Wdr5 is essential for fetal erythropoiesis and hematopoiesis.

WDR5 is a highly conserved protein that performs multiple scaffolding functions in the context of chromatin. However, efforts to understand the function of WDR5 in normal tissues physiologically are quite limited so far. In our study, we explored the function of Wdr5 in erythropoiesis and hematopoiesis by using a hematopoietic-specific Wdr5 knockout mouse model. We found that loss of Wdr5 mediated by Vav-iCre leads to embryonic lethality with defective erythropoiesis. In addition, Wdr5-deficiency completely impairs the hematopoietic stem and progenitor cells function and might alter the immunophenotype of these stem cells and progenitors by decreasing c-Kit expression. Collectively, we identified the pivotal role of Wdr5 in fetal hematopoiesis and erythropoiesis as the de novo findings.

Novel Triapine Derivative Induces Copper-Dependent Cell Death in Hematopoietic Cancers.

Triapine, an iron chelator that inhibits ribonucleotide reductase, has been evaluated in clinical trials for cancer treatment. Triapine in combination with other chemotherapeutic agents shows promising efficacy in certain hematologic malignancies; however, it is less effective against many advanced solid tumors, probably due to the unsatisfactory potency and pharmacokinetic properties. In this report, we developed a triapine derivative IC25 (10) with potent antitumor activity. 10 Preferentially inhibited the proliferation of hematopoietic cancers by inducing mitochondria reactive oxygen species production and mitochondrial dysfunction. Unlike triapine, 10 executed cytotoxic action in a copper-dependent manner. 10-Induced up-expression of thioredoxin-interacting protein resulted in decreased thioredoxin activity to permit c-Jun N-terminal kinase and p38 activation and ultimately led to the execution of the cell death program. Remarkedly, 10 showed good bioavailability and inhibited tumor growth in mouse xenograft models. Taken together, our study identifies compound 10 as a copper-dependent antitumor agent, which may be applied to the treatment of hematopoietic cancers.

Inhibition of cIAP1 as a strategy for targeting c-MYC-driven oncogenic activity.

Protooncogene c-MYC, a master transcription factor, is a major driver of human tumorigenesis. Development of pharmacological agents for inhibiting c-MYC as an anticancer therapy has been a longstanding but elusive goal in the cancer field. E3 ubiquitin ligase cIAP1 has been shown to mediate the activation of c-MYC by destabilizing MAD1, a key antagonist of c-MYC. Here we developed a high-throughput assay for cIAP1 ubiquitination and identified D19, a small-molecule inhibitor of E3 ligase activity of cIAP1. We show that D19 binds to the RING domain of cIAP1 and inhibits the E3 ligase activity of cIAP1 by interfering with the dynamics of its interaction with E2. Blocking cIAP1 with D19 antagonizes c-MYC by stabilizing MAD1 protein in cells. Furthermore, we show that D19 and an improved analog (D19-14) promote c-MYC degradation and inhibit the oncogenic function of c-MYC in cells and xenograft animal models. In contrast, we show that activating E3 ubiquitin ligase activity of cIAP1 by Smac mimetics destabilizes MAD1, the antagonist of MYC, and increases the protein levels of c-MYC. Our study provides an interesting example using chemical biological approaches for determining distinct biological consequences from inhibiting vs. activating an E3 ubiquitin ligase and suggests a potential broad therapeutic strategy for targeting c-MYC in cancer treatment by pharmacologically modulating cIAP1 E3 ligase activity.

Allosteric Inhibitors of SHP2 with Therapeutic Potential for Cancer Treatment.

SHP2, a cytoplasmic protein-tyrosine phosphatase encoded by the PTPN11 gene, is involved in multiple cell signaling processes including Ras/MAPK and Hippo/YAP pathways. SHP2 has been shown to contribute to the progression of a number of cancer types including leukemia, gastric, and breast cancers. It also regulates T-cell activation by interacting with inhibitory immune checkpoint receptors such as the programmed cell death 1 (PD-1) and B- and T-lymphocyte attenuator (BTLA). Thus, SHP2 inhibitors have drawn great attention by both inhibiting tumor cell proliferation and activating T cell immune responses toward cancer cells. In this study, we report the identification of an allosteric SHP2 inhibitor 1-(4-(6-bromonaphthalen-2-yl)thiazol-2-yl)-4-methylpiperidin-4-amine (23) that locks SHP2 in a closed conformation by binding to the interface of the N-terminal SH2, C-terminal SH2, and phosphatase domains. Compound 23 suppresses MAPK signaling pathway and YAP transcriptional activity and shows antitumor activity in vivo. The results indicate that allosteric inhibition of SHP2 could be a feasible approach for cancer therapy.

Upregulation of CD11b and CD86 through LSD1 inhibition promotes myeloid differentiation and suppresses cell proliferation in human monocytic leukemia cells.

LSD1 (Lysine Specific Demethylase1)/KDM1A (Lysine Demethylase 1A), a flavin adenine dinucleotide (FAD)-dependent histone H3K4/K9 demethylase, sustains oncogenic potential of leukemia stem cells in primary human leukemia cells. However, the pro-differentiation and anti-proliferation effects of LSD1 inhibition in acute myeloid leukemia (AML) are not yet fully understood. Here, we report that small hairpin RNA (shRNA) mediated LSD1 inhibition causes a remarkable transcriptional activation of myeloid lineage marker genes (CD11b/ITGAM and CD86), reduction of cell proliferation and decrease of clonogenic ability of human AML cells. Cell surface expression of CD11b and CD86 is significantly and dynamically increased in human AML cells upon sustained LSD1 inhibition. Chromatin immunoprecipitation and quantitative PCR (ChIP-qPCR) analyses of histone marks revealed that there is a specific increase of H3K4me2 modification and an accompanied increase of H3K4me3 modification at the respective CD11b and CD86 promoter region, whereas the global H3K4me2 level remains constant. Consistently, inhibition of LSD1 in vivo significantly blocks tumor growth and induces a prominent increase of CD11b and CD86. Taken together, our results demonstrate the anti-tumor properties of LSD1 inhibition on human AML cell line and mouse xenograft model. Our findings provide mechanistic insights into the LSD1 functions in controlling both differentiation and proliferation in AML.

Discovery of novel 1,2,3,4-tetrahydrobenzo[4, 5]thieno[2, 3-c]pyridine derivatives as potent and selective CYP17 inhibitors.

The inhibition of CYP17 to block androgen biosynthesis is a well validated strategy for the treatment of prostate cancer. Herein we reported the design, synthesis and structure-activity relationship (SAR) study for a series of novel 1,2,3,4- tetrahydrobenzo[4,5]thieno[2,3-c]pyridine derivatives. Some analogs demonstrated a potent inhibition to both rat and human CYP17 protein and reduced testosterone production in human H295R cell line. Some analogs also showed high selectivity against other CYP enzymes such as 3A4, 1A2, 2C9, 2C19 and 2D6, which may limit side effects due to drug-drug interactions. Among these analogs, the most potent compound 9c showed 1.5 fold more potent against rat and human CYP17 protein than that of abiraterone (IC50 = 16 nM and 20 nM vs. 25 nM and 36 nM respectively). In NCI-H295R cells, the inhibitory effect of compound 9c on testosterone production (52± 2%) was also more potent than that of abiraterone (74± 15%) at the concentration of 1 µM. Further, it was shown that 9c reduced plasma testosterone level in a dose-dependent manner in Sprague-Dawley rats. Thus, analog 9c maybe a potential agent used for the treatment of prostate cancer.

GDF-15 enhances intracellular Ca2+ by increasing Cav1.3 expression in rat cerebellar granule neurons.

GDF-15 (growth/differentiation factor 15) is a novel member of the TGF (transforming growth factor)-ß superfamily that has critical roles in the central and peripheral nervous systems. We reported previously that GDF-15 increased delayed rectifier outward K(+) currents and Kv2.1 α subunit expression through TßRII (TGF-ß receptor II) to activate Src kinase and Akt/mTOR (mammalian target of rapamycin) signalling in rat CGNs (cerebellar granule neurons). In the present study, we found that treatment of CGNs with GDF-15 for 24 h increased the intracellular Ca(2+) concentration ([Ca(2+)]i) in response to membrane depolarization, as determined by Ca(2+) imaging. Whole-cell current recordings indicated that GDF-15 increased the inward Ca(2+) current (ICa) without altering steady-state activation of Ca(2+) channels. Treatment with nifedipine, an inhibitor of L-type Ca(2+) channels, abrogated GDF-15-induced increases in [Ca(2+)]i and ICa The GDF-15-induced increase in ICa was mediated via up-regulation of the Cav1.3 α subunit, which was attenuated by inhibiting Akt/mTOR and ERK (extracellular-signal-regulated kinase) pathways and by pharmacological inhibition of Src-mediated TßRII phosphorylation. Given that Cav1.3 is not only a channel for Ca(2+) influx, but also a transcriptional regulator, our data confirm that GDF-15 induces protein expression via TßRII and activation of a non-Smad pathway, and provide novel insight into the mechanism of GDF-15 function in neurons.

cAMP/PKA Pathways and S56 Phosphorylation Are Involved in AA/PGE2-Induced Increases in rNaV1.4 Current.

Arachidonic acid (AA) and its metabolites are important second messengers for ion channel modulation. The effects of extracellular application of AA and its non-metabolized analogue on muscle rNaV1.4 Na+ current has been studied, but little is known about the effects of intracellular application of AA on this channel isoform. Here, we report that intracellular application of AA significantly augmented the rNaV1.4 current peak without modulating the steady-state activation and inactivation properties of the rNaV1.4 channel. These results differed from the effects of extracellular application of AA on rNaV1.4 current. The effects of intracellular AA were mimicked by prostaglandin E2 but not eicosatetraynoic acid (ETYA), the non-metabolized analogue of AA, and were eliminated by treatment with cyclooxygenase inhibitors, flufenamic acid, or indomethacin. AA/PGE2-induced activation of rNaV1.4 channels was mimicked by a cAMP analogue (db-cAMP) and eliminated by a PKA inhibitor, PKAi. Furthermore, inhibition of EP2 and EP4 (PGE2 receptors) with AH6809 and AH23848 reduced the intracellular AA/PGE2-induced increase of rNaV1.4 current. Two mutated channels, rNaV1.4S56A and rNaV1.4T21A, were designed to investigate the role of predicted phosphorylation sites in the AA/PGE2-mediated regulation of rNaV1.4 currents. In rNaV1.4S56A, the effects of intracellular db-cAMP, AA, and PGE2 were significantly reduced. The results of the present study suggest that intracellular AA augments rNaV1.4 current by PGE2/EP receptor-mediated activation of the cAMP/PKA pathway, and that the S56 residue on the channel protein is important for this process.

Exposure to extremely low-frequency electromagnetic fields modulates Na+ currents in rat cerebellar granule cells through increase of AA/PGE2 and EP receptor-mediated cAMP/PKA pathway.

Although the modulation of Ca(2+) channel activity by extremely low-frequency electromagnetic fields (ELF-EMF) has been studied previously, few reports have addressed the effects of such fields on the activity of voltage-activated Na(+) channels (Na(v)). Here, we investigated the effects of ELF-EMF on Na(v) activity in rat cerebellar granule cells (GCs). Our results reveal that exposing cerebellar GCs to ELF-EMF for 10-60 min significantly increased Na(v) currents (I(Na)) by 30-125% in a time- and intensity-dependent manner. The Na(v) channel steady-state activation curve, but not the steady-state inactivation curve, was significantly shifted (by 5.2 mV) towards hyperpolarization by ELF-EMF stimulation. This phenomenon is similar to the effect of intracellular application of arachidonic acid (AA) and prostaglandin E(2) (PGE(2)) on I(Na) in cerebellar GCs. Increases in intracellular AA, PGE(2) and phosphorylated PKA levels in cerebellar GCs were observed following ELF-EMF exposure. Western blottings indicated that the Na(V) 1.2 protein on the cerebellar GCs membrane was increased, the total expression levels of Na(V) 1.2 protein were not affected after exposure to ELF-EMF. Cyclooxygenase inhibitors and PGE(2) receptor (EP) antagonists were able to eliminate this ELF-EMF-induced increase in phosphorylated PKA and I(Na). In addition, ELF-EMF exposure significantly enhanced the activity of PLA(2) in cerebellar GCs but did not affect COX-1 or COX-2 activity. Together, these data demonstrate for the first time that neuronal I(Na) is significantly increased by ELF-EMF exposure via a cPLA2 AA PGE(2) EP receptors PKA signaling pathway.

Brain natriuretic peptide modulates the delayed rectifier outward K(+) current and promotes the proliferation of mouse Schwann cells.

Brain natriuretic peptide (BNP) may act as a neuromodulator via its associated receptors (natriuretic peptide receptors, NPRs) in the central nervous system (CNS), but few studies have reported its activity in the peripheral nervous system (PNS). In this study, we observed that BNP increased the tetraethylammonium chloride (TEA)-sensitive delayed rectifier outward potassium current (I(K)) in mouse Schwann cells (SCs) using whole-cell recording techniques. At concentrations of 1-100 nM, BNP reversibly activated I(K) in a dose-dependent manner, with modulating its steady-state activation and inactivation properties. The effect of BNP on I(K) was abolished by preincubation with the specific antagonist of NPR-A, and could not be mimicked by application of NPR-C agonist. These results were supported by immunocytochemical findings indicating that NPR-A was expressed in SCs. The application of 8-Br-guanosine 3',5'-monophosphate (8-Br-cGMP) mimicked the effect of BNP on I(K), but BNP was unable to further increase I(K) after the application of cyclic guanosine monophosphate (cGMP). Genistein blocked I(K) and also completely eliminated the effects of BNP and cGMP on I(K). The selective K(V)2.1 subunit blocker, Jingzhaotoxin-III (JZTX-III), reduced I(K) amplitude by 30%, but did not abolish the increase effect of BNP on I(K) amplitude. In addition, BNP significantly stimulated SCs proliferation and this effect could be partly inhibited by TEA. Together these results suggest that BNP modulated I(K) probably via cGMP- and tyrosine kinase-dependent pathways by activation of NPR-A. This effect of BNP on I(K) in SCs might partly explain its effect on cell proliferation.