Kar Ming Fung

Aldo-keto reductase (AKR) 1C3: role in prostate disease and the development of specific inhibitors.

Human aldo-keto reductases (AKR) of the 1A, 1B, 1C and 1D subfamilies are involved in the pre-receptor regulation of nuclear (steroid hormone and orphan) receptors by regulating the local concentrations of their lipophilic ligands. AKR1C3 is one of the most interesting isoforms. It was cloned from human prostate and the recombinant protein was found to function as a 3-, 17- and 20-ketosteroid reductase with a preference for the conversion of Delta4-androstene-3,17-dione to testosterone implicating this enzyme in the local production of active androgens within the prostate. Using a validated isoform specific real-time RT-PCR procedure the AKR1C3 transcript was shown to be more abundant in primary cultures of epithelial cells than stromal cells, and its expression in stromal cells increased with benign and malignant disease. Using a validated isoform specific monoclonal Ab, AKR1C3 protein expression was also detected in prostate epithelial cells by immunoblot analysis. Immunohistochemical staining of prostate tissue showed that AKR1C3 was expressed in adenocarcinoma and surprisingly high expression was observed in the endothelial cells. These cells are a rich source of prostaglandin G/H synthase 2 (COX-2) and vasoactive prostaglandins (PG) and thus the ability of recombinant AKR1C enzymes to act as PGF synthases was compared. AKR1C3 had the highest catalytic efficiency (kcat/Km) for the 11-ketoreduction of PGD2 to yield 9alpha,11beta-PGF2 raising the prospect that AKR1C3 may govern ligand access to peroxisome proliferator activated receptor (PPARgamma). Activation of PPARgamma is often a pro-apoptotic signal and/or leads to terminal differentiation, while 9alpha,11beta-PGF2 is a pro-proliferative signal. AKR1C3 is potently inhibited by non-steroidal anti-inflammatory drugs suggesting that the cancer chemopreventive properties of these agents may be mediated either by inhibition of AKR1C3 or COX. To discriminate between these effects we developed potent AKR1C inhibitors based on N-phenylanthranilic acids that do not inhibit COX-1 or COX-2. These compounds can now be used to determine the role of AKR1C3 in producing two proliferative signals in the prostate namely testosterone and 9alpha,11beta-PGF2.

Characterization of a monoclonal antibody for human aldo-keto reductase AKR1C3 (type 2 3α-hydroxysteroid dehydrogenase/type 5 17β-hydroxysteroid dehydrogenase); immunohistochemical detection in breast and prostate

Human aldo-keto reductase AKR1C3 (type 2 3alpha-hydroxysteroid dehydrogenase/type 5 17beta-hydroxysteroid dehydrogenase) catalyzes the reduction of Delta(4)-androstene-3,17-dione to yield testosterone, the reduction of 5alpha-dihydrotestosterone to yield 3alpha- and 3beta-androstanediol, and the reduction of estrone to yield 17beta-estradiol. Relatively, high mRNA expression of AKR1C3 was found in human prostate and mammary gland where it is implicated in regulating ligand access to the androgen and estrogen receptor, respectively. AKR1C3 shares high sequence identity >86% with related plastic human 20alpha-hydroxysteroid dehydrogenases (AKR1C1), type 3 3alpha-hydroxysteroid dehydrogenase (AKR1C2) and type 1 3alpha-hydroxysteroid dehydrogenase (AKR1C4), and reagents are urgently needed to discriminate between these enzymes at the mRNA, protein and functional level. We describe the characterization of a high-titer isoform specific monoclonal antibody (Ab) for AKR1C3. It does not cross react with human AKR1C1, AKR1C2 or AKR1C4, human aldehyde reductase AKR1A1 or rat 3alpha-hydroxysteroid dehydrogenase (AKR1C9) on immunoblot analysis. The monoclonal Ab can be used to detect AKR1C3 expression by immunohistochemistry in sections of paraffin-embedded mammary gland and prostate. In the breast enzyme staining was detected in ductal carcinoma in situ where the cancerous cells were strongly immunoreactive. In normal prostate immunoreactivity was limited to stromal cells with only faint staining in the epithelial cells. In adenocarcinoma of the prostate elevated staining was observed in the endothelial cells and carcinoma cells. The reagent thus has utility to access the localized expression of AKR1C3 in hormonal dependent malignancies of the breast and prostate.

Boswellia sacra essential oil induces tumor cell-specific apoptosis and suppresses tumor aggressiveness in cultured human breast cancer cells

BackgroundGum resins obtained from trees of the Burseraceae family (Boswellia sp.) are important ingredients in incense and perfumes. Extracts prepared from Boswellia sp. gum resins have been shown to possess anti-inflammatory and anti-neoplastic effects. Essential oil prepared by distillation of the gum resin traditionally used for aromatic therapy has also been shown to have tumor cell-specific anti-proliferative and pro-apoptotic activities. The objective of this study was to optimize conditions for preparing Boswellea sacra essential oil with the highest biological activity in inducing tumor cell-specific cytotoxicity and suppressing aggressive tumor phenotypes in human breast cancer cells.MethodsBoswellia sacra essential oil was prepared from Omani Hougari grade resins through hydrodistillation at 78 or 100 oC for 12 hours. Chemical compositions were identified by gas chromatography-mass spectrometry; and total boswellic acids contents were quantified by high-performance liquid chromatography. Boswellia sacra essential oil-mediated cell viability and death were studied in established human breast cancer cell lines (T47D, MCF7, MDA-MB-231) and an immortalized normal human breast cell line (MCF10-2A). Apoptosis was assayed by genomic DNA fragmentation. Anti-invasive and anti-multicellular tumor properties were evaluated by cellular network and spheroid formation models, respectively. Western blot analysis was performed to study Boswellia sacra essential oil-regulated proteins involved in apoptosis, signaling pathways, and cell cycle regulation.ResultsMore abundant high molecular weight compounds, including boswellic acids, were present in Boswellia sacra essential oil prepared at 100 oC hydrodistillation. All three human breast cancer cell lines were sensitive to essential oil treatment with reduced cell viability and elevated cell death, whereas the immortalized normal human breast cell line was more resistant to essential oil treatment. Boswellia sacra essential oil hydrodistilled at 100 oC was more potent than the essential oil prepared at 78 oC in inducing cancer cell death, preventing the cellular network formation (MDA-MB-231) cells on Matrigel, causing the breakdown of multicellular tumor spheroids (T47D cells), and regulating molecules involved in apoptosis, signal transduction, and cell cycle progression.ConclusionsSimilar to our previous observations in human bladder cancer cells, Boswellia sacra essential oil induces breast cancer cell-specific cytotoxicity. Suppression of cellular network formation and disruption of spheroid development of breast cancer cells by Boswellia sacra essential oil suggest that the essential oil may be effective for advanced breast cancer. Consistently, the essential oil represses signaling pathways and cell cycle regulators that have been proposed as therapeutic targets for breast cancer. Future pre-clinical and clinical studies are urgently needed to evaluate the safety and efficacy of Boswellia sacra essential oil as a therapeutic agent for treating breast cancer.

Elevated AKR1C3 expression promotes prostate cancer cell survival and prostate cell-mediated endothelial cell tube formation: implications for prostate cancer progressioan

BackgroundAldo-keto reductase (AKR) 1C family member 3 (AKR1C3), one of four identified human AKR1C enzymes, catalyzes steroid, prostaglandin, and xenobiotic metabolism. In the prostate, AKR1C3 is up-regulated in localized and advanced prostate adenocarcinoma, and is associated with prostate cancer (PCa) aggressiveness. Here we propose a novel pathological function of AKR1C3 in tumor angiogenesis and its potential role in promoting PCa progression.MethodsTo recapitulate elevated AKR1C3 expression in cancerous prostate, the human PCa PC-3 cell line was stably transfected with an AKR1C3 expression construct to establish PC3-AKR1C3 transfectants. Microarray and bioinformatics analysis were performed to identify AKR1C3-mediated pathways of activation and their potential biological consequences in PC-3 cells. Western blot analysis, reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and an in vitro Matrigel angiogenesis assays were applied to validate the pro-angiogenic activity of PC3-AKR1C3 transfectants identified by bioinformatics analysis.ResultsMicroarray and bioinformatics analysis suggested that overexpression of AKR1C3 in PC-3 cells modulates estrogen and androgen metabolism, activates insulin-like growth factor (IGF)-1 and Akt signaling pathways, as well as promotes tumor angiogenesis and aggressiveness. Levels of IGF-1 receptor (IGF-1R) and Akt activation as well as vascular endothelial growth factor (VEGF) expression and secretion were significantly elevated in PC3-AKR1C3 transfectants in comparison to PC3-mock transfectants. PC3-AKR1C3 transfectants also promoted endothelial cell (EC) tube formation on Matrigel as compared to the AKR1C3-negative parental PC-3 cells and PC3-mock transfectants. Pre-treatment of PC3-AKR1C3 transfectants with a selective IGF-1R kinase inhibitor (AG1024) or a non-selective phosphoinositide 3-kinases (PI3K) inhibitor (LY294002) abolished ability of the cells to promote EC tube formation.ConclusionsBioinformatics analysis followed by functional genomics demonstrated that AKR1C3 overexpression promotes angiogenesis and aggressiveness of PC-3 cells. These results also suggest that AKR1C3-mediated tumor angiogenesis is regulated by estrogen and androgen metabolism with subsequent IGF-1R and Akt activation followed by VEGF expression in PCa cells.

Regional variations in small intestinal submucosa evoke differences in inflammation with subsequent impact on tissue regeneration in the rat bladder augmentation model.

To examine the histological differences in the inflammatory response and regenerative outcomes of distal vs proximal porcine small intestinal submucosa (SIS) grafts in the rat bladder, as SIS from distal small intestine yields reliable and reproducible bladder regeneration, while SIS from proximal portions of small intestine does not provide similar results.

Enhanced angiogenesis of modified porcine small intestinal submucosa with hyaluronic acid-poly(lactide-co-glycolide) nanoparticles: from fabrication to preclinical validation.

Hyaluronic acid-poly(de-co-glycolide) nanoparticles (HA-PLGA NPs) were synthesized to stabilize the porous structure of porcine small intestinal submucosa (SIS), to improve surface biocompatibility and to enhance performance in tissue regeneration. HA-PLGA NPs were characterized for size, zeta potential, surface morphology, and HA loading. Human microvascular endothelial cells responded to HA-PLGA NPs and HA-PLGA modified SIS (HA-PLGA-SIS) with elevated cell proliferation. HA-PLGA-SIS significantly enhanced neo-vascularization in an in ovo chorioallantoic membrane angiogenesis model. The angiogenic capability of the newly fabricated HA-PLGA-SIS was tested in a canine bladder augmentation model. Urinary bladder augmentation was performed in beagle dogs following hemi-cystectomy using HA-PLGA-SIS. The regenerated bladder was harvested at 10 weeks post augmentation and vascularization was evaluated using CD31 immunohistochemical staining. Bladder regenerated with HA-PLGA-SIS had significantly higher vascular ingrowth compared to unmodified SIS. This study shows that HA-PLGA NPs may represent a new approach for modifying naturally derived SIS biomaterials in regenerative medicine.

AKR1C2 and AKR1C3 mediated prostaglandin D2 metabolism augments the PI3K/Akt proliferative signaling pathway in human prostate cancer cells

Members of the aldo-keto reductase (AKR) superfamily have been implicated in prostaglandin (PG) metabolism and prostate cancer. AKR1C3 possesses 11-ketoprostaglandin reductase activity and is capable of converting PGD2 to 9alpha, 11beta-PGF2alpha, whereas AKR1C2-mediated PG metabolism remains unclear. The accumulation of PGF2alpha may generate proliferative signals to promote prostate cell growth. Levels of AKR1C2 and AKR1C3 expression are elevated in localized and advanced prostate cancer. To study the significance of AKR1C2- and AKR1C3-mediated PGD2 conversion in human prostate cell proliferation, we stably transfected androgen insensitive human prostate cancer PC-3 cells with AKR1C2 or AKR1C3 cDNA. PC-3 cells overexpressing AKR1C2 and AKR1C3 had elevated cell proliferation in response to PGD2 stimulation as compared to mock transfectants. Overexpression of AKR1C2 or AKR1C3 did not alter levels of PGF receptor (FP) expression. Inclusion of an FP antagonist (AL8810) significantly suppressed PGD2-stimulated PC-3 cell proliferation in these stable transfectants. In addition, PGD2 significantly elevated levels of total Akt protein expression and Akt Ser473 phosphorylation in AKR1C2 and AKR1C3 stable transfectants; and inclusion of a phosphatidylinositol 3-kinase (PI3K) chemical inhibitor (LY294002) attenuated PGD2-stimulated cell proliferation in these transfectants. Our results suggested that both AKR1C2 and AKR1C3 mediate similar PGD2 conversion toward the accumulation of proliferative signals through FP and PI3K/Akt signaling pathways to promote prostate cell proliferation.

Rhabdoid glioblastoma in an adult

Sir, Malignant rhabdoid tumours are aggressive neoplasms with morphological features reminiscent of rhabdomyosarcomatous differentiation, but lacking genuine skeletal muscle differentiation. Rhabdoid phenotype features large, oval to round cells with medium to large amounts of cytoplasm. These cells characteristically contain a large, cytoplasmic, eosinophilic, hyaline-like inclusion that typically compresses the basophilic cytoplasm into a thin peripheral rim. The nucleus is large, vesicular, has prominent nucleoli, and is displaced by the cytoplasmic inclusion to an eccentric position. In infants and children, pure malignant rhabdoid tumours are seen in the kidney and soft tissue; atypical teratoid/rhabdoid tumour (AT/RT) occurs in the central nervous system (CNS). In adults, the rhaboid component usually arises from a pre-existing or co-existing nonrhabdoid neoplasm in different organs and these tumours are also known as composite extrarenal rhabdoid tumour (CERT). Other than rhabdoid meningioma, a form of CERT, adult cases of rhabdoid tumours of the CNS are extremely rare. Herein, we report a case of rhabdoid glioblastoma in an adult. The patient was a 66-year-old Caucasian male with no significant previous health problem. He had recently developed pressure headaches and pain behind his right ear. A 4-cm ring-enhancing lesion with extensive oedema causing midline shift was noted in the anterior region of his right temporal lobe by magnetic resonance imaging (Fig. 1). The lesion was surgically excised and the patient died of the disease shortly after surgery. The surgical resection yielded fragments of soft, pastelike, necrotic tissue, 5.062.562.0 cm in toto. Over 75% of the tumour was necrotic. Most of the residual viable tumour cells were composed of mitotically active, large, discohesive, round to oval cells. Many of the tumour cells contained a centrally located, eosinophilic, hyaline-like cytoplasmic inclusion, often surrounded by a thin rim of basophilic cytoplasm (Fig. 2A). The nuclei were large, pleomorphic, contained prominent nucleoli, and were typically displaced to the periphery by the cytoplasmic inclusion. Multinucleated giant cells were readily seen. There were small areas with classic histological features of a high-grade astrocytoma. Immunohistochemically, the tumour cells were polyphenotypic. Almost every single tumour cell was strongly immunoreactive for vimentin and many tumour cells were strongly immunoreactive for glial fibrillary acidic protein (GFAP); Fig. 2B and S100 protein. A membranous pattern of immunoreactivity for epithelial membrane antigen (EMA) was demonstrated in about 20% of the tumour cells. About 5% of the tumour cells were immunoreactive for smooth muscle actin (SMA). The

Tissue Distribution of Human AKR1C3 and Rat Homolog in the Adult Genitourinary System

Human aldo-keto reductase (AKR) 1C3 (type 2 3α-hydroxysteroid dehydrogenase/type 5 17β-hydroxysteroid dehydrogenase) catalyzes androgen, estrogen, and prostaglandin metabolism. AKR1C3 is therefore implicated in regulating ligand access to the androgen receptor, estrogen receptor, and peroxisome proliferator activating receptor γ in hormone target tissues. Recent reports on close relationships between ARK1C3 and various cancers including breast and prostate cancers implicate the involvement of AKR1C3 in cancer development or progression. We previously described the characterization of an isoform-specific monoclonal antibody against AKR1C3 that does not cross-react with related, >86% sequence identity, human AKR1C1, AKR1C2, or AKR1C4, human aldehyde reductase AKR1A1, or rat 3α-hydroxysteroid dehydrogenase (AKR1C9). In this study, a clone of murine monoclonal antibody raised against AKR1C3 was identified and characterized for its recognition of rat homolog. Tissue distribution of human AKR1C3 and its rat homolog in adult genitourinary systems including kidney, bladder, prostate, and testis was studied by IHC. A strong immunoreactivity was detected not only in classically hormone-associated tissues such as prostate and testis but also in non—hormone-associated tissues such as kidney and bladder in humans and rats. The distribution of these two enzymes was comparable but not identical between the two species. These features warrant future studies of AKR1C3 in both hormone- and non—hormone-associated tissues and identification of the rodent homolog for establishing animal models.

Biomatrices for bladder reconstruction

There is a demand for tissue engineering of the bladder needed by patients who experience a neurogenic bladder or idiopathic detrusor overactivity. To avoid complications from augmentation cystoplasty, the field of tissue engineering seeks optimal scaffolds for bladder reconstruction. Naturally derived biomaterials as well as synthetic and natural polymers have been explored as bladder substitutes. To improve regenerative properties, these biomaterials have been conjugated with functional molecules, combined with nanotechology, or seeded with exogenous cells. Although most studies reported complete and functional bladder regeneration in small-animal models, results from large-animal models and human clinical trials varied. For functional bladder regeneration, procedures for biomaterial fabrication, incorporation of biologically active agents, introduction of nanotechnology, and application of stem-cell technology need to be standardized. Advanced molecular and medical technologies such as next generation sequencing and magnetic resonance imaging can be introduced for mechanistic understanding and non-invasive monitoring of regeneration processes, respectively.