CBL

Gene Summary

Gene:CBL; Cbl proto-oncogene
Aliases: CBL2, NSLL, C-CBL, RNF55, FRA11B
Location:11q23.3
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, and expansion of CGG repeats in the 5' UTR has been associated with Jacobsen syndrome. Mutations in this gene are also the cause of Noonan syndrome-like disorder. [provided by RefSeq, Jul 2016]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:E3 ubiquitin-protein ligase CBL
Source:NCBIAccessed: 09 March, 2017

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 09 March 2017 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.

Tag cloud generated 09 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (8)

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 Publications48
Breast CancerProto-Oncogene Proteins c-cbl and Breast Cancer View Publications27
Myelodysplastic SyndromesCBL and Myelodysplastic Syndromes View Publications19
Lung CancerCBL and Lung Cancer View Publications22
Stomach CancerProto-Oncogene Proteins c-cbl and Stomach 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 Publications2
-Proto-Oncogene Proteins c-cbl and Noonan Syndrome View Publications2
von Hippel-Lindau DiseaseProto-Oncogene Proteins c-cbl and von Hippel-Lindau Disease 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)

Yu P, Fan Y, Qu X, et al.
Cbl-b regulates the sensitivity of cetuximab through ubiquitin-proteasome system in human gastric cancer cells.
J BUON. 2016 Jul-Aug; 21(4):867-873 [PubMed] Related Publications
PURPOSE: Cetuximab is a monoclonal antibody against epidermal growth factor receptor (EGFR) and is approved for clinical use in combination with chemotherapy in patients affected by colorectal cancer (CRC), non small cell lung cancer (NSCLC), and head and neck cancer. Compared with these cancers, gastric cancer is relatively resistant to cetuximab and its regulatory mechanism is still unclear.
METHODS: In this study, we assessed whether the ubiquitin- proteasome pathway is involved in regulating cetuximab-induced cells apoptosis in MGC803 and BGC823 gastric cancer cell lines.
RESULTS: The casitas B lineage lymphoma-b (Cbl-b), a kind of E3 ubiquitin ligase, was involved in this process. Specific silenced Cbl-b expression increased the expression of EGFR.
CONCLUSIONS: Our findings lead to a better understanding of the mechanism of cetuximab action, and suggests that Cbl-b increases the sensitivity of cetuximab in gastric cancer cells.

Hamadou WS, Bourdon V, Gaildrat P, et al.
Mutational analysis of JAK2, CBL, RUNX1, and NPM1 genes in familial aggregation of hematological malignancies.
Ann Hematol. 2016; 95(7):1043-50 [PubMed] Related Publications
Familial aggregation of hematological malignancies has been reported highlighting inherited genetic predisposition. In this study, we targeted four candidate genes: JAK2 and RUNX1 genes assuring a prominent function in hematological process and CBL and NPM1 as proto-oncogenes. Their disruption was described in several sporadic hematological malignancies. The aim of this study is to determine whether JAK2, CBL, RUNX1, and NPM1 germline genes mutations are involved in familial hematological malignancies. Using direct sequencing, we analyzed JAK2 (exons 12 and 14); CBL (exons 7, 8 and 9); NPM1 (exon 12) and the entire RUNX1 in 88 independent families belonging to Tunisian and French populations. Twenty-one sporadic acute leukemias were included in this study. We reported a heterozygous intronic c.1641 + 6 T > C JAK2 variant (rs182123615) found in two independent familial cases diagnosed with gastric lymphoma and Hodgkin lymphoma. The in silico analysis suggested a potential impact on splicing, but the functional splicing minigene reporter assay on rs182123615 variant showed no aberrant transcripts. In one sporadic acute myeloblastic leukemia, we reported an insertion 846 in. TGTT in exon 12 of NPM1 gene that may impact the normal reading frame. The rs182123615 JAK2 variant was described in several contexts including myeloproliferative neoplasms and congenital erythrocytosis and was supposed to be pathogenic. Through this current study, we established the assessment of pathogenicity of rs182123615 and we classified it rather as rare polymorphism.

Saeidi K
Myeloproliferative neoplasms: Current molecular biology and genetics.
Crit Rev Oncol Hematol. 2016; 98:375-89 [PubMed] Related Publications
Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by increased production of mature blood cells. Philadelphia chromosome-negative MPNs (Ph-MPNs) consist of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). A number of stem cell derived mutations have been identified in the past 10 years. These findings showed that JAK2V617F, as a diagnostic marker involving JAK2 exon 14 with a high frequency, is the best molecular characterization of Ph-MPNs. Somatic mutations in an endoplasmic reticulum chaperone, named calreticulin (CALR), is the second most common mutation in patients with ET and PMF after JAK2 V617F mutation. Discovery of CALR mutations led to the increased molecular diagnostic of ET and PMF up to 90%. It has been shown that JAK2V617F is not the unique event in disease pathogenesis. Some other genes' location such as TET oncogene family member 2 (TET2), additional sex combs-like 1 (ASXL1), casitas B-lineage lymphoma proto-oncogene (CBL), isocitrate dehydrogenase 1/2 (IDH1/IDH2), IKAROS family zinc finger 1 (IKZF1), DNA methyltransferase 3A (DNMT3A), suppressor of cytokine signaling (SOCS), enhancer of zeste homolog 2 (EZH2), tumor protein p53 (TP53), runt-related transcription factor 1 (RUNX1) and high mobility group AT-hook 2 (HMGA2) have also identified to be involved in MPNs phenotypes. Here, current molecular biology and genetic mechanisms involved in MNPs with a focus on the aforementioned factors is presented.

Li M, Kales SC, Ma K, et al.
Balancing Protein Stability and Activity in Cancer: A New Approach for Identifying Driver Mutations Affecting CBL Ubiquitin Ligase Activation.
Cancer Res. 2016; 76(3):561-71 [PubMed] Free Access to Full Article Related Publications
Oncogenic mutations in the monomeric Casitas B-lineage lymphoma (Cbl) gene have been found in many tumors, but their significance remains largely unknown. Several human c-Cbl (CBL) structures have recently been solved, depicting the protein at different stages of its activation cycle and thus providing mechanistic insight underlying how stability-activity tradeoffs in cancer-related proteins-may influence disease onset and progression. In this study, we computationally modeled the effects of missense cancer mutations on structures representing four stages of the CBL activation cycle to identify driver mutations that affect CBL stability, binding, and activity. We found that recurrent, homozygous, and leukemia-specific mutations had greater destabilizing effects on CBL states than random noncancer mutations. We further tested the ability of these computational models, assessing the changes in CBL stability and its binding to ubiquitin-conjugating enzyme E2, by performing blind CBL-mediated EGFR ubiquitination assays in cells. Experimental CBL ubiquitin ligase activity was in agreement with the predicted changes in CBL stability and, to a lesser extent, with CBL-E2 binding affinity. Two thirds of all experimentally tested mutations affected the ubiquitin ligase activity by either destabilizing CBL or disrupting CBL-E2 binding, whereas about one-third of tested mutations were found to be neutral. Collectively, our findings demonstrate that computational methods incorporating multiple protein conformations and stability and binding affinity evaluations can successfully predict the functional consequences of cancer mutations on protein activity, and provide a proof of concept for mutations in CBL.

Huang KY, Kao SH, Wang WL, et al.
Small Molecule T315 Promotes Casitas B-Lineage Lymphoma-Dependent Degradation of Epidermal Growth Factor Receptor via Y1045 Autophosphorylation.
Am J Respir Crit Care Med. 2016; 193(7):753-66 [PubMed] Related Publications
RATIONALE: Despite the fact that tyrosine kinase inhibitors (TKIs) have been found effective in treating patients harboring activating mutations of epidermal growth factor receptor (EGFR), an acquired secondary mutation, T790M, which lowers the affinity to TKIs, can lead to EGFR TKI resistance after this standard treatment.
OBJECTIVES: To evaluate the effect of small molecule T315 on EGFR degradation and its therapeutic efficacy in vitro and in vivo.
METHODS: Lung adenocarcinoma cells were treated with T315, and cell proliferation and apoptotic proportion were determined by the CellTiter 96 AQueous MTS (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt) assay and flow cytometry. The effects of T315 on EGFR mRNA and protein levels, autophosphorylation, ubiquitination, and degradation were evaluated by real-time polymerase chain reaction and Western blot, respectively. Direct targeting of T315 to EGFR was confirmed by the in vitro kinase assay and mass spectrometry. Finally, the preclinical effect of T315 was validated in the murine xenograft model in combination with a second-generation TKI, afatinib.
MEASUREMENTS AND MAIN RESULTS: We identified T315 as a novel, potent small molecule for suppressing cancer cell proliferation in vitro and in vivo. The therapeutic effect was verified after T315 was combined with a second-generation TKI, afatinib, compared with a single drug administration. We found a new mechanism of action, in that T315 appears to directly bind EGFR and triggers EGFR-Y1045 autophosphorylation, whereby its degradation is triggered through the ubiquitin-proteasome pathway.
CONCLUSIONS: Our evidence suggests that T315 is a novel class of anticancer drug that is able to inhibit the growth of EGFR-TKI-resistant lung adenocarcinoma cells by inducing the degradation of EGFR.

Zhang JB, Zhang B, Guo L, et al.
Peritumoral Cbl is a strong independent prognostic marker after curative resection of hepatocellular carcinoma.
Oncotarget. 2015; 6(37):40223-34 [PubMed] Free Access to Full Article Related Publications
Growing evidences support the concept that peritumoral microenvironment gene expression is an important element for physicians to make an accurate prognosis. Nonetheless, the correlation between peritumoral ubiquitin ligases and the hepatocellular carcinoma (HCC) survival remains unclear till this present. The expression of intratumoral and peritumoral Casitas B-lineage Lymphoma (Cbl) and epidermal growth factor receptor (EGFR) in hepatocellular carcinomas (HCCs) followed by curative resection was assessed by tissue microarray-based immune-histochemistry in two independent cohorts (n = 352). Their respective prognostic values and other clinicopathologic factors were then evaluated. The peritumoral Cbl density, much higher than that in intratumoral tissue, was an independent prognostic factor for overall survival (P < 0.001) and time to recurrence (P < 0.001) of HCCs after curative resection. The hazard ratio were 1.587 and 1.689, respectively. However, there was no correlation between intratumoral Cbl and prognosis. The peritumoral Cbl was also associated with prognosis even in HCC subgroups with small tumor size, negative AFP, without microvascular invasion and negative HBeAg. After a thorough analysis pertaining to the key role of Cbl on ubiquitination and degradation of activated receptor tyrosine kinases, we eventually discovered the negative correlation between peritumoral Cbl and EGFR (P = 0.015). Furthermore, the combination of peritumoral Cbl and EGFR serves as a much stronger indicator to make an accurate prognosis, especially during early recurrence (P < 0.001). These findings suggest that low expression of peritumoral Cbl and EGFR were positively associated with tumor size, microvascular invasion and patients survival after hepatectomy, highlighting the key role of peritumoral liver milieu in HCC progression.

Goyama S, Schibler J, Gasilina A, et al.
UBASH3B/Sts-1-CBL axis regulates myeloid proliferation in human preleukemia induced by AML1-ETO.
Leukemia. 2016; 30(3):728-39 [PubMed] Free Access to Full Article Related Publications
The t(8;21) rearrangement, which creates the AML1-ETO fusion protein, represents the most common chromosomal translocation in acute myeloid leukemia (AML). Clinical data suggest that CBL mutations are a frequent event in t(8;21) AML, but the role of CBL in AML1-ETO-induced leukemia has not been investigated. In this study, we demonstrate that CBL mutations collaborate with AML1-ETO to expand human CD34+ cells both in vitro and in a xenograft model. CBL depletion by shRNA also promotes the growth of AML1-ETO cells, demonstrating the inhibitory function of endogenous CBL in t(8;21) AML. Mechanistically, loss of CBL function confers hyper-responsiveness to thrombopoietin and enhances STAT5/AKT/ERK/Src signaling in AML1-ETO cells. Interestingly, we found the protein tyrosine phosphatase UBASH3B/Sts-1, which is known to inhibit CBL function, is upregulated by AML1-ETO through transcriptional and miR-9-mediated regulation. UBASH3B/Sts-1 depletion induces an aberrant pattern of CBL phosphorylation and impairs proliferation in AML1-ETO cells. The growth inhibition caused by UBASH3B/Sts-1 depletion can be rescued by ectopic expression of CBL mutants, suggesting that UBASH3B/Sts-1 supports the growth of AML1-ETO cells partly through modulation of CBL function. Our study reveals a role of CBL in restricting myeloid proliferation of human AML1-ETO-induced leukemia, and identifies UBASH3B/Sts-1 as a potential target for pharmaceutical intervention.

Oguro S, Ino Y, Shimada K, et al.
Clinical significance of tumor-infiltrating immune cells focusing on BTLA and Cbl-b in patients with gallbladder cancer.
Cancer Sci. 2015; 106(12):1750-60 [PubMed] Free Access to Full Article Related Publications
The host immune system plays a significant role in tumor control, although most cancers escape immune surveillance through a variety of mechanisms. The aim of the present study was to evaluate the clinicopathological significance of a novel co-inhibitory receptor, B and T lymphocyte attenuator (BTLA), the anergy cell marker Casitas-B-lineage lymphoma protein-b (Cbl-b), and clinical implications of tumor-infiltrating immune cells in gallbladder cancer (GBC) tissues. We investigated 211 cases of GBC, 21 cases of chronic cholecystitis (CC), and 11 cases of xanthogranulomatous cholecystitis (XGC) using immunohistochemistry to detect tissue-infiltrating immune cells and their expression of BTLA and Cbl-b, and carried out correlation and survival analyses. The density of infiltrating T cells was significantly higher in CC and XGC than in GBC. The density ratio of BTLA(+) cells to CD8(+) T cells (BTLA/CD8) and that of Cbl-b(+) cells to CD8(+) T cells (Cbl-b/CD8) were significantly higher in GBC than in CC and XGC. The FOXP3/CD4, BTLA/CD8, and Cbl-b/CD8 ratios were significantly correlated with each other, and also with malignant phenotypes. Survival analyses revealed that a lower density of tumor-infiltrating CD8(+) cells, and higher Foxp3/CD4, BTLA/CD8, and Cbl-b/CD8 ratios were significantly associated with shorter overall survival and disease-free survival in GBC patients. Multivariate analyses showed that M factor, perineural invasion, BTLA/CD8, and Cbl-b/CD8 were closely associated with shorter overall survival. These findings suggest that higher ratios of BTLA/CD8 and Cbl-b/CD8 are independent indicators of unfavorable outcome in GBC patients, and that upregulation of BTLA in cancer tissues is involved in inhibition of antitumor immunity.

Vennin C, Spruyt N, Dahmani F, et al.
H19 non coding RNA-derived miR-675 enhances tumorigenesis and metastasis of breast cancer cells by downregulating c-Cbl and Cbl-b.
Oncotarget. 2015; 6(30):29209-23 [PubMed] Free Access to Full Article Related Publications
H19 is a long non-coding RNA precursor of miR-675 microRNA. H19 is increasingly described to play key roles in the progression and metastasis of cancers from different tissue origins. We have previously shown that the H19 gene is activated by growth factors and increases breast cancer cell invasion. In this study, we established H19/miR-675 ectopic expression models of MDA-MB-231 breast cancer cells to further investigate the underlying mechanisms of H19 oncogenic action. We showed that overexpression of H19/miR-675 enhanced the aggressive phenotype of breast cancer cells including increased cell proliferation and migration in vitro, and increased tumor growth and metastasis in vivo. Moreover, we identified ubiquitin ligase E3 family (c-Cbl and Cbl-b) as direct targets of miR-675 in breast cancer cells. Using a luciferase assay, we demonstrated that H19, through its microRNA, decreased both c-Cbl and Cbl-b expression in all breast cancer cell lines tested. Thus, by directly binding c-Cbl and Cbl-b mRNA, miR-675 increased the stability and the activation of EGFR and c-Met, leading to sustained activation of Akt and Erk as well as enhanced cell proliferation and migration. Our data describe a novel mechanism of protumoral action of H19 in breast cancer.

Desai SS, Kharade SS, Parekh VI, et al.
Pro-oncogenic Roles of HLXB9 Protein in Insulinoma Cells through Interaction with Nono Protein and Down-regulation of the c-Met Inhibitor Cblb (Casitas B-lineage Lymphoma b).
J Biol Chem. 2015; 290(42):25595-608 [PubMed] Free Access to Full Article Related Publications
Pancreatic islet β-cells that lack the MEN1-encoded protein menin develop into tumors. Such tumors express the phosphorylated isoform of the β-cell differentiation transcription factor HLXB9. It is not known how phospho-HLXB9 acts as an oncogenic factor in insulin-secreting β-cell tumors (insulinomas). In this study we investigated the binding partners and target genes of phospho-HLXB9 in mouse insulinoma MIN6 β-cells. Co-immunoprecipitation coupled with mass spectrometry showed a significant association of phospho-HLXB9 with the survival factor p54nrb/Nono (54-kDa nuclear RNA-binding protein, non-POU-domain-containing octamer). Endogenous phospho-HLXB9 co-localized with endogenous Nono in the nucleus. Overexpression of HLXB9 decreased the level of overexpressed Nono but not endogenous Nono. Anti-phospho-HLXB9 chromatin immunoprecipitation followed by deep sequencing (ChIP-Seq) identified the c-Met inhibitor, Cblb, as a direct phospho-HLXB9 target gene. Phospho-HLXB9 occupied the promoter of Cblb and reduced the expression of Cblb mRNA. Cblb overexpression or HLXB9 knockdown decreased c-Met protein and reduced cell migration. Also, increased phospho-HLXB9 coincided with reduced Cblb and increased c-Met in insulinomas of two mouse models of menin loss. These data provide mechanistic insights into the role of phospho-HLXB9 as a pro-oncogenic factor by interacting with a survival factor and by promoting the oncogenic c-Met pathway. These mechanisms have therapeutic implications for reducing β-cell proliferation in insulinomas by inhibiting phospho-HLXB9 or its interaction with Nono and modulating the expression of its direct (Cblb) or indirect (c-Met) targets. Our data also implicate the use of pro-oncogenic activities of phospho-HLXB9 in β-cell expansion strategies to alleviate β-cell loss in diabetes.

Tüfekçi Ö, Ören H, Demir Yenigürbüz F, et al.
Management of Two Juvenile Myelomonocytic Leukemia Patients According to Clinical and Genetic Features.
Turk J Haematol. 2015; 32(2):175-9 [PubMed] Free Access to Full Article Related Publications
Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disorder of childhood. Major progress has been achieved in diagnosis and the understanding of the pathogenesis of JMML by identifying the genetic pathologies that occur in patients. Mutations of RAS, NF1, PTPN11, and CBL are found in approximately 80% of JMML patients. Distinct clinical features have been reported to be associated with specific gene mutations. The advent of genomic studies and recent identification of novel genetic mutations in JMML are important not only in diagnosis but also in the management and prognosis of the disease. Herein, we present 2 patients with JMML harboring different mutations, NRAS and c-CBL, respectively, with distinct clinical features and different therapeutic approaches.

Bunaciu RP, Jensen HA, MacDonald RJ, et al.
6-Formylindolo(3,2-b)Carbazole (FICZ) Modulates the Signalsome Responsible for RA-Induced Differentiation of HL-60 Myeloblastic Leukemia Cells.
PLoS One. 2015; 10(8):e0135668 [PubMed] Free Access to Full Article Related Publications
6-Formylindolo(3,2-b)carbazole (FICZ) is a photoproduct of tryptophan and an endogenous high affinity ligand for aryl hydrocarbon receptor (AhR). It was previously reported that, in patient-derived HL-60 myeloblastic leukemia cells, retinoic acid (RA)-induced differentiation is driven by a signalsome containing c-Cbl and AhR. FICZ enhances RA-induced differentiation, assessed by expression of the membrane differentiation markers CD38 and CD11b, cell cycle arrest and the functional differentiation marker, inducible oxidative metabolism. Moreover, FICZ augments the expression of a number of the members of the RA-induced signalsome, such as c-Cbl, Vav1, Slp76, PI3K, and the Src family kinases Fgr and Lyn. Pursuing the molecular signaling responsible for RA-induced differentiation, we characterized, using FRET and clustering analysis, associations of key molecules thought to drive differentiation. Here we report that, assayed by FRET, AhR interacts with c-Cbl upon FICZ plus RA-induced differentiation, whereas AhR constitutively interacts with Cbl-b. Moreover, correlation analysis based on the flow cytometric assessment of differentiation markers and western blot detection of signaling factors reveal that Cbl-b, p-p38α and pT390-GSK3β, are not correlated with other known RA-induced signaling components or with a phenotypic outcome. We note that FICZ plus RA elicited signaling responses that were not typical of RA alone, but may represent alternative differentiation-driving pathways. In clusters of signaling molecules seminal to cell differentiation, FICZ co-administered with RA augments type and intensity of the dynamic changes induced by RA. Our data suggest relevance for FICZ in differentiation-induction therapy. The mechanism of action includes modulation of a SFK and MAPK centered signalsome and c-Cbl-AhR association.

Seong MW, Ka SH, Park JH, et al.
Deleterious c-Cbl Exon Skipping Contributes to Human Glioma.
Neoplasia. 2015; 17(6):518-24 [PubMed] Free Access to Full Article Related Publications
c-Cbl, a RING-type ubiquitin E3 ligase, downregulates various receptor tyrosine kinases (e.g., epidermal growth factor receptor (EGFR)), leading to inhibition of cell proliferation. Moreover, patients with myeloid neoplasm frequently harbor c-Cbl mutations, implicating the role of c-Cbl as a tumor suppressor. Recently, we have shown that c-Cbl downregulates αPix-mediated cell migration and invasion, and the lack of c-Cbl in the rat C6 and human A172 glioma cells is responsible for their malignant behavior. Here, we showed that c-Cbl exon skipping occurs in the glioma cells and the brain tissues from glioblastoma patients lacking c-Cbl. This exon skipping resulted in generation of two types of c-Cbl isoforms: type I lacking exon-9 and type II lacking exon-9 and exon-10. However, the c-Cbl isoforms in the cells and tissues could not be detected as they were rapidly degraded by proteasome. Consequently, C6 and A172 cells showed sustained EGFR activation. However, no splice site mutation was found in the region from exon-7 to exon-11 of the c-Cbl gene in C6 cells and a glioblastoma tissue lacking c-Cbl. In addition, c-Cbl exon skipping could be induced when cells transfected with a c-Cbl mini-gene were grown to high density or under hypoxic stress. These results suggest that unknown alternations (e.g., mutation) of splicing machinery in C6 and A172 cells and the glioblastoma brain tissues are responsible for the deleterious exon skipping. Collectively, these findings indicate that the c-Cbl exon skipping contributes to human glioma and its malignant behavior.

Zhitao J, Long L, Jia L, et al.
Temozolomide sensitizes stem-like cells of glioma spheres to TRAIL-induced apoptosis via upregulation of casitas B-lineage lymphoma (c-Cbl) protein.
Tumour Biol. 2015; 36(12):9621-30 [PubMed] Related Publications
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has potent antitumor effects in glioma cell lines but has shown little clinical benefit for patients. We investigated whether the widely used chemotherapeutic agent temozolomide (TMZ) can sensitize glioma stem-like cells (GSCs) from human glioblastoma multiforme (GBM) to TRAIL-induced apoptosis. GSCs were isolated from GBM, and stem cell properties were confirmed by immunocytochemistry and in vivo tumorigenicity. Primary GSCs (PGCs) were produced by serum treatment of GBM-derived cells. Changes in expression levels of various TRAIL-related signaling factors before and after TRAIL or TRAIL + TMZ treatment were measured by Western blotting. Overexpression vectors and siRNAs were used to investigate mechanism of TRAIL sensitivity. GSCs showed greater resistance to TRAIL-induced apoptosis than PGCs and had lower basal caspase activity. Caspase knockdown in PGCs reduced TRAIL sensitivity. Expression levels of c-Fas-associated death domain-like interleukin 1-converting enzyme-like inhibitory protein long and short isoforms (c-FLIPL and c-FLIPS) were significantly higher in GSCs than PGCs, and siRNA-mediated c-FLIP knockdown in GSCs enhanced TRAIL-induced apoptosis. TMZ enhanced TRAIL-induced apoptosis in GSCs and downregulated c-FLIP expression. Add of TMZ also upregulated the expression of the E3 ubiquitin ligase casitas B-lineage lymphoma (c-Cbl). Moreover, overexpression of c-Cbl alone reduced c-FLIP expression, and c-Cbl knockdown both enhanced c-FLIP expression and reduced the potentiating effect of TMZ on TRAIL-induced apoptosis. The result indicated that TMZ may overcome TRAIL resistance in GSCs by suppressing c-FLIP expression through c-Cbl-mediated ubiquitination and degradation.

Zhang L, Teng Y, Fan Y, et al.
The E3 ubiquitin ligase Cbl-b improves the prognosis of RANK positive breast cancer patients by inhibiting RANKL-induced cell migration and metastasis.
Oncotarget. 2015; 6(26):22918-33 [PubMed] Free Access to Full Article Related Publications
The receptor activator of nuclear factor κ-B ligand (RANKL)/RANK pathway plays an important role in breast cancer progression. Despite the known role of Casitas B-lineage lymphoma (Cbl)-b as an essential regulator of the RANKL/RANK pathway, its effect on RANK pathway in breast cancer remains unclear. Thus, the present study investigated the effect of Cbl-b on the prognosis of RANK-expressing breast cancer patients, as well as on RANKL/RANK pathway. The results showed that RANK and Cbl-b expression was separately detected in 154 (154/300, 51.3%) and 165 (165/300, 55.0%) breast cancer tissue samples. In RANK-expressing breast cancer patients, Cbl-b expression was correlated with low metastasis rate (p = 0.004), better disease-free survival (DFS) and breast cancer-specific survival (BCSS) (p = 0.004 and p = 0.036, respectively). In addition, multivariate analysis showed that Cbl-b expression was an independent predictor of DFS (p = 0.038). Animal experiment results demonstrated that silencing Cbl-b expression in breast cancer cells increased the incidence of lung metastasis in nude mice. Further mechanism investigation revealed that Cbl-b down-regulated RANK protein expression and inhibited RANKL-induced breast cancer cell migration by negatively regulating the Src-Akt/ERK pathway. Our results suggest that Cbl-b improves the prognosis of RANK-expressing breast cancer patients by inhibiting RANKL-induced breast cancer cell migration and metastasis.

Katzav S, Schmitz ML
Mutations of c-Cbl in myeloid malignancies.
Oncotarget. 2015; 6(13):10689-96 [PubMed] Free Access to Full Article Related Publications
Next generation sequencing has shown the frequent occurrence of point mutations in the ubiquitin E3 ligase c-Cbl in myeloid malignancies. Mouse models revealed a causal contribution of c-Cbl for the onset of such neoplasms. The point mutations typically cluster in the linker region and RING finger domain and affect both alleles by acquired uniparental disomy. The fast progress in the detection of c-Cbl mutations is contrasted by our scarce knowledge on their functional consequences. The c-Cbl protein displays several enzymatic functions by promoting the attachment of differentially composed ubiquitin chains and of the ubiquitin-like protein NEDD8 to its target proteins. In addition, c-Cbl functions as an adapter protein and undergoes phosphorylation-dependent inducible conformation changes. Studies on the impact of c-Cbl mutations on its functions as a dynamic and versatile adapter protein, its interactomes and on its various enzymatic activities are now important to allow the identification of druggable targets within the c-Cbl signaling network.

Wei TT, Lin YC, Lin PH, et al.
Induction of c-Cbl contributes to anti-cancer effects of HDAC inhibitor in lung cancer.
Oncotarget. 2015; 6(14):12481-92 [PubMed] Free Access to Full Article Related Publications
Here we found loss of c-Cbl, an E3 ligase, expression in non-small cell lung cancer (NSCLC) compared with its adjacent normal tissue in patient specimens. HDAC inhibition by WJ or knockdown of HDAC 1, HDAC2, HDAC3 or HDAC6 all induced c-Cbl. Ectopic expression of c-Cbl induced decreased EGFR, inhibited growth in NSCLC cells. Knockdown of EGFR inhibited NSCLC growth. Mutation of EGFR at Y1045 decreased WJ-induced growth inhibition as well as in vivo anti-cancer effect and EGFR degradation mediated by WJ. Time-lapse confocal analysis showed co-localization of c-Cbl and EGFR after WJ treatment. Furthermore, WJ inhibited lung tumor growth through c-Cbl induction in orthotopic and tail vein injected models. C-Cbl up-regulation induced by HDACi is a potential strategy for NSCLC treatment.

Gioia R, Trégoat C, Dumas PY, et al.
CBL controls a tyrosine kinase network involving AXL, SYK and LYN in nilotinib-resistant chronic myeloid leukaemia.
J Pathol. 2015; 237(1):14-24 [PubMed] Related Publications
A tyrosine kinase network composed of the TAM receptor AXL and the cytoplasmic kinases LYN and SYK is involved in nilotinib-resistance of chronic myeloid leukaemia (CML) cells. Here, we show that the E3-ubiquitin ligase CBL down-regulation occurring during prolonged drug treatment plays a critical role in this process. Depletion of CBL in K562 cells increases AXL and LYN protein levels, promoting cell resistance to nilotinib. Conversely, forced expression of CBL in nilotinib-resistant K562 cells (K562-rn) dramatically reduces AXL and LYN expression and resensitizes K562-rn cells to nilotinib. A similar mechanism was found to operate in primary CML CD34(+) cells. Mechanistically, the E3-ligase CBL counteracts AXL/SYK signalling, promoting LYN transcription by controlling AXL protein stability. Surprisingly, the role of AXL in resistance was independent of its ligand GAS6 binding and its TK activity, in accordance with a scaffold activity for this receptor being involved in this cellular process. Collectively, our results demonstrate a pivotal role for CBL in the control of a tyrosine kinase network mediating resistance to nilotinib treatment in CML cells.

Pathak A, Pemov A, McMaster ML, et al.
Juvenile myelomonocytic leukemia due to a germline CBL Y371C mutation: 35-year follow-up of a large family.
Hum Genet. 2015; 134(7):775-87 [PubMed] Related Publications
Juvenile myelomonocytic leukemia (JMML) is a pediatric myeloproliferative neoplasm that arises from malignant transformation of the stem cell compartment and results in increased production of myeloid cells. Somatic and germline variants in CBL (Casitas B-lineage lymphoma proto-oncogene) have been associated with JMML. We report an incompletely penetrant CBL Y371C mutation discovered by whole-exome sequencing in three individuals with JMML in a large pedigree with 35 years of follow-up. The Y371 residue is highly evolutionarily conserved among CBL orthologs and paralogs. In silico bioinformatics prediction programs suggested that the Y371C mutation is highly deleterious. Protein structural modeling revealed that the Y371C mutation abrogated the ability of the CBL protein to adopt a conformation that is required for ubiquitination. Clinically, the three mutation-positive JMML individuals exhibited variable clinical courses; in two out of three, primary hematologic abnormalities persisted into adulthood with minimal clinical symptoms. The penetrance of the CBL Y371C mutation was 30% for JMML and 40% for all leukemia. Of the 8 mutation carriers in the family with available photographs, only one had significant dysmorphic features; we found no evidence of a clinical phenotype consistent with a "CBL syndrome". Although CBL Y371C has been previously reported in familial JMML, we are the first group to follow a complete pedigree harboring this mutation for an extended period, revealing additional information about this variant's penetrance, function and natural history.

Park SH, Lee HJ, Kim IS, et al.
Incidences and Prognostic Impact of c-KIT, WT1, CEBPA, and CBL Mutations, and Mutations Associated With Epigenetic Modification in Core Binding Factor Acute Myeloid Leukemia: A Multicenter Study in a Korean Population.
Ann Lab Med. 2015; 35(3):288-97 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: To identify potential molecular prognostic markers in core binding factor (CBF) AML, we analyzed incidences and prognostic impacts of mutations in c-KIT, WT1, CEBPA, CBL, and a number of epigenetic genes in CBF AML.
METHODS: Seventy one and 21 AML patients with t(8;21) and inv(16) were enrolled in this study, respectively. NPM1, CEBPA, c-KIT, IDH1/2, DNMT3A, EZH2, WT1, and CBL mutations were analyzed by direct sequencing. Patients were categorized with respect to c-KIT and WT1 mutation status, and both clinical features and prognoses were compared.
RESULTS: The incidences of FLT3 internal tandem duplication (ITD), NPM1, CEBPA, IDH1/2, DNMT3A, EZH2, and CBL mutations were low (≤5%) in CBF AML patients. However, c-KIT and WT1 mutations occurred frequently (10.9% and 13.8%, respectively). t(8;21) patients with c-KIT mutations showed significantly shorter overall survival (OS) and disease free survival (DFS) periods than those without mutations (P<0.001, for both); however, although the limited number of t(8;21) patients were analyzed, WT1 mutation status did not affect prognosis significantly. Relapse or death during follow-up occurred more frequently in t(8;21) patients carrying c-KIT mutations than in those without the mutation, although the difference was significant only in a specific patient subgroup with no WT1 mutations (P=0.014).
CONCLUSIONS: The incidences of mutations in epigenetic genes are very low in CBF AML; however, c-KIT and WT1 mutations occur more frequently than others. The poor prognostic impact of c-KIT mutation in t(8;21) AML patients only applies in a specific patient subgroup without WT1 mutations. The prognostic impact of WT1 mutation in CBF AML is not evident and further investigation is required.

Emdal KB, Pedersen AK, Bekker-Jensen DB, et al.
Temporal proteomics of NGF-TrkA signaling identifies an inhibitory role for the E3 ligase Cbl-b in neuroblastoma cell differentiation.
Sci Signal. 2015; 8(374):ra40 [PubMed] Related Publications
SH-SY5Y neuroblastoma cells respond to nerve growth factor (NGF)-mediated activation of the tropomyosin-related kinase A (TrkA) with neurite outgrowth, thereby providing a model to study neuronal differentiation. We performed a time-resolved analysis of NGF-TrkA signaling in neuroblastoma cells using mass spectrometry-based quantitative proteomics. The combination of interactome, phosphoproteome, and proteome data provided temporal insights into the molecular events downstream of NGF binding to TrkA. We showed that upon NGF stimulation, TrkA recruits the E3 ubiquitin ligase Cbl-b, which then becomes phosphorylated and ubiquitylated and decreases in abundance. We also found that recruitment of Cbl-b promotes TrkA ubiquitylation and degradation. Furthermore, the amount of phosphorylation of the kinase ERK and neurite outgrowth increased upon Cbl-b depletion in several neuroblastoma cell lines. Our findings suggest that Cbl-b limits NGF-TrkA signaling to control the length of neurites.

Frankum J, Moudry P, Brough R, et al.
Complementary genetic screens identify the E3 ubiquitin ligase CBLC, as a modifier of PARP inhibitor sensitivity.
Oncotarget. 2015; 6(13):10746-58 [PubMed] Free Access to Full Article Related Publications
Based on a series of basic, preclinical and clinical studies, the Poly (ADP-ribose) Polymerase 1 (PARP1) inhibitor, olaparib, has recently been approved for use in ovarian cancer patients with BRCA1 or BRCA2 mutations. By identifying novel predictive biomarkers of tumour cell sensitivity to olaparib, it is possible that the utility of PARP inhibitors could be extended beyond this patient subgroup. Many of the known genetic determinants of PARP inhibitor response have key roles in DNA damage response (DDR) pathways. Although protein ubiquitylation is known to play an important role in regulating the DDR, the exact mechanisms by which this occurs are not fully understood. Using two parallel RNA interference-based screening approaches, we identified the E3 ubiquitin ligase, CBLC, as a candidate biomarker of response to olaparib. We validated this observation by demonstrating that silencing of CBLC causes increased sensitivity to olaparib in breast cancer cell line models and that defective homologous recombination (HR) DNA repair is the likely cause. This data provides an example of how defects in the ubiquitin machinery have the potential to influence the response of tumour cells to PARP inhibitors.

An W, Nadeau SA, Mohapatra BC, et al.
Loss of Cbl and Cbl-b ubiquitin ligases abrogates hematopoietic stem cell quiescence and sensitizes leukemic disease to chemotherapy.
Oncotarget. 2015; 6(12):10498-509 [PubMed] Free Access to Full Article Related Publications
Cbl and Cbl-b are tyrosine kinase-directed RING finger type ubiquitin ligases (E3s) that negatively regulate cellular activation pathways. E3 activity-disrupting human Cbl mutations are associated with myeloproliferative disorders (MPD) that are reproduced in mice with Cbl RING finger mutant knock-in or hematopoietic Cbl and Cbl-b double knockout. However, the role of Cbl proteins in hematopoietic stem cell (HSC) homeostasis, especially in the context of MPD is unclear. Here we demonstrate that HSC expansion and MPD development upon combined Cbl and Cbl-b deletion are dependent on HSCs. Cell cycle analysis demonstrated that DKO HSCs exhibit reduced quiescence associated with compromised reconstitution ability and propensity to undergo exhaustion. We show that sustained c-Kit and FLT3 signaling in DKO HSCs promotes loss of colony-forming potential, and c-Kit or FLT3 inhibition in vitro protects HSCs from exhaustion. In vivo, treatment with 5-fluorouracil hastens DKO HSC exhaustion and protects mice from death due to MPD. Our data reveal a novel and leukemia therapy-relevant role of Cbl and Cbl-b in the maintenance of HSC quiescence and protection against exhaustion, through negative regulation of tyrosine kinase-coupled receptor signaling.

Song J, Kwon Y, Kim S, Lee SK
Antitumor activity of phenanthroindolizidine alkaloids is associated with negative regulation of Met endosomal signaling in renal cancer cells.
Chem Biol. 2015; 22(4):504-15 [PubMed] Related Publications
Met is a receptor tyrosine kinase for hepatocyte growth factor. Met mutations have been considered as a major cause of primary resistance to Met tyrosine kinase inhibitors (TKIs). Mutated Met enhances its endosomal signaling, which includes internalization, signaling within endosomes, recycling to membrane, and sorting for degradation. These sequential events lead to a plausible mechanism for resistance. (-)-Antofine, a phenanthroindolizidine alkaloid, has exhibited potent antitumor activity but the precise underlying mechanism has been poorly understood. We found that (-)-antofine effectively inhibited the proliferation of Met-mutated Caki-1 cells, which were resistant to well-known Met TKIs. (-)-Antofine negatively regulated Met endosomal signaling and consequently inhibited the nuclear translocation of STAT3 both in vitro and in vivo. These findings emphasize the potential of Met endosomal signaling as a novel target for Met TKI-resistant cancers and (-)-antofine as a novel lead compound associated with the suppression of Met endosomal signaling.

Costa V, Esposito R, Ziviello C, et al.
New somatic mutations and WNK1-B4GALNT3 gene fusion in papillary thyroid carcinoma.
Oncotarget. 2015; 6(13):11242-51 [PubMed] Free Access to Full Article Related Publications
Papillary thyroid carcinoma (PTC) is the most frequent thyroid malignant neoplasia. Oncogene activation occurs in more than 70% of the cases. Indeed, about 40% of PTCs harbor mutations in BRAF gene, whereas RET rearrangements (RET/PTC oncogenes) are present in about 20% of cases. Finally, RAS mutations and TRK rearrangements account for about 5% each of these malignancies. We used RNA-Sequencing to identify fusion transcripts and mutations in cancer driver genes in a cohort of 18 PTC patients. Furthermore, we used targeted DNA sequencing to validate identified mutations. We extended the screening to 50 PTC patients and 30 healthy individuals. Using this approach we identified new missense mutations in CBL, NOTCH1, PIK3R4 and SMARCA4 genes. We found somatic mutations in DICER1, MET and VHL genes, previously found mutated in other tumors, but not described in PTC. We identified a new chimeric transcript generated by the fusion of WNK1 and B4GALNT3 genes, correlated with B4GALNT3 overexpression. Our data confirmed PTC genetic heterogeneity, revealing that gene expression correlates more with the mutation pattern than with tumor staging. Overall, this study provides new data about mutational landscape of this neoplasia, suggesting potential pharmacological adjuvant therapies against Notch signaling and chromatin remodeling enzymes.

Zhang Y, Qu X, Teng Y, et al.
Cbl-b inhibits P-gp transporter function by preventing its translocation into caveolae in multiple drug-resistant gastric and breast cancers.
Oncotarget. 2015; 6(9):6737-48 [PubMed] Free Access to Full Article Related Publications
The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function. However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown. In the present study, we showed that c-Src dependent Caveolin-1 phosphorylation promoted the translocation of P-gp into caveolae, resulting in multidrug resistance in adriamycin resistant gastric cancer SGC7901/Adr and breast cancer MCF-7/Adr cells. In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src. Clinical data showed a significant positive relationship between Cbl-b expression and survival in P-gp positive breast cancer patients who received anthracycline-based chemotherapy. Our findings identified a new regulatory mechanism of P-gp transport function in multiple drug-resistant gastric and breast cancers.

Gui Y, Yeganeh M, Donates YC, et al.
Regulation of MET receptor tyrosine kinase signaling by suppressor of cytokine signaling 1 in hepatocellular carcinoma.
Oncogene. 2015; 34(46):5718-28 [PubMed] Related Publications
Suppressor of cytokine signaling 1 (SOCS1) is considered as a tumor suppressor protein in hepatocellular carcinoma (HCC), but the underlying mechanisms remain unclear. Previously, we have shown that SOCS1-deficient hepatocytes displayed increased responsiveness to hepatocyte growth factor (HGF) due to enhanced signaling via the MET receptor tyrosine kinase. As aberrant MET activation occurs in many tumors including HCC, here we elucidated the mechanisms of SOCS1-mediated regulation. SOCS1 attenuated HGF-induced proliferation of human and mouse HCC cell lines and their growth as tumors in NOD.scid.gamma mice. Tumors formed by SOCS1 expressing HCC cells showed significantly reduced MET expression, indicating that SOCS1 not only attenuates MET signaling but also regulates MET expression. Mechanistically, SOCS1 interacted with MET via the Src homology 2 domain and this interaction was promoted by MET tyrosine kinase activity. The SOCS1-mediated reduction in MET expression does not require the juxtamembrane Y1003 residue implicated in Cbl-mediated downmodulation. Moreover, the proteasome inhibitor MG-132, but not the inhibitors of lysosomal degradation bafilomycin and chloroquine, reversed the SOCS1-mediated reduction in MET expression, indicating that this process is distinct from Cbl-mediated downmodulation. Accordingly, SOCS1 promoted polyubiquitination of MET via K48-dependent but not K63-mediated ubiquitin chain elongation. Furthermore, siRNA-mediated downmodulation of Cbl did not abolish SOCS1-mediated reduction in MET expression in HCC cells. SOCS1-dependent ubiquitination of endogenous MET receptor occurred rapidly following HGF stimulation in HCC cells, leading to proteasomal degradation of phosphorylated MET receptor. These findings indicate that SOCS1 mediates its tumor suppressor functions, at least partly, by binding to MET and interfering with downstream signaling pathways as well as by promoting the turnover of the activated MET receptor. We propose that loss of this control mechanism due to epigenetic repression of SOCS1 could contribute to oncogenic MET signaling in HCC and other cancers, and that MET inhibitors might be useful in treating these patients.

Cao Y, Qu J, Li C, et al.
Celecoxib sensitizes gastric cancer to rapamycin via inhibition of the Cbl-b-regulated PI3K/Akt pathway.
Tumour Biol. 2015; 36(7):5607-15 [PubMed] Related Publications
Mammalian target of rapamycin (mTOR) has emerged as a new potential therapeutic target for gastric cancer. However, a phase III clinical trial found that monotherapy with the mTOR inhibitor everolimus did not significantly improve the overall survival of patients with advanced gastric cancer. This has led to the exploration of more effective combinatorial regimens to enhance the effectiveness of mTOR inhibitors. Here, we demonstrate that Akt phosphorylation is increased in the rapamycin-resistant gastric cancer cell lines MGC803 and SGC7901. We further show that combined treatment with celecoxib and rapamycin results in an additive inhibitory effect on the growth of gastric cancer cells through suppression of rapamycin-induced Akt activation. Moreover, celecoxib upregulated the expression of the ubiquitin ligase casitas B-lineage lymphoma-b (Cbl-b). Knockdown of Cbl-b significantly attenuated celecoxib-mediated inhibition of Akt phosphorylation and impaired the additive anticancer effect of celecoxib and rapamycin. Our results suggest that celecoxib-mediated upregulation of Cbl-b is responsible, at least in part, for the additive antitumor effect of celecoxib and rapamycin via inhibition of rapamycin-induced Akt activation.

Kwak SY, Kim BY, Ahn HJ, et al.
Ionizing radiation-inducible miR-30e promotes glioma cell invasion through EGFR stabilization by directly targeting CBL-B.
FEBS J. 2015; 282(8):1512-25 [PubMed] Related Publications
MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the transcriptional and post-transcriptional levels. Here we show that miR-30e, which was previously identified as an ionizing radiation-inducible miRNA, enhances cellular invasion by promoting secretion of the matrix metalloproteinase MMP-2. The enhancement of cellular invasion by miR-30e involved up-regulation of the epidermal growth factor receptor (EGFR) and subsequent activation of its downstream signaling mediators, AKT and extracellular signal-regulated kinase. EGFR up-regulation by miR-30e occurred due to stabilization of the EGFR protein. The E3 ubiquitin ligase casitas B-lineage lymphoma B (CBL-B) was down-regulated by miR-30e, and this led to increased EGFR abundance. A 3' UTR reporter assay confirmed that CBL-B is a direct target of miR-30e. Knocking down CBL-B expression phenocopied the effects of miR-30e, whereas ectopic expression of CBL-B suppressed miR-30e-induced EGFR up-regulation and invasion. Collectively, our results suggest that targeting miR-30e may limit the invasiveness induced during glioma radiotherapy.

Bu N, Wu H, Zhang G, et al.
Exosomes from Dendritic Cells Loaded with Chaperone-Rich Cell Lysates Elicit a Potent T Cell Immune Response Against Intracranial Glioma in Mice.
J Mol Neurosci. 2015; 56(3):631-43 [PubMed] Related Publications
Chaperone-rich cell lysates (CRCLs) may play an important role in the development of anti-tumor vaccines. Tumor-derived CRCLs have been reported to activate dendritic cells (DCs) to elicit potent anti-tumor activity. However, the role of DC-derived exosomes (DEXs) secreted from DCs loaded with CRCLs in the treatment of tumors has not been clearly determined. In the present study, DEXs were generated from DCs loaded with CRCLs derived from GL261 glioma cells. These DEXs, designated DEX (CRCL-GL261), were then used to treat DCs to create DEX (CRCL-GL261)-DCs. The DEX (CRCL-GL261)-DCs were found to promote cell proliferation and cytotoxic T lymphocyte (CTL) activity of CD4(+) and CD8(+) T cells in vitro compared with DEX (GL261)-DCs, which were loaded with DEXs derived from DCs loaded with GL261 tumor cell lysates. DEX (CRCL-GL261)-DCs significantly prolonged the survival of mice with tumors and inhibited tumor growth in vivo. In addition, DEX (CRCL-GL261)-DCs induced enhanced T cell infiltration in intracranial glioma tissues compared with other treatments. DEX (CRCL-GL261)-DCs induced strong production of anti-tumor cytokines, including interleukin-2 and interferon-γ. Moreover, depletion of CD4(+) and CD8(+) T cells significantly impaired the anti-tumor effect of DEX (CRCL-GL261)-DCs. Finally, DEX (CRCL-GL261)-DCs were found to negatively regulate Casitas B cell lineage lymphoma (Cbl)-b and c-Cbl signaling, leading to the activation of phosphatidyl inositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) signaling in T cells. In summary, we present evidence that DEX (CRCL-GL261)-DCs induce more potent and effective anti-tumor T cell immune responses and delineate the underlying mechanism by which DEX (CRCL-GL261)-DCs exerted their anti-tumor activity through modulating Cbl-b and c-Cbl signaling. These results provide novel and promising insight for the development of an anti-tumor vaccine.

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