Time from definitive therapy to onset of metastatic disease predicts outcomes in men with metastatic hormone sensitive prostate cancer.

PURPOSE: Contemporary treatment for metastatic hormone sensitive prostate cancer (mHSPC) includes androgen deprivation therapy (ADT) plus abiraterone or docetaxel. While these intensified regimens have improved efficacy, they are also associated with increased cost and toxicities. Not all men with mHSPC may be candidates for these intensified regimens, yet there are no clinical models or biomarkers used to optimize treatment selection. Herein, we hypothesized that longer time from prior definitive therapy (DT), either radical prostatectomy, definitive radiotherapy, or both, to onset of metastatic disease is associated with improved survival outcomes in men with newly diagnosed mHSPC. METHODS: This multicenter retrospective study included men initiating systemic therapy with ADT for new mHSPC. Kaplan-Meier and COX proportional hazard models assessed time to metastatic castration-resistant prostate cancer (mCRPC) and overall survival (OS) by receipt of prior DT. RESULTS: Of the 253 men with new mHSPC, 115 (45%) had received prior DT. In a multivariate analysis, increasing years from DT to the start of ADT was an independent predictor of time to mCRPC (per year: hazard ratio 0.91 95% confidence interval 0.84-0.99, P = 0.020) and improved OS (per year: hazard ratio 0.87, 95% confidence interval 0.74-0.99, P = 0.0025) in patients with new mHSPC, and may assist with risk stratification in these patients at time of mHSPC. CONCLUSION: Time from DT to start of ADT is an independent predictor of time to mCRPC and OS in men with new mHSPC, and may assist with risk stratification of these patients for systemic therapy selection.

CYP17 inhibitors in prostate cancer: latest evidence and clinical potential.

Since androgen signaling plays a pivotal role in the proliferation and metastasis of prostate cancer, androgen deprivation therapy (ADT) or castration therapy is considered the backbone of treatment for newly diagnosed metastatic prostate cancer. However, almost all men experience disease progression on ADT to a state known as metastatic castration-resistant prostate cancer (mCRPC), which continues to be driven by intratumoral androgen synthesis or androgen receptor signaling. Hence, the extragonadal ablation of androgen synthesis from pregnane precursors holds much promise. An inhibitor of cytochrome P450 17α-hydroxy/17,20-lyase (CYP17) enzymes, abiraterone acetate, has already been approved for men with mCRPC. Newer CYP17 inhibitors continue to be developed which are either more selective or have concomitant inhibitory actions on AR signaling. These include VT-464, orteronel, and galeterone. Herein, we focus on the molecular mechanism of action, efficacy, latest evidence, and clinical potential of CYP17 inhibitors in prostate cancer.

Inherited Variants in SULT1E1 and Response to Abiraterone Acetate by Men with Metastatic Castration Refractory Prostate Cancer.

PURPOSE: Germline variations in genes involved in androgen biosynthesis and metabolic pathways may predict the response to abiraterone acetate in men with metastatic, castration refractory prostate cancer. The variations may serve as prognostic and predictive biomarkers to allow for more individualized therapy. MATERIALS AND METHODS: We evaluated 832 single nucleotide polymorphisms from the OmniExpress genotyping platform (Illumina®) in the boundaries of 61 candidate genes reported to be involved in the androgen metabolic pathway. The purpose was to investigate them for an association with time to treatment failure in 68 white men with metastatic, castration refractory prostate cancer undergoing treatment with abiraterone acetate. Cox proportional hazard analysis was used with Gleason score, age, level of alkaline phosphatase and prostate specific antigen at treatment initiation as covariates. Each single nucleotide polymorphism was assessed using an allele carriage genetic model in which carriage of 1 or more minor alleles contributes to increased risk. Subset analyses were done to determine whether metastasis site, or prior treatment with ketoconazole or docetaxel would interact with the single nucleotide polymorphisms investigated. RESULTS: Six single nucleotide polymorphisms in the estrogen sulfotransferase gene SULT1E1 were associated with time to treatment failure on abiraterone acetate therapy after false discovery rate (q value) correction for multiple testing while controlling for Gleason score, age, level of alkaline phosphatase and prostate specific antigen at treatment initiation (q <0.05). CONCLUSIONS: Single nucleotide polymorphisms in SULT1E1 were significantly associated with time to treatment failure in men on abiraterone acetate therapy. The single nucleotide polymorphisms may serve as predictive markers for treatment with abiraterone acetate.

Impaired cognitive ability and anxiety-like behavior following acute seizures in the Theiler's virus model of temporal lobe epilepsy.

Viral infection of the CNS can result in encephalitis and acute seizures, increasing the risk for later-life epilepsy. We have previously characterized a novel animal model of temporal lobe epilepsy that recapitulates key sequela in the development of epilepsy following viral infection. C57BL/6J mice inoculated with the Daniel's strain of Theiler's Murine Encephalomyelitis Virus (TMEV; 3×10(5) PFU, i.c.) display acute limbic seizures that secondarily generalize. A majority of acutely seized animals develop spontaneous seizures weeks to months later. As part of our investigation, we sought to assess behavioral comorbidity following TMEV inoculation. Anxiety, depression, cognitive impairment, and certain psychoses are diagnosed in persons with epilepsy at rates far more frequent than in the general population. We used a battery of behavioral tests to assess anxiety, depression, cognitive impairment, and general health in acutely seized animals inoculated with TMEV and compared behavioral outcomes against age-matched controls receiving a sham injection. We determined that TMEV-seized animals are less likely to move through the exposed center of an open field and are less likely to enter into the lighted half of a light/dark box; both behaviors may be indicative of anxiety-like behavior. TMEV-seized animals also display early and persistent reductions in novel object exploration during novel object place tasks and do not improve in their ability to find a hidden escape platform in Morris water maze testing, indicative of impairment in episodic and spatial memory, respectively. Cresyl violet staining at 35 and 250 days after injection reveals bilateral reductions in hippocampal area, with extensive sclerosis of CA1 evident bilaterally along the rostral-caudal axis. Early and persistent behavioral changes in the TMEV model provide surrogate markers for assessing disease progression as well as endpoints in screening for the efficacy of novel compounds to manage both seizure burden and comorbid conditions.

Pulmonary oedema producing toxin from Mesobuthus tamulus venom augments cardio-respiratory reflexes through B2 kinin receptors.

The current study was undertaken to compare the effects of pulmonary oedema producing toxin (PO-Tx) isolated from Mesobuthus tamulus venom on cardio-respiratory reflexes with exogenously administered bradykinin (BK) and to delineate the type of BK receptors mediating these responses. Jugular venous injection of phenyldiguanide (PDG) in anaesthetized rats produced reflex bradycardia, hypotension and apnoea. The PDG-induced reflex was augmented (two folds) by PO-Tx. The pulmonary water content in PO-Tx treated group was also increased. The PO-Tx-induced reflex changes as well as pulmonary oedema were blocked by-Hoe-140 implicating the involvement of B2 kinin receptors. Exogenous BK also produced augmentation (two folds) of the PDG-induced reflexes and increased the pulmonary water content. The BK-induced augmentation was blocked by pre-treatment with des-Arg10 Hoe 140 (a B1 receptor antagonist) and Hoe 140 (B2 receptor antagonist). However, these antagonists did not prevent the development of BK-induced pulmonary oedema. Present results indicate that PO-Tx augmented the PDG-induced reflex responses similar to BK and the PO-Tx induced augmentation of reflexes is mediated through B2 receptors.

Rapid loss of efficacy to the antiseizure drugs lamotrigine and carbamazepine: a novel experimental model of pharmacoresistant epilepsy.

PURPOSE: Kindling is a well-established model of secondarily generalized partial seizures that is widely employed in the search for novel antiseizure drugs. During the kindling and postkindling acquisition phase, an active process of neuronal remodeling occurs. We tested the hypothesis that exposure to the voltage-gated sodium channel blockers lamotrigine (LTG) and carbamazepine (CBZ) during the period of active remodeling will lead to a diminished therapeutic effect. METHODS: Two days after the last kindling stimulation, fully kindled rats were randomized to receive either 0.5% methyl cellulose (MC), LTG (30 mg/kg), or CBZ (40 mg/kg). The effect of LTG and CBZ on behavioral seizure severity and electrographic afterdischarge duration (ADD) was recorded. One week after this treatment, rats in both groups were rechallenged with LTG 30 or CBZ 40 mg/kg and their seizure score and ADD recorded. In vitro efficacy of LTG on neuronal action potentials was also evaluated using whole cell current clamp recording in hippocampal brain slices obtained from kindled control rats, LTG-sensitive kindled rats, and LTG-resistant kindled rats. KEY FINDINGS: When acutely administered 48 h after the last kindling stimulation, LTG and CBZ blocked the expression of behavioral seizures and reduced the ADD. In contrast, a second challenge dose of LTG or CBZ administered after a 7-day "no drug, no stimulation" period did not result in reduction of either the seizure score or the ADD. Interestingly, the potassium channel opener, ezogabine, also known as retigabine (EZG; 40 mg/kg), blocked the expression of behavioral seizures at both time points evaluated (i.e., 2 days and 9 days after last stimulation). In vivo resistance to LTG was associated with a similar reduction in the ability of LTG to limit action potential firing in CA1 neurons. LTG (50 µm) significantly decreased the number of action potentials generated by a depolarizing current pulse in neurons recorded from slices obtained from kindled control and LTG-sensitive rats, but not in slices obtained from LTG-resistant rats. SIGNIFICANCE: Collectively, results obtained from both in vivo and in vitro studies demonstrate that even a single exposure to the sodium channel blockers LTG, or CBZ, during the postkindling remodeling phase leads to an altered pharmacologic response to these two ASDs, but not to EZG. The LTG- and CBZ-resistant amygdala kindled rats may serve as a useful model of therapy-resistant epilepsy.

A new derivative of valproic acid amide possesses a broad-spectrum antiseizure profile and unique activity against status epilepticus and organophosphate neuronal damage.

PURPOSE: sec-Butyl-propylacetamide (SPD) is a one-carbon homolog of valnoctamide (VCD), a central nervous system (CNS)-active amide derivative of valproic acid (VPA) currently in phase II clinical trials. The study reported herein evaluated the anticonvulsant activity of SPD in a battery of rodent seizure and epilepsy models and assessed its efficacy in rat and guinea pig models of status epilepticus (SE) and neuroprotection in an organotypic hippocampal slice model of excitotoxic cell death. METHODS: The anticonvulsant activity of SPD was evaluated in several rodent seizure and epilepsy models, including maximal electroshock (MES), 6-Hz psychomotor; subcutaneous (s.c.) metrazol-, s.c. picrotoxin, s.c. bicuculline, and audiogenic, corneal, and hippocampal kindled seizures following intraperitoneal administration. Results obtained with SPD are discussed in relationship to those obtained with VPA and VCD. SPD was also evaluated for its ability to block benzodiazepine-resistant SE induced by pilocarpine (rats) and soman (rats and guinea pigs) following intraperitoneal administration. SPD was tested for its ability to block excitotoxic cell death induced by the glutamate agonists N-methyl-D-aspartate (NMDA) and kainic acid (KA) using organotypic hippocampal slices and SE-induced hippocampal cell death using FluoroJade B staining. The cognitive function of SPD-treated rats that were protected against pilocarpine-induced convulsive SE was examined 10-14 days post-SE using the Morris water maze (MWM). The relationship between the pharmacokinetic profile of SPD and its efficacy against soman-induced SE was evaluated in two parallel studies following SPD (60 mg/kg, i.p.) administration in the soman SE rat model. KEY FINDINGS: SPD was highly effective and displayed a wide protective index (PI = median neurotoxic dose/median effective dose [TD(50)/ED(50)]) in the standardized seizure and epilepsy models employed. The wide PI values of SPD demonstrate that it is effective at doses well below those that produce behavioral impairment. Unlike VCD, SPD also displayed anticonvulsant activity in the rat pilocarpine model of SE. Thirty minutes after the induction of SE, the calculated rat ED(50) for SPD against convulsive SE in this model was 84 mg/kg. SPD was not neuroprotective in the organotypic hippocampal slice preparation; however, it did display hippocampal neuroprotection in both SE models and cognitive sparing in the MWM, which was associated with its antiseizure effect against pilocarpine-induced SE. When administered 20 and 40 min after SE onset, SPD (100-174 mg/kg) produced long-lasting efficacy (e.g., 4-8 h) against soman-induced convulsive and electrographic SE in both rats and guinea pigs. SPD ED(50) values in guinea pigs were 67 and 92 mg/kg when administered at SE onset or 40 min after SE onset, respectively. Assuming linear pharmacokinetics (PK), the PK-PD (pharmacodynamic) results (rats) suggests that effective SPD plasma levels ranged between 8 and 40 mg/L (20 min after the onset of soman-induced seizures) and 12-50 mg/L (40 min after the onset of soman-induced seizures). The time to peak (t(max)) pharmacodynamic effect (PD-t(max)) occurred after the PK-t(max), suggesting that SPD undergoes slow distribution to extraplasmatic sites, which is likely responsible for antiseizure activity of SPD. SIGNIFICANCE: The results demonstrate that SPD is a broad-spectrum antiseizure compound that blocks SE induced by pilocarpine and soman and affords in vivo neuroprotection that is associated with cognitive sparing. Its activity against SE is superior to that of diazepam in terms of rapid onset, potency, and its effect on animal mortality and functional improvement.

CGX-1007 prevents excitotoxic cell death via actions at multiple types of NMDA receptors.

Glutamate induced excitotoxic injury through over-activation of N-methyl-D-aspartate receptors (NMDARs) plays a critical role in the development of many neurodegenerative diseases. The present study was undertaken to evaluate the role of CGX-1007 (Conantokin G) as a neuroprotective agent against NMDA-induced excitotoxicity. Conantokin G, a cone snail peptide isolated from Conus geographus is reported to selectively inhibit NR2B containing NMDARs with high specificity and is shown to have potent anticonvulsant and antinociceptive effects. CGX-1007 significantly reduced the excitotoxic cell death induced by NMDA in organotypic hippocampal brain slice cultures in a concentration-dependent manner. In contrast, ifenprodil, another NR2B specific antagonist failed to offer neuroprotection against NMDA-induced excitotoxicity. We further determined that the neuroprotection observed is likely due to the action of CGX-1007 at multiple NMDA receptor subtypes. In a series of electrophysiology experiments, CGX-1007 inhibited NMDA-gated currents in human embryonic kidney (HEK) 293 cells expressing NMDA receptors containing either NR1a/NR2B or NR1a/NR2A subunit combinations. CGX-1007 produced a weak inhibition at NR1a/NR2C receptors, whereas it had no effect on NR1a/NR2D receptors. Further, the inhibition of NMDA receptors by CGX-1007 was voltage-dependent with greater inhibition seen at hyperpolarized membrane potentials. The voltage-dependence of CGX-1007 activity was also observed in recordings of NMDA-gated currents evoked in native receptors expressed in cortical neurons in culture. Based on our results, we conclude that CGX-1007 is a potent neuroprotective agent that acts as an antagonist at both NR2A and NR2B containing receptors.

Cardiac dysrhythmia produced by Mesobuthus tamulus venom involves NO-dependent G-Cyclase signaling pathway.

Role of G-protein coupled pathways in modulating the cardiotoxic effects produced by Indian red scorpion (Mesobuthus tamulus) venom were examined. The isometric contractions of spontaneously beating or paced (3.5 Hz) rat right atrial preparations in vitro were recorded. The cumulative concentration (0.01-3.0 microg/ml)-response of venom on spontaneously beating atria exhibited a marked decrease in rate (by 55%) and an increase in force (by 92%) only at a higher concentration (3.0 microg/ml). The venom-induced decrease in rate and increase in force were sensitive to atropine, N-omega-nitro-L-arginine methylester (NO synthase inhibitor) and methylene blue (guanylyl cyclase inhibitor). Further, nifedipine, a Ca(2+) channel antagonist, blocked the force changes but not the rate changes induced by venom. In the paced atrium, on the other hand, a concentration-dependent decrease in force was observed, and at 3 microg/ml, the decrease was 50%. Pretreatment with nifedipine, but not with methylene blue, significantly attenuated the venom-induced force changes in paced atrium. The observations of this study demonstrate that the venom-induced atrial dysrhythmia is mediated through the muscarinic receptor-dependent NO-G-cyclase cell-signaling pathways.

Bradycardia induced by Mesobuthus tamulus scorpion venom involves muscarinic receptor-G-protein-coupled cell signaling pathways.

Indian red scorpion (Mesobuthus tamulus; MBT) envenomation produces various cardio-respiratory abnormalities including cardiac dysrhythmias. The underlying cell signaling pathways for the cardiac dysrhythmias produced by MBT venom are not known. The present study was therefore conducted to delineate the second messenger signaling pathways involved in MBT venom-induced atrial rhythm changes. The effects of venom and various antagonists were examined on spontaneously beating rat right atrial preparations in vitro. The MBT-venom produced an increase (35%), a decrease (45%) and again an increase (50%) in rate at 0.03, 0.3 and 3.0 microg/ml of venom, respectively. On the other hand, force of contraction exhibited a concentration-dependent rise (up to 40%) at all concentrations of venom. Pretreatment with atropine (0.3 microM) blocked the decrease in atrial rate at 0.3 microg/ml concentration of venom while no such blockade was seen in force of contraction. Submaximal concentration of ACh (0.1 nM) decreased the atrial rate by 25%. In the presence of MBT venom (0.3 microg/ml), ACh-induced fall in atrial rate was enhanced. The venom-induced fall in atrial rate and augmentation of ACh response were blocked by pertussis toxin (PTx; a Gi-inhibitor) or methylene blue (a G-cyclase inhibitor). The results indicate that the decrease in atrial rate produced by venom is mediated muscarinic by receptors via Gi-guanylyl cyclase mediated cell signaling pathways.

Estrogen modulates in vitro atrial bradycardia induced by Indian red scorpion venom via G-protein coupled mechanisms.

Role of estrogen on cardiac dysrhythmia produced by Indian red scorpion (Mesobuthus tamulus) venom was examined using rat right atrial preparations in vitro. In females, the M. tamulus venom produced an increase, a decrease and an increase in rate at 0.03, 0.3 and 3 microg/ml of venom, respectively, producing N-shaped response curve, whereas no such response pattern was observed in males. Force of contraction in females was increased at all the concentrations of the venom, while in males the increase was seen only at 3 microg/ml. Castration of male rats did not alter the venom response to female type, while 'estrogenisation of castrated male rats' (pseudofemales) produced a response similar to females. Tamoxifen reversed the venom-induced responses both in females and pseudofemales. Further in females, the venom action at 0.3 microg/ml was blocked by atropine. Response at this concentration was also blocked by pertussis toxin and methylene blue. Results suggest that the cholinergic component of venom response is modulated by estrogen receptors via G(i)-protein-guanylyl cyclase mechanism.

Effect of Conantokin G on NMDA receptor-mediated spontaneous EPSCs in cultured cortical neurons.

Conantokin G (Con G), derived from the venom of Conus geographus, is the most characterized natural peptide antagonist targeted to N-methyl-D-aspartate (NMDA) receptors. Although Con G is known to bind to the glutamate binding site on the NR2 subunit of the receptor, it is unclear whether it can allosterically modulate the function of the receptor through the glycine binding site on the NR1 subunit. This study was designed to evaluate the action of Con G on NMDA receptor-mediated spontaneous excitatory postsynaptic currents (sEPSCs) and its modulation by glycine in cultured cortical neurons (13-19 days in vitro) using the whole cell patch-clamp technique. Con G inhibited NMDA receptor-mediated sEPSCs in a concentration-dependent manner. Also, the potency of Con G decreased as a function of time in culture. The inhibition of EPSCs observed after application of Con G in the presence of high (10 microM) and nominal (no added) concentrations of glycine was not different at 13 days in vitro (DIV). Furthermore, similar results were obtained with experiments on Con G-induced inhibition of NMDA-evoked whole cell currents. These results indicate that glycine concentrations do not have a direct effect on Con G-induced inhibition of NMDA currents. In addition, age dependency in the action of Con G on cortical neurons in vitro suggests that this model system would be useful in examining the effects of different agonists/antagonists on native synaptic NMDA receptors.