HEXIM knockdown triggers apoptosis-induced proliferation and deregulates Hedgehog signaling
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE54590 | GEO | 2014/07/31
SECONDARY ACCESSION(S): PRJNA237103
REPOSITORIES: GEO
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Project description:We address the function of HEXIM, an inhibitor of the general transcriptional elongation regulator P-TEFb which regulates the transcriptional status of many developmental genes, during Drosophila development. We showed that HEXIM knockdown mutants display organs development failure. In the wing disc, it induces apoptosis and affects Hh signaling. The continuous death of proliferative cells is compensated by apoptosis-induced cell proliferation, in a manner similar to that of differentiated cells, together with high levels of Hh and Ci. We completed this analysis with microarrays to characterize the molecular phenotype of HEXIM knockdown during eye differentiation. HEXIM knockdown during eye differentiation was carried out with a UAS-Hexim-RNAi strain crossed with a GMR-Gal4 driver strain (Bloomington stock center)). Adult GMR>RNAi Hexim flies display slightly smaller, rough and often necrosed eyes. Total RNA were collected from isolated heads. We then used microarray to compare the transcriptome of HEXIM knockdown mutant with that of wild type flies.
2014-07-31 | E-GEOD-54590 | biostudies-arrayexpress
Project description:Signaling between cells in the Anterior (A) and Posterior (P) compartments directs Drosophila wing disc development and is dependent on expression of the homeodomain transcription factor Engrailed (En) in P cells. Downstream of en, posteriorly expressed Hedgehog (Hh) protein signals across the A/P border to establish a developmental organizer that directs pattern formation and growth throughout the wing primordium. Here we extend investigations of the processes downstream of en by using expression array analysis to compare A and P cells. 102 candidate genes were identified that express differentially in the A and P compartments; four were characterized: Stubble (Sb) expression is restricted to A cells due to repression by en. CG15905, CG16884, and CG10200/hase und igel (hui) are expressed in A cells downstream of Hh signaling; and RNA interference for hui, Stubble, and CG16884 revealed that each is essential to wing development. We carried out a global screen for genes with compartment-specific expression using expression array hybridization to compare transcript levels in A and P wing disc cells.
2013-05-04 | GSE46601 | GEO
Project description:Signaling between cells in the Anterior (A) and Posterior (P) compartments directs Drosophila wing disc development and is dependent on expression of the homeodomain transcription factor Engrailed (En) in P cells. Downstream of en, posteriorly expressed Hedgehog (Hh) protein signals across the A/P border to establish a developmental organizer that directs pattern formation and growth throughout the wing primordium. Here we extend investigations of the processes downstream of en by using expression array analysis to compare A and P cells. 102 candidate genes were identified that express differentially in the A and P compartments; four were characterized: Stubble (Sb) expression is restricted to A cells due to repression by en. CG15905, CG16884, and CG10200/hase und igel (hui) are expressed in A cells downstream of Hh signaling; and RNA interference for hui, Stubble, and CG16884 revealed that each is essential to wing development. We carried out a global screen for genes with compartment-specific expression using expression array hybridization to compare transcript levels in A and P wing disc cells. GFP-labeled wing imaginal discs (ptc-Gal4/UAS-GFP and hh-Gal4/UAS-GFP) were micro-dissected under a fluorescence dissecting microscope. RNA isolation, amplification and microarray procedures were previously described (Klebes et al., 2002; Klebes et al., 2005; Klebes and Kornberg, 2008). In brief, hybridization probes were generated by two rounds of T7-catalyzed linear RNA amplification and labeled with Cy3 and Cy5 dyes. Reciprocally labeled probes (M-bM-^@M-^Xdye flipM-bM-^@M-^Y) were hybridized to custom produced glass microarrays (GPL2581) that contained approximately 14,000 100-600 bp exon sequences that were generated by PCR. Signal intensities were collected with a GenePix 4000B Scanner and processed with GenePix software (Molecular Devices) and global median normalized with NOMAD (http://ucsf-nomad.sourceforge.net/).
2013-05-04 | E-GEOD-46601 | biostudies-arrayexpress
Project description:HEXIM knockdown triggers apoptosis-induced proliferation and deregulates Hedgehog signaling
| PRJNA237103 | ENA
Project description:Recent evidence suggests that leflunomide, a DHODH inhibitor, disrupts neural crest development and melanoma pathogenesis via inhibiting transcription elongation. Here, we provide evidence that a transcriptional regulator, HEXIM1, is upregulated in response to leflunomide. HEXIM1 is assembled into the 7SK snRNP complex to sequester and inhibit the kinase P-TEFb. P-TEFb triggers elongation by phosphorylating RNA polymerase II and pausing factors. Knockdown of hexim in zebrafish rescues the effects of leflunomide. HEXIM1 expression is low in human melanoma. In addition, HEXIM1 overexpression can suppress melanoma onset in zebrafish. Increased HEXIM1 expression, in response to low nucleotides triggered by DHODH inhibition, sequesters P-TEFb away from melanoma pathogenesis, proliferation and cell cycle genes based on GRO-seq and ChIP-seq analyses. This reduces productive elongation at genes that maintain the tumorigenic state. Our study illustrates that HEXIM1 is a tumor suppressor that responds to cell stress, consequently inhibiting productive elongation of proliferative genes in melanoma.
2016-04-08 | GSE57431 | GEO
Project description:Recent evidence suggests that leflunomide, a DHODH inhibitor, disrupts neural crest development and melanoma pathogenesis via inhibiting transcription elongation. Here, we provide evidence that a transcriptional regulator, HEXIM1, is upregulated in response to leflunomide. HEXIM1 is assembled into the 7SK snRNP complex to sequester and inhibit the kinase P-TEFb. P-TEFb triggers elongation by phosphorylating RNA polymerase II and pausing factors. Knockdown of hexim in zebrafish rescues the effects of leflunomide. HEXIM1 expression is low in human melanoma. In addition, HEXIM1 overexpression can suppress melanoma onset in zebrafish. Increased HEXIM1 expression, in response to low nucleotides triggered by DHODH inhibition, sequesters P-TEFb away from melanoma pathogenesis, proliferation and cell cycle genes based on GRO-seq and ChIP-seq analyses. This reduces productive elongation at genes that maintain the tumorigenic state. Our study illustrates that HEXIM1 is a tumor suppressor that responds to cell stress, consequently inhibiting productive elongation of proliferative genes in melanoma.
2016-04-08 | GSE57430 | GEO
Project description:Aberrant activation of the Hedgehog (Hh) signaling pathway is implicated in the pathogenesis of many cancers, including medulloblastoma and basal cell carcinoma (BCC). In this study, using neonatally irradiated Ptch1+/- mice as a model of Hh-dependent tumors, we investigated the in vivo effects of MK-4101, a novel SMO antagonist, for treatment of medulloblastoma and BCC. Results clearly demonstrate a robust antitumor activity of MK-4101, achieved through the inhibition of proliferation and induction of extensive apoptosis in tumor cells. Of note, beside antitumor activity on transplanted tumors, MK-4101 was highly efficacious against primary medulloblastoma and BCC developing in the cerebellum and skin of Ptch1+/- mice. By identifying the changes induced by MK-4101 in gene expression profiles in tumors, we also elucidate the mechanism of action of this novel, orally administrable compound. MK-4101 targets the Hh pathway in the tumor cells, showing the maximum inhibitory effect on Gli1 activity. MK-4101 also induced deregulation of cell cycle and block of DNA replication in tumors. Members of the IGF and Wnt signaling pathways , were among the most highly deregulated genes by MK-4101, suggesting that the interplay among Hh, IGF and Wnt is crucial in Hh-dependent tumorigenesis. Altogether, the results of this preclinical study support a therapeutic opportunity for MK-4101 in the treatment of Hh-driven cancers, also providing useful information for combination therapy with drugs targeting pathways cooperating with Hh oncogenic activity. Gene expression data was generated (in replicates) from Medulloblastoma allografts collected at various time points and following low (40mpk) or high (80 mpk) or vehicle single dose (QD) or mutiple dose (BID) treatment with a SHH pathway inhibitor.
2016-03-14 | E-GEOD-77042 | biostudies-arrayexpress
Project description:We investigated the changes in gene expression in response to reduced levels of Ecdysoneless (Ecd) in the developing wing disc of Drosophila. To do this we utilized the GAL4/UAS system to express UAS-ecd-RNAi in the nubbin-domain (nub-Gal4, UAS-mRFP, UAS-ecd-RNAi) of the wing disc and used Nub-Gal4/+ wing discs as controls. We quantified transcriptomic expression analysis from four biological replicates for both experimental groups
2024-01-31 | GSE203127 | GEO
Project description:Aberrant activation of the Hedgehog (Hh) signaling pathway is implicated in the pathogenesis of many cancers, including medulloblastoma and basal cell carcinoma (BCC). In this study, using neonatally irradiated Ptch1+/- mice as a model of Hh-dependent tumors, we investigated the in vivo effects of MK-4101, a novel SMO antagonist, for treatment of medulloblastoma and BCC. Results clearly demonstrate a robust antitumor activity of MK-4101, achieved through the inhibition of proliferation and induction of extensive apoptosis in tumor cells. Of note, beside antitumor activity on transplanted tumors, MK-4101 was highly efficacious against primary medulloblastoma and BCC developing in the cerebellum and skin of Ptch1+/- mice. By identifying the changes induced by MK-4101 in gene expression profiles in tumors, we also elucidate the mechanism of action of this novel, orally administrable compound. MK-4101 targets the Hh pathway in the tumor cells, showing the maximum inhibitory effect on Gli1 activity. MK-4101 also induced deregulation of cell cycle and block of DNA replication in tumors. Members of the IGF and Wnt signaling pathways , were among the most highly deregulated genes by MK-4101, suggesting that the interplay among Hh, IGF and Wnt is crucial in Hh-dependent tumorigenesis. Altogether, the results of this preclinical study support a therapeutic opportunity for MK-4101 in the treatment of Hh-driven cancers, also providing useful information for combination therapy with drugs targeting pathways cooperating with Hh oncogenic activity.
2016-03-14 | GSE77042 | GEO
Project description:Aberrant activation of Hedgehog (HH) signaling has been identified as a key etiologic factor of many human malignancies. Signal strength, target gene specificity, and oncogenic activity of HH signaling profoundly depend on interactions with other pathways such as epidermal growth factor receptor-mediated signaling which has been shown to cooperate with HH/GLI in basal cell carcinoma and pancreatic cancer. We demonstrate that the human medulloblastoma cell line Daoy possesses a fully inducible endogenous HH pathway. Treatment of Daoy cells with Sonic Hedgehog or Smoothened agonist induced expression of GLI1 protein and prevented processing of GLI3 to its repressor form. To study interactions between HH- and EGF-induced signaling in greater detail, time-resolved measurements were carried out and analyzed on the transcriptomic as well as proteomic level. Daoy cells responded to the co-treatment by downregulating GLI1, PTCH, and HHIP on the transcript level which was also seen when Amphiregulin (AREG) was used instead of EGF. The finding that EGFR signaling silences proteins acting as negative regulators of HH signaling is firstly described here as a novel crosstalk mechanism. Furthermore, combined EGFR/HH signaling maintains high GLI1 protein levels contrasting its downregulation on the transcript level. On the other hand, high level synergism was observed with respect to a strong and significant upregulation of numerous canonical EGF-targets with putative tumor-promoting properties such as MMP7, VEGFA, and IL-8. In conclusion, synergistic effects between EGFR and HH signaling can selectively induce a switch from a canonical HH/GLI profile to a modulated specific target gene profile pointing to more wide-spread, yet context-dependent, interactions between HH/GLI and growth factor receptor signaling in human malignancies. To study interactions between HH- and EGF-induced signaling, time-resolved measurements were carried out over a period of 24 h at 14 different time points after stimulation by EGF with and without additional stimulation by SHH. Furthermore, as a control, cells without any stimulation by EGF and SHH (control) and cells in the presents of SHH were analyzed. Overall, three biological replicates of 60 different treatment/timepoints were analyzed yielding 180 different samples.
2014-07-31 | E-GEOD-46045 | biostudies-arrayexpress