The unrestrained growth of tumor cells is generally attributed to mutations in essential growth control genes but tumor cells are also influenced by signals from the environment. several Frizzled receptors. This interaction leads to intracellular signals that control gene expression cell behavior cell adhesion and cell polarity during both embryonic development and postnatal life (11 12 The key event in this signaling pathway is the stabilization of β-catenin. In the absence of WNT Saxagliptin signals a dedicated complex of proteins including the tumor suppressor gene product APC axin and glycogen synthase kinase-3β (GSK3β) controls phosphorylation of specific serine and threonine residues in the N-terminal region of β-catenin. This GSK3β-mediated phosphorylation Saxagliptin marks β-catenin for ubiquitination and degradation by the proteasome. Signaling by WNT factors blocks GSK3β activity resulting in the accumulation of nonphosphorylated β-catenin which will translocate to the nucleus. Here it interacts with T cell factor (TCF) transcription factors (13 14 to drive transcription of target genes (9 15 16 It is now well established that unrestrained β-catenin/TCF activity plays a major role in many human cancers (4 5 Mutations of the tumor suppressor gene or of the sequences encoding the crucial GSK3β phosphorylation sites in the N-terminal domain of β-catenin have been found in the vast majority of colorectal cancers as well as many other cancer types (4-6). The Saxagliptin critical consequence of these mutations is the elevation of the levels of β-catenin leading to the formation of constitutive nuclear β-catenin/TCF complexes and altered expression of TCF target genes (5 9 Target genes which likely cooperate in neoplastic transformation include (cyclin D1) (15) (9 15 (17) Saxagliptin and (18). Members of the TCF/LEF family of transcription factors were initially discovered in models of early lymphocyte development. In mice and humans T lineage cells express both TCF1 and LEF1 (7 19 and studies in knockout mice have demonstrated that these factors are essential for the maintenance of progenitor T cell compartments (7 23 24 Similarly during early B cell development in the fetal liver and adult BM LEF1 is involved in the regulation of pro-B cell proliferation and survival (8). By inference these observations suggest a role for WNT signaling in the control of cell proliferation and Saxagliptin survival during lymphocyte development. Indeed recent and studies demonstrating that WNT factors and β-catenin also affect lymphocyte progenitor fate as well as stem cell self-renewal confirm this role (8 10 25 26 The involvement of the WNT pathway in the regulation of the survival and expansion of progenitor and stem cells in combination with its oncogenic potential in nonlymphoid cells prompted us to test whether deregulation of the WNT pathway occurs in lymphoid neoplasia. Whereas the specificity of WNT signals with respect to target cells is relatively unknown there are now powerful methods to examine whether cells are activated by a WNT signal. These tools include measuring the levels of the β-catenin protein in particular a nonphosphorylated form of β-catenin that is generated by active WNT signaling (27 28 In the nucleus WNT signaling proceeds through the transcription factor TCF and by interfering with TCF activity [using a dominant-negative form of TCF (ΔTCF4)] one can examine to what extend the behavior and growth of cells depends on an active WNT signal. Here we show that WNT signaling is active in MMs and that WNT signals are involved in the control of MM growth. Materials and Methods Antibodies. Mouse mAbs used were: anti-CD138 BB4 (IgG1) (Instruchemie Hilversum The Netherlands); anti-β-catenin (clone 14 IgG1) (BD Biosciences Erembodegem Belgium); anti-active (nonphosphorylated) β-catenin (anti-ABC IgG1) (27 28 anti-active (nonphosphorylated) β-catenin (clone 8E4 IgG1) (Alexis Biochemicals Lausanne Switzerland); anti β-actin Mst1 (clone AC15 IgG1) (Sigma); allophycocyanin-conjugated anti-CD19 (IgG1); FITC-conjugated anti-IgD (IgG1); FITC-conjugated anti-CD45RA (IgG2b) (all BD Biosciences); biotin-conjugated anti-CD38 (IgG1) (Caltag Burlingame CA). Polyclonal antibodies used were: rabbit anti-human ERK2 (C14 Santa Cruz Biotechnology); Dynabead-conjugated goat anti-mouse IgG (Dynal Wirral U.K.); horseradish peroxidase-conjugated rabbit anti-mouse; FITC-conjugated rabbit anti-mouse; and horseradish peroxidase-conjugated goat anti-rabbit (all DAKO). Myelomas Cell Cultures and Transfections. Primary myeloma samples and normal BM samples were obtained during routine diagnostic procedures. Mononuclear cells were harvested by.

The unrestrained growth of tumor cells is generally attributed to mutations
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