Application Methods: IHC-Leica® Bond™, Immunohistochemistry (Paraffin)
Background: Chromosomal translocations result in misregulation of the proto-oncogene BCL6 in patients with B cell-derived non-Hodgkin's lymphoma (1). The BCL6 gene is selectively expressed in mature B cells and encodes a nuclear phosphoprotein that belongs to the BTB/POZ zinc finger family of transcription factors (2,3). BCL6 protein can bind to target DNA sequences of Stat6 and, analogous to Stat6, modulate the expression of interleukin-4-induced genes (4). Furthermore, BCL6 restrains p53-dependent senescence, making BCL6-active tumors functionally p53-negative (5). The mitogen-activated protein kinases, Erk1 and Erk2, but not JNK, phosphorylate BCL6 at multiple sites. Phosphorylation of BCL6 at Ser333 and Ser343 results in degradation of BCL6 by the ubiquitin/proteasome pathway in B cells (6,7). In addition, BCL6 is acetylated and its transcriptional repressor function is inhibited by the transcriptional co-activator p300 (8).
Application Methods: IHC-Leica® Bond™, Immunohistochemistry (Paraffin), Immunoprecipitation, Western Blotting
Background: c-Kit is a member of the subfamily of receptor tyrosine kinases that includes PDGF, CSF-1, and FLT3/flk-2 receptors (1,2). It plays a critical role in activation and growth in a number of cell types including hematopoietic stem cells, mast cells, melanocytes, and germ cells (3). Upon binding with its stem cell factor (SCF) ligand, c-Kit undergoes dimerization/oligomerization and autophosphorylation. Activation of c-Kit results in the recruitment and tyrosine phosphorylation of downstream SH2-containing signaling components including PLCγ, the p85 subunit of PI3 kinase, SHP2, and CrkL (4). Molecular lesions that impair the kinase activity of c-Kit are associated with a variety of developmental disorders (5), and mutations that constitutively activate c-Kit can lead to pathogenesis of mastocytosis and gastrointestinal stromal tumors (6). Tyr719 is located in the kinase insert region of the catalytic domain. c-Kit phosphorylated at Tyr719 binds to the p85 subunit of PI3 kinase in vitro and in vivo (7).