Drug Discovery and Development

Normal T and B lymphocytes arise from stem cells that undergo several well-defined stages of maturation. Malignant transformation can occur at any step along this differentiation pathway resulting in the spectrum of malignant lymphoid disorders seen in man (e.g. acute lymphoblastic leukemia, non Hodgkins lymphoma, chronic lymphocytic leukemia, multiple myeloma, etc.). In order to understand the pathophysiology of these tumors, we catalogue them according to their state of differentiation. We have established a number of permanent cell lines from patients with different lymphoid malignancies. The immunophenotypes and genetic defects of these lines are well defined and reflect those seen in patients. These cell lines grow in liquid culture, soft agar and some grow in severe combined immune deficient (SCID) mice. Such features make these cell lines and the SCID xenograft models a unique resource for research. Currently, we have four SCID xenograft models well established and are in routine use in the laboratory: WSU-DLCL2 (large cell lymphoma), WSU-FSCCL (follicular low grade lymphoma), WSU-CL (chronic lymhocytic leukemia, and WSU-WM (Waldenstrom’s macroglobulinemia). Fundamental questions regarding pathogenesis and new therapies of these disorders are being addressed in this laboratory. Using a natural marine animal product (bryostatin 1), we have been able to induce terminal differentiation of some of these tumors to a non-proliferative state. The underlying mechanisms of such differentiation are being addressed as a long term project. Based on work in this laboratory, bryostatin 1 has entered clinical trials in the US under NCI sponsership.Among other projects are antiangiogenesis in lymphoma and efficacy of antisense bcl2 oligonucleotides in follicular lymphoma. The eventual aim of those studies is to bring a rationally developed new agent/modalities for the treatment of patients with these otherwise fatal illnesses. The team of investigators in this laboratory encompasses both clinical and laboratory scientists that facilitates the transition of research from the bench to the bedside.

Selected Publications
Mohammad RM, Wang S, Aboukameel A, Chen B, Wu X, Chen J, Al-Katib A. Preclinical studies of a nonpeptidic small-molecule inhibitor of Bcl-2 and Bcl-XL [(-)-gossypol] against diffuse large cell lymphoma. Mol Cancer Ther,  4:13-21, 2005.

Hamdy N, Goustin AS, Chow C, Desaulniers J-P, Al-Katib, A.  Sheep red blood cells armed with anti-CD20 single-chain variable fragments (scFvs) fused to a glycosylphosphatidylinositol (GPI) anchor: a strategy to target CD20-positive tumor cells. J Immunol Methods, 297:109-124, 2005.

Al-Katib AM, Mohamed AN. Non-Hodgkin’s Lymphoma and Chronic Lymphocytic Leukemia. In:,2nd Ed (M Runge and C Patterson eds.), Chapter 82, pp: 794-803, Humana Press, Inc., May, 2006.

Mohammad RM, Goustin AS, Aboukameel A, Chen B, Banerjee S, Wang S, Al-Katib A. Preclinical studies of TW-37, a new nonpeptidic small molecule inhibitor of Bcl-2, in diffuse large cell lymphoma xenograft model reveal drug action on both Bcl-2 and Mcl-1. Clin Can Research, 13: 001-011, 2007.

Mohamed AN, Bentley G, Bennett ML, Zonder J, Al-Katib A. Chromosome aberrations in a series of 120 multiple myeloma cases with abnormal karyotypes. Am J Hematol Jul 25;82(12):1080-1087, 2007.

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Ben Chen Ph.D.
Drug Discovery and Development
Ph.D., Vanderbilt University, 1977

The main objective in his laboratory is aimed at studying how macrophage colony-stimulating factor (M-CSF) molecules interact with the receptors (c-fms proto-oncogene product) and the metabolic events involved in the signaling pathway leading to monocytic differentiation. His laboratory employs two cell models: 1) a primary culture of bone marrow cells induced to undergo monocytic differentiation by M-CSF and2) human leukemia cell models that can be induced to undergo monocytic differentiation by protein kinase C activator. Current projects include the identification of tyrosine kinases associated with these receptors and their role in the process. The underlying biochemical and molecular basis for signal transduction in leukemia cells and normal hematopoietic cell are being studied to determine which metabolic cascades might be involved inleukemogenesis.Another project in his laboratory is aimed at studying the development of anti-apoptotic mechanisms during monocytic differentiation. Macrophage precursors in the bone marrow are highly dependent on exogenous cytokine for survival in vitro. Differentiation of monocytic cells into mature macrophages is associated with the development of antiapoptotic mechanisms that prevent them from undergoing apoptosis in vitro. The objectives include the elucidation of underlying mechanisms such as the expression of inhibitors of apoptosis protein (IAP) and how the expression of these anti-apoptotic regulators is regulated. This project is being carried out using cytokine dependent bone marrow cells as well as leukemia cells that are resistant to starvation-induced apoptosis. The objective is to investigate the role of such anti apoptotic mechanisms during thedevelopment of leukemias.

Selected Publications
Lin, H. C. Chen and B. Chen. Resistance of bone marrow-derived macrophages to apoptosis is associated with the expression of X-linked inhibitor of apoptosis protein in primary cultures of bone marrow cells. Biochem. J. 353:299-306, 2001.

Lin, H., Subramanian, B., Nakeff, A., and Chen, B.D. XK469, a novel antitumor agent, inhibits signaling by the MEK/MAPK signaling pathway. Cancer Chemotherapy Pharmacol. 49:281-286, 2002.

Zhang, J., Li, Y., Yu, M., Chen, B. and Shen, B. Lineage-dependent NF-kB activation contributes to the resistance of human macrophages to apoptosis. Hematology J. 4:277-84, 2003.

Ren, W. Wu, B. Peng, P. Mayton, L. Ren, J. Chen, B. and Wooley, P. Erythromycin Inhibits Wear Debris-Induced Inflammatory Osteolysis in a Murine Model  J. Orthopaedic Res. 280-290, 2006

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David R. Evans, Ph.D.
Drug Discovery and Development Ph.D.,
Wayne State University, 1968

The proliferation of cancer cells requires a continuous supply of pyrimidine nucleotides for RNA and DNA synthesis. The pyrimidine supply is regulated by CAD, a 1.5 megadalton multifunctional complex that catalyzes the first three steps in the de novo pyrimidine biosynthetic pathway. The activity of the complex is invariably elevated in tumor cells, so CAD represents a potential target for chemotherapeutic agents.  The central role that the complex plays in cell growth is reflected by the intricate network of regulatory controls exerted on its activity. We are especially interested in discovering how signal transduction pathways involved in proliferation regulate the CAD complex. The MAP kinase cascade transmits signals induced by the binding of growth factors and hormones to extracellular receptors. The signals are relayed to intracellular targets that promote cell proliferation.  Phosphorylation of a specific CAD threonine residue by MAP kinase, just prior to the onset of the S phase of the cell cycle, where the demand for pyrimidine nucleotides is the greatest, activates CAD and accelerates the production of pyrimidine biosynthesis.  As cells emerge from S phase, CAD is down-regulated by dephosphorylation of the MAP kinase site and phosphorylation of a specific serine residue by protein kinase A.  The timing of the sequential phosphorylation and dephosphorylation events that control CAD activity must be precisely regulated perhaps by the ordered assembly of complexes that include CAD, the kinases and phosphatases.  These control mechanisms breakdown in breast cancer cells with the result that CAD activity is persistently elevated, thus providing an ample supply of nucleotides to fuel the growth of tumors cells.  Fluorescence microscopy has recently revealed that CAD is translocated from the cytoplasm into the nucleus just before S phase and that most of the activated form of CAD is nuclear.  Moreover, if the expression of the CAD gene is knocked down using a RNA interference method, cell growth is arrested and cannot be rescued by feeding the cells exogenous pyrimidines.   This discovery and other evidence support a second unexpected role for CAD in cell division that is unrelated to pyrimidine biosynthesis.  A major goal is now to decipher the significance of this novel CAD function in normal and proliferating cells. 

Selected Publications
David R. Evans Carbamoyl Phosphate Synthetase. Encyclopedia of Molecular Medicine, (Ed. T. E. Creighton) John Wiley and Sons, New York, 449-453, 2002.

Frederic D. Sigoillot, Severine M. Sigoillot and Hedeel I. Guy.  Breakdown of the Regulatory Control of Pyrimidine Biosynthesis in Human Breast Cancer Cells.  Int. J. Cancer, 109(4):491-8. (see Breast Cancer Newsletter, Feb 26, 2004), 2004.

Evans DR, Guy HI. Mammalian pyrimidine biosynthesis: Fresh insights into an ancient pathway J Biol Chem. 279: 33035-33038. (JBC Minireview), 2004.

Philip I. Martin, Cristina Purcarea, Pengfei Zhang, Asmita Vaishnav, Sharon Sadecki, Hedeel I. Guy-Evans, David R. Evans and Brian F. P. Edwards.  The Crystal Structure of a Novel, Latent Dihydroorotase from Aquifex aeolicus at 1.7 A Resolution.  J. Mol. Biol.  348:535-47, 2005.

Frederic D. Sigoillot, Damian H. Kotsis, Valerie Serre, Severine M. Sigoillot, David R. Evans and Hedeel I. Guy.  Nuclear localization of the multifunctional protein CAD  phosphorylated by the MAP kinase cascade.  J. Biol. Chem. 280, 25611-20, 2005.

Damian H. Kotsis, Elizabeth M. Masko, Frederic D. Sigoillot, Roberto Di Gregorio, Hedeel I. Guy-Evans and David R. Evans.  Protein Kinase A Phosphorylation of the Multifunctional Protein CAD Antagonizes Activation by the MAP Kinase Cascade.  Mol. Cell. Biochem. Jan 6; [Epub ahead of print], 2007.

Frederic D Sigoillot, Damian H. Kotsis, Elizabeth Masko, Monica Bame, David R. Evans and Hedeel I. Guy Evans.  Protein kinase C modulates the up-regulation of the pyrimidine biosynthetic complex, CAD by Map kinase.  Frontiers in Bioscience 12, 3892-3898, 2007.

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Michael C. Joiner, Ph.D.
Drug Discovery and Development
Ph.D., University of London, England, 1980

Our overarching mission is to explore the biological basis for radiotherapy in order to develop strategies for overcoming its limitations and to better understand the biology and treatment of cancer in general. A key issue is to identify the molecular basis for radiation resistance and sensitivity, so that appropriately intense radiotherapy can be prescribed to patients which will control their cancer without excessive normal tissue complications. As part of this goal, we have discovered that cells respond hypersensitively to very small doses of radiation in a number of malignant cell lines, particularly those which are resistant to the higher dose fractions used in conventional radiotherapy. Evidence implicates reduced DNA repair following the smaller doses and our work aims to understand the molecular basis for this. A particular focus is on regulation of double-strand break repair by cell-cycle checkpoints. We have found that cells have a threshold for detection of DNA damage which corresponds to radiation doses of about one tenth those given in daily radiotherapy. Below this dose, cells fail to recognize damage and initiate cell division which causes death. Above this threshold dose, damage is detected by the ATM protein which activates downstream cell cycle checkpoints which allow DNA repair to take place which in turn increases the probability of the cell surviving. We expect to translate these observations at the cellular level into more effective therapy for resistant tumors. Another facet of hypersensitivity to low radiation doses, is that environmental exposures, or those low exposures received received outside the target volume in radiotherapy, might cause excess incidence of cancer compared with higher doses. We arestudying this issue by evaluating cytogenetic changes in response to small radiation exposures.

Selected Publications
Joiner M.C., Marples B., Lambin P., Short S.C. and Turesson I. Low-dose hypersensitivity: current status and possible mechanisms. Int. J. Radiat. Oncol. Biol. Phys. 49: 379-389, 2001.

Short S.C., Kelly J., Mayes C.R., Woodcock M. and Joiner M.C. Low-dose hypersensitivity after fractionated low-dose irradiation in vitro. Int. J. Radiat. Biol. 77: 655-664, 2001.

Mitchell C.R., Folkard M. and Joiner M.C. Effects of low dose-rate 60Co gamma-ray exposure on human tumor cells in vitro. Radiat. Res. 158: 311-318, 2002.

Marples B., Wouters B.G. and Joiner M.C. An association between the radiation-induced arrest of G2 cells and low-dose hyper-radiosensitivity: A plausible underlying mechanism? Radiat. Res.  160: 38-45, 2003.

Harney J., Short S., Shah N., Joiner M.C. and Saunders M.I. Low dose hyper-radiosensitivity in metastatic tumors. Int. J. Radiat. Oncol. Biol. Phys. 59: 1190-1195, 2004.

Wykes S.M., Piasentin E., Joiner M.C., Wilson G.D. and Marples B. Low-dose hyper-radiosensitivity is not a failure to recognize DNA double-strand breaks. Radiat. Res. 165: 516-524, 2006.

Krueger S.A., Joiner M.C., Weinfeld M., Piasentin E. and Marples B. Role of apoptosis in low-dose hyper-radiosensitivity. Radiat. Res. 167: 260-267, 2007.

David H. Kessel, Ph.D.
Drug Discovery and Development
Ph.D., University of Michigan, 1959

The main objective in his laboratory is the study of photodynamic therapy (PDT). Photosensitizing agents, mainly porphyrin-like compounds, tend to localize in malignant cells and tissues and are attracted to different sub-cellular organelles. Irradiation with (usually) red light leads to a highly-selective form of cell death. This approach has been successfully applied in the clinic to treatment of skin, esophageal, lung, bladder and brain tumors. The mechanism of tumor eradication is being explored. Apoptotic death occurs when the anti-apoptotic protein Bcl-2, located in the ER or mitochondria, is among the targets. Lysosomal photodamage results in a different pathway to apoptosis involving activation of the pro-apoptotic protein Bid. Even cells lacking the apoptotic program can be killed, an explanation for the broad spectrum of activity observed in the clinic. We have recently found that a recycling process termed autophagy‚ plays a dual role here. Autophagy is responsible for the survival of some cells receiving low-dose PDT. This can occur when the light dose is unable to penetrate the entire tumor depth. We have also identified autophagy as a death mode under some circumstances, e.g., in heavily photodamaged cells that are unable to undergo apoptosis because of mutations. Autophagy can also play a role in the death of cells that have avoided apoptosis by the prompt recycling of photodamaged mitochondria and/or ER, but still cannot recover from the extensive amount of organelle recycling involved. References shown below include those relating to work done by two cancer biology students: Conley and Castelli.

Selected Publications
Kessel D, Castelli M, Reiners Jr, J. Ruthenium red-mediated suppression of Bcl-2 loss and Ca2+ release initiated by photodamage to the endoplasmic reticulum: scavenging of reactive oxygen species. Cell Death Differ 12:502-511, 2005.

Kessel D, Conley M, Vicente MGH and Reiners JJ. Studies on the sub-cellular localization of the porphycene CPO. Photochem Photobiol., 81:569-572, 2005.

Kessel D, Vicente MG, Reiners JJ Jr. Initiation of apoptosis and autophagy by photodynamic therapy. Lasers Surg Med. 38, 482-48, 2006.

Kessel D. Protection of Bcl-2 by salubrinal. Biochem Biophys Res Commun. 346, 1320-132, 2006.

Kessel D, Reiners, JJ Jr, Hazeldine ST, Polin L  and Horwitz JP. The drugs XK469 and SH80 induce autophagic death in mouse leukemia  L1210 cells. Mol Cancer Ther.6, 370-379, 2007.

Kessel D, Reiners Jr, JJ. Initiation of apoptosis and autophagy by the Bcl-2 antagonist HA14-1 Cancer Lett 249, 294-299, 2007.

Kessel D, Reiners JJ Jr. Apoptosis and autophagy after mitochondrial or endoplasmic reticulum photodamage. Photochem Photobiol. 83, 1024-1028, 2007.
 
Kessel D and Segarra  Arroyo A. , Apoptotic and autophagic responses to Bcl-2 inhibition and photodamage,  Photochem. Photobiol. Sci., 6, 1290-1295, 2007.

Kessel D. Promotion of PDT efficacy by a Bcl-2 antagonist. Photochem Photobiol In Press, 2008.

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A major research interest of the Matherly laboratory involves the structure and regulation of the reduced folate carrier (RFC), the predominant transport system for the natural folates in mammalian cells and tissues. RFC levels and function are important determinants of the antitumor effectiveness of methotrexate and a new generation of antifolate chemotherapeutic drugs typified by Pemetrexed and Raltitrexed. Defects in the regulation and/or biosynthesis of RFC commonly result in impaired antifolate membrane transport and resistance. Studies in the Matherly laboratory range from characterizing RFC structure and function through the use of specific (radio)affinity ligands and systematic site-directed mutagenesis, to expression of a functional “cysteine-less” human RFC and use of scanning cysteine mutagenesis and thiol modification techniques for mapping membrane topology, and for identifying functionally important domains in the RFC molecule. In collaboration with medicinal chemists at Duquesne University, the laboratory is developing a new catalog of drugs related to pemetrexed to probe features critical for drug binding to the carrier and that may have potential for clinical application for cancer. Other studies are focusing on other approaches for chemotherapy drug targeting and delivery via high affinity folate receptors expressed on the surface of epithelial (e.g., ovarian) tumors. Our RFC studies have included characterization of transcriptional and posttranscriptional regulatory mechanisms and are based on identification of up to 6 alternate non-coding upstream exons and promoters by the Matherly laboratory in 2002. Studies characterizing the complex regulatory machinery of the RFC gene include its transcriptional and epigenetic controls, and post-translational mechanisms associated with alternate use of 5’ non-coding exons. Very recent studies in rodent models demonstrate striking alterations in RFC levels in small intestine and colon in relation to age and dietary folates, suggesting a possible role for the carrier in the etiology of diseases associated with folate deficiency such as colon cancer. These questions are being further explored through the use of “humanized” mouse models of RFC in which the mouse RFC gene has been replaced by the human RFC gene. Finally, in collaboration with pediatric oncologists at the Children’s Hospital of Michigan, Dr. Matherly and co-workers are studying molecularly based prognostic markers of treatment response in pediatric leukemias. These translational studies range from understanding responses to chemotherapy in relation to polymorphisms for drug-specific genes such as RFC, to probing other aspects of leukemia biology such as the relationships between characteristic chromosomal alterations [hyperdiploidy and t(12;21) in B-precursor acute lymphoblastic leukemia] and aberrant signaling pathways (e.g., Notch1 in T-cell acute lymphoblastic leukemia) to treatment response and leukemogenesis. Our results should identify new prognostic features and entirely new mechanistically-based strategies for treating acute lymphoblastic leukemia in both children and adults.

Selected Publications
Hou,  Z., Stapels, S.E., Haska, C.L., Matherly, L.H.: Localization of a substrate binding domain of the human reduced folate carrier to transmembrane domain 11 by radioaffinity labeling and cysteine-substituted accessibility methods. J. Biol. Chem. 280: 36206-13, 2005.

Hou, Z., Ye, J., Haska, C.L., Matherly, L.H.: Transmembrane domains 4, 5, 7, 8, and 10 of the human reduced folate carrier are important structural or functional components of the transmembrane channel for folate substrates. J. Biol. Chem.  281:33588-96, 2006.

Ge, Y., Haska, C.L., LaFiura, K., Devidas, M., Linda, S.B., Liu, M., Thomas, R., Taub, J.W., Matherly, L.H.:Prognostic role of the reduced folate carrier, the major membrane transporter for methotrexate, in childhood acute lymphoblastic leukemia: a report from the Children's Oncology Group. Clin. Cancer Res. 13: 451-7, 2007.

Payton, S.G., Haska, C.L., Flatley, R.M., Ge, Y., Matherly, L.H.: Effects of 5’untranslated region diversity on the posttranscriptional regulation of the human reduced folate carrier. Biochem. Biophys. Acta 1769: 131-8, 2007

Matherly, L.H., Hou, Z., Deng, Y.:  Human reduced folate carrier: translation of basic biology to cancer etiology and therapy.  Cancer and Metastasis Reviews 26:111-28, 2007

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Death (apoptosis) is a distinct cellular process promising a new avenue for cancer chemotherapy.  Cells have anti-apoptotic proteins which, function by neutralizing pro-apoptotic proteins. The balance between anti and pro decides life or death for the cell. We have new BH3-mimetic small molecule inhibitors (SMIs), which disarm anti-apoptotic BCL2-family proteins, by displacing natural pro-apoptotic proteins, which use their BH3 domain to bind to Bcl-2. We have established mouse xenograft models from several B-lymphomas and pancreatic cancer enabling analysis of efficacy and mechanism of action in vivo. Our SMIs disarm a broader spectrum of anti-apoptotic proteins, including Mcl-1. In my laboratory we study efficacy and mechanism of action of these novel BH3-mimetic SMIs in cultured cells and animal models.  After generating a quantitative inventory of BCL2-family proteins in established cancer cell lines and in freshly-isolated cells from patients which vary in their IC50 to the BH3 mimetics, we will refine the Korsmeyer hypothesis and identify the best quantitative molecular correlates predictive of the IC50 of our drugs on those cells.  Since BH3-mimetics act on mitochondria to induce apoptosis, it is likely that these mimetics will synergize with traditional cytotoxic drugs usually used in the clinic hence increasing the cure rate and achieve cure in some lymphomas, which are not curable by cytotoxic drugs alone.

Selected Publications
Mohammad RM, Wang S, Aboukameel A, Chen B, Wu X, Chen J, Al-Katib A. Preclinical studies of a nonpeptidic small-molecule inhibitor of Bcl-2 and Bcl-XL [(-)-gossypol] against diffuse large cell lymphoma. Molecular Cancer Therapeutics, 4:13-21, 2005.

Liu M, Ge Y, Cabelof DC, Aboukameel A, Heydari AR, Mohammad RM, Matherly LH. Structure and regulation of the murine reduced folate carrier gene: Identification of 4 Non-coding exons and promoters and regulation by dietary folates. J Biol Chem. 280:5588-5597, 2005.

Mohammad RM, Wang S, Banerjee S, Wu X, Chen J, Sarkar FH. Nonpeptidic small-molecule inhibitor of Bcl-2 and Bcl-XL, (-)-gossypol, enhances biological effect of genistein against BxPC-3 human pancreatic cancer cell line. Pancreas, 31-317-324, 2005.

Mohammad RM, Aboukameel A, Kucuk O, Sarkar HF. Anti-Tumor Activity of Cisplatin is Potentiated by Soy Isoflavone Genistein in BxPC-3 Pancreatic Tumor Xenograft. Cancer, 15; 106(6): 1260-1268, 2006.

Zhang Y, Banerjee S, Wang Z, Xu H, Zhang L, Mohammad RM, Aboukameel A, Adsay N, Abbruzzese J, Majumdar A, Sarkar FH. Antitumor activity of epidermal growth factor receptor-related protein is mediated by inactivation of ErbB receptors and nuclear factor-kB in pancreatic cancer. Cancer Research, 66:1025-1032, 2006.

Wang Z, Sengupta R, Banerjee S, Li Y, Zhang Y, Rahman KM, Aboukameel A, Mohammad R, Majumdar AP, Abbruzzese JH, Sarkar FH. Epidermal growth factor receptor-related protein inhibits cell growth and invasion in pancreatic cancer. Cancer Res. 1; 66(15):7653-60, 2006.

Mohammad R, Goustin A, Aboukameel A, Chen B, Banerjee S, Wang S, Al-Katib A. Preclinical studies of TW-37, a new nonpeptidic small-molecule inhibitor of Bcl-2, in diffuse large cell lymphoma xenograft model reveal drug action on both Bcl-2 and Mcl-1. Clinical Cancer Research, 13: 2226-2235, 2007.

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My research interests center on the development of new and
efficient synthetic method-ologies and subsequent application of these methods to the total synthesis of biologically significant natural products. Areas currently under active investigation include a major program to exploit the unusual reactivities exhibited by tropone and related functionalized cycloheptane derivatives. From these useful starting materials we are targeting structurally complex natural products such as ingenol, phorbol, dolatriol, and ophiobolin F. The first two compounds exhibit potent tumor promoting activity and the latter targets display antitumor and antibiotic activity. We are also heavily involved in a program designed to examine the utility of vinyl isocyanates in heterocyclic synthesis. The interesting fungal metabolite tenellin is a typical target which highlights important reactivity characteristics of vinyl isocyanates which we recently discovered. We are also applying this methodology to the synthesis of several pyridone containing cardiotonic agents such as milrinone. We have also initiated a program to examine the 1,3-benzodithiole system as a novel synthetic equivalent for the corresponding 1,1-dipole reactive species.

Rigby, J.H., Kierkus, P.Ch., and Head, D. Studies on the stereoselective construction of the tigliane ring system. Tetrahedron Lett. 30:5073,1989.

Rigby, J.H., and Ateeq, H.S. Synthetic studies on transition metal mediated higher order cycloaddition reactions. J. Am. Chem. Soc. 112:6442,1990.

Rigby, J.H., and Sandanayaka, V.P. Intramolecular chromium (O) promoted higher-order cycloaddition reactions. Tetrahedron Lett. 34:935,1993.

Rigby, J.H., and Cuisiat, S.V. Synthetic studies on the ingenane diterpenes. Construction of a tetracydic 8 isoingenane model. J. Org. Chem. 58:1993.

Rigby, J.H., Niyaz, N.M., Short, K.M. and Heeg, M.J. A unified approach into the ingenane, tigliane and tazane ring systems. J. Org. Chem. 60:7720,1995.

Rigby, J.H., deSainte Claire, V., Cuisiat, S.V. and Heeg, M.J. Synthetic studies on the ingenane diterpenes. J. Org. Chem. 61:7992,1996.

Rigby, J.H., Hu, J., Heeg, M.J. Synthetic studies on the ingenane and diterpenes. Construction of an ABC Tricycle Exhibiting Trans-Intrabridge Lead Stereo Chemistry Tetrahedron Letter. 39:2265,1998.

Rigby, J. H.; Maharoof, U.S.M., Mateo, M. “Total Synthesis of (+)-Narciclasine and (+)-Pancratistatin” J. Am. Chem. Soc., 122, 6624-8, 2000.

Rigby, J. H.; Kondratenko, M.A.; Fiedler, C. “Preparation of a Resin-Based Chronium Catalyst for Effecting [6p + 2p] Cycloaddition Reactions” Org. Letters, 2, 3917-9, 2000

Rigby, J. H., Laurent, S., Dong, W., Danca, M.D. “Bis(alkylthio)carbenes as Novel Reagents for Organic Synthesis” Tetrahedron Symposium-in-Print, 56, 10101-10111, 2000.

Rigby, J. H.; Payen, A.; Warshakoon, N., “Alkoxy Radical Accelerated b-fragmentation of Alchohols and Lactols” Tetrahedron Lett, 42, 2047-9, 2001.

Rigby, J. H.; Niyaz, N. M. “Studies on Tansannular Rearrangement Pathways in the Bicyclo[4.4.1]undecane Ring System. A Novel Entry into the Bicyclo[4.2.1]nonene Ring System. Tetrahedron, 57, 5091-5, 2001. 

Rigby, J. H., Laxmisha, M. S., Hudson, A. R., Heap, C. H. Heeg, M. J. "Chromium(0)-Promoted Multicomponent Cycloaddition of Tethered Diynes with Cyclic Trienes: Application to the Total Synthesis of 9-epi-Pentalenic Acid"  J. Org. Chem., 69, 6751-60, 2004.

Rigby, J. H., Sidique, S. "Total Synthesis of Phenserine via [4+1] Cyclization of Bis(alkylthio)carbene and an Indole Isocyanate"  Org Lett, 9, 1219-21, 2007.

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The ultimate goal of the research is to develop an understanding of the response of cancer to therapy using measurements of DNA synthetic pathways as imaged by positron emission tomography (PET). To make valid measurements of cellular proliferation using PET, we are developing labeled nucleosides and producing detailed biochemical and kinetic models of their metabolism. Ongoing studies have developed the techniques needed to obtain PET images with [C-11]thymidine, which is incorporated in DNA and can be used to monitor cellular proliferation. Studies that began in tissue culture and mice have now progressed to clinical trials. r agents.We have already addressed a number of the problems associated with interpreting the PET images of [C-11]thymidine including the contributions to thymidine metabolism of intracellular pools, reutilization, and degradation. In order to develop a simpler method of measure DNAsynthetic activity we have studied a number of thymidine analogs. We have sought compounds that, unlike thymidine, could be more easily synthesized using the longer lived F-18, and undergo little degradation. The most promising compound we have used to date is [F-18]FLT ( 3'-deoxy-3'- fluorothymidine), which is an antiviral compound like AZT. It is trapped intracellularly after phosphorylation by thymidine kinase (TK), in a manner similar to the trapping of glucose analogs (FDG) after phosphorylation by hexokinase. This compound is stable to degradation and undergoes little metabolism, aside from glucuronidation. Studies in dogs and patients indicate that it readily visualizes proliferating organs such as the bone marrow, as well as tumors. Further studies of this compound are being conducted to determine its utility in the detection of tumors and measurement of therapeutic response. This technique will need to be validated against more conventional measures of response and biopsies based measurements of cell proliferation and TK activity. Use of FLT and such imaging markers of proliferation may provide a ready means for assessing new drug efficacy. One approach to improving the assessment of new drugs is to label them for PET imaging. This allows one to follow their in vivo biodistribution and retention in tumors and normal tissues. We are also seeking to label drugs for imaging to study the in vivo pharmacokinetics and pharmacodynamics of the agents as and determine if such agents can be used to measure specific drug pathways in the cell. Finally, PET can be used to measure tumor blood flow and it is being applied to the study of new antivascula

Selected Publications
Sun H, Mangner TJ, Collins JM, Muzik O, Douglas K, Shields AF.  Imaging DNA synthesis in vivo with [F-18] FMAU and positron emission tomography.  J Nucl Med. 46:292-96. 2005.

Shields, A.F., Briston, D.A, Chandupatla, S, Douglas, K.A., Lawhorn-Crews, J., Collins, J.M., Mangner, T.J., Heilbrun, L.K., Muzik, O.  A simplified analysis of [(18)F] 3’-fluorothymidine metabolism and retention. Eur J Nucl Med Mol Imaging. 32:1269-75. 2005.

Nimmagadda S, Mangner TJ, Sun H, Klecker RW, Muzik O, Lawhorn-Crews J, Douglas KA, Collins JM, Shields AF, Biodistribution and radiation dosimetry estimates of (1-(2’-deoxy-2’-[18F] fluoro-1-b-D-arabinofuranosyl)-5-bromouracil): PET imaging studies in dogs. J Nucl Med, 46:1916-22, 2005.

Sun H, Collins  JM, Mangner TJ, Muzik O, Shields AF. Imaging the pharmacokinetics of [F-18]FAU in patients with tumors: PET studies. Cancer Chemother Pharmacol. 57:343-8. 2006. 

Peng F,  Lu X,  Janisse J, Muzik O, Shields AF.  Positron emission tomography of human prostate cancer xenografts in mice with increased uptake of copper (II)-64 chlorides.  J Nucl Med.  47:164-52. 2006.

Nimmagadda S, Mangner TJ, Douglas KA, Muzik O, Shields AF.  Biodistribution, PET imaging, and radiation dosimetry estimates of HSV-tk gene expression imaging agent (1-(2'-deoxy-2'-[F-18]fluoro-b-D-arabinofuranosyl)-5-iodouracil) in normal dogs.  J Nucl Med, 48:655-660.  2007.   

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