Multi-drug loaded micelles delivering chemotherapy and targeted therapies directed against HSP90 and the PI3K/AKT/mTOR pathway in prostate cancer.

BACKGROUND: Advanced prostate cancers that are resistant to all current therapies create a need for new therapeutic strategies. One recent innovative approach to cancer therapy is the simultaneous use of multiple FDA-approved drugs to target multiple pathways. A challenge for this approach is caused by the different solubility requirements of each individual drug, resulting in the need for a drug vehicle that is non-toxic and capable of carrying multiple water-insoluble antitumor drugs. Micelles have recently been shown to be new candidate drug solubilizers for anti cancer therapy. METHODS: This study set out to examine the potential use of multi-drug loaded micelles for prostate cancer treatment in preclinical models including cell line and mouse models for prostate cancers with Pten deletions. Specifically antimitotic agent docetaxel, mTOR inhibitor rapamycin, and HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin were incorporated into the micelle system (DR17) and tested for antitumor efficacy. RESULTS: In vitro growth inhibition of prostate cancer cells was greater when all three drugs were used in combination compared to each individual drug, and packaging the drugs into micelles enhanced the cytotoxic effects. At the molecular level DR17 targeted simultaneously several molecular signaling axes important in prostate cancer including androgen receptor, mTOR, and PI3K/AKT. In a mouse genetic model of prostate cancer, DR17 treatment decreased prostate weight, which was achieved by both increasing caspase-dependent cell death and decreasing cell proliferation. Similar effects were also observed when DR17 was administered to nude mice bearing prostate cancer cells xenografts. CONCLUSION: These results suggest that combining these three cancer drugs in multi-drug loaded micelles may be a promising strategy for prostate cancer therapy.

Ornithine Decarboxylase Activity Is Required for Prostatic Budding in the Developing Mouse Prostate.

The prostate is a male accessory sex gland that produces secretions in seminal fluid to facilitate fertilization. Prostate secretory function is dependent on androgens, although the mechanism by which androgens exert their effects is still unclear. Polyamines are small cationic molecules that play pivotal roles in DNA transcription, translation and gene regulation. The rate-limiting enzyme in polyamine biosynthesis is ornithine decarboxylase, which is encoded by the gene Odc1. Ornithine decarboxylase mRNA decreases in the prostate upon castration and increases upon administration of androgens. Furthermore, testosterone administered to castrated male mice restores prostate secretory activity, whereas administering testosterone and the ornithine decarboxylase inhibitor D,L-α-difluromethylornithine (DFMO) to castrated males does not restore prostate secretory activity, suggesting that polyamines are required for androgens to exert their effects. To date, no one has examined polyamines in prostate development, which is also androgen dependent. In this study, we showed that ornithine decarboxylase protein was expressed in the epithelium of the ventral, dorsolateral and anterior lobes of the adult mouse prostate. Ornithine decarboxylase protein was also expressed in the urogenital sinus (UGS) epithelium of the male and female embryo prior to prostate development, and expression continued in prostatic epithelial buds as they emerged from the UGS. Inhibiting ornithine decarboxylase using DFMO in UGS organ culture blocked the induction of prostatic buds by androgens, and significantly decreased expression of key prostate transcription factor, Nkx3.1, by androgens. DFMO also significantly decreased the expression of developmental regulatory gene Notch1. Other genes implicated in prostatic development including Sox9, Wif1 and Srd5a2 were unaffected by DFMO. Together these results indicate that Odc1 and polyamines are required for androgens to exert their effect in mediating prostatic bud induction, and are required for the expression of a subset of prostatic developmental regulatory genes including Notch1 and Nkx3.1.

Phosphodiesterase 4D inhibitors limit prostate cancer growth potential.

UNLABELLED: Phosphodiesterase 4D (PDE4D) has recently been implicated as a proliferation-promoting factor in prostate cancer and is overexpressed in human prostate carcinoma. However, the effects of PDE4D inhibition using pharmacologic inhibitors have not been examined in prostate cancer. These studies examined the effects of selective PDE4D inhibitors, NVP-ABE171 and cilomilast, as anti-prostate cancer therapies in both in vitro and in vivo models. The effects of PDE4D inhibitors on pathways that are critical in prostate cancer and/or downstream of cyclic AMP (cAMP) were examined. Both NVP-ABE171 and cilomilast decreased cell growth. In vitro, PDE4D inhibitors lead to decreased signaling of the sonic hedgehog (SHH), androgen receptor (AR), and MAPK pathways, but growth inhibition was best correlated to the SHH pathway. PDE4D inhibition also reduced proliferation of epithelial cells induced by paracrine signaling from cocultured stromal cells that had activated hedgehog signaling. In addition, PDE4D inhibitors decreased the weight of the prostate in wild-type mice. Prostate cancer xenografts grown in nude mice that were treated with cilomilast or NVP-ABE171 had decreased wet weight and increased apoptosis compared with vehicle-treated controls. These studies suggest the pharmacologic inhibition of PDE4D using small-molecule inhibitors is an effective option for prostate cancer therapy. IMPLICATIONS: PDE4D inhibitors decrease the growth of prostate cancer cells in vivo and in vitro, and PDE4D inhibition has therapeutic potential in prostate cancer.

A novel method for somatic transgenesis of the mouse prostate using the Sleeping Beauty transposon system.

BACKGROUND: In vivo ectopic gene expression is a common approach for prostate research through the use of transgenes in germline transgenic mice. For some other organs, somatic transgenesis with the Sleeping Beauty transposon system has allowed in vivo ectopic gene expression with higher throughput and lower cost than germline transgenic approaches. METHODS: Mouse e16 urogenital sinuses (UGSs) were co-injected with plasmids expressing the Sleeping Beauty transposase and plasmids with control or activated BRAF expressing transposons. Following electroporation, the transduced UGSs were grown as allografts in mouse hosts for 8 weeks, and the resulting allografts were evaluated for several endpoints. RESULTS: Transposon-transduced UGS allografts developed into prostatic tissue with normal tissue structure and cellular differentiation. Integration of transposon vectors into the genomes of transduced allografts was confirmed using linker-mediated PCR, sequencing, and in situ PCR. Transduction of UGS allografts with transposons expressing activated BRAF resulted in ectopic BRAF expression that was detectable at both the mRNA and protein levels. Prostatic ducts over-expressing activated BRAF also had ectopic activation of the ERK1/2 mitogen activated kinases and increased epithelial cell proliferation. CONCLUSIONS: The Sleeping Beauty transposon system can be used to achieve somatic transgenesis of prostatic allografts. This new method for achieving ectopic gene expression in the prostate will complement other existing approaches such as ectopic gene expression in cell lines and in germline transgenic mice. Advantages of this new approach include preservation of stromal-epithelial interactions not possible with cell lines, and higher throughput and lower cost than traditional germline transgenic approaches.

Distinct expression patterns of Sulf1 and Hs6st1 spatially regulate heparan sulfate sulfation during prostate development.

BACKGROUND: Prostate morphogenesis initiates in the urogenital sinus (UGS) with epithelial bud development. Sulfatase-1 (SULF1) inhibits bud development by reducing extracellular heparan sulfate (HS) 6-O sulfation and impairing FGF10 signaling by means of the ERK1/2 mitogen activated kinases. RESULTS: We characterized the expression patterns of HS 6-O sulfation modifying enzymes in the developing prostate by in situ hybridization and showed that Sulf1 and Hs6st1 had overlapping but distinct expression domains. Notably, Hs6st1 was present while Sulf1 was excluded from the tips of elongating epithelial buds. This predicted relatively high HS 6-O sulfation at the tips of elongating epithelial buds that was confirmed by immunohistochemistry. The pattern of Sulf1 expression in the peri-mesenchymal epithelium matched predicted locations of bone morphogenetic protein (BMP) signaling. Exogenous BMP4 and BMP7 induced Sulf1 expression in the UGS, decreased epithelial HS 6-O sulfation, and reduced ERK1/2 activation in response to FGF10. CONCLUSIONS: These data suggest that BMPs limit FGF10 action in the developing prostate at least in part by inducing Sulf1.

Identification of PDE4D as a proliferation promoting factor in prostate cancer using a Sleeping Beauty transposon-based somatic mutagenesis screen.

Retroviral and transposon-based mutagenesis screens in mice have been useful for identifying candidate cancer genes for some tumor types. However, many of the organs that exhibit the highest cancer rates in humans, including the prostate, have not previously been amenable to these approaches. This study shows for the first time that the Sleeping Beauty transposon system can be used to identify candidate prostate cancer genes in mice. Somatic mobilization of a mutagenic transposon resulted in focal epithelial proliferation and hyperplasia in the prostate. Efficient methods were established to identify transposon insertion sites in these lesions, and analysis of transposon insertions identified candidate prostate cancer genes at common insertion sites, including Pde4d. PDE4D was also overexpressed in human prostate cancer patient samples and cell lines, and changes in PDE4D mRNA isoform expression were observed in human prostate cancers. Furthermore, knockdown of PDE4D reduced the growth and migration of prostate cancer cells in vitro, and knockdown of PDE4D reduced the growth and proliferation rate of prostate cancer xenografts in vivo. These data indicate that PDE4D functions as a proliferation promoting factor in prostate cancer, and the Sleeping Beauty transposon system is a useful tool for identifying candidate prostate cancer genes.

Antisense to transforming growth factor-beta(1) facilitates the apoptosis of macrophages in rat vein grafts.

BACKGROUND: The success of peripheral vein grafts is limited by intimal hyperplasia. Transforming growth factor (TGF)-beta(1) has effects on cell proliferation, apoptosis and extracellular matrix synthesis. We have previously observed positive changes in vessel healing with antisense to TGF-beta(1). METHODS: Adenovirus was used to transduce rat femoral artery vein grafts with antisense to TGF-beta(1) (Ad-AST) or the sequence encoding the bioactive form of TGF-beta(1) (Ad-BAT). Grafts were harvested at 1, 2, 4 and 12 weeks and formalin fixed for immunohistochemical studies of the cell markers proliferating cellular nuclear antigen (proliferation) and active caspase 3 (apoptosis). In situ DNA fragmentation assays were also performed to confirm active caspase 3 results. RESULTS: Ad-AST treatment significantly (p = 0.05) increased apoptosis of macrophages inside the internal elastic lamina. In addition, Ad-AST treatment significantly increased the cellularity of the graft at early time points and reduced it at later time points (p = 0.01). CONCLUSION: The low levels of TGF-beta(1) in Ad-AST treatment promote apoptosis of macrophages and provide an environment that is more conducive to the proliferation or infiltration of cells that contribute to healthy vessels.

Transforming growth factor-beta1 antisense treatment of rat vein grafts reduces the accumulation of collagen and increases the accumulation of h-caldesmon.

BACKGROUND: The main cause of occlusion and vein graft failure after peripheral and coronary arterial reconstruction is intimal hyperplasia. Transforming growth factor beta-1 (TGF-beta1) is a pleiotropic cytokine known to have powerful effects on cell growth, apoptosis, cell differentiation, and extracellular matrix synthesis. METHODS: To investigate the role of TGF-beta1 in intimal hyperplasia, we used adenovirus to deliver to superficial epigastric vein messenger RNA (mRNA) antisense to TGF-beta1 (Ad-AST) or the sequence encoding the bioactive form of TGF-beta1 (Ad-BAT). Infection with "empty" virus was used as a control (Ad-CMVpLpA). The treated vein was then used for an interposition graft into rat femoral artery. Grafts were harvested at 1, 2, 4, and 12 weeks and formalin-fixed for histologic studies or placed in liquid nitrogen for mRNA studies. RESULTS: Ad-AST treatment resulted in an overall reduction of TGF-beta1 expression (P = .001), and Ad-BAT treatment resulted in an overall increase in TGF-beta1 expression (P = .007). Histologic analysis showed Ad-AST caused reduced collagen build up in the neointima at 12 weeks (P = .0001). Immunohistochemical staining for h-caldesmon at 12 weeks indicated Ad-AST increased smooth muscle cells throughout the vessel wall compared with Ad-CMVpLpA (P = .0024) or Ad-BAT (P = .04). Ad-AST also resulted in reduced CD68-positive cells in the media/adventitia (P = .005 vs Ad-CMVpLpA, P = .01 vs Ad-BAT). To further understand how Ad-AST was influencing the build up of collagen, we performed quantitative polymerase chain reaction on complimentary DNA (cDNA) from homogenates of the vein grafts. Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) was increased at 1 week by Ad-BAT (P = .048 vs Ad-CMVpLpA) and decreased by Ad-AST at all time points (P