15 research outputs found
Deregulated Syk inhibits differentiation and induces growth factorâindependent proliferation of preâB cells
The nonreceptor protein spleen tyrosine kinase (Syk) is a key mediator of signal transduction in a variety of cell types, including B lymphocytes. We show that deregulated Syk activity allows growth factorâindependent proliferation and transforms bone marrowâderived preâB cells that are then able to induce leukemia in mice. Syk-transformed preâB cells show a characteristic pattern of tyrosine phosphorylation, increased c-Myc expression, and defective differentiation. Treatment of Syk-transformed preâB cells with a novel Syk-specific inhibitor (R406) reduces tyrosine phosphorylation and c-Myc expression. In addition, R406 treatment removes the developmental block and allows the differentiation of the Syk-transformed preâB cells into immature B cells. Because R406 treatment also prevents the proliferation of c-Mycâtransformed preâB cells, our data indicate that endogenous Syk kinase activity may be required for the survival of preâB cells transformed by other oncogenes. Collectively, our data suggest that Syk is a protooncogene involved in the transformation of lymphocytes, thus making Syk a potential target for the treatment of leukemia
AID-expressing epithelium is protected from oncogenic transformation by an NKG2D surveillance pathway
Activation-induced deaminase (AID) initiates secondary antibody diversification in germinal center B cells, giving rise to higher affinity antibodies through somatic hypermutation (SHM) or to isotype-switched antibodies through class switch recombination (CSR). SHM and CSR are triggered by AID-mediated deamination of cytosines in immunoglobulin genes. Importantly, AID activity in B cells is not restricted to Ig loci and can promote mutations and pro-lymphomagenic translocations, establishing a direct oncogenic mechanism for germinal center-derived neoplasias. AID is also expressed in response to inflammatory cues in epithelial cells, raising the possibility that AID mutagenic activity might drive carcinoma development. We directly tested this hypothesis by generating conditional knock-in mouse models for AID overexpression in colon and pancreas epithelium. AID overexpression alone was not sufficient to promote epithelial cell neoplasia in these tissues, in spite of displaying mutagenic and genotoxic activity. Instead, we found that heterologous AID expression in pancreas promotes the expression of NKG2D ligands, the recruitment of CD8(+) T cells, and the induction of epithelial cell death. Our results indicate that AID oncogenic potential in epithelial cells can be neutralized by immunosurveillance protective mechanisms.APâG is a fellow of the research training program (FPUâ AP2009â1732) funded by the Ministerio de EducaciĂłn, Cultura y Deporte, PPâD was an FPI fellow from the Ministerio de Ciencia e InnovaciĂłn. ARR is supported by Centro Nacional de Investigaciones Cardiovaculares (CNIC). This work was funded by grants from the Ministerio de EconomĂa y Competitividad (SAF2010â21394, SAF2013â42767âR) and the European Research Council Starting Grant program (BCLYMâ207844) to ARR. The CNIC is supported by the Ministerio de EconomĂa y Competitividad and the ProâCNIC Foundation. FXR is supported by SAF2011â29530 and ONCOBIO Consolider grants from Ministerio de EconomĂa y Competitividad (Madrid, Spain), RTICC from Instituto de Salud Carlos III, and grant 256974 from European Union Seventh Framework Programme to FXR
AID-expressing epithelium is protected from oncogenic transformation by an NKG2D surveillance pathway
Activation-induced deaminase (AID) initiates secondary antibody diversification in germinal center B cells, giving rise to higher affinity antibodies through somatic hypermutation (SHM) or to isotype-switched antibodies through class switch recombination (CSR). SHM and CSR are triggered by AID-mediated deamination of cytosines in immunoglobulin genes. Importantly, AID activity in B cells is not restricted to Ig loci and can promote mutations and pro-lymphomagenic translocations, establishing a direct oncogenic mechanism for germinal center-derived neoplasias. AID is also expressed in response to inflammatory cues in epithelial cells, raising the possibility that AID mutagenic activity might drive carcinoma development. We directly tested this hypothesis by generating conditional knock-in mouse models for AID overexpression in colon and pancreas epithelium. AID overexpression alone was not sufficient to promote epithelial cell neoplasia in these tissues, in spite of displaying mutagenic and genotoxic activity. Instead, we found that heterologous AID expression in pancreas promotes the expression of NKG2D ligands, the recruitment of CD8(+) T cells, and the induction of epithelial cell death. Our results indicate that AID oncogenic potential in epithelial cells can be neutralized by immunosurveillance protective mechanisms.APâG is a fellow of the research training program (FPUâ AP2009â1732) funded by the Ministerio de EducaciĂłn, Cultura y Deporte, PPâD was an FPI fellow from the Ministerio de Ciencia e InnovaciĂłn. ARR is supported by Centro Nacional de Investigaciones Cardiovaculares (CNIC). This work was funded by grants from the Ministerio de EconomĂa y Competitividad (SAF2010â21394, SAF2013â42767âR) and the European Research Council Starting Grant program (BCLYMâ207844) to ARR. The CNIC is supported by the Ministerio de EconomĂa y Competitividad and the ProâCNIC Foundation. FXR is supported by SAF2011â29530 and ONCOBIO Consolider grants from Ministerio de EconomĂa y Competitividad (Madrid, Spain), RTICC from Instituto de Salud Carlos III, and grant 256974 from European Union Seventh Framework Programme to FXR
SYK-dependent tonic B-cell receptor signaling is a rational treatment target in diffuse large B-cell lymphoma
The role of B-cell receptor (BCR)âmediated survival signals in diffuse large B-cell lymphoma (DLBCL) remains undefined. Ligand-induced BCR signaling induces receptor oligomerization, Igα/ÎČ immunoreceptor tyrosine-based activation motif (ITAM) phosphorylation, and activation of the spleen tyrosine kinase (SYK), which initiates downstream events and amplifies the initial BCR signal. BCRs also transmit low-level tonic survival signals in the absence of receptor engagement. Herein, we assess the role of SYK-dependent tonic BCR survival signals in DLBCL cell lines and primary tumors and evaluate the efficacy of an ATP-competitive inhibitor of SYK, R406, in vitro. R406 induced apoptosis of the majority of examined DLBCL cell lines. In R406-sensitive DLBCL cell lines, R406 specifically inhibited both tonic- and ligand-induced BCR signaling (autophosphorylation of SYK525/526 and SYK-dependent phosphorylation of the B-cell linker protein [BLNK]). The majority of examined primary DLBCLs also exhibited tonic- and ligand-induced BCR signaling; in these primary tumors, BCR signaling was also inhibited by R406. Of note, BCR-dependent and R406-sensitive DLBCL cell lines were independently identified as âBCR-typeâ tumors by transcriptional profiling. Therefore, SYK-dependent tonic BCR signaling is an important and potentially targetable survival pathway in some, but not all, DLBCLs. In addition, R406-sensitive DLBCLs can be identified by their transcriptional profiles