Abstract
PAX5, a B cell-specific transcription factor, is overexpressed through chromosomal translocations in a subset of B cell lymphomas. Previously, we had shown that activation of immunoreceptor tyrosine-based activation motif (ITAM) proteins and B cell receptor (BCR) signaling by PAX5 contributes to B-lymphomagenesis. However, the effect of PAX5 on other oncogenic transcription factor-controlled pathways is unknown. Using a MYC-induced murine lymphoma model as well as MYC-transformed human B cell lines, we found that PAX5 controls c-MYC protein stability and steady-state levels. This promoter-independent, posttranslational mechanism of c-MYC regulation was independent of ITAM/BCR activity. Instead it was controlled by another PAX5 target, CD19, through the PI3K-AKT-GSK3β axis. Consequently, MYC levels in B cells from CD19-deficient mice were sharply reduced. Conversely, reexpression of CD19 in murine lymphomas with spontaneous silencing of PAX5 boosted MYC levels, expression of its key target genes, cell proliferation in vitro, and overall tumor growth in vivo. In human B-lymphomas, CD19 mRNA levels were found to correlate with those of MYC-activated genes. They also negatively correlated with the overall survival of patients with lymphoma in the same way that MYC levels do. Thus, CD19 is a major BCR-independent regulator of MYC-driven neoplastic growth in B cell neoplasms.
Publication types
-
Research Support, N.I.H., Extramural
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Antigens, CD19 / genetics
-
Antigens, CD19 / immunology*
-
B-Lymphocytes / immunology*
-
B-Lymphocytes / pathology
-
Cell Line, Transformed
-
Gene Expression Regulation, Neoplastic / genetics
-
Gene Expression Regulation, Neoplastic / immunology
-
Glycogen Synthase Kinase 3 / genetics
-
Glycogen Synthase Kinase 3 / immunology
-
Glycogen Synthase Kinase 3 beta
-
Humans
-
Lymphoma, B-Cell / genetics
-
Lymphoma, B-Cell / immunology*
-
Lymphoma, B-Cell / pathology
-
Mice
-
Neoplasms, Experimental / genetics
-
Neoplasms, Experimental / immunology
-
Neoplasms, Experimental / pathology
-
PAX5 Transcription Factor / genetics
-
PAX5 Transcription Factor / immunology
-
Phosphatidylinositol 3-Kinases / genetics
-
Phosphatidylinositol 3-Kinases / immunology
-
Proto-Oncogene Proteins c-akt / genetics
-
Proto-Oncogene Proteins c-akt / immunology
-
Proto-Oncogene Proteins c-myc / genetics
-
Proto-Oncogene Proteins c-myc / immunology*
-
RNA, Messenger / genetics
-
RNA, Messenger / immunology
-
RNA, Neoplasm / genetics
-
RNA, Neoplasm / immunology
-
Receptors, Antigen, B-Cell / genetics
-
Receptors, Antigen, B-Cell / immunology*
-
Signal Transduction / genetics
-
Signal Transduction / immunology*
Substances
-
Antigens, CD19
-
Myc protein, mouse
-
PAX5 Transcription Factor
-
Pax5 protein, mouse
-
Proto-Oncogene Proteins c-myc
-
RNA, Messenger
-
RNA, Neoplasm
-
Receptors, Antigen, B-Cell
-
Phosphatidylinositol 3-Kinases
-
GSK3B protein, human
-
Glycogen Synthase Kinase 3 beta
-
Gsk3b protein, mouse
-
Proto-Oncogene Proteins c-akt
-
Glycogen Synthase Kinase 3