scholarly journals Id1 is a common downstream target of oncogenic tyrosine kinases in leukemic cells

Blood ◽  
2008 ◽  
Vol 112 (5) ◽  
pp. 1981-1992 ◽  
Author(s):  
Winnie F. Tam ◽  
Ting-Lei Gu ◽  
Jing Chen ◽  
Benjamin H. Lee ◽  
Lars Bullinger ◽  
...  
Keyword(s):  
Cell Lines ◽  
Tyrosine Kinases ◽  
Target Genes ◽  
Bone Marrow Cells ◽  
Leukemic Cells ◽  
Hematopoietic Malignancy ◽  
Downstream Target ◽  
Models Of Disease ◽  
Induced Apoptosis

Abstract Oncogenic tyrosine kinases, such as BCR-ABL, TEL-ABL, TEL-PDGFβR, and FLT3-ITD, play a major role in the development of hematopoietic malignancy. They activate many of the same signal transduction pathways. To identify the critical target genes required for transformation in hematopoietic cells, we used a comparative gene expression strategy in which selective small molecules were applied to 32Dcl3 cells that had been transformed to factor-independent growth by these respective oncogenic alleles. We identified inhibitor of DNA binding 1 (Id1), a gene involved in development, cell cycle, and tumorigenesis, as a common target of these oncogenic kinases. These findings were prospectively confirmed in cell lines and primary bone marrow cells engineered to express the respective tyrosine kinase alleles and were also confirmed in vivo in murine models of disease. Moreover, human AML cell lines Molm-14 and K562, which express the FLT3-ITD and BCR-ABL tyrosine kinases, respectively, showed high levels of Id1 expression. Antisense and siRNA based knockdown of Id1-inhibited growth of these cells associated with increased p27Kip1 expression and increased sensitivity to Trail-induced apoptosis. These findings indicate that Id1 is an important target of constitutively activated tyrosine kinases and may be a therapeutic target for leukemias associated with oncogenic tyrosine kinases.

scholarly journals Alantolactone inhibits cell autophagy and promotes apoptosis via AP2M1 in acute lymphoblastic leukemia

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Ce Shi ◽  
Wenjia Lan ◽  
Zhenkun Wang ◽  
Dongguang Yang ◽  
Jia Wei ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Tumor Growth ◽  
Cell Lines ◽  
Lymphoblastic Leukemia ◽  
Dependent Manner ◽  
Nude Mouse Model ◽  
Hematopoietic Malignancy ◽  
Induced Apoptosis ◽  
Anti Tumor Activity

Abstract Background Acute lymphoblastic leukemia (ALL) is an aggressive hematopoietic malignancy that is most commonly observed in children. Alantolactone (ALT) has been reported to exhibit anti-tumor activity in different types of cancer. The aim of the present study was to investigate the anti-tumor activity and molecular mechanism of ALT in ALL. Methods ALL cell lines were treated with 1, 5 and 10 μM ALT, and cell viability was assessed using an MTT assay and RNA sequencing. Flow cytometry, JC-1 staining and immunofluorescence staining assays were used to measure cell apoptosis and autophagy. Additionally, western blot analysis was used to detect expression of apoptosis and autophagy related proteins. Finally, the effects of ALT on tumor growth were assessed in a BV173 xenograft nude mouse model. Results ALT inhibited the proliferation of ALL cells in a dose-dependent manner. Additionally, it was demonstrated that ALT inhibited cell proliferation, colony formation, autophagy, induced apoptosis and reduced tumor growth in vivo through upregulating the expression of adaptor related protein complex 2 subunit mu 1 (AP2M1). Moreover, the autophagy activator rapamycin, attenuated the pro-apoptotic effects of ALT on BV173 and NALM6 cell lines. Overexpression of AP2M1 decreased the expression of Beclin1 and the LC3-II/LC3-1 ratio, and increased p62 expression. Knockdown of Beclin1 increased the levels of bax, cleaved caspase 3 and cytochrome C, and decreased bcl-2 expression. Conclusions The present study demonstrated that ALT exerts anti-tumor activity through inducing apoptosis and inhibiting autophagy by upregulating AP2M1 in ALL, highlighting a potential therapeutic strategy for treatment of ALL.

scholarly journals Alantolactone inhibits cell autophagy and promotes apoptosis through targeting AP2M1 in acute lymphotic leukemia

2020 ◽  
Author(s):  
Ce Shi ◽  
Zhenkun Wang ◽  
Dongguang Yang ◽  
Jia Wei ◽  
Zhiyu Liu ◽  
...  
Keyword(s):  
Antitumor Activity ◽  
Tumor Growth ◽  
Cell Lines ◽  
Lymphoblastic Leukemia ◽  
Dependent Manner ◽  
Nude Mouse Model ◽  
Hematopoietic Malignancy ◽  
Apoptotic Effect ◽  
Induced Apoptosis

Abstract Background: Acute lymphoblastic leukemia (ALL) is an aggressive hematopoietic malignancy that is most common in children. Alantolactone (ALT) has been reported to have antitumor activity in different types of cancers. This study aimed to investigate the antitumor activity and molecular mechanism of ALT in ALL. Methods: The ALL cell lines were treated with 1, 5 and 10μM of ALT, and then subjected to MTT assay and RNA sequencing. Flow cytometry, JC-1 staining and immunofluorescence staining assays were employed to measure cell apoptosis and autophagy. Meanwhile, Western blot analysis was used to detect apoptosis and autophagy related proteins. Finally, the effect of ALT on tumor growth was measured in BV173 xenograft nude mouse model. Results: In this study, we demonstrated that ALT inhibited the proliferation of ALL cells in does-dependent manner. A series of experiments demonstrated that ALT inhibited cell proliferation, colony formation, autophagy, induced apoptosis and restained tumor growth in vivo through upregulating adaptor related protein complex 2 subunit mu 1 (AP2M1). Moreover, autophagy activator rapamycin attenuated the pro-apoptotic effect of ALT on BV173 and NALM6 cell lines. Further, overexpressed AP2M1 decreased the expression of Beclin1, LC3-II/LC3-1 ratio and increased p62 expression. Fianally, knockdown of Beclin1 increased the levels of bax, cleaved caspase 3 and cytochrome C and decreased bcl-2 expression. Conclusions: This study demonstrated that ALT exerts antitumor activity through inducing apoptosis and inhibiting autophagy by upregulating AP2M1 in ALL, indicating a potential therapeutic strategy for ALL treatment.

Linkage of the potent leukemogenic activity of Meis1 to cell-cycle entry and transcriptional regulation of cyclin D3

Blood ◽  
2010 ◽  
Vol 115 (20) ◽  
pp. 4071-4082 ◽  
Author(s):  
Bob Argiropoulos ◽  
Eric Yung ◽  
Ping Xiang ◽  
Chao Yu Lo ◽  
Florian Kuchenbauer ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Hox Genes ◽  
Cell Cycle Control ◽  
Cyclin D3 ◽  
Leukemic Cells ◽  
Downstream Target

MEIS1 is a three–amino acid loop extension class homeodomain-containing homeobox (HOX) cofactor that plays key roles in normal hematopoiesis and leukemogenesis. Expression of Meis1 is rate-limiting in MLL-associated leukemias and potently interacts with Hox and NUP98-HOX genes in leukemic transformation to promote self-renewal and proliferation of hematopoietic progenitors. The oncogenicity of MEIS1 has been linked to its transcriptional activation properties. To further reveal the pathways triggered by Meis1, we assessed the function of a novel engineered fusion form of Meis1, M33-MEIS1, designed to confer transcriptional repression to Meis1 target genes that are otherwise up-regulated in normal and malignant hematopoiesis. Retroviral overexpression of M33-Meis1 resulted in the rapid and complete eradication of M33-Meis1–transduced normal and leukemic cells in vivo. Cell-cycle analysis showed that M33-Meis1 impeded the progression of cells from G1-to-S phase, which correlated with significant reduction of cyclin D3 levels and the inhibition of retinoblastoma (pRb) hyperphosphorylation. We identified cyclin D3 as a direct downstream target of MEIS1 and M33-MEIS1 and showed that the G1-phase accumulation and growth suppression induced by M33-Meis1 was partially relieved by overexpression of cyclin D3. This study provides strong evidence linking the growth-promoting activities of Meis1 to the cyclin D-pRb cell-cycle control pathway.

The Anti-Apoptotic Gene BCL2A1 Is Transcriptionally Regulated by PU.1

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3579-3579
Author(s):  
Mathias Jenal ◽  
Venkateshwar A. Reddy ◽  
Judith Laedrach ◽  
Deborah Shan ◽  
Andreas Tobler ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Target Genes ◽  
Leukemic Cells ◽  
Related Factor ◽  
Mrna Levels ◽  
Atra Treatment ◽  
Aberrant Expression ◽  
Mrna Induction

Abstract PU.1 is a hematopoietic transcriptional regulator that is necessary for the development of both myeloid and B cells. To identify new PU.1 target genes in neutrophil development PU.1 was introduced into mouse 503 PU.1-null cells using lentiviral gene transfer and microarray analyses of two independent 503 PU.1-rescued and parental 503 cells were compared. The BCL2A1 gene was found to be more than 50-fold induced in 503 PU.1- restored as compared to the parental 503-null cells. BCL2A1 (also known as BFL-1/A1) is an anti-apoptotic member of the BCL2 family. BCL2A1 was initially identified as a tissue-specific BCL2-related factor that is induced by different reagents such as granulocyte macrophage colony-stimulating factor (GM-CSF) or all-trans retinoic acid (ATRA) during myeloid differentiation. Upregulation of BCL2A1 in granulocytes may promote a time-dependent survival. To follow up on our microarray findings we evaluated loss of PU.1 function in human NB4 acute promyelocytic leukemia (APL) cells using lentivector delivered, short hairpin (sh) RNAs targeting PU.1. Knockdown efficacy upon ATRA-treatment in the two shPU.1 expressing NB4 cell lines was 67 and 30%, respectively. Silencing of PU.1 markedly reduced BCL2A1 mRNA induction upon ATRA-treatment from 167-fold in control cells to 47- and 112-fold in the two PU.1 knockdown NB4 cell lines, respectively (Figure A). Co-transfection of PU.1 with a human BCL2A1 promoter reporter resulted in a 7-fold activation, suggesting PU.1 can directly regulate BCL2A1. Co-transfection with NF-kappaB, used as positive control, induced the BCL2A1 promoter 14.5-fold. Moreover, in vivo binding of the transcription factor PU.1 to 2/8 putative PU.1 binding sites in the BCL2A1 promoter was shown by chromatin immunoprecipitation in HL60 promyelocytic cells further supporting a role for PU.1 regulation of BCL2A1. Evaluation of BCL2A1 and PU.1 mRNA expression in CD34+ hematopoietic progenitors, granulocytes, and primary acute myeloid leukemia (AML) cells was assessed using real-time quantitative RT-PCR. BCL2A1 and PU.1 mRNA levels were significantly lower in primary AML patient samples (n=80; p<0.0001) and in CD34+ progenitor cells (n=4; p=0.0095) than in granulocytes (n=6; Figure B). In line with this observation, we found that upon ATRA therapy BCL2A1 levels were increased in 5/5 APL patients and PU.1 mRNA levels in 4/5 APL cases, respectively. Altogether, these results clearly indicate that PU.1 and BCL2A1 are co-regulated during granulocyte differentiation. Lastly, we confirmed earlier data showing that ATRA-pretreatment of NB4 cells and thus induction of PU.1 and BCL2A1, rendered these cells less sensitive to arsenic trioxide (As2O3)- induced cell death. Conversely, NB4 PU.1 knockdown cells were markedly more sensitive to As2O3 -induced cell death upon ATRA-pretreatment than the parental NB4 control cells. The increase in sensitivity to As2O3 correlated with the lower BCL2A1 levels found in the PU.1 knockdown cells. In summary, we identified the anti-apoptotic BCL2A1 gene as direct, transcriptional target of PU.1 in myeloid leukemic cells. We hypothesize that PU.1-dependent induction of BCL2A1 is necessary for the survival of normal, terminally differentiated myeloid cells. Furthermore, aberrant expression of PU.1 in erythroleukemia may result in elevated BCL2A1 levels that support increased survival of erythroblasts in this particular type of leukemia. Figure Figure

scholarly journals P11.54 Identification of PDGFRA and MYC(N) as somatic driver genes in Glioblastoma

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii55-iii56
Author(s):  
A D Berezovsky ◽  
A Transou ◽  
S Irtenkauf ◽  
L Poisson ◽  
K Hank Wu ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Cell Lines ◽  
Gene Amplification ◽  
Median Survival ◽  
Tyrosine Kinases ◽  
Target Genes ◽  
Expression Patterns ◽  
Mycn Amplification ◽  
Driver Genes

Abstract BACKGROUND Somatic oncogene amplification happens frequently in glioblastoma (GBM). The second most frequently amplified gene encoding receptor tyrosine kinases in GBMs is platelet derived growth factor alpha (PDGFRA) (15%). In contrast, MYC and MYCN amplification occurs in 1.6% and 2.9%, respectively. Our goal was to characterize the role of PDGFRɑ and Myc in GBM. MATERIAL AND METHODS Neurosphere cultures were implanted in cohorts of 10–15 nude mice. 5 PDX lines, presenting median survival of 29–59 days were classified as short survivors, and 5 lines with median survival between 104–134 days classified as long survivors. Total RNA was extracted from PDX terminal tumors (3 biological replicates) and sequenced in a paired-end read format. Mouse reads were filtered out using Xenome. MYC and PDGFRA expression patterns were analyzed in tissue microarrays representing duplicated samples from 40 glioma neurosphere-derived PDX lines by IHC (1 anaplastic oligodendroglioma, 8 recurrent GBM with 2 newly diagnosed/recurrent pairs). Normalized staining intensity (MI) and area (A) were quantified using Fiji/ImageJ. RESULTS PDGFRA, MYC, MYCN gene amplifications were represented in a molecularly diverse panel of GBM patient-derived cancer stem-like cells (CSC) and orthotopic mouse xenografts (PDX). Transforming to a normal distribution (log10), 4/13 of cell lines had a PDGFRA mRNA expression (RPKM) higher than 1.5. Similarly, one PDX line had a staining index of greater than 10, 11 (27.5%) had an index between 5–10. The range of intra-tumoral variance, represented by standard deviation, was 0.09–24.25 highlighting the heterogeneity of PDGFRɑ expression. PDGFRɑ phosphorylation (Y754) did not differ between 8 cell lines cultured in NMGF, but deviated in alternate medias without growth factors, supplemented with FBS. In comparison, MYC(N) mRNA expression is only elevated in the context of a known amplification. Furthermore, a a MYC activity signature consisting of 18 target genes was only evident in the 5 amplified CSC lines. Taking advantage of genomic heterogeneity, we have isolated subclones lacking PDGFRA amplification from a PDGFRA amplified GBM CSC. The absence of PDGFRA amplification reduced the self-renewal potential to 37% of the PDGFRA amplified cell population (p=0.001) in clone 1 and 57% in clone 2 (p=0.013). Pertaining to determinants of in vivo survival, MYC was altered in 80% of short survivors (2/5 MYC, 2/5 MYCN amplification) and in 0% of long survivors. Myc signature was highly correlated with in vivo survival (Pearsons’ corr. = -0.77) and MYC gene expression was correlated with in vivo TMZ resistance (corr. = 0.7). CONCLUSION These results suggest that PDGFRɑ expression and activity can occur in the absence of gene amplification, while Myc activity is dependent on gene amplification. Both oncogenes drive oncogenic pathways that should be explored as therapeutic targets.

scholarly journals Oridonin, a diterpenoid extracted from medicinal herbs, targets AML1-ETO fusion protein and shows potent antitumor activity with low adverse effects on t(8;21) leukemia in vitro and in vivo

Blood ◽  
2006 ◽  
Vol 109 (8) ◽  
pp. 3441-3450 ◽  
Author(s):  
Guang-Biao Zhou ◽  
Hui Kang ◽  
Lan Wang ◽  
Li Gao ◽  
Ping Liu ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Target Genes ◽  
Critical Role ◽  
Ectopic Expression ◽  
Medicinal Herbs ◽  
Leukemic Cells ◽  
Apoptotic Effect ◽  
Induced Apoptosis

Abstract Studies have documented the potential antitumor activities of oridonin, a compound extracted from medicinal herbs. However, whether oridonin can be used in the selected setting of hematology/oncology remains obscure. Here, we reported that oridonin induced apoptosis of t(8;21) acute myeloid leukemic (AML) cells. Intriguingly, the t(8;21) product AML1-ETO (AE) fusion protein, which plays a critical role in leukemogenesis, was degraded with generation of a catabolic fragment, while the expression pattern of AE target genes investigated could be reprogrammed. The ectopic expression of AE enhanced the apoptotic effect of oridonin in U937 cells. Preincubation with caspase inhibitors blocked oridonin-triggered cleavage of AE, while substitution of Ala for Asp at residues 188 in ETO moiety of the fusion abrogated AE degradation. Furthermore, oridonin prolonged lifespan of C57 mice bearing truncated AE-expressing leukemic cells without suppression of bone marrow or reduction of body weight of animals, and exerted synergic effects while combined with cytosine arabinoside. Oridonin also inhibited tumor growth in nude mice inoculated with t(8;21)-harboring Kasumi-1 cells. These results suggest that oridonin may be a potential antileukemia agent that targets AE oncoprotein at residue D188 with low adverse effect, and may be helpful for the treatment of patients with t(8;21) AML.

Oncogenic Tyrosine Kinases Regulate Proliferative and Survival Signals through Activation of Id1.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 417-417
Author(s):  
Ting-Lei Gu ◽  
Winnie F. Tam ◽  
Jing Chen ◽  
Benjamin H. Lee ◽  
Andrew Z. Wang ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Cell Lines ◽  
Tyrosine Kinases ◽  
Target Genes ◽  
Kinase Inhibitors ◽  
Mapk Pathway ◽  
Leukemia Cell ◽  
Signal Transduction Pathway ◽  
Human Leukemia ◽  
Hematopoietic Malignancy

Abstract The oncogenic tyrosine kinases, such as BCR-ABL, TEL-ABL, TEL-PDGFbR and FLT3-ITD, play a major role in the development of hematopoietic malignancy. They activate many of the same signal transduction pathways, including the RAS/MAPK pathway, STAT/JAK pathway and PI3-K/AKT pathway. Although activation of signal transduction pathway has been extensively studied, few bone fide target genes have been identified. To identify the critical target genes that are required for transformation in hematopoietic cells, specific tyrosine kinase inhibitors were applied to 32Dcl3 cells expressing various activated tyrosine kinases. Using Affymetrix oligonucleotide arrays, we have identified inhibitor of DNA binding 1 (Id1), which is involved in development, cell cycle and tumorigenesis, as a common target gene of oncogenic tyrosine kinases. To characterize the biological consequence of Id1 expression, we inhibited the expression of Id1 in two human leukemia cell lines (Molm-14 and K562) by an antisense Id1 construct. In both cell lines, we observed a growth inhibition associated with release of inhibition of p27Kip. In addition, inactivation of Id1 sensitized K562 cells to Trail-induced apoptosis. Our findings suggest that Id1 is an important target of constitutively activated tyrosine kinases, and may be a therapeutic target for leukemias involving oncogenic tyrosine kinases.

scholarly journals Absence of SKP2 expression attenuates BCR-ABL–induced myeloproliferative disease

Blood ◽  
2008 ◽  
Vol 112 (5) ◽  
pp. 1960-1970 ◽  
Author(s):  
Anupriya Agarwal ◽  
Thomas G. P. Bumm ◽  
Amie S. Corbin ◽  
Thomas O'Hare ◽  
Marc Loriaux ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Lines ◽  
Tyrosine Kinases ◽  
Cell Cycle Progression ◽  
Cell Cycle Control ◽  
Ectopic Expression ◽  
Leukemic Cells ◽  
G1 Arrest ◽  
Myeloproliferative Disease

Abstract BCR-ABL is proposed to impair cell-cycle control by disabling p27, a tumor suppressor that inhibits cyclin-dependent kinases. We show that in cell lines p27 expression is inversely correlated with expression of SKP2, the F-box protein of SCFSKP2 (SKP1/Cul1/F-box), the E3 ubiquitin ligase that promotes proteasomal degradation of p27. Inhibition of BCR-ABL kinase causes G1 arrest, down-regulation of SKP2, and accumulation of p27. Ectopic expression of wild-type SKP2, but not a mutant unable to recognize p27, partially rescues cell-cycle progression. A similar regulation pattern is seen in cell lines transformed by FLT3-ITD, JAK2V617F, and TEL-PDGFRβ, suggesting that the SKP2/p27 conduit may be a universal target for leukemogenic tyrosine kinases. Mice that received transplants of BCR-ABL–infected SKP2−/− marrow developed a myeloproliferative syndrome but survival was significantly prolonged compared with recipients of BCR-ABL-expressing SKP2+/+ marrow. SKP2−/− leukemic cells demonstrated higher levels of nuclear p27 than SKP2+/+ counterparts, suggesting that the attenuation of leukemogenesis depends on increased p27 expression. Our data identify SKP2 as a crucial mediator of BCR-ABL–induced leukemogenesis and provide the first in vivo evidence that SKP2 promotes oncogenesis. Hence, stabilization of p27 by inhibiting its recognition by SCFSKP2 may be therapeutically useful.

scholarly journals Alantolactone inhibits cell autophagy and promotes apoptosis via AP2M1 in acute lymphoblastic leukemia

2020 ◽  
Author(s):  
Ce Shi ◽  
Wenjia Lan ◽  
Zhenkun Wang ◽  
Dongguang Yang ◽  
Jia Wei ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Tumor Growth ◽  
Cell Lines ◽  
Lymphoblastic Leukemia ◽  
Dependent Manner ◽  
Nude Mouse Model ◽  
Hematopoietic Malignancy ◽  
Induced Apoptosis ◽  
Anti Tumor Activity

Abstract Background: Acute lymphoblastic leukemia (ALL) is an aggressive hematopoietic malignancy that is most commonly observed in children. Alantolactone (ALT) has been reported to exhibit anti-tumor activity in different types of cancer. The aim of the present study was to investigate the anti-tumor activity and molecular mechanism of ALT in ALL. Methods: ALL cell lines were treated with 1, 5 and 10 μM ALT, and cell viability was assessed using an MTT assay and RNA sequencing. Flow cytometry, JC-1 staining and immunofluorescence staining assays were used to measure cell apoptosis and autophagy. Additionally, western blot analysis was used to detect expression of apoptosis and autophagy related proteins. Finally, the effects of ALT on tumor growth were assessed in a BV173 xenograft nude mouse model. Results: ALT inhibited the proliferation of ALL cells in a dose-dependent manner. Additionally, it was demonstrated that ALT inhibited cell proliferation, colony formation, autophagy, induced apoptosis and reduced tumor growth in vivo through upregulating the expression of adaptor related protein complex 2 subunit mu 1 (AP2M1). Moreover, the autophagy activator rapamycin, attenuated the pro-apoptotic effects of ALT on BV173 and NALM6 cell lines. Overexpression of AP2M1 decreased the expression of Beclin1 and the LC3-II/LC3-1 ratio, and increased p62 expression. Knockdown of Beclin1 increased the levels of bax, cleaved caspase 3 and cytochrome C, and decreased bcl-2 expression. Conclusions: The present study demonstrated that ALT exerts anti-tumor activity through inducing apoptosis and inhibiting autophagy by upregulating AP2M1 in ALL, highlighting a potential therapeutic strategy for treatment of ALL.

Drosophila Gain-of-Function Mutant RTK Torso Triggers Ectopic Dpp and STAT Signaling

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 247-258 ◽  
Author(s):  
Jinghong Li ◽  
Willis X Li
Keyword(s):  
Tyrosine Kinases ◽  
Target Genes ◽  
Tor Signaling ◽  
Gain Of Function ◽  
Essential Requirement ◽  
Downstream Target ◽  
Rtk Signaling ◽  
Genome Wide ◽  
A Genome ◽  
Genomic Regions

Abstract Overactivation of receptor tyrosine kinases (RTKs) has been linked to tumorigenesis. To understand how a hyperactivated RTK functions differently from wild-type RTK, we conducted a genome-wide systematic survey for genes that are required for signaling by a gain-of-function mutant Drosophila RTK Torso (Tor). We screened chromosomal deficiencies for suppression of a gain-of-function mutation tor (torGOF), which led to the identification of 26 genomic regions that, when in half dosage, suppressed the defects caused by torGOF. Testing of candidate genes in these regions revealed many genes known to be involved in Tor signaling (such as those encoding the Ras-MAPK cassette, adaptor and structural molecules of RTK signaling, and downstream target genes of Tor), confirming the specificity of this genetic screen. Importantly, this screen also identified components of the TGFβ (Dpp) and JAK/STAT pathways as being required for TorGOF signaling. Specifically, we found that reducing the dosage of thickveins (tkv), Mothers against dpp (Mad), or STAT92E (aka marelle), respectively, suppressed torGOF phenotypes. Furthermore, we demonstrate that in torGOF embryos, dpp is ectopically expressed and thus may contribute to the patterning defects. These results demonstrate an essential requirement of noncanonical signaling pathways for a persistently activated RTK to cause pathological defects in an organism.

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