NF-kB and Notch signaling are activated in almost all common B cell lymphomas due to either activating somatic mutations or upregulation of pathway regulators. However, how these two pathways synergistically regulate B cell development and lymphomatous transformation are unclear. B cell plasticity has been recognized clinically decades ago. Patient with B cell lymphoma occasionally develop clonally-related myeloid tumors, suggesting that at least some myeloid tumors develop from malignant or premalignant B cells. Clinically, these patients typically present with advanced disease with a poor prognosis due to diagnostic difficulties and lack of standard treatment. The question is, how do B cells convert to myeloid lineage? Experimentally, forced expression of myeloid transcription factor, CEBPa, in mature B cells induces B-myeloid conversion. However, whether CEBPa initiates B-myeloid conversion in pathological conditions and whether other signaling pathways are also involved are largely unknown. Our preliminary data show that concurrent activation of both pathways in CD19+ B cells efficiently induces B cell lymphomatous transformation in sharp contrast to activation of either pathway alone. Intriguingly and unexpectedly, transplanted doubly-activated marginal zone precursor B cells, but not marginal zone B cells, converted to myeloid cells through dedifferentiation, and some transformed to myeloid leukemia with clonal immunoglobulin VDJ recombination. Our central hypothesis is that concurrent activation of NF-kB and Notch signaling accelerates B cell transformation and triggers B-myeloid conversion mainly through downregulation of Bach2 and upregulation of Ezh2. We will test this hypothesis with the following two independent specific aims: 1) To determine the mechanism whereby concurrent activation of NF-kB/Notch signaling induces B cell transformation, and 2) To determine the mechanism whereby concurrent activation of NF-kB/Notch signaling induces B-myeloid conversion and transformation. The expected results are highly relevant to understanding the synergistic role of NF-kB/Notch signaling in B cell plasticity and malignant transformation. Importantly, our results suggest that adding Notch, NF-kB and/or Ezh2 inhibitors to the current lymphoma therapeutic regimens could not only improve lymphoma treatment, but also prevent myeloid neoplasm conversion.
NF-kB and Notch signaling are activated in almost all common B cell lymphomas. Patients with B cell lymphoma occasionally develop clonally-related myeloid tumors. Clinically, these patients typically present with advanced disease and have a poor prognosis due to difficulties in diagnosing them definitely and lack of standard therapeutic regimens. The proposed research aims to uncover the potential mechanisms whereby activation of NF-kB/Notch signaling in committed B cells induces lymphomatous transformation and B-myeloid conversion. As Hodgkin?s lymphoma and non-Hodgkin?s lymphoma are presumptive diseases associated with exposure to Agent Orange or other herbicides during military service, the results will facilitate our understanding and treatment of both lymphomas and those uncommon, but fatal myeloid neoplasms converted from B cells and thus improve the health of veterans.
