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Many cancer types carry mutations in protein tyrosine kinase (PTK) and such alterations frequently drive tumor progression. One category is gene translocation of PTKs yielding chimeric proteins with transforming capacity. In this study, we characterized the role of ITK-FER [Interleukin-2-inducible T-cell Kinase (ITK) gene fused with Feline Encephalitis Virus-Related kinase (FER) gene] and ITK-SYK [Interleukin-2-inducible T-cell Kinase (ITK) gene fused with the Spleen Tyrosine Kinase (SYK)] in Peripheral T Cell Lymphoma (PTCL) signaling. We observed an induction of tyrosine phosphorylation events in the presence of both ITK-FER and ITK-SYK. The downstream targets of ITK-FER and ITK-SYK were explored and STAT3 was found to be highly phosphorylated by these fusion kinases. In addition, the CD69 T-cell activation marker was significantly elevated. Apart from tyrosine kinase inhibitors acting directly on the fusions, we believe that drugs acting on downstream targets could serve as alternative cancer therapies for fusion PTKs., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The Protein kinase B (AKT) regulates a plethora of intracellular signaling proteins to fine-tune signaling of multiple pathways. Here, we found that following B-cell receptor (BCR)-induced tyrosine phosphorylation of the cytoplasmic tyrosine kinase SYK and the adaptor BLNK, the AKT/PKB enzyme strongly induced BLNK (>100-fold) and SYK (>100-fold) serine/threonine phosphorylation (pS/pT). Increased phosphorylation promoted 14-3-3 binding to BLNK (37-fold) and SYK (2.5-fold) in a pS/pT-concentration dependent manner. We also demonstrated that the AKT inhibitor MK2206 reduced pS/pT of both BLNK (3-fold) and SYK (2.5-fold). Notably, the AKT phosphatase, PHLPP2 maintained the activating phosphorylation of BLNK at Y84 and increased protein stability (8.5-fold). In addition, 14-3-3 was required for the regulation SYK's interaction with BLNK and attenuated SYK binding to Importin 7 (5-fold), thereby perturbing shuttling to the nucleus. Moreover, 14-3-3 proteins also sustained tyrosine phosphorylation of SYK and BLNK. Furthermore, substitution of S295 or S297 for alanine abrogated SYK's binding to Importin 7. SYK with S295A or S297A replacements showed intense pY525/526 phosphorylation, and BLNK pY84 phosphorylation correlated with the SYK pY525/526 phosphorylation level. Conversely, the corresponding mutations to aspartic acid in SYK reduced pY525/526 phosphorylation. Collectively, these and previous results suggest that AKT and 14-3-3 proteins down-regulate the activity of several BCR-associated components, including BTK, BLNK and SYK and also inhibit SYK's interaction with Importin 7., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The DT40 cell-line has been extensively used to create deletion mutants, one of which lacks Bruton's tyrosine kinase (Btk). Btk is a cytoplasmic tyrosine kinase important for B-lymphocyte maturation. It was previously shown that there are differences in gene expression between wild-type and Btk-deficient animals. Global gene expression profiling of the avian B-lymphoma DT40 cell-line was used as a model to differentiate among Btk knockout (KO) and Btk KO cells reconstituted with human Btk. Differences in the gene expression pattern showed statistically significant changes between parental DT40 and all the Btk KO cell populations irrespective of whether they are reconstituted or not. These results imply that in the process of generating a knockout cell-line, sub-clones are selected, which have multiple changes in their gene expression pattern (p<0.01). Although other parameters could also influence the expression profile, this potentially has important implications when interpreting microarray data from gene-deleted cell-lines.