Gene Summary

Gene:CBL; Cbl proto-oncogene, E3 ubiquitin protein ligase
Aliases: CBL2, NSLL, C-CBL, RNF55, FRA11B
Summary:This gene is a proto-oncogene that encodes a RING finger E3 ubiquitin ligase. The encoded protein is one of the enzymes required for targeting substrates for degradation by the proteasome. This protein mediates the transfer of ubiquitin from ubiquitin conjugating enzymes (E2) to specific substrates. This protein also contains an N-terminal phosphotyrosine binding domain that allows it to interact with numerous tyrosine-phosphorylated substrates and target them for proteasome degradation. As such it functions as a negative regulator of many signal transduction pathways. This gene has been found to be mutated or translocated in many cancers including acute myeloid leukaemia. Mutations in this gene are also the cause of Noonan syndrome-like disorder. [provided by RefSeq, Mar 2012]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:E3 ubiquitin-protein ligase CBL
Source:NCBIAccessed: 18 March, 2015


What does this gene/protein do?
Show (23)
Pathways:What pathways are this gene/protein implicaed in?
Show (6)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 18 March 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Receptor Protein-Tyrosine Kinases
  • Repressor Proteins
  • Up-Regulation
  • Lung Cancer
  • p38 Mitogen-Activated Protein Kinases
  • Vascular Endothelial Growth Factor Receptor-2
  • Noonan Syndrome
  • Ubiquitination
  • Proto-Oncogene Proteins c-cbl
  • Proto-Oncogene Proteins
  • RNA Splice Sites
  • SOS1 Protein
  • Mutation
  • DNA-Binding Proteins
  • Sodium-Hydrogen Antiporter
  • Translocation
  • Cell Proliferation
  • Acute Myeloid Leukaemia
  • mRNA Cleavage and Polyadenylation Factors
  • Neoplastic Cell Transformation
  • von Hippel-Lindau Disease
  • Tumor Markers
  • Tyrosine
  • Zinc Fingers
  • src-Family Kinases
  • Protein-Tyrosine Kinases
  • Myelodysplastic Syndromes
  • Apoptosis
  • Ubiquitin-Protein Ligases
  • Epidermal Growth Factor Receptor
  • Cell Line
  • src Homology Domains
  • Chromosome 11
  • ras Proteins
  • Down-Regulation
  • Protein Binding
  • Transfection
  • Phosphorylation
  • beta Catenin
  • ZAP-70 Protein-Tyrosine Kinase
  • Molecular Sequence Data
  • Signal Transduction
  • Signal Transducing Adaptor Proteins
Tag cloud generated 18 March, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
Acute Myeloid Leukaemia (AML)CBL and Acute Myeloid Leukaemia View Publications43
Myelodysplastic SyndromesCBL and Myelodysplastic Syndromes View Publications19
Lung CancerCBL and Lung Cancer View Publications17
Noonan SyndromeCBL mutation in Noonan Syndrome
Noonan Syndrome is an autosamal dominant multi-system disorder, characterised by facial anomalies, short stature, developmental delay, cardiac abnormalities and other symptoms. The syndrome pre-disposes to myeloproliferative disorders ( mainly chronic myeolomonocytic leukemia / juvenile myelomonocytic leukemia and acute lymphoblastic leukemia), with reports of neuroblastoma, rhabdomyosarcoma and a wide range of other tumors.
View Publications1
von Hippel-Lindau DiseaseProto-Oncogene Proteins c-cbl and von Hippel-Lindau Disease View Publications1
-Proto-Oncogene Proteins c-cbl and Noonan Syndrome View Publications1

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: CBL (cancer-related)

Seong MW, Park JH, Yoo HM, et al.
c-Cbl regulates αPix-mediated cell migration and invasion.
Biochem Biophys Res Commun. 2014; 455(3-4):153-8 [PubMed] Related Publications
c-Cbl, a RING-type ubiquitin E3 ligase, down-regulates receptor tyrosine kinases, including EGF receptor, and inhibits cell proliferation. Moreover, c-Cbl mutations are frequently found in patients with myeloid neoplasm. Therefore, c-Cbl is known as a tumor suppressor. αPix is expressed only in highly proliferative and mobile cells, including immune cells, and up-regulated in certain invasive tumors, such as glioblastoma multiforme. Here, we showed that c-Cbl serves as an ubiquitin E3 ligase for proteasome-mediated degradation of αPix, but not βPix. Remarkably, the rat C6 and human A172 glioma cells were unable to express c-Cbl, which leads to a dramatic accumulation of αPix. Depletion of αPix by shRNA markedly reduced the ability of the glioma cells to migrate and invade, whereas complementation of shRNA-insensitive αPix promoted it. These results indicate that c-Cbl negatively regulates αPix-mediated cell migration and invasion and the lack of c-Cbl in the C6 and A172 glioma cells is responsible for their malignant behavior.

Li H, Xu L, Li C, et al.
Ubiquitin ligase Cbl-b represses IGF-I-induced epithelial mesenchymal transition via ZEB2 and microRNA-200c regulation in gastric cancer cells.
Mol Cancer. 2014; 13:136 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Insulin-like growth factor I (IGF-I) can induce epithelial mesenchymal transition (EMT) in many epithelial tumors; however, the molecular mechanism by which this occurs is not clearly understood. Additionally, little is known about the involvement of IGF-I in gastric cancer.
METHODS: Two gastric cancer cell lines were treated with IGF-I to induce EMT and levels of transcription factor ZEB2 and microRNA-200c (miR-200c) were measured. Cells were treated with Akt/ERK inhibitors to investigate the role of these pathways in IGF-I-mediated EMT. Transfection of shRNA plasmids was used to silence the ubiquitin ligase Cbl-b to assess its involvement in this process. The relationship between IGF-IR and Cbl-b expression, and the effect of IGF-IR and Cbl-b on metastasis were analyzed in primary gastric adenocarcinoma patients.
RESULTS: IGF-I-induced gastric cancer cell EMT was accompanied by ZEB2 up-regulation. Furthermore, both Akt/ERK inhibitors and knockdown of Akt/ERK gene reversed IGF-I-induced ZEB2 up-regulation and EMT through up-regulation of miR-200c, suggesting the involvement of an Akt/ERK-miR-200c-ZEB2 axis in IGF-I-induced EMT. The ubiquitin ligase Cbl-b also ubiquitinated and degraded IGF-IR and inhibited the Akt/ERK-miR-200c-ZEB2 axis, leading to the repression of IGF-I-induced EMT. There was a significant negative correlation between the expression of IGF-IR and Cbl-b in gastric cancer patient tissues (r = -0.265, p < 0.05). More of patients with IGF-IR-positive expression and Cbl-b-negative expression were with lymph node metastasis (p < 0.001).
CONCLUSIONS: Together, these findings demonstrate that the ubiquitin ligase Cbl-b represses IGF-I-induced EMT, likely through targeting IGF-IR for degradation and further inhibiting the Akt/ERK-miR-200c-ZEB2 axis in gastric cancer cells.

Liu Q, Zhou H, Langdon WY, Zhang J
E3 ubiquitin ligase Cbl-b in innate and adaptive immunity.
Cell Cycle. 2014; 13(12):1875-84 [PubMed] Article available free on PMC after 15/06/2015 Related Publications
Casitas B-lineage lymphoma proto-oncogene-b (Cbl-b), a RING finger E3 ubiquitin-protein ligase, has been demonstrated to play a crucial role in establishing the threshold for T-cell activation and controlling peripheral T-cell tolerance via multiple mechanisms. Accumulating evidence suggests that Cbl-b also regulates innate immune responses and plays an important role in host defense to pathogens. Understanding the signaling pathways regulated by Cbl-b in innate and adaptive immune cells is therefore essential for efficient manipulation of Cbl-b in emerging immunotherapies for human disorders such as autoimmune diseases, allergic inflammation, infections, and cancer. In this article, we review the latest developments in the molecular structural basis of Cbl-b function, the regulation of Cbl-b expression, the signaling mechanisms of Cbl-b in immune cells, as well as the biological function of Cbl-b in physiological and pathological immune responses in animal models and human diseases.

Varghese AM, Zakowski MF, Yu HA, et al.
Small-cell lung cancers in patients who never smoked cigarettes.
J Thorac Oncol. 2014; 9(6):892-6 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
INTRODUCTION: We describe clinical, pathologic, and molecular characteristics of never-smoker patients with small-cell lung cancers (SCLCs).
METHODS: We identified cases of SCLCs evaluated at our institution from 2005 to 2012. We collected smoking history, demographic, treatment, and survival data. EGFR, KRAS, PIK3CA, ALK testing, RB protein expression, and next generation sequencing were performed on available samples.
RESULTS: Two percent (23 of 1040) of patients with SCLCs were never-smokers. Eighty-three percent (19 of 23) had de novo SCLCs, whereas 17% had SCLC transformation as acquired resistance to erlotinib after treatment for EGFR-mutant lung carcinomas. Median survival from SCLC diagnosis was 23 months. Of de novo SCLCs, ALK rearrangement, KRAS mutations, EGFR mutations, and RB loss were identified in zero of five, zero of eight, two of eight, and six of seven, respectively. Two de novo samples underwent next generation sequencing. One had mutations in p53 and RB1 with amplification in TERT, and a second had mutations in CBL and GNAS with amplification in MYCL1.
CONCLUSIONS: Two percent of patients with SCLCs are never-smokers. Although transformation to SCLC can rarely occur in acquired resistance to erlotinib, 83% of never-smokers with SCLCs had de novo SCLC. RB loss was noted in 86% of cases. Multiplexed genotyping can be performed on tissues to identify potentially actionable oncogenic drivers.

Bernard V, Gebauer N, Dinh T, et al.
Applicability of next-generation sequencing to decalcified formalin-fixed and paraffin-embedded chronic myelomonocytic leukaemia samples.
Int J Clin Exp Pathol. 2014; 7(4):1667-76 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Decalcified formalin-fixed and paraffin-embedded (dFFPE) bone marrow trephines remain the primary source of gDNA in hematopathological diagnostics. Here, we investigated the applicability of next-generation sequencing (NGS) to dFFPE samples. Chronic myelomonocytic leukaemia (CMML) is a haematopoietic stem cell malignancy delineated by genetic heterogeneity. Recently characteristic mutations have been identified for this entity in a distinct group of genes (TET2, CBL, KRAS). We comparatively investigated DNA extracted from fresh mononuclear cells as well as dFFPE samples from four CMML patients employing a commercially available primer set covering the above mentioned and well characterized mutational hotspots in CMML followed by an amplicon based next-generation deep-sequencing (NGS) approach. As we observed high quality run data as well as complete concordance between both sample types in all cases, we further validated the potential of NGS in hematopathology on a larger cohort of CMML patients (n=39), detecting sequence variations in 84.6% of patients. Sequence analysis revealed 92 variants, including five known polymorphisms, ten silent mutations, 36 missense mutations, 14 nonsense mutations, 24 frame shift mutations and three potential splice site mutations. Our findings ultimately demonstrate the applicability of NGS to dFFPE biopsy specimen in CMML and thus allowing the pathologist to evaluate prognostically relevant mutations at a high resolution and further contribute to risk stratification for the individual patient.

Lachenaud J, Strullu M, Baruchel A, Cavé H
[Juvenile myelomonocytic leukemias].
Bull Cancer. 2014; 101(3):302-13 [PubMed] Related Publications
Juvenile myelomonocytic leukemias (JMML) are rare but severe myelodysplastic and myeloproliferative neoplasms of infancy. They represent about 10 new cases per year in France and preferentially affect males. JMML are all stem cell diseases the common denominator of which is RAS pathway dysregulation, due to mutations in RAS (NRAS, KRAS) or RAS regulatory components (PTPN11, NF1 or CBL). This leads to an hypersensivity of myeloid progenitors to GM-CSF (granulo-macrophagic colony stimulating factor) which induces in turn excessive monocytic and macrophagic proliferation in blood and bone marrow. All organs can be infiltrated by this monocytic proliferation leading to multisystemic failure. Blast crisis with transformation into acute myeloid leukemia occurs in one third of patients. A salient feature of JMML is their frequent association with predisposition syndromes such as Noonan syndrome, neurofibromatosis and CBL syndrome, which are developmental diseases associated with a constitutional RAS pathway deregulation, now grouped under the name RASopathies. Clinical heterogeneity makes JMML diagnosis difficult. Splenomagaly is the most constant sign. Palor, adenopathy, respiratory or cutaneous symptoms can also be present. Blood smear shows monocytosis (>1×10(9)/L) presence of myeloid progenitors and abnormal basophils. The demonstration of an endogeneous in vitro growth of myeloid progenitors although not very specific can help JMML diagnosis. Nowadays, genetic typing has to be included in the workup of JMML diagnosis and allows to evidence a mutation in more than 90% of cases. JMML have a poor prognosis. The only curative treatment is bone marrow transplantation but approximately 35% of patients relapse. JMML clinical course is highly heterogeneous and unpredictable. Some rare patients have an indolent evolution or even spontaneous remission. Age over two years, thrombopenia below 33×10(9)/L and high foetal hemoglobin (HbF) level for age are poor prognosis criteria but hardly predict individual outcome. Several research directions are currently being explored to improve prognosis prediction and provide more effective targeted treatments.

Flemming A
Cancer: Unleashing NK cell anti-metastatic activity.
Nat Rev Drug Discov. 2014; 13(4):257 [PubMed] Related Publications

Congleton J, Shen M, MacDonald R, et al.
Phosphorylation of c-Cbl and p85 PI3K driven by all-trans retinoic acid and CD38 depends on Lyn kinase activity.
Cell Signal. 2014; 26(7):1589-97 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
The leukocyte antigen CD38 is expressed after all-trans retinoic acid (ATRA) treatment in HL-60 myelogenous leukemia cells and promotes induced myeloid differentiation when overexpressed. We found that Vav1 and SLP-76 associate with CD38 in two cell lines, and that these proteins complex with Lyn, a Src family kinase (SFK) upregulated by ATRA. SFK inhibitors PP2 and dasatinib, which enhance ATRA-induced differentiation, were used to evaluate the involvement of Lyn kinase activity in CD38-driven signaling. Cells treated with ATRA for 48h followed by one hour of PP2 incubation show SFK/Lyn kinase inhibition. We observed that Lyn inhibition blocked c-Cbl and p85/p55 PI3K phosphorylation driven by the anti-CD38 agonistic mAb IB4 in ATRA-treated HL-60 cells and untreated CD38+ transfectants. In contrast, cells cultured for 48h following concurrent ATRA and PP2 treatment did not show Lyn inhibition, suggesting ATRA regulates the effects on Lyn. 48h of co-treatment preserved CD38-stimulated c-Cbl and p85/p55 PI3K phosphorylation indicating Lyn kinase activity is necessary for these events. In contrast another SFK inhibitor (dasatinib) which blocks Lyn activity with ATRA co-treatment prevented ATRA-induced c-Cbl phosphorylation and crippled p85 PI3K phosphorylation, indicating Lyn kinase activity is important for ATRA-propelled events potentially regulated by CD38. We found that loss of Lyn activity coincided with a decrease in Vav1/Lyn/CD38 and SLP-76/Lyn/CD38 interaction, suggesting these molecules form a complex that regulates CD38 signaling. Lyn inhibition also reduced Lyn and CD38 binding to p85 PI3K, indicating CD38 facilitates a complex responsible for PI3K phosphorylation. Therefore, Lyn kinase activity is important for CD38-associated signaling that may drive ATRA-induced differentiation.

Lokody I
Signalling: loss of Cbl-b unleashes anti-metastatic natural killer cells.
Nat Rev Cancer. 2014; 14(4):218 [PubMed] Related Publications

Villanueva MT
Immunotherapy: killing with natural killers, naturally.
Nat Rev Clin Oncol. 2014; 11(4):180 [PubMed] Related Publications

Paolino M, Choidas A, Wallner S, et al.
The E3 ligase Cbl-b and TAM receptors regulate cancer metastasis via natural killer cells.
Nature. 2014; 507(7493):508-12 [PubMed] Related Publications
Tumour metastasis is the primary cause of mortality in cancer patients and remains the key challenge for cancer therapy. New therapeutic approaches to block inhibitory pathways of the immune system have renewed hopes for the utility of such therapies. Here we show that genetic deletion of the E3 ubiquitin ligase Cbl-b (casitas B-lineage lymphoma-b) or targeted inactivation of its E3 ligase activity licenses natural killer (NK) cells to spontaneously reject metastatic tumours. The TAM tyrosine kinase receptors Tyro3, Axl and Mer (also known as Mertk) were identified as ubiquitylation substrates for Cbl-b. Treatment of wild-type NK cells with a newly developed small molecule TAM kinase inhibitor conferred therapeutic potential, efficiently enhancing anti-metastatic NK cell activity in vivo. Oral or intraperitoneal administration using this TAM inhibitor markedly reduced murine mammary cancer and melanoma metastases dependent on NK cells. We further report that the anticoagulant warfarin exerts anti-metastatic activity in mice via Cbl-b/TAM receptors in NK cells, providing a molecular explanation for a 50-year-old puzzle in cancer biology. This novel TAM/Cbl-b inhibitory pathway shows that it might be possible to develop a 'pill' that awakens the innate immune system to kill cancer metastases.

Cristóbal I, Manso R, Rincón R, et al.
Up-regulation of c-Cbl suggests its potential role as oncogene in primary colorectal cancer.
Int J Colorectal Dis. 2014; 29(5):641 [PubMed] Related Publications

Becker H, Yoshida K, Blagitko-Dorfs N, et al.
Tracing the development of acute myeloid leukemia in CBL syndrome.
Blood. 2014; 123(12):1883-6 [PubMed] Related Publications
We describe the development of acute myeloid leukemia (AML) in an adult with CBL syndrome caused by a heterozygous de novo germline mutation in CBL codon D390. In the AML bone marrow, the mutated CBL allele was homozygous after copy number-neutral loss-of-heterozygosity and amplified through a chromosomal gain; moreover, an inv(16)(p13q22) and, as assessed by whole-exome sequencing, 12 gene mutations (eg, in CAND1, NID2, PTPRT, DOCK6) were additionally acquired. During complete remission of the AML, in the presence of normal blood counts, the hematopoiesis stably maintained the homozygous CBL mutation, which is reminiscent of the situation in children with CBL syndrome and transient juvenile myelomonocytic leukemia. No additional mutations were identified by whole-exome sequencing in granulocytes during complete remission. The study highlights the development of AML in an adult with CBL syndrome and, more generally, in genetically aberrant but clinically inconspicuous hematopoiesis.

Kales SC, Nau MM, Merchant AS, Lipkowitz S
Enigma prevents Cbl-c-mediated ubiquitination and degradation of RETMEN2A.
PLoS One. 2014; 9(1):e87116 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
The Cbl proteins (Cbl, Cbl-b, and Cbl-c) are a highly conserved family of RING finger ubiquitin ligases (E3s) that function as negative regulators of tyrosine kinases in a wide variety of signal transduction pathways. In this study, we identify a new Cbl-c interacting protein, Enigma (PDLIM7). This interaction is specific to Cbl-c as Enigma fails to bind either of its closely related homologues, Cbl and Cbl-b. The binding between Enigma and Cbl-c is mediated through the LIM domains of Enigma as removal of all three LIM domains abrogates this interaction, while only LIM1 is sufficient for binding. Here we show that Cbl-c binds wild-type and MEN2A isoforms of the receptor tyrosine kinase, RET, and that Cbl-c enhances ubiquitination and degradation of activated RET. Enigma blocks Cbl-c-mediated RETMEN2A ubiquitination and degradation. Cbl-c decreased downstream ERK activation by RETMEN2A and co-expression of Enigma blocked the Cbl-c-mediated decrease in ERK activation. Enigma showed no detectable effect on Cbl-c-mediated ubiquitination of activated EGFR suggesting that this effect is specific to RET. Through mapping studies, we show that Cbl-c and Enigma bind RETMEN2A at different residues. However, binding of Enigma to RETMENA prevents Cbl-c recruitment to RETMEN2A. Consistent with these biochemical data, exploratory analyses of breast cancer patients with high expression of RET suggest that high expression of Cbl-c correlates with a good outcome, and high expression of Enigma correlates with a poor outcome. Together, these data demonstrate that Cbl-c can ubiquitinate and downregulate RETMEN2A and implicate Enigma as a positive regulator of RETMEN2A through blocking of Cbl-mediated ubiquitination and degradation.

Damaj G, Joris M, Chandesris O, et al.
ASXL1 but not TET2 mutations adversely impact overall survival of patients suffering systemic mastocytosis with associated clonal hematologic non-mast-cell diseases.
PLoS One. 2014; 9(1):e85362 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
Systemic mastocytosis with associated hematologic clonal non-mast cell disease (SM-AHNMD) is a rare and heterogeneous subtype of SM and few studies on this specific entity have been reported. Sixty two patients with Systemic mastocytosis with associated hematologic clonal non-mast cell disease (SM-AHNMD) were presented. Myeloid AHNMD was the most frequent (82%) cases. This subset of patients were older, had more cutaneous lesions, splenomegaly, liver enlargement, ascites; lower bone mineral density and hemoglobin levels and higher tryptase level than lymphoid AHNMD. Defects in KIT, TET2, ASXL1 and CBL were positive in 87%, 27%, 14%, and 11% of cases respectively. The overall survival of patients with SM-AHNMD was 85.2 months. Within the myeloid group, SM-MPN fared better than SM-MDS or SM-AML (p = 0.044,). In univariate analysis, the presence of C-findings, the AHNMD subtypes (SM-MDS/CMML/AML versus SM-MPN/hypereosinophilia) (p = 0.044), Neutropenia (p = 0.015), high monocyte level (p = 0.015) and the presence of ASXL1 mutation had detrimental effects on OS (p = 0.007). In multivariate analysis and penalized Cox model, only the presence of ASXL1 mutation remained an independent prognostic factor that negatively affected OS (p = 0.035). SM-AHNMD is heterogeneous with variable prognosis according to the type of the AHNMD. ASXL1 is mutated in a subset of myeloid AHNMD and adversely impact on OS.

Stevens BM, Folts CJ, Cui W, et al.
Cool-1-mediated inhibition of c-Cbl modulates multiple critical properties of glioblastomas, including the ability to generate tumors in vivo.
Stem Cells. 2014; 32(5):1124-35 [PubMed] Related Publications
We discovered that glioblastoma (GBM) cells use Cool-1/β-pix to inhibit normal activation of the c-Cbl ubiquitin ligase via the redox/Fyn/c-Cbl pathway and that c-Cbl inhibition is critical for GBM cell function. Restoring normal c-Cbl activity by Cool-1 knockdown in vitro reduced GBM cell division, almost eliminated generation of adhesion-independent spheroids, reduced the representation of cells expressing antigens thought to identify tumor initiating cells (TICs), reduced levels of several proteins of critical importance in TIC function (such as Notch-1 and Sox2), and increased sensitivity to BCNU (carmustine) and temozolomide (TMZ). In vivo, Cool-1 knockdown greatly suppressed the ability of GBM cells to generate tumors, an outcome that was c-Cbl dependent. In contrast, Cool-1 knockdown did not reduce division or increase BCNU or TMZ sensitivity in primary glial progenitor cells and Cool-1/c-Cbl complexes were not found in normal brain tissue. Our studies provide the first evidence that Cool-1 may be critical in the biology of human tumors, that suppression of c-Cbl by Cool-1 may be critical for generation of at least a subset of GBMs and offer a novel target that appears to be selectively necessary for TIC function and modulates chemoresistance in GBM cells. Targeting such proteins that inhibit c-Cbl offers potentially attractive opportunities for therapeutic development.

Hanson HL, Wilson MJ, Short JP, et al.
Germline CBL mutation associated with a noonan-like syndrome with primary lymphedema and teratoma associated with acquired uniparental isodisomy of chromosome 11q23.
Am J Med Genet A. 2014; 164A(4):1003-9 [PubMed] Related Publications
Germline mutations in the gene CBL (Casitas B-lineage lymphoma), involved in the RAS-MAPK signaling pathway, have been found as a rare cause of the neuro-cardio-facial-cutaneous syndromes. Somatically acquired homozygous CBL mutations were initially identified in association with myeloproliferative disorders, particularly juvenile myelomonocytic leukemia (JMML). We describe a girl with a Noonan-like phenotype of bilateral ptosis, lymphedema of the lower limbs and moderate intellectual disability, due to a de novo heterozygous mutation in CBL. She developed an ovarian mixed germ cell/teratoma with later occurrence of mature liver, omental, and ovarian teratomas. Copy neutral loss of heterozygosity for the CBL mutation due to acquired segmental uniparental disomy of 11q23 was observed in three teratomas, suggesting a specific association of CBL mutations in germ cell tumor predisposition.

Walsh AM, Lazzara MJ
Differential parsing of EGFR endocytic flux among parallel internalization pathways in lung cancer cells with EGFR-activating mutations.
Integr Biol (Camb). 2014; 6(3):312-23 [PubMed] Related Publications
Due to the existence of parallel pathways for receptor endocytosis and their complexities, a quantitative understanding of receptor endocytosis in normal and pathological settings requires computational analysis. Here, we develop a mechanistic model of epidermal growth factor receptor (EGFR) endocytosis to determine the relative contributions of three parallel pathways: clathrin-dependent internalization mediated by mitogen-inducible gene 6 (MIG6), an endogenous EGFR kinase inhibitor that links EGFR to endocytic proteins; clathrin-dependent internalization mediated by the ubiquitin ligase CBL, which can be sequestered by the regulatory protein Sprouty2; or alternative pathways that may be non-clathrin mediated. We applied the model to interpret our previous measurements of EGFR endocytosis in lung cancer cells. Interestingly, our results suggest that MIG6 is responsible for at least as much wild-type EGFR internalization as CBL, indicating that a significant fraction of internalizing EGFR may be incapable of driving signaling. Model results also suggest that MIG6's endocytic function is reduced for the kinase-activated and internalization-impaired EGFR mutants found in some lung cancers. Analysis of Sprouty2 knockdown data indicates that Sprouty2 regulates EGFR endocytosis primarily by controlling EGFR expression, rather than by sequestering CBL, and supports the notion that CBL-mediated internalization is impaired for EGFR mutants. We further demonstrate that differences in internalization between wild-type and mutant EGFR cannot explain differences in EGF-mediated EGFR degradation without concomitant changes in EGFR recycling, which we previously quantified. This work provides new quantitative insights into EGFR trafficking in lung cancer and provides a framework for studying parallel endocytosis pathways for other receptors.

Feng D, Ma Y, Liu J, et al.
Cbl-b enhances sensitivity to 5-fluorouracil via EGFR- and mitochondria-mediated pathways in gastric cancer cells.
Int J Mol Sci. 2013; 14(12):24399-411 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
5-Fluorouracil (5-FU) is an essential component of anticancer chemotherapy against gastric cancer. However, the response rate of single drug is still limited. The ubiquitin ligase Cbl-b is a negative regulator of growth factor receptor signaling and is involved in the suppression of cancer cell proliferation. However, whether Cbl-b could affect 5-FU sensitivity remains unclear. The present study showed that Cbl-b knockdown caused higher proliferation concomitant with the decrease of apoptosis induced by 5-FU treatment in gastric cancer cell. Further mechanism investigation demonstrated that Cbl-b knockdown caused significant increase of phosphorylation of EGFR, ERK and Akt, decrease of mitochondrial membrane potential, and increase of expression ratio of Bcl-2/Bax. These results suggest that Cbl-b enhances sensitivity to 5-FU via EGFR- and mitochondria-mediated pathways in gastric cancer cells.

Xie X, Sun L, Pessetto ZY, et al.
Development of a fluorescence polarization based high-throughput assay to identify Casitas B-lineage lymphoma RING domain regulators.
PLoS One. 2013; 8(10):e78042 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
The E3 ubiquitin protein ligase Casitas B-lineage Lymphoma (Cbl) proteins and their binding partners play an important role in regulating signal transduction pathways. It is important to utilize regulators to study the protein-protein interactions (PPIs) between these proteins. However, finding specific small-molecule regulators of PPIs remains a significant challenge due to the fact that the interfaces involved in PPIs are not well suited for effective small molecule binding. We report the development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay to identify small molecule regulators of Cbl (RING) domain. The FP assay was used to measure binding affinities and inhibition constants of UbCH7 peptides and small molecule regulators of Cbl (RING) domains, respectively. In order to rule out promiscuous, aggregation-based inhibition, two assay conditions were developed and compared side by side. Under optimized conditions, we screened a 10,000 natural compound library in detergent-free and detergent-present (0.01% Triton X-100) systems. The results indicate that the detergent-present system is more suitable for high-throughput screens. Three potential compounds, methylprotodioscin, leonuride and catalpol, have been identified that bind to Cbl (RING) domain and interfere with the Cbl (RING)-UbCH7 protein-protein interaction.

Kobashigawa Y, Inagaki F
[Structural basis for phosphorylation induced regulation mechanism of human cancer and autoimmune diseases related ubiquitin ligase Cbl].
Seikagaku. 2013; 85(9):794-8 [PubMed] Related Publications

Sato S, Zhao Y, Imai M, et al.
Inhibition of CIN85-mediated invasion by a novel SH3 domain binding motif in the lysyl oxidase propeptide.
PLoS One. 2013; 8(10):e77288 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
The lysyl oxidase gene inhibits Ras signaling in transformed fibroblasts and breast cancer cells. Its activity was mapped to the 162 amino acid propeptide domain (LOX-PP) of the lysyl oxidase precursor protein. LOX-PP inhibited the Her-2/Ras signaling axis in breast cancer cells, and reduced the Her-2-driven breast tumor burden in a xenograft model. Since its mechanism of action is largely unknown, co-affinity-purification/mass spectrometry was performed and the "Cbl-interacting protein of 85-kDa" (CIN85) identified as an associating protein. CIN85 is an SH3-containing adapter protein that is overexpressed in invasive breast cancers. The CIN85 SH3 domains interact with c-Cbl, an E3 ubiquitin ligase, via an unconventional PxxxPR ligand sequence, with the highest affinity displayed by the SH3-B domain. Interaction with CIN85 recruits c-Cbl to the AMAP1 complex where its ubiquitination activity is necessary for cancer cells to develop an invasive phenotype and to degrade the matrix. Direct interaction of LOX-PP with CIN85 was confirmed using co-immunoprecipitation analysis of lysates from breast cancer cells and of purified expressed proteins. CIN85 interaction with c-Cbl was reduced by LOX-PP. Domain specific CIN85 regions and deletion mutants of LOX-PP were prepared and used to map the sites of interaction to the SH3-B domain of CIN85 and to an epitope encompassing amino acids 111 to 116 of LOX-PP. Specific LOX-PP point mutant proteins P111A and R116A failed to interact with CIN85 or to compete for CIN85 binding with c-Cbl. Structural modeling identified a new atypical PxpxxRh SH3-binding motif in this region of LOX-PP. The LOX-PP interaction with CIN85 was shown to reduce the invasive phenotype of breast cancer cells, including their ability to degrade the surrounding extracellular matrix and for Matrigel outgrowth. Thus, LOX-PP interacts with CIN85 via a novel SH3-binding motif and this association reduces CIN85-promoted invasion by breast cancer cells.

Xu L, Qu X, Hu X, et al.
Lipid raft-regulated IGF-1R activation antagonizes TRAIL-induced apoptosis in gastric cancer cells.
FEBS Lett. 2013; 587(23):3815-23 [PubMed] Related Publications
Gastric cancer cells are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and the resistance mechanism is not fully understood. In human gastric cancer MGC803 and BGC823 cells, TRAIL induces insulin-like growth factor-1 receptor (IGF-1R) pathway activation. Treatment with IGF-1R inhibitor OSI-906 or small interfering RNAs against IGF-1R, prevents IGF-1R pathway activation and increases TRAIL-induced apoptosis. The TRAIL-induced IGF-1R pathway activation is promoted by IGF-1R translocation into lipid rafts. Moreover, the translocation of IGF-1R into lipid rafts is regulated by Casitas B-lineage lymphoma b (Cbl-b). Taken together, TRAIL-induced IGF-1R activation antagonizes TRAIL-induced apoptosis by Cbl-b-regulated distribution of IGF-1R in lipid rafts.

Klampfl T, Milosevic JD, Puda A, et al.
Complex patterns of chromosome 11 aberrations in myeloid malignancies target CBL, MLL, DDB1 and LMO2.
PLoS One. 2013; 8(10):e77819 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
Exome sequencing of primary tumors identifies complex somatic mutation patterns. Assignment of relevance of individual somatic mutations is difficult and poses the next challenge for interpretation of next generation sequencing data. Here we present an approach how exome sequencing in combination with SNP microarray data may identify targets of chromosomal aberrations in myeloid malignancies. The rationale of this approach is that hotspots of chromosomal aberrations might also harbor point mutations in the target genes of deletions, gains or uniparental disomies (UPDs). Chromosome 11 is a frequent target of lesions in myeloid malignancies. Therefore, we studied chromosome 11 in a total of 813 samples from 773 individual patients with different myeloid malignancies by SNP microarrays and complemented the data with exome sequencing in selected cases exhibiting chromosome 11 defects. We found gains, losses and UPDs of chromosome 11 in 52 of the 813 samples (6.4%). Chromosome 11q UPDs frequently associated with mutations of CBL. In one patient the 11qUPD amplified somatic mutations in both CBL and the DNA repair gene DDB1. A duplication within MLL exon 3 was detected in another patient with 11qUPD. We identified several common deleted regions (CDR) on chromosome 11. One of the CDRs associated with de novo acute myeloid leukemia (P=0.013). One patient with a deletion at the LMO2 locus harbored an additional point mutation on the other allele indicating that LMO2 might be a tumor suppressor frequently targeted by 11p deletions. Our chromosome-centered analysis indicates that chromosome 11 contains a number of tumor suppressor genes and that the role of this chromosome in myeloid malignancies is more complex than previously recognized.

Fang S, Guo X, Leng X, et al.
[Expression down-regulation of c-Cbl and Cbl-b genes in peripheral blood mononuclear cells from multiple myeloma patients].
Xi Bao Yu Fen Zi Mian Yi Xue Za Zhi. 2013; 29(8):842-5 [PubMed] Related Publications
OBJECTIVE: To investigate c-Cbl and Cbl-b gene expressions in peripheral blood mononuclear cells (PBMCs) from multiple myeloma (MM) patients.
METHODS: SYBR(R); Green PCR technique was used to detect c-Cbl and Cbl-b gene expressions in PBMCs from 23 MM patients and 22 healthy individuals, and RT-PCR and DNA sequence analysis were performed to analyze the mutations of 7-10 exons of c-Cbl.
RESULTS: The expression of c-Cbl gene in MM patients (median: 0.798%) significantly decreased as compared with that in healthy controls (median: 2.443%) (P<0.05). The expression of Cbl-b gene in MM patients (median: 0.714%) also dropped significantly as compared with that in healthy controls (median: 2.179%) (P<0.05). The 7-10 exons of c-Cbl gene had two different sizes of fragments in 2 MM patients: 483 bp and 148 bp which were wild-type and deletion mutants type of c-Cbl gene. c-Cbl gene mutations were not found in all MM patients.
CONCLUSION: The expressions of c-Cbl and Cbl-b genes in PBMCs from MM patients are down-regulated.

Strullu M, Caye A, Cassinat B, et al.
In hematopoietic cells with a germline mutation of CBL, loss of heterozygosity is not a signature of juvenile myelo-monocytic leukemia.
Leukemia. 2013; 27(12):2404-7 [PubMed] Related Publications

Allen C, Hills RK, Lamb K, et al.
The importance of relative mutant level for evaluating impact on outcome of KIT, FLT3 and CBL mutations in core-binding factor acute myeloid leukemia.
Leukemia. 2013; 27(9):1891-901 [PubMed] Related Publications
Several different mutations collaborate with the fusion proteins in core-binding factor acute myeloid leukemia (CBF-AML) to induce leukemogenesis, but their prognostic significance remains unclear. We screened 354 predominantly younger (<60 years) adults with t(8;21) (n=199) or inv(16) (n=155) entered into UK MRC trials for KIT, FLT3 tyrosine kinase domain (FLT3(TKD)), N-RAS, K-RAS and c-CBL mutations and FLT3 internal tandem duplications (FLT3(ITD)) and assessed the impact of relative mutant level on outcome. Overall, 28% had KIT, 6% FLT3(ITD), 10% FLT3(TKD), 27% RAS and 6% CBL mutations. Mutant levels for all genes/loci were highly variable. KIT mutations were associated with a higher cumulative incidence of relapse but in multivariate analysis this was only significant for cases with a higher mutant level of 25% or greater (95% confidence interval (CI)=1.01-1.52, P=0.04). Similarly, only FLT3(ITD-HIGH) was a significant adverse factor for overall survival (OS; CI=1.27-5.39, P=0.004). Conversely, FLT3(TKD-HIGH) and CBL(HIGH) were both favorable factors for OS (CI= 0.31-0.89, P=0.01 and CI=0.05-0.85, P=0.02, respectively). KIT mutations were frequently lost at relapse, which is relevant to minimal residual disease detection and the clinical use of KIT inhibitors. These results indicate that relative mutant level should be taken into account when evaluating the impact of mutations in CBF-AML.

Hong SY, Shih YP, Li T, et al.
CTEN prolongs signaling by EGFR through reducing its ligand-induced degradation.
Cancer Res. 2013; 73(16):5266-76 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
Activation of EGF receptor (EGFR) triggers signaling pathways regulating various cellular events that contribute to tissue development and function. Aberrant activation of EGFR contributes to tumor progression as well as therapeutic resistance in patients with cancer. C-terminal tensin-like (CTEN; TNS4) is a focal adhesion molecule that is a member of the tensin family. Its expression is upregulated by EGF and elevated CTEN mediates EGF-induced cell migration. In the presence of CTEN, we found that EGF treatment elevated the level of EGFR protein but not mRNA. The extended half-life of activated EGFR sustained its signaling cascades. CTEN reduced ligand-induced EGFR degradation by binding to the E3 ubiquitin ligase c-Cbl and decreasing the ubiquitination of EGFR. The Src homology 2 domain of CTEN is not only required for binding to the phosphorylated tyrosine residue at codon 774 of c-Cbl, but is also essential for the tumorigenicity observed in the presence of CTEN. Public database analyses indicated that CTEN mRNA levels are elevated in breast, colon, lung, and pancreas cancers, but not correlated with EGFR mRNA levels in these cancers. In contrast, immunohistochemistry analyses of lung cancer specimens showed that CTEN and EGFR protein levels were positively associated, in support of our finding that CTEN regulates EGFR protein levels through a posttranslational mechanism. Overall, this work defines a function for CTEN in prolonging signaling from EGFR by reducing its ligand-induced degradation.

Wallner S, Lutz-Nicoladoni C, Tripp CH, et al.
The role of the e3 ligase cbl-B in murine dendritic cells.
PLoS One. 2013; 8(6):e65178 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
Dendritic cells (DCs) are potent antigen-presenting cells with a promising potential in cancer immunotherapy. Cbl proteins are E3 ubiquitin ligases and have been implicated in regulating the functional activity of various immune cells. As an example, c-Cbl negatively affects DC activation. We here describe that another member of the Cbl-protein family (i.e. Cbl-b) is highly expressed in murine bone-marrow-derived DCs (BMDCs). Differentiation of cblb-/- bone marrow mononuclear cells into classical BMDCs is unaltered, except enhanced induction of DEC-205 (CD205) expression. When tested in mixed-lymphocyte reaction (MLR), cblb-/- BMDCs exhibit increased allo-stimulatory capacity in vitro. BMDCs were next in vitro stimulated by various toll like receptor (TLR)-agonists (LPS, Poly(I:C), CpG) and exposed to FITC-labeled dextran. Upon TLR-stimulation, cblb-/- BMDCs produce higher levels of proinflammatory cytokines (IL-1α, IL-6 and TNF-α) and exhibit a slightly higher level of FITC-dextran uptake. To further characterize the functional significance of cblb-/- BMDCs we tested them in antigen-specific T cell responses against ovalbumin (OVA) protein and peptides, activating either CD8(+) OT-I or CD4(+) OT-II transgenic T cells. However, cblb-/- BMDCs are equally effective in inducing antigen-specific T cell responses when compared to wildtype BMDCs both in vitro and in vivo. The migratory capacity into lymph nodes during inflammation was similarly not affected by the absence of Cbl-b. In line with these observations, cblb-/- peptide-pulsed BMDCs are equally effective vaccines against OVA-expressing B16 tumors in vivo when compared to wildtype BMDCs. We conclude that in contrast to c-Cbl, Cbl-b plays only a limited role in the induction of Ag-specific T cell responses by murine BMDCs in vitro and in vivo.

Javadi M, Richmond TD, Huang K, Barber DL
CBL linker region and RING finger mutations lead to enhanced granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling via elevated levels of JAK2 and LYN.
J Biol Chem. 2013; 288(27):19459-70 [PubMed] Article available free on PMC after 01/07/2015 Related Publications
Juvenile myelomonocytic leukemia (JMML) is characterized by hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). SHP2, NF-1, KRAS, and NRAS are mutated in JMML patients, leading to aberrant regulation of RAS signaling. A subset of JMML patients harbor CBL mutations associated with 11q acquired uniparental disomy. Many of these mutations are in the linker region and the RING finger of CBL, leading to a loss of E3 ligase activity. We investigated the mechanism by which CBL-Y371H, a linker region mutant, and CBL-C384R, a RING finger mutant, lead to enhanced GM-CSF signaling. Expression of CBL mutants in the TF-1 cell line resulted in enhanced survival in the absence of GM-CSF. Cells expressing CBL mutations displayed increased phosphorylation of GM-CSF receptor βc subunit in response to stimulation, although expression of total GM-CSFR βc was lower. This suggested enhanced kinase activity downstream of GM-CSFR. JAK2 and LYN kinase expression is elevated in CBL-Y371H and CBL-C384R mutant cells, resulting in enhanced phosphorylation of CBL and S6 in response to GM-CSF stimulation. Incubation with the JAK2 inhibitor, TG101348, abolished the increased phosphorylation of GM-CSFR βc in cells expressing CBL mutants, whereas treatment with the SRC kinase inhibitor dasatinib resulted in equalization of GM-CSFR βc phosphorylation signal between wild type CBL and CBL mutant samples. Dasatinib treatment inhibited the elevated phosphorylation of CBL-Y371H and CBL-C384R mutants. Our study indicates that CBL linker and RING finger mutants lead to enhanced GM-CSF signaling due to elevated kinase expression, which can be blocked using small molecule inhibitors targeting specific downstream pathways.

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