Search

The prostate-expressed sulfotransferase SULT2B1b (SULT2B) regulates intracrine androgen homeostasis by mediating 3β-sulfation of DHEA, thus reducing the precursor pool in the androgen biosynthesis pathway. We explored how loss of SULT2B might influence prostate cancer progression. Results show that SULT2B ablation in castration-resistant prostate cancer (CRPC) cells, generated by stable RNA interference or gene knockout, led to robust activation of the ERK1/2 Map kinase survival signal and induction of epithelial to mesenchymal transition (EMT). EMT activation was concluded on the basis of increased levels of vimentin (a mesenchymal protein) and the EMT-activating transcription factors SNAI1 (Snail) and TWIST1, shown by Western blotting, mass spectrometry and single-cell mass cytometry. Loss of SULT2B was associated with enhanced motility and invasive activity of CRPC cells in vitro and their growth escalation in vivo as xenografts. Higher invasion and metastasis potential of SULT2B-ablated CRPC cells was further indicated by results that these cells are less adhesive (i.e. easily detachable) and less stiff (i.e. more pliable) based on atomic force microscopy analysis of individual cells. Notably, AKR1C3, an aldo-keto reductase, which is elevated frequently in advanced prostate cancer, showed marked upregulation in SULT2B-deficient cells. AKR1C3 regulates androgen receptor (AR) signaling by promoting androgen biosynthesis and functioning as an AR-selective coactivator. While levels of AR and DHT did not change, AR activity was elevated, since PSA and FKBP5 mRNA induction by DHT-activated AR was several fold higher in SULT2B-silenced cells. The DHT-metabolizing AKR1C2 aldo-keto reductase was also upregulated, which likely accounts for a steady-state androgen level despite elevated AKR1C3 expression. Phosphorylation of ERK decreased in AKR1C3-silenced cells, signifying a causal link between AKR1C3 upregulation and ERK1/2 activation. SULT2B was undetectable immunohistochemically in tissue microarrays of clinical CRPC metastases, while SULT2B-negative samples showed AKR1C3-positive immunostaining. Primary prostate cancer exhibited variable, Gleason score independent SULT2B levels -- varying from strong positive to significantly reduced or undetectable. The reciprocal expression pattern for SULT2B and AKR1C3 in clinical CRPC suggests that AKR1C3 upregulation, ERK1/2 activation and increased aggressive traits of SULT2B-ablated cells, observed in vitro in cell models, may be clinically significant. Pathways regulating the inhibitory SULT2B-AKR1C3 axis may inform new avenue(s) for delaying disease progression in SULT2B-deficient prostate cancer.Funding Support: 1I01BX000280, VA (BC); W81XWH-14-1-0606, DOD (BC); IK6 BX004207, VA (BC); P50 CA97186, NIH & W81XWH-12-1-0208, DOD (EAM)

In mature B-cell malignancies, chromosomal translocations often juxtapose an oncogenic locus to the regulatory regions of the immunoglobulin genes. These genomic rearrangements can associate with specific clinical/pathological sub-entities and inform diagnosis and treatment decisions. Recently, we characterized the t(14;16)(q32;q24) in diffuse large B-cell lymphoma (DLBCL), and showed that it targets the transcription factor IRF8, which is also somatically mutated in ~10% of DLBCLs. IRF8 regulates innate and adaptive immune responses mediated by myeloid/monocytic and lymphoid cells. While the role of IRF8 in human myeloid/dendritic-cell disorders is well established, less is known of its contribution to the pathogenesis of mature B-cell malignancies. To address this knowledge gap, we generated the Eμ-Irf8 mouse model, which mimics the IRF8 deregulation associated with t(14;16) of DLBCL. Eμ-Irf8 mice develop normally and display peripheral blood cell parameters within normal range. However, Eμ-Irf8 mice accumulate pre-pro-B-cells and transitional B-cells in the bone marrow and spleen, respectively, confirming that this model amplifies the physiologic role of Irf8 in B-cell development. Notably, in Eμ-Irf8 mice, the lymphomagenic Irf8 targets Aicda and Bcl6 are overexpressed in mature B-cells. Yet, the incidence of B-cell lymphomas is not increased in the Eμ-Irf8 model, even though their estimated survival probability is significantly lower than that of WT controls. Together, these observations suggest that the penetrance on the Irf8-driven phenotype may be incomplete and that introduction of second genetic hit, a common strategy in mouse models of lymphoma, may be necessary to uncover the pro-lymphoma phenotype of the Eμ-Irf8 mice.

SULT2B1b (SULT2B) is a prostate-expressed hydroxysteroid sulfotransferase, which may regulate intracrine androgen homeostasis by mediating 3β-sulfation of dehydroepiandrosterone (DHEA), the precursor for 5α-dihydrotestosterone (DHT) biosynthesis. The aldo-keto reductase (AKR)1C3 regulates androgen receptor (AR) activity in castration-resistant prostate cancer (CRPC) by promoting tumor tissue androgen biosynthesis from adrenal DHEA and also by functioning as an AR-selective coactivator. Herein we report that SULT2B-depleted CRPC cells, arising from stable RNA interference or gene knockout (KO), are markedly upregulated for AKR1C3, activated for ERK1/2 survival signal, and induced for epithelial-to-mesenchymal (EMT)-like changes. EMT was evident from increased mesenchymal proteins and elevated EMT-inducing transcription factors SNAI1 and TWIST1 in immunoblot and single-cell mass cytometry analyses. SULT2B KO cells showed greater motility and invasion in vitro; growth escalation in xenograft study; and enhanced metastatic potential predicted on the basis of decreased cell stiffness and adhesion revealed from atomic force microscopy analysis. While AR and androgen levels were unchanged, AR activity was elevated, since PSA and FKBP5 mRNA induction by DHT-activated AR was several-fold higher in SULT2B-silenced cells. AKR1C3 silencing prevented ERK1/2 activation and SNAI1 induction in SULT2B-depleted cells. SULT2B was undetectable in nearly all CRPC metastases from 50 autopsy cases. Primary tumors showed variable and Gleason score (GS)-independent SULT2B levels. CRPC metastases lacking SULT2B expressed AKR1C3. Since AKR1C3 is frequently elevated in advanced prostate cancer, the inhibitory influence of SULT2B on AKR1C3 upregulation, ERK1/2 activation, EMT-like induction, and on cell motility and invasiveness may be clinically significant. Pathways regulating the inhibitory SULT2B-AKR1C3 axis may inform new avenue(s) for targeting SULT2B-deficient prostate cancer.

Androgen receptor (AR) and PI3K/AKT/mTORC1 are major survival signals that drive prostate cancer to a lethal disease. Reciprocal activation of these oncogenic pathways from negative cross talks contributes to low/limited success of pathway-selective inhibitors in curbing prostate cancer progression. We report that the antibiotic salinomycin, a cancer stem cell blocker, is a dual-acting AR and mTORC1 inhibitor, inhibiting PTEN-deficient castration-sensitive and castration-resistant prostate cancer in culture and xenograft tumors. AR expression, its transcriptional activity, and androgen biosynthesis regulating enzymes CYP17A1, HSD3β1 were reduced by sub-micro molar salinomycin. Estrogen receptor-α expression was unchanged. Loss of phosphorylated AR at serine-81, which is an index for nuclear AR activity, preceded total AR reduction. Rapamycin enhanced the AR protein level without altering phosphoAR-Ser81 and CYP17A1. Inactivation of mTORC1, evident from reduced phosphorylation of mTOR and downstream effectors, as well as AMPK activation led to robust autophagy induction. Apoptosis increased modestly, albeit significantly, by sub-micro molar salinomycin. Enhanced stimulatory TSC2 phosphorylation at Ser-1387 by AMPK, and reduced inhibitory TSC2 phosphorylation at Ser-939/Thr-1462 catalyzed by AKT augmented TSC2/TSC1 activity, which led to mTORC1 inhibition. AMPK-mediated raptor phosphorylation further reduced mTOR's kinase function and mTORC1 activity. Our novel finding on dual inhibition of AR and mTORC1 suggests that salinomycin is potentially active as monotherapy against advanced prostate cancer.

Mitochondrial D2HGDH and L2HGDH catalyze the oxidation of D-2-HG and L-2-HG, respectively, into αKG. This contributes to cellular homeostasis in part by modulating the activity of αKG-dependent dioxygenases. Signals that control the expression/activity of D2HGDH/L2HGDH are presumed to broadly influence physiology and pathology. Using cell and mouse models, we discovered that MYC directly induces D2HGDH and L2HGDH transcription. Furthermore, in a manner suggestive of D2HGDH, L2HGDH, and αKG dependency, MYC activates TET enzymes and RNA demethylases, and promotes their nuclear localization. Consistent with these observations, in primary B cell lymphomas MYC expression positively correlated with enhancer hypomethylation and overexpression of lymphomagenic genes. Together, these data provide additional evidence for the role of mitochondria metabolism in influencing the epigenome and epitranscriptome, and imply that in specific contexts wild-type TET enzymes could demethylate and activate oncogenic enhancers.

Aging signals a gradual deregulation of physiological homeostasis. Steroid hormone actions are an important contributor to this deregulation because of their key involvements in the growth, metabolism, survival, and functional vigor of cells, tissues, and organs. Accumulated evidences show that aging is associated with reduced circulating levels of male and female sex hormones, i.e., androgens and estrogens, respectively, which in turn alter physiological milieu and lead to specific deficits in the organismal vitality. While a number of articles in the literature have provided a generalized description of age-related decline of physiological control mechanisms, in the current chapter, we have focused specifically on the role of sex hormones and sex steroid receptors in age-related bodily dysfunctions. Various segments of our article delved into the current understanding on influences of sex steroids and steroid receptors. Specifically, the roles of androgens, estrogens, and cognate sex steroid receptors in age-accompanied physiological and pathophysiological changes in gene expression and organ functions are discussed. In addition to citing our own studies, information from diverse fields of biology and medicine is taken into consideration in order to present a comprehensive view of sex steroid action with advancing age.

Antigen-specific T lymphocytes can recognize and eliminate aberrant cells. Cancer cells halt this process by hijacking a system of immune checkpoints, the programmed cell death 1 (PD-1) and its ligands (PD-L1/2) pathway, which physiologically regulates the quantity and activity of T cells, establishing peripheral T cell tolerance and limiting tissue damage. PD-L1-expressing cancer cells interact with and inhibit PD-1 positive T cells, thus abrogating anti-cancer immunity, which can be restored by checkpoint inhibitors (CPI). Improved understanding of the regulation of PD-L1 expression will shed further light on how cancer cells escape immune surveillance, and it may help in the design of combinatorial therapeutic strategies that expand the activity of CPI. Oncogenes (e.g., MYC, STAT3, HIF1 and NF-KB) have been shown to directly induce PD-L1 transcription. In addition, pro-inflammatory cytokines, notably IFN-γ, via the JAK/STAT pathway, also increase PD-L1 expression, an intuitive counteracting regulatory axis that prevents unchecked inflammation and auto-immunity. The second messenger cyclic-AMP (cAMP) is a classical mediator of anti-inflammatory and immunosuppressive inputs. However, its putative role in PD-L1 regulation is unknown. Addressing this knowledge gap is especially relevant because this signaling node can be modulated with a class of FDA-approved agents, the phosphodiesterase 4 (PDE4) inhibitors. We have recently reviewed the pleiotropic roles that cAMP/PDE4 plays in diffuse large B-cell lymphoma (DLBCL) biology (BloodPMID: 27756749). Thus, to examine if cAMP modulates PD-L1 expression, we first used DLBCL cell lines (n=10). Raising the levels of intracellular cAMP readily induced PD-L1 expression (measured by WB and FACS) in ABC-DLBCLs but not in GCB-DLBCLs. This cAMP-mediated induction of PD-L1 occurred also at RNA level; however, using reporter assays we found that the canonical cAMP-PKA-CREB pathway does not directly activate the PD-L1 promoter. The immune modulatory activity of cAMP is mediated, at least in part, by transcriptional activation/secretion of cytokines. Thus, we considered that cAMP induction of PD-L1 in DLBCL may be driven by an autocrine loop. In agreement with this idea, cAMP promoted JAK/STAT activation and culturing DLBCL cell lines in conditioned media (CM) from cAMP-high models induced PD-L1 expression. These assays pointed to secreted factor(s) as intermediaries in the cAMP/PD-L1 axis. Therefore, we screened a panel of 105 cytokines to identify those secreted by DLBCL cell lines following cAMP up-modulation - in most models, we detected a significant cAMP-driven increase in IL-6, IL-8, IL-10 and IL-1α secretion. For validation, we focused on IL-10 because this was the most commonly cAMP-induced cytokine across the DLBCL models. We found that recombinant IL-10 induced PD-L1, albeit this induction was significantly less marked than that observed following an increase in intra-cellular cAMP. Concordantly, antibody-based blocking of the IL-10 signals, and pharmacologically inhibiting the JAK/STAT pathway, only partially abrogated the cAMP-mediated induction of PD-L1. We concluded that IL-10 and JAK/STAT signals relay part, but not all, of the cAMP effects on PD-L1 expression in DLBCL. Next, we utilized the Pde4b null mouse model to examine if these observations were present in an organismal level and in non-immortalized immune cells. In these assays, spleens of Pde4b WT, +/- and -/- mice (8-16 weeks old, male and female, n=8) were collected and analyzed by WB and FACS. Spleen cells from Pde4b deficient mice had markedly higher expression of PD-L1 (WB). By FACS, we found that the increase in PDL1 expression in Pde4b null mice derived from T cells, B cells, but from the smaller non-B/T cell population (CD19/CD3 negative). Finally, we found that the PDE4 inhibitor roflumilast used as a single agent in vitro robustly induced PD-L1 expression in DLBCL cell lines. In summary, we identified cAMP as an "actionable" novel regulator of PD-L1 expression in normal and malignant immune cells. Mechanistically, cAMP drives an autocrine loop enacted by cytokines and transduced in part by JAK/STAT. This finding supports the clinical testing of roflumilast to induce PD-L1 expression, a strategy that may improve the activity of checkpoint inhibitors in DLBCL and related tumor types. Disclosures No relevant conflicts of interest to declare.

Mitochondria play a role in epigenetic remodeling by generating intermediate metabolites (αKG, 2-HG, succinate, etc.) and modulating the activity of enzymes that control DNA, RNA and histone demethylation. The mitochondrial dehydrogenases D2HGDH and L2HGDH regulate 2-HG/αKG homeostasis by catalyzing the oxidation of D2-HG and L2-HG, respectively, into αKG. In humans, loss of either enzyme causes neuro-metabolic syndromes and early mortality, pointing to their essential role in physiology. Yet, the regulation of D2HGDH and L2HGDH remains to be characterized. To address this issue, we mapped the D2HGDH and L2HGDH promoter regions. Using reporter and ChIP assays, lymphoma cell lines and a mouse model, we discovered that MYC binds to E-boxes in these promoters and directly induce D2HGDH and L2HGDH transcription. We created CRISPR KOs of D2HGDH or L2HGDH in MYC-inducible P493-6 cells, and quantified αKG, D2-HG and L2-HG by LC/MS. We found that turning MYC expression ON led to significantly higher accumulation of αKG (and decrease in 2-HG) in cells expressing D2/L2HGDH than in the KO models, confirming that MYC's transcriptional activation of D2/L2HGDH directly influences 2-HG/αKG balance. Then, we tested whether the metabolic output of the MYC-D2/L2HGDH axis influenced the activity of the αKG-dependent TET enzymes, and of the RNA demethylases FTO and ALKBH5. In P493-6 cells, B cells from Eμ-Myc mice and DLBCL cell lines, MYC expression led to a significant increase in 5hmC, decrease in 5mC DNA, and reduction in m6A RNA marks. These MYC-induced changes were blunted in D2HGDH or L2HGDH KO cells. In addition, the effects of MYC on 5hmC/5mC and m6A were blocked in cells exposed to cell-permeable D2-HG or L2-HG, while synthetic αKG rescued D2HGDH and L2HGDH KO cells. Next, we quantified TET and FTO/ALKBH5 activity in the nuclear lysates of our models. In all instances, MYC significantly elevated TET/FTO/ALKBH5 activity in D2HGDH/L2HGDH WT cells, an outcome that was significantly dampened in the KO models. These data suggested that the MYC-D2/L2HGDH axis increases the activity of these enzymes by generating αKG. To examine whether additional layers of control were also operational, we quantified the expression of TET1-3, FTO and ALKBH5, and of members of the RNA methyltransferase complex, METLL3, METLL14 and WTAP, and confirmed that their global expression were unmodified by MYC or other genetic and metabolic perturbations. Strikingly, however, when examining subcellular localization, we found that MYC, in a D2/L2HGDH dependent manner, promoted the nuclear localization of TET1-3, FTO and ALKBH5 (but not METTL3/14). Remarkably, these effects were readily recapitulated by αKG, whereas 2-HG retained these proteins in the cytoplasm, effectively reducing their ability to chemically modify DNA and RNA. Lastly, to test if the MYC-driven increase of TET activity was also present in primary tumors, we explored the DLBCL TCGA dataset. We mapped all enhancers that are active in DLBCL and found that enhancer hypomethylation (a putative consequence of TET activity) significantly correlated with MYC expression (r=0.38, p=0.009) or activity (ssGSEA-derived MYC activity score, r=0.46, p=0.0013); this finding remained significant after excluding potentially cofounding TET2-mutant DLBCLs. We next tested if this MYC-driven/TET-mediated enhancer demethylation was functionally relevant by correlating it to the expression of the gene closest to, or overlapping with, the enhancer. A biologically coherent negative correlation between enhancer methylation and target transcript expression was found for multiple genes, including several products previously implicated in lymphoma pathogenesis, including, FOXP1, PIM1, ATF5, KLHL14 and BRD2. In summary, we showed that D2HGDH and L2HGDH are transcriptional targets of MYC, and that the control of αKG levels by the MYC-D2/L2HGDH axis activates TETs and RNA demethylases. We discovered that MYC and intermediate metabolites control the sub-cellular localization of these enzymes, possibly via covalent modifications, thus adding an new layer of complexity to the remodeling of the epigenome and epitranscriptome in cancer. We showed in primary DLBCLs that MYC expression/activity correlates with hypomethylated/active oncogenic enhancers. Thus, we postulate that downstream to MYC TET enzymes may in specific contexts function as oncogenes. Disclosures No relevant conflicts of interest to declare.

Orally delivered small-molecule therapeutics are metabolized in the liver and intestine by phase I and phase II drug-metabolizing enzymes (DMEs), and transport proteins coordinate drug influx (phase 0) and drug/drug-metabolite efflux (phase III). Genes involved in drug metabolism and disposition are induced by xenobiotic-activated nuclear receptors (NRs), i.e. PXR (pregnane X receptor) and CAR (constitutive androstane receptor), and by the 1α, 25-dihydroxy vitamin D3-activated vitamin D receptor (VDR), due to transactivation of xenobiotic-response elements (XREs) present in phase 0-III genes. Additional NRs, like HNF4-α, FXR, LXR-α play important roles in drug metabolism in certain settings, such as in relation to cholesterol and bile acid metabolism. The phase I enzymes CYP3A4/A5, CYP2D6, CYP2B6, CYP2C9, CYP2C19, CYP1A2, CYP2C8, CYP2A6, CYP2J2, and CYP2E1 metabolize >90% of all prescription drugs, and phase II conjugation of hydrophilic functional groups (with/without phase I modification) facilitates drug clearance. The conjugation step is mediated by broad-specificity transferases like UGTs, SULTs, GSTs. This review delves into our current understanding of PXR/CAR/VDR-mediated regulation of DME and transporter expression, as well as effects of single nucleotide polymorphism (SNP) and epigenome (specified by promoter methylation, histone modification, microRNAs, long non coding RNAs) on the expression of PXR/CAR/VDR and phase 0-III mediators, and their impacts on variable drug response. Therapeutic agents that target epigenetic regulation and the molecular basis and consequences (overdosing, underdosing, or beneficial outcome) of drug-drug/drug-food/drug-herb interactions are also discussed. Precision medicine requires understanding of a drug's impact on DME and transporter activity and their NR-regulated expression in order to achieve optimal drug efficacy without adverse drug reactions. In future drug screening, new tools such as humanized mouse models and microfluidic organs-on-chips, which mimic the physiology of a multicellular environment, will likely replace the current cell-based workflow.

Alveolar macrophages (AMs) are the first immune cells to respond to an invading pathogen and coordinate the inflammatory response within the lungs. Studies suggest that macrophages exhibit age-related deficiencies in Toll-like receptor (TLR) function; however, the impact of this dysfunction during pneumonia, the leading cause of infectious death in the elderly, and the underlying mechanisms responsible remain unclear. We examined disease severity in young, mature, and aged BALB/cBy mice following intratracheal infection with the Gram-positive bacteria Streptococcus pneumoniae (Spn). Both mature and aged mice failed to clear bacteria and as a result had increased mortality, tissue damage and vascular leakage. Early production of TNFα, IL-1β, and IL-6 during pneumonia declined with age and was associated with an inability of isolated AMs to respond to pneumococcal cell wall (CW) and ethanol-killed Spn ex vivo. Total levels of TLR1 were unaffected by age and TLR2 surface expression was slightly yet significantly increased on aged AMs suggesting that intracellular TLR signaling defects were responsible for the age-related decline in cytokine responsiveness. Following infection of isolated AMs with live Spn, a significant age-related decline in TLR2-induced phosphorylation of p65 NFκB, JNK and p38 MAPK, and an increase in ERK phosphorylation was observed by immunoblotting. These data are the first to demonstrate that TLR2-dependent recognition of Spn by aged AMs is impaired and is associated with a delayed pro-inflammatory cytokine response in vivo along with enhanced susceptibility to pneumococcal pneumonia.

Mutation of Pro94 to phenylalanine or alanine significantly alters the redox properties of the type I copper center of amicyanin. Each mutation increases the redox midpoint potential (E(m)) value by at least 140 mV and shifts the pK(a) for the pH dependence of the E(m) value to a more acidic value. Atomic resolution (0.99-1.1 A) structures of both the P94F and P94A amicyanin have been determined in the oxidized and reduced states. In each amicyanin mutant, an electron-withdrawing hydrogen bond to the copper-coordinating thiolate sulfur of Cys92 is introduced by movement of the amide nitrogens of Phe94 and Ala94 much closer to the thiolate sulfur than in wild-type amicyanin. This is the likely explanation for the much more positive E(m) values which result from each of these mutations. The observed decrease in the pK(a) value for the pH dependence of the E(m) value that is seen in the mutants seems to be correlated with steric hindrance to the rotation of the His95 copper ligand which results from the mutations. In wild-type amicyanin the His95 side chain undergoes a redox and pH-dependent conformational change which accounts for the pH dependence of the E(m) value of amicyanin. The reduced P94A amicyanin exhibits two alternate conformations with the positions of the copper 1.4 A apart. In one of these conformations, a water molecule appears to have replaced Met98 as a copper ligand. The relevance of these structures to the electron transfer properties of P94F and P94A amicyanin are also discussed.

e23066 Background: Proteasome as a hub protease of the ubiquitin proteasome pathway is an established anticancer drug target. Several drugs that inhibit proteasome are currently used to successfully treat aggressive blood cancers. These drugs are based on their competition with protein substrates of proteasome. However, efficacy of these drugs toward solid cancers is inadequate. Besides, the side effects and developing drug resistance are increasingly hampering the therapy. Therefore, there is an unmet challenge to develop new types of proteasome targeting compounds that are efficient against solid cancers and utilize other mechanisms to stop proteasome. Here we present a compound with a novel molecular mechanism, potentially bypassing limitations of the available drugs. Methods: We rationally designed and synthesized a series of small molecule “B” compounds, derivatives of a binding domain of seco-rapamycin that noncompetitively interfere with peptidase activities of proteasome. We tested effects of the compounds in vitro on purified proteasome, in cellulo with selected cancer cell lines and in a xenograft mouse model of prostate cancer. Results: We found that compound B1 binds to the catalytic core of proteasome far from the catalytic sites, destabilizes assembly of the 26S proteasome responsible for digest of polyUb substrates and allosterically inhibits its proteolytic activities. Molecularly, B1 impedes the gating mechanism responsible for substrate uptake as found with AFM. Tryptophan fluorescence indicates that B1 changes proteasome fold and the binding mode of competitive inhibitors. B1 substantially decreases viability of selected cancer cell lines and shifts their mechanical phenotype toward noncancerous status. B1 synergizes with bortezomib decreasing the IC50 5-10 fold. In a xenograft hormone resistant prostate cancer model, B1 treatment leads to shrinkage of the tumor size, decreases enumeration of aggressive, EpCAM+ CTCs and shifts the macrophage profile toward predator M1 type. Conclusions: B1 compounds constitute a new class of noncompetitive allosteric inhibitors of proteasome that could be useful to develop to treat aggressive prostate cancers alone or in synergy with competitive inhibitors.

Characterization of the entire spectrum of cancer-associated genetic disruptions is an overarching goal of contemporary and future oncology and can inform on patient diagnosis, treatment, and surveillance. Hereditary endocrine tumors, by having the potential to reveal the cancer's primary molecular defect, have been especially informative in this realm. Within this group, pheochromocytomas and paragangliomas, neural crest-derived, catecholamine-secreting tumors have come to represent true conduits for gene discovery. About one-third of pheochromocytomas and paragangliomas are now known to result from germline mutations in one of at least eight genes that belong to a variety of functional classes. Greater understanding of the molecular signals transduced by these genes and their respective mutants has advanced our understanding of kinase signaling pathways, hypoxia regulation, and the link between metabolic disruptions and cell growth. A new susceptibility gene without homology to other functional classes has been recently identified and encodes for a three-spanner transmembrane protein, transmembrane protein 127 (TMEM127). Initial insights from in vitro and patient data suggest that this candidate tumor suppressor is linked to the endosomal system and the mechanistic target of rapamycin [formerly mammalian target of rapamycin (mTOR)] pathway, and that mutation carriers often have clinical features that are typically associated with sporadic forms of pheochromocytoma. Functional characterization of transmembrane protein 127 (TMEM127) and discovery of additional pheochromocytoma/paraganglioma susceptibility genes is likely to shed light on our understanding of these tumors and extend these insights to other cancers.

SummaryElevated Aurora kinase-A expression is correlated with abrogation of DNA damage-induced apoptotic response and mitotic spindle assembly checkpoint (SAC) override in human tumor cells. We report that Aurora-A phosphorylation of p73 at serine235 abrogates its transactivation function and causes cytoplasmic sequestration in a complex with the chaperon protein mortalin. Aurora-A phosphorylated p73 also facilitates inactivation of SAC through dissociation of the MAD2-CDC20 complex in cells undergoing mitosis. Cells expressing phosphor-mimetic mutant (S235D) of p73 manifest altered growth properties, resistance to cisplatin- induced apoptosis, as well as premature dissociation of the MAD2-CDC20 complex, and accelerated mitotic exit with SAC override in the presence of spindle damage. Elevated cytoplasmic p73 in Aurora-A overexpressing primary human tumors corroborates the experimental findings.

Controversy remains about the identity of the transcription factor(s) which bind to the two E-box elements (CACGTG, proximal and distal) of the human telomerase (hTERT) gene promoter, the essential elements in the regulation of telomerase. Here, systematic oligonucleotide trapping supplemented with two-dimensional gel electrophoresis (2-DE) and proteomic methods was used to identify E-box binding transcription factors. Although insufficient purity was obtained from the proximal E-box element trapping, further fractionation provided by 2-DE and specific identification from Southwestern blotting analysis allow us to clearly identify an E-box binding transcription factor. The protein spot was cut from 2-DE and in-gel digested with trypsin for LC-nanosprayESItandem MS analysis. This identified upstream stimulatory factor-2 (USF-2). Western blotting analysis with specific antibodies clearly shows USF-2 present in the purified fraction and USF-2 antibody supershifts the specific DNA-binding complex on nondenaturing gels. Furthermore, a novel method was developed in which the specific DNA-transcription factor complex was separated on a non-denaturing gel, the band was cut and applied to SDS-PAGE for a second dimension. Western blots of this second gel also confirmed the presence of USF-2.

Aurora-A is a proto-oncogenic mitotic kinase that is frequently overexpressed in human epithelial malignancies including in breast and ovarian cancers. The mechanism of transcriptional upregulation of Aurora-A in human breast cancer is not yet elucidated. We report herein that Aurora-A transcription is positively regulated by GATA-3 in response to estrogen in estrogen receptor α (ERα)-positive cells. Transient expression of aurora-A promoter deletion mutants in luciferase constructs identified a GATA binding sequence motif as a functional regulatory element in ERα-positive breast cancer cells. Electrophoretic mobility shift assay identified the binding of regulatory proteins to the GATA element. Anti-GATA-3 antibody generated a supershifted complex. Recruitment of GATA-3 to the aurora-A promoter was verified by chromatin immunoprecipitation analysis with GATA-3 antibody. Ectopic expression of GATA-3 resulted in elevated expression of Aurora-A in both ERα-positive and negative cells while siRNA-mediated silencing led to downregulation of endogenous Aurora-A in ERα-positive cells. Estrogen treatment of ERα-positive cells induced increased Aurora-A expression with enhanced recruitment of GATA-3 to the aurora-A promoter. Finally, in the ACI rat model of estrogen-induced breast cancer, known to be associated with elevated Aurora-A expression, we observed increased expression of GATA-3 in preinvasive and invasive mammary epithelial cells exposed to prolonged estrogen treatment and in developing breast tumors. These results demonstrate a direct positive role of estrogen in regulating Aurora-A expression through activation of the ERα-GATA-3 signaling cascade and suggest that this pathway may be critical in the origin of estrogen-stimulated sporadic breast cancer.

A method to purify enzymes utilizing their specific biological affinity and catalytic specificity is described. For this chromatographic technique, an enzyme binds immobilized substrate coupled to a column in the absence of a cofactor required for catalysis but permissive for substrate binding. After washing, the missing cofactor is added to the column mobile phase, and the enzyme converts substrate into product and elutes from the column. A single-step purification of EcoRI endonuclease using a sequence-specific DNA column (containing the GAATTC motif coupled to cyanogen bromide-activated Sepharose 4B) binds EcoRI in the absence of Mg2+ and elutes when Mg2+ is applied in a highly purified state. Although the method described is specific for EcoRI, it can be readily modified for the purification of DNA polymerases and other enzymes. Furthermore, many of the same materials are also used for transcription factor purification. This protocol can be completed within 4–6 d.

Eukaryotic valyl-tRNA synthetase (ValRS) and the heavy form of elongation factor 1 (EF-1H) are isolated as a stable high molecular mass complex that catalyzes consecutive steps in protein biosynthesis – aminoacylation of tRNA and its transfer to elongation factor. Herein is the first three-dimensional structure of the particle as calculated from electron microscopic images of negatively stained samples of the human ValRS/EF-1H complex. The ca. 12×8nm particle has two distinct domains and each appears to have twofold symmetry. Bound antibodies place two δ subunits near the particle’s center. These data support a dimeric head-to-head arrangement of particle components.