrotestosterone (15) showed competitive binding to recombinant rat AR ligand binding domain protein. The IC₅₀ value of 15 (13.0 ± 3.3 nM) was higher than 7 (47.8 ± 10.0 nM). In contrast to the AR binding affinity, the ventral prostate uptake of [¹⁸F]7 and [¹⁸F]15 at 2 h post-injection was similar (0.07 % injected dose/g of tissue). A blocking study indicated that specific binding of [¹⁸F]15 is observed in the ventral prostate. [¹⁸F]7 and [¹⁸F]15 showed moderate levels of bone uptake, which indicates moderate metabolic de-fluorination in rodents.

CONCLUSION

[¹⁸F]15 is better than [¹⁸F]7 in terms of radiochemical yield, in vitro binding affinity, prostate specific binding and stability against in vivo metabolic de-fluorination. However, the net uptake level of [¹⁸F]15 in prostate might be insufficient for in vivo visualization. Although [¹⁸F]7 and [¹⁸F]15 improved in vivo stability against de-fluorination, other basic characterization data in rodents were not superior to the current standard tracer 16β-[¹⁸F]fluoro-5α-dihydrotestosterone. It is also revealed that the shorter side chain length of 7α-[¹⁸F]fluoromethyl-dihydrotestosterone is superior to the longer three carbon chain in [¹⁸F]15, in terms of net prostate uptake and in vivo metabolic stability.

Coumestrol Inhibits Proliferation and Migration of Prostate Cancer Cells by Regulating AKT, ERK1/2, and JNK MAPK Cell Signaling Cascades

Coumestrol is the one of the major phytoestrogens which is abundant in soybeans, legumes, brussel sprouts, and spinach. The beneficial effects of coumestrol are well known in various biological processes including; neuroprotective effects on the nervous system, function of the female reproductive system, anti-bacterial properties, and anti-cancer effects. Although the anti-tumor activity of coumestrol has been demonstrated for ovarian, breast, lung, and cervical cancers, little is known of its effects on prostate cancer. Therefore, in the present study, we investigated the chemotherapeutic effects of coumestrol on two prostate cancer cell lines, PC3 and LNCaP. Our results showed that coumestrol decreased proliferation and migration and induced apoptosis in both PC3 and LNCaP cells. Moreover, effects of coumestrol on cell signaling pathways were investigated and it increased phosphorylation of ERK1/2, JNK, P90RSK, and P53 proteins in a dose- and time-dependent manner whereas phosphorylation of AKT was reduced by coumestrol under the same conditions for culture of PC3 and LNCaP cells. In addition, mitochondrial dysfunction was induced by coumestrol as evidenced by a significant loss of mitochondrial membrane potential. Furthermore, cleavage of caspase-3 and caspase-9, the apoptotic proteins associated with mitochondria, also changed in response to coumestrol. Coumestrol also caused mitochondrial dysfunction resulting in an increase in ROS production in PC3 and LNCaP cells. These results suggest that coumestrol can inhibit progression of prostate cancer and may be a novel chemotherapeutic agent for treatment of prostate cancer via effects mediated via the PI3K/AKT and ERK1/2 and JNK MAPK cell signaling pathways. J. Cell. Physiol. 232: 862-871, 2017. © 2016 Wiley Periodicals, Inc.