TCL1 is a protooncogene overexpressed in many mature B cell lymphomas. TCL1 is also expressed in precursor T cells and absent by the CD4+ CD8+ stage of thymocyte development. In B cells, TCL1 is first expressed in pro-B cells, and is completely absent in memory B cells and plasma cells.
UCLA researchers have developed a murine model in which a TCL1 transgene is overexpressed in both B and T cells. These transgenic mice develop Burkitt-like lymphoma and diffuse large B cell lymphoma at 4 months. This phenotype is accompanied by attendant Bcl-6 expression and mutated JH antibody gene segments. Interestingly, TCL1 is a more powerful initiator of B cell malignancies when compared to the low frequency of T cell malignancies with this model. This is mirrored in humans as >85% of human immune system malignancies are B cell derived.
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