Non-Cell-Autonomous Regulation of Prostate Epithelial Homeostasis by Androgen Receptor.

Prostate inflammation has been suggested as an etiology for benign prostatic hyperplasia (BPH). We show that decreased expression of the androgen receptor (AR) in luminal cells of human BPH specimens correlates with a higher degree of regional prostatic inflammation. However, the cause-and-effect relationship between the two events remains unclear. We investigated specifically whether attenuating AR activity in prostate luminal cells induces inflammation. Disrupting luminal cell AR signaling in mouse models promotes cytokine production cell-autonomously, impairs epithelial barrier function, and induces immune cell infiltration, which further augments local production of cytokines and chemokines including Il-1 and Ccl2. This inflammatory microenvironment promotes AR-independent prostatic epithelial proliferation, which can be abolished by ablating IL-1 signaling or depleting its major cellular source, the macrophages. This study demonstrates that disrupting luminal AR signaling promotes prostate inflammation, which may serve as a mechanism for resistance to androgen-targeted therapy for prostate-related diseases.

Romancing mitosis and the mitotic apparatus.

One of the earliest lessons students learn in biology is the process of mitosis and how cells divide to produce daughter cells. Although first described more than a century ago by early investigators such as E. B. Wilson, many aspects of mitosis and cell division remain the subject of considerable research today. My personal investigations and research contributions to the study of mitosis were made possible by recent developments in the field when I began my career, including access to novel mammalian cell culture models and electron and fluorescence microscopy. Building upon those innovations, my laboratory and other contemporary investigators first charted the ultrastructure and molecular organization of mitosis and chromosome movement and the assembly and function of the cytoskeleton. This field of research remains a significant challenge for future investigators in cell biology and medicine.

A genetic variant of Aurora kinase A promotes genomic instability leading to highly malignant skin tumors.

Aurora kinase A (Aurora-A) belongs to a highly conserved family of mitotis-regulating serine/threonine kinases implicated in epithelial cancers. Initially we examined Aurora-A expression levels at different stages of human skin cancer. Nuclear Aurora-A was detected in benign lesions and became more diffused but broadly expressed in well and poorly differentiated squamous cell carcinomas (SCC), indicating that Aurora-A deregulation may contribute to SCC development. To mimic the overexpression of Aurora-A observed in human skin cancers, we established a gene-switch mouse model in which the human variant of Aurora-A (Phe31Ile) was expressed in the epidermis upon topical application of the inducer RU486 (Aurora-AGS). Overexpression of Aurora-A alone or in combination with the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA), did not result in SCC formation in Aurora-AGS mice. Moreover, Aurora-A overexpression in naive keratinocytes resulted in spindle defects in vitro and marked cell death in vivo, suggesting that the failure of Aurora-A to initiate tumorigenesis was due to induction of catastrophic cell death. However, Aurora-A overexpression combined with exposure to TPA and the mutagen 7,12-dimethylbenz(a)anthracene accelerated SCC development with greater metastatic activity than control mice, indicating that Aurora-A cannot initiate skin carcinogenesis but rather promotes the malignant conversion of skin papillomas. Further characterization of SCCs revealed centrosome amplification and genomic alterations by array CGH analysis, indicating that Aurora-A overexpression induces a high level of genomic instability that favors the development of aggressive and metastatic tumors. Our findings strongly implicate Aurora-A overexpression in the malignant progression of skin tumors and suggest that Aurora-A may be an important therapeutic target.

Targeting aurora kinase with MK-0457 inhibits ovarian cancer growth.

PURPOSE: The Aurora kinase family plays pivotal roles in mitotic integrity and cell cycle. We sought to determine the effects of inhibiting Aurora kinase on ovarian cancer growth in an orthotopic mouse model using a small molecule pan-Aurora kinase inhibitor, MK-0457. EXPERIMENTAL DESIGN: We examined cell cycle regulatory effects and ascertained the therapeutic efficacy of Aurora kinase inhibition both alone and combined with docetaxel using both in vitro and in vivo ovarian cancer models. RESULTS: In vitro cytotoxicity assays with HeyA8 and SKOV3ip1 cells revealed >10-fold greater docetaxel cytotoxicity in combination with MK-0457. After in vivo dose kinetics were determined using phospho-histone H3 status, therapy experiments with the chemosensitive HeyA8 and SKOV3ip1 as well as the chemoresistant HeyA8-MDR and A2780-CP20 models showed that Aurora kinase inhibition alone significantly reduced tumor burden compared with controls (P values<0.01). Combination treatment with docetaxel resulted in significantly improved reduction in tumor growth beyond that afforded by docetaxel alone (P

CENP-B controls centromere formation depending on the chromatin context.

The centromere is a chromatin region that serves as the spindle attachment point and directs accurate inheritance of eukaryotic chromosomes during cell divisions. However, the mechanism by which the centromere assembles and stabilizes at a specific genomic region is not clear. The de novo formation of a human/mammalian artificial chromosome (HAC/MAC) with a functional centromere assembly requires the presence of alpha-satellite DNA containing binding motifs for the centromeric CENP-B protein. We demonstrate here that de novo centromere assembly on HAC/MAC is dependent on CENP-B. In contrast, centromere formation is suppressed in cells expressing CENP-B when alpha-satellite DNA was integrated into a chromosomal site. Remarkably, on those integration sites CENP-B enhances histone H3-K9 trimethylation and DNA methylation, thereby stimulating heterochromatin formation. Thus, we propose that CENP-B plays a dual role in centromere formation, ensuring de novo formation on DNA lacking a functional centromere but preventing the formation of excess centromeres on chromosomes.

Identification of a novel mitotic phosphorylation motif associated with protein localization to the mitotic apparatus.

The chromosomal passenger complex (CPC) is a crucial regulator of chromosome, cytoskeleton and membrane dynamics during mitosis. Here, using liquid chromatography coupled to mass spectrometry (LC-MS), we identified phosphopeptides and phosphoprotein complexes recognized by a phosphorylation-specific antibody that labels the CPC. A mitotic phosphorylation motif {PX[G/T/S][L/M]S(P) P or WGLS(P) P} was identified by MS in 11 proteins, including FZR1 (Cdh1) and RIC8A-two proteins with potential links to the CPC. Phosphoprotein complexes contained the known CPC components INCENP, Aurora-B (Aurkb) and TD-60 (Rcc2, RCC1-like), as well as SMAD2, 14-3-3 proteins, PP2A and Cdk1 (Cdc2a), a probable kinase for this motif. Protein sequence analysis identified phosphorylation motifs in additional proteins, including SMAD2, PLK3 and INCENP. Mitotic SMAD2 and PLK3 phosphorylation was confirmed using phosphorylation-specific antibodies, and, in the case of Plk3, phosphorylation correlated with its localization to the mitotic apparatus and the midbody. A mutagenesis approach was used to show that INCENP phosphorylation is required for its localization to the midbody. These results provide evidence for a shared phosphorylation event that regulates localization of crucial proteins during mitosis.

Overexpression of the centrosomal protein Aurora-A kinase is associated with poor prognosis in epithelial ovarian cancer patients.

PURPOSE: To assess the clinical significance of Aurora-A kinase, a centrosome-regulating serine-threonine kinase, in ovarian carcinoma. EXPERIMENTAL DESIGN: Aurora-A kinase expression was assessed by Western blot (cell lines) or immunohistochemistry (high-grade epithelial ovarian cancers), and clinical variables were collected by retrospective chart review. Centrosome amplification was assessed by immunofluorescence in cell lines, and by immunohistochemistry in patient samples. RESULTS: All ovarian cancer cell lines exhibited significant Aurora-A kinase protein overexpression, and all except A2780-par had centrosome amplification, a characteristic of mitotic dysregulation leading to genomic instability. Fifty-eight of 70 patient samples (82.8%) exhibited Aurora-A kinase overexpression compared with normal ovarian surface epithelium. High Aurora-A kinase expression was strongly associated with supernumerary centrosome count in tumor cells (P<0.001). Tumors with the greatest Aurora-A overexpression (n=24) had decreased patient survival (median survival, 1.44 versus 2.81 years; P=0.01). High Aurora-A expression and suboptimal surgical cytoreduction remained predictors of poor survival (P<0.05) by multivariate analysis. CONCLUSIONS: Aurora-A kinase is overexpressed by a substantial proportion of ovarian cancers and is associated with centrosome amplification and poor survival. It may be a useful prognostic marker and target in ovarian cancer.

Aurora-C kinase is a novel chromosomal passenger protein that can complement Aurora-B kinase function in mitotic cells.

The function of Aurora-C kinase, a member of the Aurora kinase family identified in mammals, is currently unknown. We present evidence that Aurora-C, like Aurora-B kinase, is a chromosomal passenger protein localizing first to centromeres and then to the midzone of mitotic cells. Aurora-C transcript is expressed at a moderate level albeit about an order of magnitude lower than Aurora-B transcript in diploid human fibroblasts. The level of Aurora-C transcript is elevated in several human cancer cell types. Aurora-C and Aurora-B mRNA and protein expressions are maximally elevated during the G2/M phase but their expression profiles in synchronized cells reveal differential temporal regulation through the cell cycle with Aurora-C level peaking after that of Aurora-B during the later part of the M phase. Aurora-C, like Aurora-B, interacts with the inner centromere protein (INCENP) at the carboxyl terminal end spanning the conserved IN box domain. Competition binding assays and transfection experiments revealed that, compared with Aurora-C, Aurora-B has preferential binding affinity to INCENP and co-expression of the two in vivo interferes with INCENP binding, localization, and stability of these proteins. A kinase-dead mutant of Aurora-C had a dominant negative effect inducing multinucleation in a dose-dependent manner. siRNA mediated silencing of Aurora-C and Aurora-B also gave rise to multinucleated cells with the two kinases silenced at the same time displaying an additive effect. Finally, Aurora-C could rescue the Aurora-B silenced multinucleation phenotype, demonstrating that Aurora-C kinase function overlaps with and complements Aurora-B kinase function in mitosis.

Phase II trial of combination interferon-alpha and thalidomide as first-line therapy in metastatic renal cell carcinoma.

OBJECTIVES: To present the results of a Phase II trial of thalidomide and interferon-alpha in renal cell carcinoma. METHODS: Patients with metastatic clear cell renal cell carcinoma and no prior systemic therapy were accrued. Interferon-alpha was administered at 5 million units subcutaneously three times per week. Thalidomide was started at 100 mg/day for 2 weeks and then escalated 200 mg every 2 weeks to 1000 mg or until grade 3-4 toxicity developed. Patients were assessed radiographically at baseline and after 12 weeks. Steady-state thalidomide plasma concentrations were determined. RESULTS: Thirty patients were enrolled. The median age was 62 years. Seventeen patients (57%) had undergone nephrectomy before therapy. One patient died during therapy. Of the 30 patients, 29 had at least grade 2 toxicity and 17 patients had at least grade 3. At 12 weeks, no patient had a complete response, 2 had a partial response (6.7%), 8 had stable disease (26.7%), and 11 (including 1 patient with an initial partial response) had disease progression (36.7%). Nine patients were removed from the study before 12 weeks. The median follow-up was 49.6 weeks (range 2.4 to 123.7). The median time of participation in the study was 11.1 weeks (range 1.4 to 63.9). At last follow-up, 2 patients were receiving the study therapy, 1 with stable disease at 64 weeks and 1 with a partial response at 53 weeks. The median survival was 68 weeks. A linear relationship was found between the thalidomide plasma concentration and dose. No relationship was apparent between the concentration and either treatment-related toxicity or response. CONCLUSIONS: Interferon-alpha and thalidomide as front-line therapy for metastatic renal cell carcinoma showed limited activity. The objective response rate was 7%. One third of patients experienced toxicity that required discontinuation of thalidomide. Randomized controlled studies are needed to determine any objective benefit of this regimen over either drug alone.

Assessment of oxidative stress in lungs from sheep after inhalation of wood smoke.

To elucidate potential dose-dependent mechanisms associated with wood smoke inhalation injury, the present study evaluated antioxidant status and the extent of pulmonary injury in sheep after graded exposure to smoke. Adult, male sheep (n=4-5 per group) were anesthetized and received 0, 5, 10 or 16 units of cooled western pine bark smoke, corresponding to 0, 175, 350 and 560 s, respectively, of smoke dwell time in the airways and lung. Smoke was mixed at a 1:1 ratio with 100% O2 to minimize hypoxia. Plasma and expired breath samples were collected pre-smoke, and 6, 12, 18, 24, 36 and 48 h after smoke exposure. Sheep were euthanatized 48 h after smoke exposure and lung and airway sections were evaluated histologically for injury and biochemically for indices of oxidative stress. Plasma thiobarbituric acid reactive substances (TBARS) were 66 and 69% higher than controls after moderate and severe smoke exposure at 48 h, whereas total antioxidant potential was not statistically different among groups at any time after exposure. Lung TBARS showed a dose-dependent response to smoke inhalation and were approximately 2-, 3- and 4-fold higher, respectively, than controls after exposure to 5, 10 and 16 units of smoke. Lung myeloperoxidase (MPO) activity was also higher in smoke-exposed animals than controls, and MPO activity was markedly elevated (19- and 22-fold higher than controls in right apical and medial lobes) in response to severe smoke exposure. Smoke exposure also induced a dose-dependent injury to tracheobronchial epithelium and lung parenchyma. Taken together these data show that few indices of oxidative stress responded in a dose-dependent manner to graded doses of smoke inhalation, although most of the indices measured in lung were affected by the highest dose of smoke. Additional time course studies are necessary to determine whether these oxidants are a cause or a consequence of the airway and lung injury associated with exposure to wood smoke.

Assessment of severity of ovine smoke inhalation injury by analysis of computed tomographic scans.

BACKGROUND: Our goal was to evaluate computed tomographic (CT) scans of the chest as a means of stratifying smoke inhalation injury (SII) severity. METHODS: Twenty anesthetized sheep underwent graded SII: group I, no smoke; group II, 5 smoke units; group III, 10 units; and group IV, 16 units. CT scans were obtained at 6, 12, and 24 hours after injury. Each quadrant of each slice was scored subjectively: 0 = normal, 1 = interstitial markings, 2 = ground-glass appearance, and 3 = consolidation. The sum of all scores was the radiologist's score (RADS) for that scan. Computerized analysis of three-dimensional reconstructed scans was also performed, based on Hounsfield unit ranges: hyperinflated, -1,000 to -900; normal, -899 to -500; poorly aerated, -499 to -100; and nonaerated, -99 to +100. The fraction of abnormal lung tissue (FALT) was computed from poorly aerated, nonaerated, and total volumes. Mean gray-scale density (DENS) was also computed. RESULTS: SII resulted in severity- and time-related changes in oxygenation (alveolar-arterial gradient), ventilation (respiratory rate-pressure product), DENS, FALT, and RADS. Ordinal logistic regression generated a predictive model for severity of injury (r2 = 0.623, p = 0.001), retaining RADS at 24 hours and rejecting the other variables. CONCLUSION: At 24 hours, CT scanning enabled SII severity stratification; qualitative evaluation (RADS) outperformed current semiautomated methods (DENS, FALT).

The Aurora kinases: role in cell transformation and tumorigenesis.

Aurora kinases representing a novel family of serine/threonine kinases have been identified as key regulators of the mitotic cell division process. The three members of this kinase family, identified so far, referred to as Aurora-A, Aurora-B and Aurora-C kinases, are close homologues of the prototypic yeast Ipll and Drosophila aurora kinases, which are known to be involved in the regulation of centrosome function, bipolar spindle assembly and chromosome segregation processes. All three members of the mammalian kinase family have a catalytic domain that is highly conserved with a short C-terminal domain and an N-terminal domain of varying sizes. Following their discovery about five years ago, extensive research has focused on understanding the biological roles of these kinases and elucidation of their pathways, which regulate cell proliferation and maintenance of normal cellular phenotypes. Significant interest in the subject was generated since all three Aurora kinases family members were reported to be overexpressed in many human cancers, and elevated expression has been correlated with chromosomal instability and clinically aggressive disease in some instances. Ectopic overexpression of one member of the family, Aurora-A, was shown to induce oncogenic transformation in cells. Unlike most other putative oncogenes identified, so far, members of this kinase family are expressed and active at the highest level during G2-M phase of the cell cycle. Aurora kinases are localized at the centrosomes of interphase cells, at the poles of the bipolar spindle and in the midbody of the mitotic apparatus. Substrates identified for the Aurora-A and Aurora-B kinases, include a kinesin-like motor protein, spindle apparatus proteins, histone H3 protein, kinetochore protein and the tumor suppressor protein p53. Identification of Aurora kinases as RasGAP Src homology 3 domain binding protein, also implicates these kinases as potential effectors in the Ras pathway relevant to oncogenesis. Abnormal elevated expression of Aurora kinases detected in human cancer cells could help explain the underlying biological mechanisms responsible for the development of many cellular phenotypes associated with malignant cells. Identification of these mechanisms offers the possibility of designing novel targeted therapies for cancer in the future.

Molecular and histological responses in rat skin exposed to m-xylene.

Solvents, surfactants, cutting fluids, hydrocarbons, and oils cause skin irritation by incompletely understood mechanisms. This study examined histological and molecular changes in rodent skin caused by brief topical exposures to m-xylene. At 0, 1, 2, 4, and 6 h after 1-h exposure, skin samples were removed and analyzed for histopathological changes and interleukin-1 alpha (IL-1 alpha) and inducible nitric oxide synthase (iNOS) protein levels. Histopathological changes (epidermal-dermal separation and granulocyte infiltration) and increases in IL-1 alpha and iNOS protein expression occurred during our observation period. IL-1 alpha levels increased by 80% immediately after exposure and iNOS levels increased about 60% 4 hours after exposure. Our study demonstrates that dermal exposure to m-xylene promotes IL-1 alpha and iNOS production in skin and these proteins may serve as early indicators of skin irritation.

Essential role for the dimerization domain of NuMA-RARalpha in its oncogenic activities and localization to NuMA sites within the nucleus.

Nuclear mitotic apparatus protein-retinoic acid receptor alpha (NuMA-RARalpha) is the fourth of five fusion proteins identified in acute promyelocytic leukemia (APL) patients. The molecular basis for its oncogenic activity has not been delineated. In gel-shift assays, NuMA-RARalpha bound to retinoic acid response elements (RAREs) both as a homodimer and as a heterodimer with RXRalpha. The binding profile of NuMA-RARalpha to a panel of RAREs was very similar to PML-RARalpha and PLZF-RARalpha. In transient transfection assays using HepG2 cells, NuMA-RARalpha inhibited wild-type RARalpha transcriptional activity, while it augmented STAT3 transcriptional activity. In GST-pull down experiments, NuMA-RARalpha formed a complex with the corepressor SMRT, was released from the NuMA-RARalpha/SMRT complexes by all-trans retinoic acid (ATRA) at 10(-7)-10(-6) M and became associated with the coactivator TRAM-1 at 10(-8) M ATRA. Studies comparing NuMA-RARalpha with NuMA-RARalpha(deltaCC) demonstrated that the dimerization or alpha-helical coiled-coil domain of NuMA was required for homodimer formation, transcriptional repression of wild-type RARalpha, transcriptional activation of STAT3, and stability of the NuMA-RARalpha/SMRT complex. Confocal fluorescent microscopy of HeLa cells was performed following transient expression of cyan fluorescent protein (CFP)-tagged proteins and incubation of cells with or without ATRA. Within the nucleus, CFP-NuMA-RARalpha exhibited a speckled pattern identical to that observed in cells transfected with CFP-NuMA. Furthermore, CFP-NuMA-RARalpha colocalized with yellow fluorescent protein-tagged (YFP)-NuMA. In contrast, CFP-NuMA-RARalpha(deltaCC) exhibited a diffuse granular pattern within the nucleus, similar to RARalpha. These results indicate that the dimerization domain of NuMA-RARalpha is critical for each of the known oncogenic activities of NuMA fusion proteins as well as its sequestration to nuclear sites normally occupied by NuMA and is distinct from RARalpha.

Amplification/overexpression of a mitotic kinase gene in human bladder cancer.

BACKGROUND: The mitotic kinase-encoding gene STK15/BTAK/ AuroraA is associated with aneuploidy and transformation when overexpressed in mammalian cells. STK15 overexpression activates an unknown oncogenic pathway that involves centrosome amplification and results in missegregation of chromosomes. Because clinical prognosis and tumor aneuploidy are tightly linked in human bladder cancer, we examined whether increased STK15 copy number and protein levels are linked to aneuploidy in bladder cancers. METHODS: STK15 protein was visualized by immunohistochemistry in 205 formalin-fixed, paraffin-embedded human bladder tumors. STK15 gene copy number was evaluated in 61 tumors by Southern blot hybridization and in 21 of these 61 tumors by fluorescence in situ hybridization (FISH). Copy numbers of chromosomes 3, 17, 20, and 21 were evaluated by FISH with chromosome-specific probes. STK15 expression levels were related to histologic grade, stage, and DNA ploidy of the tumors and to the patients' follow-up data. The chi-square test for association was used to analyze the relationship between STK15 expression and pathologic features. All statistical tests were two-sided. RESULTS: Tumors with low levels of STK15 amplification (3-4 copies) showed minimal deviation in their chromosome copy number and diploid or near-diploid total nuclear DNA content. Tumors with higher levels of STK15 amplification (>4 copies) had a major increase of chromosome copy number and of their total nuclear DNA content, i.e., exhibited pronounced aneuploidy. Elevated expression of STK15 was strongly associated with parameters of clinical aggressiveness including high histologic grade (P<.001), invasion (P<.001), increased rate of metastasis (P<.001), and decreased metastasis-free (P<.001) and overall (P<.001) survival of patients with bladder cancer. CONCLUSION: STK15 gene amplification and associated increased expression of the mitotic kinase it encodes are associated with aneuploidy and aggressive clinical behavior in human bladder cancer.

Centrosome amplification and overexpression of aurora A are early events in rat mammary carcinogenesis.

The cells of many solid tumors have been found to contain supernumerary centrosomes, a condition known as centrosome amplification. Centrosome amplification, accompanied by the overexpression of an associated kinase, Aurora A (AurA), has been implicated in mechanisms leading to mitotic spindle aberrations, aneuploidy, and genomic instability. Using a well-established rat mammary model favorable for experimental carcinogenesis, we analyzed centrosome amplification as a cellular marker for early stages of transformation and its regulation by the kinase ratAurA. Parity or treatment with estrogen and progesterone conferred resistance to tumorigenesis, as well as to overexpression of ratAurA and to centrosome amplification. ratAurA, cloned from a rat mammary gland cDNA library, is a bona fide Ser/Thr kinase, and sequence comparison demonstrated high homology to members of the entire AurA kinase family. Using immunocytochemical localization with confocal microscopy, we found ratAurA to be localized at the centrosome in normal and neoplastic tissues of the rat mammary gland. Normal ductal epithelium and stromal cells displayed an expected complement of one to two centrosomes/cell, whereas comparable cells in methylnitrosourea-treated animals displayed significantly elevated centrosome numbers. In tumors, 46% of cells showed more than two centrosomes/cell, and ratAurA expression levels coincided with higher centrosome numbers. Both centrosome numbers and ratAurA expression were permanently elevated. Centrosome amplification was found to occur at a very early, premalignant stage prior to detectable lesions after treatment with methylnitrosourea, a condition that was not detected in mammary glands of rats made refractory to the carcinogen via pregnancy or estrogen and progesterone treatment. Our results indicate that hormones influence kinase expression, and progesterone had the major effect on ratAurA expression levels. Cumulatively, these results suggest that ratAurA overexpression and centrosome amplification were linked to tumor development and progression and may serve as early markers in tumorigenesis.