Líneas de Investigación

Immune System Development and Cancer

With a novel gene subtraction strategy from minute quantities of patient samples (Teitell PNAS 1999; Henson Mut Res 2006) , we discovered abnormally high levels of TCL1 oncoprotein expression in the most common types of human leukemias and lymphomas (Teitell PNAS 1999; Said Lab Invest 2001; Teitell AJCP 2005) . TCL1 acts as a signaling “rheostat”, to regulate the strength of signaling in the AKT and PKC/MAPK/ERK pathways by mechanisms that are not well understood (French Biochemistry 2002; Hoyer J Immunol 2005) . We established a role for aberrant TCL1 expression in initiating cancer by creating a mouse model that develops mainly germinal center B cell cancers with a TCL1 transgene (Hoyer PNAS 2002) . This model requires the formation of germinal centers for aggressive lymphoma formation (Teitell Trends Immunol 2003; Shen Blood 2006) and is the first to replicate the pathophysiology and origins of follicular, Burkitt and diffuse large B cell lymphomas as well as, more rarely, chronic B and T cell lymphocytic leukemias. Current studies include understanding the regulation and dysregulation of TCL1 in B cell development and cancer (Malone PNAS 2001; French J Biol Chem 2003; Doerr J Mol Biol 2005; Kuraishy PNAS 2007) , deciphering the molecular mechanisms for TCL1 action, determining how TCL1 dysregulation is linked to tumor formation, and discovering the germinal center factors that synergize with TCL1 to cause cancer (Hoyer J Immunol 2005; Shen Blood 2006; Dawson Oncogene 2006).

Regulation of Gene Expression in Development and Malignancy

A failure to properly execute developmental gene expression and repression programs may lead to cancer. The TCL1 oncoprotein is normally repressed in germinal center B cells, with continued pre-germinal center expression levels promoting malignant transformation (Hoyer PNAS 2002) . We determined that TCL1 gene silencing occurs in post-germinal center memory B and plasma cells (Said Lab Invest 2001) . Tumors arising from these late and terminal stages in B cell development exhibit unique patterns of DNA methylation on the TCL1 promoter that suggest a staged progression in epigenetic silencing (Doerr J Mol Biol 2005) with usual CpG island methylation (French J Biol Chem 2003) as well as rare CCWGG methylation (Malone PNAS 2001) of unknown significance. To discover the source(s) for aberrant TCL1 expression, we are determining the mechanisms that normally regulate TCL1 as a basis for making comparisons. Patterns of DNA methylation and histone modifications and the roles of newly identified transcriptional activators, co-activators, and repressors in both developing and malignant immune cells are being evaluated. Recent studies of TCL1 repression in germinal center B cells has lead to the discovery of a transcriptional coactivator that is driven from the nucleus by environmental signaling and DNA damage (Kuraishy PNAS 2007) . We predict this novel regulatory mechanism has a major role in controlling the expression and repression of an integrated package of germinal center B cell genes, including TCL1. Ongoing studies are determining the genes in this regulatory package that are controlled by this coactivator and a detailed investigation of the ordered events and signals that regulate gene silencing or activation, such as for TCL1, in B cell development and cancer.

Linking RNA Processing with Metabolism and Cell Survival

A mass spectrometry search for proteins that interact with the TCL1 oncoprotein to potentially promote cancer yielded polynucleotide phosphorylase (PNPase) as a promising candidate (French Cancer Lett 2006) . PNPase is an evolutionarily conserved exoribonuclease that unexpectedly localizes in the intermembrane space of mammalian mitochondria (Chen MCB 2006; Rainey MCB 2006) . We determined that PNPase supports respiration, maintains mitochondria homeostasis with an unknown role in affecting fusion versus fission, regulates energy metabolism, and controls cell proliferation (Chen MCB 2006; Rainey MCB 2006) . The interaction with TCL1, which is an AKT coactivator and stimulates signaling in the AKT and PKC/MAPK/ERK pathways (French Biochemistry 2002; Hoyer J Immunol 2005) , potentially links control of mitochondria function to major signal transduction pathways implicated in a large variety of human malignancies. Current studies include determining the molecular mechanisms for the effect of PNPase on mitochondria structure and function and the role that altered metabolism plays in supporting malignancy within the immune system.

Nanoscale Evaluation of Malignant Transformation

Our group has been examining the nanoscale structural and functional characteristics of cells with an atomic force microscope (AFM) (Pelling Nanomedicine 2006) and micron sized particles embedded within cells using bio-microrheology techniques (Weihs Biophys J 2006; Weihs Microfluidics & Nanofluidics 2007) . AFM and particle tracking methods enable detection of the changes in cells during their progression toward malignancy or increasingly aggressive malignant behavior. Our methods help determine cell damage before biochemical evidence of damage is obtained, with current studies targeting the processes that regulate structural changes at the membrane and within the cytoplasm, to provide a novel, integrated view of cancerous transformation. To further support these studies, we are co-recipients of a 5-yearNanomedicine Development Center (NDC) Award from the NIH Nanomedicine Roadmap Initiative. Ongoing studies include 1) a collaboration to further the development of optoelectronic tweezers (OET) technology for moving cells and subcellular structures without damage for multiplex single cell analysis; 2) a collaboration to develop interferometric microscopy with cell nanomirrors to evaluate malignant progression and identify “outlier” cells in a pool of seemingly identical cancer cells that may be particularly harmful (Reed Nanotechnology 2007) ; 3) a collaboration to identify specific DNA molecules in complex mixtures using AFM techniques (Reed Nanotechnology 2007) ; 4) an NDC collaboration to develop quantitative technologies for evaluating signal transduction kinetics and strength in live cells; and 5) a collaboration to develop a new type of live cell surgery to facilitate the repair and manipulation of somatic and approved human embryonic stem cells and their derivatives.