Lentiviral (HIV)-based RNA interference screen in human B-cell receptor regulatory networks reveals MCL1-induced oncogenic pathways

Abstract

IntroductionReciprocal chromosomal translocations involving one of the IG loci and a proto-oncogene are hallmarks of many types of human B-cell non-Hodgkin lymphomas (B-NHL). 1 As a consequence of such translocations, several proto-oncogenes are placed under the transcriptional control of the active IG locus, causing constitutive expression of the oncogenes with subsequent B-cell transformation. 2 During B-cell tumor progression, IG chromosomal translocations are thought to be early events in the pathogenesis of these neoplasias and result in critical deregulation of multiple oncogenes such as BCL2 t(14;18)(q32;q21) in follicular lymphomas, MYC t(8;14)(q24;q32) in Burkitt lymphomas, CCND1 t(11;14)(q13;q32) in mantle cell lymphomas, MALT1 t(1;14)(p21;q32) in extranodal MALT lymphomas, or BCL6 t(3;V)(q27;V) in diffuse large cell lymphomas. 3 In addition to these chromosomal aberrations, several observations suggest that B-cell receptor (BCR) signaling supplies important tonic survival signals that might be required for the maintenance of B-cell lymphomas. 4 Considering the allelic exclusion model, chromosomal translocation events should occur at equal frequency on the expressed IGH allele and the nonexpressed IGH allele. Because translocations of proto-oncogenes into the IGH-loci are always found on the nonproductively rearranged IGH loci, with few exceptions 5 ; these findings suggest that survival of B-cell lymphoma clones is incompatible with translocations of protooncogenes into the productively rearranged IGH loci because this type of translocation would induce inability to express immunoglobulin (Ig), 2 and suggests the dependency of Ig expression for B-cell lymphoma survival. Moreover, taking into account that the somatic hypermutation machinery induces 2 types of destructive somatic mutations (nonsense mutations and duplications causing reading-frame shifts); these events would lead to the generation of B-cell lymphoma clones that lack Ig expression under nonselective conditions. 6 Because that treatment of patients with anti-idiotypic antibodies (a selective condition) did not result in the selection of Ig-negative B-cell lymphoma clones, 7 this observation also suggests the dependency of Ig expression for the survival of many B-cell lymphomas. 2 In support of this hypothesis, several molecules integrated in the BCR regulatory network appear to act as oncoproteins, such as SYK, 8 ZAP70, 9 BLK, 10 and MALT1, 11 whereas other BCR regulatory molecules surprisingly promote programmed cell death, such as LYN, 12 IP3R, 13 calpains, 14 SLP65, 15 and BTK. 16 These observations exemplify both positive and negative regulatory roles for BCR in signaling and raise the question of how the BCR signal transduction pathway can generate such distinct outcomes and what is the contribution of BCR signaling in B-cell transformation.B-cell antigen receptors specific for self-molecules are normally produced as a consequence of the random VDJ recombination. B cells that recognize a self-antigen undergo programmed cell death ser...

Deregulated Expression of the Polycomb-Group Protein SUZ12 Target Genes Characterizes Mantle Cell Lymphoma

“…Slides were scanned in an Agilent G2565AA microarray scanner system and data were extracted with feature extraction software (Agilent Technologies). 39 …”

“…shRNAs were cloned as previously described. 39 shRNA sequences used for control and SUZ12 knockdown were as follows: Scramble: (5Ј-GAGGAACCAAACCATAACA-3Ј); shSUZ12.783: (5Ј-GGATGTAAGTTGTCCAATA-3Ј); shSUZ12.2076: (5Ј-GCTGACAATCAAATGAATCAT-3Ј).…”

“…For co-transfection, plasmids pCMVdeltaR8.91 (derived from pCMVR8.9 37 ), pMD.G and the lentiviral vector pA179.Helix 38 containing the shRNAi sequences were used. Plasmids were co-transfected using FuGene 6 (Roche, Basel, Switzerland) following the manufacturer's recommendations.…”

TCL1A expression delineates biological and clinical variability in B-cell lymphoma

“…token ¼ ftenzyyykicqqfi&acc ¼ GSE9327) were used in this study. The microarray data have been previously published by our group and include those for Burkitt's lymphoma (9 cases), diffuse large B-cell lymphoma (36 cases), 15 mantle cell lymphoma (38 cases), 16 chronic lymphocytic leukemia (38 cases), 17 follicular lymphoma (33 cases), 18 nodal marginal zone lymphoma (6), and splenic marginal zone lymphoma (27 cases). 19 Reactive lymph nodes from eight patients and spleen from three patients were also analyzed.…”

B-cell signaling networks reveal a negative prognostic human lymphoma cell subset that emerges during tumor progression

“…BCR signaling has been implicated in other B cell lymphomas (13)(14)(15)(16), and carbohydrate modifications to the BCR may alter signaling interactions of FL cells (17). Because BCR activation can initiate signals resulting in either survival or apoptosis of B cells (18)(19)(20)(21), this pathway provides many opportunities for selective pressure to elicit the emergence of lymphoma subsets.…”