Pathogenesis of B-cell Malignancies Recent work has shown that the majority of B-cell non-Hodgkin's lymphomas (NHL) and a significant proportion of B-cell chronic lymphocytic leukemias are derived from germinal center (GC) B cells or their descendents, implicating passage through the GC reaction as a factor in lymphomagenesis. The GC is the site of considerable genetic plasticity in the form of the physiological processes of V(D)J recombination, isotype switching, and somatic hypermutation. Our overall hypothesis is that the genomic instability occurring in the context of the normal immune response increases the probability of sustaining genetic alterations that result in lymphoid transformation. The long term goals of this research are to understand the properties of the GC that predispose GC B cells to transformation. As part of this aim we are engaged in developing a mouse model of B-cell malignancies that arise from the GC B cell, and also identifying genes that are turned on or off upon entry into the GC.

Developing Novel Assays for Kinase Activity in Human Leukemias The molecular analysis of the growth-promoting signal transduction pathways holds tremendous potential for the diagnosis and treatment of cancer. However, traditional biochemical assays have inherent limitations when used for clinically-based molecular assays in cancer patients. New approaches are needed to assess the activity of the different signal transduction pathways involved in the development and maintenance of cancer. The Laser Micropipet System (LMS) is a new and enabling technology for performing biochemical assays of the activity of key signal transduction enzymes within living cells. In collaboration with Christopher Sims, we will be developing assays for two oncoproteins, Bcr-Abl in chronic myelogenous leukemia (CML) and the c-kit receptor in acute myelogenous leukemia (AML), in order to demonstrate the power of this tool for pharmacological and clinical applications. While these assays will be of value in the diagnosis and follow-up of patients with CML and AML, these studies will also lay the groundwork for a new paradigm of molecular diagnosis based on the direct measurement of the activity of enzymes in patient cells. Such assays will have general applicability to a number of cancers in which the abnormal regulation of signal transduction proteins fuels the oncogenic state.