Teitell Laboratory Research Description Research in the Teitell group focuses on mechanisms of cancer formation and progression. We place a special emphasis on studies of leukemia and lymphoma that arise during normal B cell development. Our work has evolved into several areas with distinct sets of techniques and approaches; however, all project areas address fundamental questions concerning the etiology and progression of cancer, providing a common link for the group. Areas of active research in our group include:
Immune System Development and Cancer (see Teitell Nature Rev. Cancer 2005) 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.
Mitochondria in Human Embryonic Stem Cell Self-Renewal vs. Differentiation A new area of investigation links developing expertise in the group in two areas- mitochondrial and human embryonic stem cell (hESC) biology. The rationale for these studies is the need to understand how changes in metabolism, which normally shifts from glycolysis to aerobic respiration as fertilized ova implant during embryogenesis, shifts back again to a main dependence on glycolysis (the Warburg effect) with malignant transformation. We reason that dynamic changes in mitochondria function and hESC dependence on oxygen tension will mimic key features of malignant degeneration. Current studies include evaluating the role of native and damaged mitochondria in normoxic and hypoxic oxygen tension environments to determine a role in controlling hESC decisions for self-renewal, differentiation, or quiescence, which could resemble similar decisions in “cancer stem cells”. Human Embryonic Stem Cells and Cancer Mouse Tcl1 is the only known member of an oncogene family thus far shown to control basic embryonic stem cell decisions, such as self-renewal. Human TCL1 family members are expressed in early embryonic development, in skin appendage stem cells, and in germ cell tumors, which share many characteristics with hESCs. Furthermore, the major signaling pathway that controls hESC survival is the PI3K/AKT pathway, which TCL1 coactivates. Since aberrant TCL1 expression causes models for major human leukemias and lymphomas in transgenic mice (Hoyer PNAS 2002; Teitell Nature Rev Cancer 2005; Shen Blood 2006) , and many human germ cell tumors and germinal center derived Burkitt lymphomas demonstrate aberrant TCL1 expression (Teitell AJCP 2005) , we reason that TCL1 family member expression in hESCs could controls decisions regulating self-renewal, differentiation, survival, and quiescence. Understanding this regulation should provide clues to the malignancy-inducing mechanism of aberrant TCL1 expression in human cancers and perhaps insight into the pathophysiology of “cancer stem cells”. Current studies include manipulations of TCL1 family expression levels in hESCs with determination of effects decisions to proliferate, apoptose, or differentiate. |
