Steroidogenesis in Peripheral and Transition Zones of Human Prostate Cancer Tissue.

The peripheral zone (PZ) and transition zone (TZ) represent about 70% of the human prostate gland with each zone having differential ability to develop prostate cancer. Androgens and their receptor are the primary driving cause of prostate cancer growth and eventually castration-resistant prostate cancer (CRPC). De novo steroidogenesis has been identified as a key mechanism that develops during CRPC. Currently, there is very limited information available on human prostate tissue steroidogenesis. The purpose of the present study was to investigate steroid metabolism in human prostate cancer tissues with comparison between PZ and TZ. Human prostate cancer tumors were procured from the patients who underwent radical prostatectomy without any neoadjuvant therapy. Human prostate homogenates were used to quantify steroid levels intrinsically present in the tissues as well as formed after incubation with 2 µg/mL of 17-hydroxypregnenolone (17-OH-pregnenolone) or progesterone. A Waters Acquity ultraperformance liquid chromatography coupled to a Quattro Premier XE tandem quadrupole mass spectrometer using a C18 column was used to measure thirteen steroids from the classical and backdoor steroidogenesis pathways. The intrinsic prostate tissue steroid levels were similar between PZ and TZ with dehydroepiandrosterone (DHEA), dihydrotestosterone (DHT), pregnenolone and 17-OH-pregnenolone levels higher than the other steroids measured. Interestingly, 5-pregnan-3,20-dione, 5-pregnan-3-ol-20-one, and 5-pregnan-17-ol-3,20-dione formation was significantly higher in both the zones of prostate tissues, whereas, androstenedione, testosterone, DHT, and progesterone levels were significantly lower after 60 min incubation compared to the 0 min control incubations. The incubations with progesterone had a similar outcome with 5-pregnan-3,20-dione and 5-pregnan-3-ol-20-one levels were elevated and the levels of DHT were lower in both PZ and TZ tissues. The net changes in steroid formation after the incubation were more observable with 17-OH-pregnenolone than with progesterone. In our knowledge, this is the first report of comprehensive analyses of intrinsic prostate tissue steroids and precursor-driven steroid metabolism using a sensitive liquid chromatography-mass spectrometry assay. In summary, the PZ and TZ of human prostate exhibited similar steroidogenic ability with distinction in the manner each zone utilizes the steroid precursors to divert the activity towards backdoor pathway through a complex matrix of steroidogenic mechanisms.

Autophagy inhibition improves the chemotherapeutic efficacy of cruciferous vegetable-derived diindolymethane in a murine prostate cancer xenograft model.

Prostate cancer is the second leading cause of cancer-related deaths in men in North America and there is an urgent need for development of more effective therapeutic treatments against this disease. We have recently shown that diindolylmethane (DIM) and several of its halogenated derivatives (ring-DIMs) induce death and protective autophagy in human prostate cancer cells. However, the in vivo efficacy of ring-DIMs and the use of autophagy inhibitors as adjuvant therapy have not yet been studied in vivo. The objective of this study was to determine these effects on tumor growth in nude CD-1 mice bearing bioluminescent androgen-independent PC-3 human prostate cancer cells. We found that chloroquine (CQ) significantly sensitized PC-3 cells to death in the presence of sub-toxic concentrations of DIM or 4,4'-Br2DIM in vitro. Moreover, a combination of DIM (10 mg/kg) and CQ (60 mg/kg), 3× per week, significantly decreased PC-3 tumor growth in vivo after 3 and 4 weeks of treatment. Furthermore, 4,4'-Br2DIM at 10 mg/kg (3× per week) significantly inhibited tumour growth after 4 weeks of treatment. Tissues microarray analysis showed that DIM alone or combined with CQ induced apoptosis marker TUNEL; the combination also significantly inhibited the cell proliferation marker Ki67. In conclusion, we have confirmed that DIM and 4,4'-Br2DIM are effective agents against prostate cancer in vivo and shown that inhibition of autophagy with CQ enhances the anticancer efficacy of DIM. Our results suggest that including selective autophagy inhibitors as adjuvants may improve the efficacy of existing and novel drug therapies against prostate cancer.

Paracrine sonic hedgehog signaling contributes significantly to acquired steroidogenesis in the prostate tumor microenvironment.

Despite the substantial benefit of androgen deprivation therapy (ADT) for metastatic prostate cancer, patients often progress to castration-resistant disease (CRPC) that is more difficult to treat. CRPC is associated with renewed androgen receptor activity in tumor cells and restoration of tumor androgen levels through acquired intratumoral steroidogenesis (AIS). Although prostate cancer (PCa) cells have been shown to have steroidogenic capability in vitro, we previously found that benign prostate stromal cells (PrSCs) can also synthesize testosterone (T) from an adrenal precursor, DHEA, when stimulated with a hedgehog (Hh) pathway agonist, SAG. Here, we show exposure of PrSCs to a different Smoothened (Smo) agonist, Ag1.5, or to conditioned medium from sonic hedgehog overexpressing LNCaP cells induces steroidogenic enzyme expression in PrSCs and significantly increases production of T and its precursor steroids in a Smo-dependent manner from 22-OH-cholesterol substrate. Hh agonist-/ligand-treated PrSCs produced androgens at a rate similar to or greater than that of PCa cell lines. Likewise, primary bone marrow stromal cells became more steroidogenic and produced T under the influence of Smo agonist. Treatment of mice bearing LNCaP xenografts with a Smo antagonist, TAK-441, delayed the onset of CRPC after castration and substantially reduced androgen levels in residual tumors. These outcomes support the idea that stromal cells in ADT-treated primary or metastatic prostate tumors can contribute to AIS as a consequence of a paracrine Hh signaling microenvironment. As such, Smo antagonists may be useful for targeting prostate tumor stromal cell-derived AIS and delaying the onset of CRPC after ADT.

Sex steroid profiles in zebra finches: Effects of reproductive state and domestication.

The zebra finch is a common model organism in neuroscience, endocrinology, and ethology. Zebra finches are generally considered opportunistic breeders, but the extent of their opportunism depends on the predictability of their habitat. This plasticity in the timing of breeding raises the question of how domestication, a process that increases environmental predictability, has affected their reproductive physiology. Here, we compared circulating steroid levels in various "strains" of zebra finches. In Study 1, using radioimmunoassay, we examined circulating testosterone levels in several strains of zebra finches (males and females). Subjects were wild or captive (Captive Wild-Caught, Wild-Derived, or Domesticated). In Study 2, using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we examined circulating sex steroid profiles in wild and domesticated zebra finches (males and females). In Study 1, circulating testosterone levels in males differed across strains. In Study 2, six steroids were detectable in plasma from wild zebra finches (pregnenolone, progesterone, dehydroepiandrosterone (DHEA), testosterone, androsterone, and 5α-dihydrotestosterone (5α-DHT)). Only pregnenolone and progesterone levels changed across reproductive states in wild finches. Compared to wild zebra finches, domesticated zebra finches had elevated levels of circulating pregnenolone, progesterone, DHEA, testosterone, androstenedione, and androsterone. These data suggest that domestication has profoundly altered the endocrinology of this common model organism. These results have implications for interpreting studies of domesticated zebra finches, as well as studies of other domesticated species.

Regulation of local steroidogenesis in the brain and in prostate cancer: lessons learned from interdisciplinary collaboration.

Sex steroids play critical roles in the regulation of the brain and many other organs. Traditionally, researchers have focused on sex steroid signaling that involves travel from the gonads via the circulation to intracellular receptors in target tissues. This classic concept has been challenged, however, by the growing number of cases in which steroids are synthesized locally and act locally within diverse tissues. For example, the brain and prostate carcinoma were previously considered targets of gonadal sex steroids, but under certain circumstances, these tissues can upregulate their steroidogenic potential, particularly when circulating sex steroid concentrations are low. We review some of the similarities and differences between local sex steroid synthesis in the brain and prostate cancer. We also share five lessons that we have learned during the course of our interdisciplinary collaboration, which brought together neuroendocrinologists and cancer biologists. These lessons have important implications for future research in both fields.

Sex steroid profiles and pair-maintenance behavior of captive wild-caught zebra finches (Taeniopygia guttata).

Here, we studied the life-long monogamous zebra finch, to examine the relationship between circulating sex steroid profiles and pair-maintenance behavior in pairs of wild-caught zebra finches (paired in the laboratory for >1 month). We used liquid chromatography-tandem mass spectrometry to examine a total of eight androgens and progestins [pregnenolone, progesterone, dehydroepiandrosterone (DHEA), androstenediol, pregnan-3,17-diol-20-one, androsterone, androstanediol, and testosterone]. In the plasma, only pregnenolone, progesterone, DHEA, and testosterone were above the limit of quantification. Sex steroid profiles were similar between males and females, with only circulating progesterone levels significantly different between the sexes (female > male). Circulating pregnenolone levels were high in both sexes, suggesting that pregnenolone might serve as a circulating prohormone for local steroid synthesis in zebra finches. Furthermore, circulating testosterone levels were extremely low in both sexes. Additionally, we found no correlations between circulating steroid levels and pair-maintenance behavior. Taken together, our data raise several interesting questions about the neuroendocrinology of zebra finches.

Selectively targeting the DNA-binding domain of the androgen receptor as a prospective therapy for prostate cancer.

The androgen receptor (AR) is a transcription factor that has a pivotal role in the occurrence and progression of prostate cancer. The AR is activated by androgens that bind to its ligand-binding domain (LBD), causing the transcription factor to enter the nucleus and interact with genes via its conserved DNA-binding domain (DBD). Treatment for prostate cancer involves reducing androgen production or using anti-androgen drugs to block the interaction of hormones with the AR-LBD. Eventually the disease changes into a castration-resistant form of PCa where LBD mutations render anti-androgens ineffective or where constitutively active AR splice variants, lacking the LBD, become overexpressed. Recently, we identified a surfaced exposed pocket on the AR-DBD as an alternative drug-target site for AR inhibition. Here, we demonstrate that small molecules designed to selectively bind the pocket effectively block transcriptional activity of full-length and splice variant AR forms at low to sub-micromolar concentrations. The inhibition is lost when residues involved in drug interactions are mutated. Furthermore, the compounds did not impede nuclear localization of the AR and blocked interactions with chromatin, indicating the interference of DNA binding with the nuclear form of the transcription factor. Finally, we demonstrate the inhibition of gene expression and tumor volume in mouse xenografts. Our results indicate that the AR-DBD has a surface site that can be targeted to inhibit all forms of the AR, including enzalutamide-resistant and constitutively active splice variants and thus may serve as a potential avenue for the treatment of recurrent and metastatic prostate cancer.

The effect of pomegranate fruit extract on testosterone-induced BPH in rats.

BACKGROUND: Benign prostatic hyperplasia (BPH) affects many men after the age of 50 years. Inflammation and oxidative stress along with apoptotic changes are thought to play an important role in the pathology of BPH. Pomegranate contains a variety of polyphenolic compounds that have been studied in a medley of diseases for their anti-oxidant, anti-inflammatory and pro-apoptotic properties. Therefore, this study examined the effect of Pomegranate Fruit Extract (PFE) on the development of BPH using a testosterone-induced BPH model in rats. METHODS: A total of 48 rats were randomly divided into six groups of eight, one group served as the control, BPH was induced by testosterone 3 mg/kg S.C. daily in four groups, three of them received PFE by oral gavage daily at doses of 25, 50, and 100 mg/kg respectively, while one group received PFE at a dose of 50 mg/kg without induction of BPH. RESULTS: PFE at a dose of 100 mg/kg was the most effective in decreasing testosterone-induced increase in prostate weight, prostate weight/body weight ratio, and PAP levels by 30.8%, 55%, and 68% respectively and in preventing the accompanying histological changes. In the BPH model, testosterone significantly decreased GSH, SOD, and CAT to 0.45, 0.64, and 0.88 of the control group values respectively, and significantly increased MDA by >6-fold. In combination with testosterone, PFE dosed at 100 mg/kg significantly increased GSH, SOD, and CAT to 0.83, 0.92, and 0.93 of the control group values respectively, whereas MDA was significantly decreased by 72% compared with the testosterone treated group. In addition to this, at the range of doses studied, PFE lowered COX-II, iNOS, Ki-67 expression, and increased apoptotic index. CONCLUSION: The current findings elucidate the effectiveness of PFE in preventing testosterone-induced BPH in rats. This could be attributed, at least partly, to its anti-oxidant, anti-inflammatory, and pro-apoptotic properties.

A low carbohydrate, high protein diet combined with celecoxib markedly reduces metastasis.

We recently demonstrated that both murine and human carcinomas grow significantly slower in mice on low carbohydrate (CHO), high protein diets than on isocaloric Western diets and that a further reduction in tumor growth rates occur when the low CHO diets are combined with the cyclooxygenase-2 inhibitor, celecoxib. Following upon these studies, we asked herein what effect low CHO, high protein diets, with or without celecoxib, might have on tumor metastasis. In the highly metastatic 4T1 mouse mammary tumor model, a 15% CHO, high protein diet supplemented with celecoxib (1 g/kg chow) markedly reduced lung metastases. Moreover, in longer-term studies using male Transgenic Adenocarcinoma of the Mouse Prostate mice, which are predisposed to metastatic prostate cancer, the 15% CHO diet, with and without celecoxib (0.3 g/kg chow), gave the lowest incidence of metastases, but a more moderate 25% CHO diet containing celecoxib led to the best survival. Metabolic studies with 4T1 tumors suggested that the low CHO, high protein diets may be forcing tumors to become dependent on amino acid catabolism for survival/growth. Taken together, our results suggest that a combination of a low CHO, high protein diet with celecoxib substantially reduces metastasis.

Exosomes as biomarker enriched microvesicles: characterization of exosomal proteins derived from a panel of prostate cell lines with distinct AR phenotypes.

Prostate cancer is the leading type of cancer diagnosed in men. In 2010, ~217,730 new cases of prostate cancer were reported in the United States. Prompt diagnosis of the disease can substantially improve its clinical outcome. Improving capability for early detection, as well as developing new therapeutic targets in advanced disease are research priorities that will ultimately lead to better patient survival. Eukaryotic cells secrete proteins via distinct regulated mechanisms which are either ER/Golgi dependent or microvesicle mediated. The release of microvesicles has been shown to provide a novel mechanism for intercellular communication. Exosomes are nanometer sized cup-shaped membrane vesicles which are secreted from normal and cancerous cells. They are present in various biological fluids and are rich in characteristic proteins. Exosomes may thus have potential both in facilitating early diagnosis via less invasive procedures or be candidates for novel therapeutic approaches for castration resistance prostate cancer. Because exosomes have been shown previously to have a role in cell-cell communication in the local tumor microenvironment, conferring activation of numerous survival mechanisms, we characterized constitutive lipids, cholesterol and proteins from exosomes derived from six prostate cell lines and tracked their uptake in both cancerous and benign prostate cell lines respectively. Our comprehensive proteomic and lipidomic analysis of prostate derived exosomes could provide insight for future work on both biomarker and therapeutic targets for the treatment of prostate cancer.

Identification of human cytochrome P450 enzymes involved in the hepatic and intestinal biotransformation of 20(S)-protopanaxadiol.

20(S)-Protopanaxadiol (aPPD), a ginseng sapogenin, has been shown to be a promising anti-cancer compound and anti-depressant agent. Although the bacterial biotransformation of ginsenosides has been studied thoroughly, few have reported on the cytochrome P450 (P450) mediated metabolism of aPPD. Taken orally, aPPD must first undergo absorption and metabolism in the intestine before further metabolism in the liver. The present study investigated the comparative biotransformation profile of aPPD in human intestinal microsomes (HIM) and human liver microsomes (HLM) and characterized the human P450 enzymes involved in aPPD metabolism. Three major monooxygenated metabolites and five minor dioxygenated metabolites were identified as the predominant products in aPPD incubations with HIM and HLM using liquid chromatography-mass spectrometry. Reaction phenotyping studies were performed with a panel of specific P450 chemical inhibitors, antibody inhibition and human recombinant P450 enzymes. Ketoconazole, a CYP3A inhibitor, blocked the formation of oxygenated metabolites of aPPD in both HIM and HLM in a concentration dependent manner. Among the human recombinant P450 enzymes assayed, CYP3A4 exhibited the highest activity towards aPPD oxidative metabolite formation, followed by CYP3A5. In summary, the results have shown that aPPD is extensively metabolized by HIM and the metabolite profile following in vitro incubations is similar in HIM and HLM. CYP3A4 and CYP3A5 isoforms are the predominant enzymes responsible for oxygenation of aPPD in HIM and HLM. The characterization of aPPD as a CYP3A substrate may facilitate better prediction of drug-herb interactions when aPPD is taken concomitantly with other therapeutic agents.

Age-dependent alterations of the kynurenine pathway in the YAC128 mouse model of Huntington disease.

Indoleamine 2,3 dioxygenase (Ido1), the first and rate-limiting enzyme of the kynurenine pathway (KP), is a striatally enriched gene with increased expression levels in the YAC128 mouse model of Huntington disease (HD). Our objective in this study was to delineate age-related KP alterations in this model. Three enzymes potentially catalyze the first step of the KP; Ido1 and Indoleamine 2,3 dioxygenase-2 were highly expressed in the striatum and Tryptophan 2,3 dioxygenase (Tdo2) in the cerebellum. During development, Ido1 mRNA expression is dynamically regulated and chronically up-regulated in YAC128 mice. Kynurenine (Kyn) to tryptophan (Trp) ratio, a measure of activity in the first step of the KP, was elevated in YAC128 striatum, but no change in Tdo2 mRNA levels or Kyn to Trp ratio was detected in the cerebellum. Ido1 induction was coincident with Trp depletion at 3 months and Kyn accumulation at 12 months of age in striatum. Changes in downstream KP metabolites of YAC128 mice generally followed a biphasic pattern with neurotoxic metabolites reduced at 3 months and increased at 12 months of age. Striatally specific induction of Ido1 and downstream KP alterations suggest involvement in HD pathogenesis, and should be taken into account in future therapeutic developments for HD.

Pharmacokinetics and pharmacodynamics of Rh2 and aPPD ginsenosides in prostate cancer: a drug interaction perspective.

Ginsenoside Rh2 and its aglycon (aPPD) are one of the major metabolites from Panax ginseng. Preclinical studies suggest that Rh2 and aPPD have antitumor effects in prostate cancer (PCa). Our aims in this review are (1) to describe the pharmacokinetic (PK) properties of Rh2 and aPPD ginsenosides; 2) to provide an overview of the preclinical findings on the use of Rh2 and aPPD in the treatment of PCa; and (3) to highlight the mechanisms of its PK and pharmacodynamic (PD) drug interactions. Increasing evidence points to the potential efficacy of Rh2 or aPPD for PCa treatment. Based on the laboratory studies, Rh2 or aPPD combinations revealed an additive or synergistic interaction or enhanced sensitivity of anticancer drugs toward PCa. This review reveals that enhanced anticancer activities were demonstrated in preclinical studies through interactions of Rh2 and/or aPPD with the proteins related to PK (e.g., cytochrome P450 enzymes, transporters) or PD of the other anticancer drugs or PCa signaling pathways. In conclusion, combining Rh2 or aPPD with anti-prostate cancer drugs leads to PK or PD interactions which could facilitate either therapeutically beneficial or toxic effects.

Effect of Dexamethasone on Abiraterone Pharmacokinetics in Mice: Determined by LC/MS Analysis.

Background: Abiraterone acetate is a cytochrome P450 17A1 (CYP17A1) inhibitor that is indicated for use in both castration-resistant and castration-sensitive prostate cancer patients. To manage the mineralocorticoid effects of CYP17A1 inhibition, a glucocorticoid such as dexamethasone is co-administered with abiraterone. The goal of the present study was to understand the effect of dexamethasone on the disposition of abiraterone. Methods: Adult male CD-1 mice were treated with either dexamethasone (80 mg/kg/day) or vehicle for three consecutive days, followed by the administration of a single dose of abiraterone acetate (180 mg/kg) as an oral gavage. Blood samples were collected by tail bleeding at timepoints between 0 to 24 h. Subsequently, abiraterone was extracted from the mouse serum using a neutral pH condition and serum abiraterone levels were determined using a liquid chromatography-mass spectrometry assay. Results: Our results demonstrated that dexamethasone lowered the maximum plasma concentration and area under the curve parameters by approximately five- and ten-fold, respectively. Similar effects were also observed on the plasma half-life and oral clearance parameters. This is the first report of dexamethasone effect on abiraterone disposition in vivo. Conclusions: We conclude that dexamethasone has the potential to reduce the plasma abiraterone level and thus compromise its CYP17A1 inhibitory ability in the procancerous androgen biosynthesis pathway. Thus, use of a higher abiraterone dose may be warranted when used alongside dexamethasone.

Extracellular vesicles from biological fluids as potential markers in castration resistant prostate cancer.

PURPOSE: Extracellular vesicles (EV) secreted from cancer cells are present in various biological fluids, carrying distinctly different cellular components compared to normal cells, and have great potential to be used as markers for disease initiation, progression, and response to treatment. This under-utilised tool provides insights into a better understanding of prostate cancer. METHODS: EV from serum and urine of healthy men and castration-resistant prostate cancer (CRPC) patients were isolated and characterised by transmission electron microscopy, particle size analysis, and western blot. Proteomic and cholesterol liquid chromatography-mass spectrometry (LC-MS) analyses were conducted. RESULTS: There was a successful enrichment of small EV/exosomes isolated from serum and urine. EV derived from biological fluids of CRPC patients had significant differences in composition when compared with those from healthy controls. Analysis of matched serum and urine samples from six prostate cancer patients revealed specific EV proteins common in both types of biological fluid for each patient. CONCLUSION: Some of the EV proteins identified from our analyses have potential to be used as CRPC markers. These markers may depict a pattern in cancer progression through non-invasive sample collection.

Semaphorin 3C promotes de novo steroidogenesis in prostate cancer cells.

Intratumoral androgen biosynthesis contributes to castration-resistant prostate cancer progression in patients treated with androgen deprivation therapy. The molecular mechanisms by which castration-resistant prostate cancer acquires the capacity for androgen biosynthesis to bypass androgen deprivation therapy are not entirely known. Here, we show that semaphorin 3C, a secreted signaling protein that is highly expressed in castration-resistant prostate cancer, can promote steroidogenesis by altering the expression profile of key steroidogenic enzymes. Semaphorin 3C not only upregulates enzymes required for androgen synthesis from dehydroepiandrosterone or de novo from cholesterol but also simultaneously downregulates enzymes involved in the androgen inactivation pathway. These changes in gene expression correlate with increased production of androgens induced by semaphorin 3C in prostate cancer model cells. Moreover, semaphorin 3C upregulates androgen synthesis in LNCaP cell-derived xenograft tumors, likely contributing to the enhanced in vivo tumor growth rate post castration. Furthermore, semaphorin 3C activates sterol regulatory element-binding protein, a transcription factor that upregulates enzymes involved in the synthesis of cholesterol, a sole precursor for de novo steroidogenesis. The ability of semaphorin 3C to promote intratumoral androgen synthesis may be a key mechanism contributing to the reactivation of the androgen receptor pathway in castration-resistant prostate cancer, conferring continued growth under androgen deprivation therapy. These findings identify semaphorin 3C as a potential therapeutic target for suppressing intratumoral steroidogenesis.

Cytochrome P450 3A-mediated microsomal biotransformation of 1α,25-dihydroxyvitamin D3 in mouse and human liver: drug-related induction and inhibition of catabolism.

The biological activities of vitamin D(3) are exerted through the dihydroxy metabolite of vitamin D(3) [1α,25(OH)(2)D(3)]. Hepatic biotransformation of 1α,25(OH)(2)D(3) by cytochrome P450 (P450) enzymes could be an important determinant of bioavailability in serum and tissues. In the present study, we investigated the comparative biotransformation of 1α,25(OH)(2)D(3) in mouse and human liver microsomes and determined the effects of commonly used drugs on the catabolism of 1α,25(OH)(2)D(3). Severe symptoms of vitamin D deficiency have historically been observed in patients who received dexamethasone. To compare the effects of clinically important glucocorticoids with hepatic biotransformation of 1α,25(OH)(2)D(3), adult male CD-1 mice were given intraperitoneal injections of either vehicle (50% ethanol), dexamethasone (80 mg/kg per day), or prednisone (80 mg/kg per day) for three consecutive days. Hydroxy metabolite formation pattern and the extent of substrate depletion were similar in mouse liver microsomes (MLM) from vehicle- or prednisone-treated mice, whereas treatment with dexamethasone led to the emergence of additional metabolites and increased substrate depletion, as determined by liquid chromatography/mass spectrometry. The metabolite formation profile in vehicle-treated mice was different from that of human liver microsomes (HLM). Selective P450 chemical inhibitors have demonstrated that CYP3A isoforms are responsible for the microsomal biotransformation of 1α,25(OH)(2)D(3) in MLM. Coincubation of 1α,25(OH)(2)D(3) with commonly used drugs led to approximately 60 to 100% inhibition of CYP3A4-mediated catabolism of 1α,25-(OH)(2)D(3) in HLM. A species-based difference was identified between CYP3A-mediated hepatic microsomal metabolism of 1α,25(OH)(2)D(3) in humans and mice. We have shown that the clinical importance of glucocorticoids differentially modulates catabolism of active vitamin D(3) and that commonly used drugs could affect vitamin D homeostasis.

A novel oral dosage formulation of the ginsenoside aglycone protopanaxadiol exhibits therapeutic activity against a hormone-insensitive model of prostate cancer.

This study focuses on determining the pharmacokinetics, biodistribution, and efficacy of the ginsenoside aglycone protopanaxadiol (aPPD) administered as a single agent in a novel oral dosage formulation. To obtain these data and to characterize the stability of aPPD, appropriate analytical assay development was carried out. The solubility and stability of aPPD were determined, and the compound was formulated for oral gavage. aPPD levels in blood and tissues following oral administration to nu/nu nude mice were determined using liquid chromatography-mass spectrometry/mass spectrometry. The efficacy of aPPD was determined upon oral administration to nu/nu nude mice bearing PC-3 human prostate cancer xenograft tumors. Immunohistochemical analysis of tumor tissues was performed to establish apoptotic indices and Ki-67 expression as markers of proliferation. The maximum solubility of aPPD in ethanol was 68.4 mg/ml. aPPD administered at a dose of 70 mg/kg yielded a T(max) of approximately 40 min and a C(max) value of 3.9 ± 1.4 µg/ml, and no toxicity was observed. aPPD accumulated largely in the stomach and small intestine and was also present in the brain. This dose engendered a significant delay in PC-3 tumor growth, an increase in apoptotic index, and a decrease in Ki-67 levels. We have shown that aPPD is a stable compound that can be formulated for oral gavage. Pharmacokinetic studies demonstrate the ability of this compound to be absorbed after oral administration. Future studies will assess the activity and pharmacokinetics of aPPD when administered in combination with standard chemotherapy.