Dr. Carol E. Cass, PhD, FRSC, FCAHS

Dr. Carol E. Cass, PhD, FRSC, FCAHS Department of Oncology University of Alberta Cross Cancer Institute 11560 University Avenue Edmonton, Alberta, T6G 1Z2 Phone: (780) 432-8320 Fax: (780) 432-8425 Email: carol.cass@cancerboard.ab.ca

Division of Experimental Oncology - Primary Appointments

BSc & MSc
University of Oklahoma), PhD (University of California, Berkeley)
Professor, Oncology
Adjunct Professor, Biochemistry
Director, Cross Cancer Institute
Vice-President, Alberta Health Services-Alberta Cancer Board

Nucleoside Transporter Proteins: Studies of their Roles in Nucleoside Biology and Therapeutics

We study nucleoside transporter proteins and their role in nucleotide metabolism, with a focus on nucleoside drugs. Examples of clinically important anticancer nucleoside drugs are capecitabine, cladribine, cytarabine, fludarabine, and gemcitabine and of antiviral nucleoside drugs are lamivudine, zalcitabine, and zidovudine. We are also interested in the role of nucleoside transporters in cell signaling by adenosine.

We were among the first to describe and characterize nucleoside transporter proteins and are now applying molecular knowledge of the transporter proteins to studies of the pharmacology of nucleoside drugs. Our fundamental discovery research is directed towards understanding the mechanisms of transport of nucleosides across biological membranes and the role of nucleoside transporter proteins in the biology of nucleosides. Our translational applied research is directed towards understanding the role of nucleoside transporters in the pharmacology of nucleoside drugs. Our goal is to develop strategies to guide clinicians in the use of nucleoside drugs in treatment of cancer and viral diseases.

Members of my research group have broad expertise in a variety of disciplines important for innovative research in molecular therapeutics, membrane biochemistry and nucleoside biology.

Opportunities for research training are available for undergraduate summer students, postdoctoral fellows and clinical fellows.

Research Facilities

My laboratory is in the research wing of the Cross Cancer Institute and is equipped for standard applications of molecular biology, biochemistry and cell biology, with in-lab facilities for transport studies, cell culture and production and characterization of recombinant proteins in bacteria, yeast and mammalian cells. We also have access to a wide range of advanced technologies in Experimental Oncology (e.g., cellular imaging, microarray technologies, animal PET imaging) or on the U of A campus (e.g., mass spectrometry proteomics).

Research Support

1. Operating grants from the National Cancer Institute of Canada (NCIC), the Canadian Institutes of Health Research (CIHR) and the Research Initiatives Program of the Alberta Cancer Board (RIP-ACB).
2. Equipment grants funded by the Alberta Cancer Foundation (ACF), the Alberta Heritage Foundation for Medical Research (AHFMR), and the Canadian Foundation for Innovation (CFI).
3. Studentships and fellowships from the Alberta Heritage Foundation for Medical Research Program and the Translational Training in Cancer Research Program jointly funded by CIHR, NCIC and ACF.

Cass Research Team, 2008

Research Associates: K. Graham, Ph.D., Vijaya Damaraju, Ph.D.

Postdoctoral Fellows: Yan Gong, Ph.D. (supervised by Dr. Liang Li, Chemistry, and co-supervised by myself and Dr. Sambu Damaraju, Laboratory Medicine & Pathology).

Graduate Students: Adam Elwi (co-supervised with Dr. Michael Sawyer, Oncology), Robert Paproski.

Research Staff : D. Mowlesand Lorelei Johnson.

Research Collaborators

I share my laboratory with three clinician scientists at the Cross Cancer Institute who are members of the Division of Medical Oncology, Department of Oncology, who have translational research programs in cancer therapeutics: Drs. John Mackey (Professor), Michael Sawyer (Associate Professor) and Karen King (Assistant Professor). Major collaborators external to Oncology are Drs. S.R. Baldwin (School of Molecular Biology and Biochemistry, University of Leeds) and J.D. Young (Physiology, University of Alberta) on identification, structure and function of nucleoside transporter proteins, S. Ericksson (Veterinary Medical Chemistry, Swedish University of Agricultural Sciences on deoxycytidine kinase and mitochondrial transport of nucleosides/nucleotides, L. Li (Chemistry, University of Alberta) and S. Damaraju (Laboratory Medicine & Pathology, University of Alberta) on breast cancer genomics and proteomics, and M.J. Robins (Chemistry, Brigham Young University) on structure-activity studies of nucleoside transporters.

Awards

2008 J. Gordin Kaplan Award for Excellence in Research, University of Alberta

2006 Robert L. Noble Prize for Excellence in Cancer Research, National Cancer Institute of Canada

Elected to Canadian Academic of Health Sciences, 2006

Alberta Centennial Medal, 2005

Elected to Academy of Sciences, Royal Society of Canada, 2002

Recipient of Tier I Canada Research Chair, 2001-2008

Total:  189 articles in peer-reviewed journals & 39 review articles and book chapters.   Abstracts can be obtained at the US National Library of Medicine Website

Recent Reviews

Damaraju, V.L., Damaraju, S., Young, J.D., Baldwin, S.A., Mackey, J.R., Sawyer, M.B. and Cass, C.E. Nucleoside anticancer drugs: the role of nucleoside transporters in resistance to cancer chemotherapy. Oncogene 22:7524-7536 (2003).

Elwi, A.E., Damaraju, V.L., Baldwin, S.A., Young, J.D., Sawyer, M.B., and Cass, C.E. Renal nucleoside transporters: physiological and clinical implications. Biochem. Cell Biol. 84: 844-858 (2006).

King, A.E., Ackley, M.A., Cass, C.E., Young, J.D., and Baldwin, S.A. Nucleoside Transporters: From Scavengers to Key Players and Novel Therapeutic Targets. Trends Pharmacol Sci. 27: 416-425 (2006).

Zhang, J.,Visser, F.,King, K.M., Baldwin, S.A., Young, J.D., and Cass, C.E. The role of nucleoside transporters in cancer chemotherapy with nucleoside drugs. Cancer and Metastasis Reviews. Cancer Metastasis Rev. 26: 85-110 (2007).

King, K.M. and Cass, C.E.  The role of nucleoside transport in the antineoplastic activity of purine nucleoside chemotherapeutic agents.  Current Cancer Therapy Reviews 4:21-30 (2008).

Selected Original Research Papers

Transporter Discovery

Huang, Q.-Q., Yao, S.Y.M., Ritzel, M.W.L., Paterson, A.R.P., Cass, C.E., and Young, J.D. Cloning and functional expression of a complementary DNA encoding a mammalian nucleoside transport protein. J. Biol. Chem. 269:17757-17760 (1994).

Hogue, D.L., Ellison, M.J., Young, J.D., Cass, C.E. Identification of a novel membrane transporter associated with intracellular membranes by phenotypic complementation in the yeast Saccharomyces cerevisiae. J. Biol. Chem., 271:9801-9808 (1996).

Griffiths, M., Beaumont, N., Yao, S.Y.M., Sundaram, M., Boumah, C. E., Davies, A., Kwong, F.Y.P., Coe, I., Cass, C.E., Young, J.D. and Baldwin, S.A. Cloning of a human nucleoside transporter implicated in the cellular uptake of adenosine and chemotherapeutic drugs. Nat. Medicine, 3:89-93 (1997).

Ritzel, M.W.L., Yao, S.Y.M., Huang, M.-Y., Elliott, J.F., Cass, C.E. and Young, J.D. Molecular cloning and functional expression of cDNAs encoding a human Na+/nucleoside cotransporter (hCNT1). Am. J. Physiol. 272:C707-C714(1997).

Yao, S.Y.M., Ng, A.M.L., Muzyka, W.R., Griffiths, M, Cass, C.E., Baldwin, S.A., and Young, J.D. Molecular cloning and functional characterization of nitrobenzylthioinosine (NBMPR)-sensitive (es) and NBMPR-insensitive (ei) equilibrative nucleoside transporter proteins (rENT1 and rETN2) from rat tissues. J. Biol. Chem. 271:28423-28430 (1997).

Griffiths, M., Yao, S.M., Abidi, F., Phillips, S.E.V., Cass, C.E., Young, J.D., and Baldwin, S.A. Molecular cloning and characterization of a nitrobenzylthioinosine (NBMPR)-insensitive (ei) equilibrative nucleoside transporter from human placenta. Biochem. J. 328:739-743 (1997).

Ritzel, M.W.L., Yao, S.Y.M., Ng, A.M.L., Mackey, J.R., Cass, C.E., and Young, J.D. Molecular cloning, functional expression and chromosomal localization of a cDNA encoding a human Na+/nucleoside cotransporter (hCNT2) selective for purine nucleosides and uridine. Mol. Memb. Biol., 15:203-211 (1998).

Vickers, M.F., Yao, S.Y.M., Young, J.D., Baldwin, S.A., and Cass, C.E. Nucleoside transporter proteins of Saccharomyces cerevisiae: Demonstration of a transporter (FUI1) with high uridine selectivity in plasma membranes and a transporter (FUN26) with broad nucleoside selectivity in intracellular membranes. J. Biol. Chem., 275:25931-25938 (2000).

Ritzel, M.W.L., Ng, A.M.L., Yao, S.Y.M., Graham, K., Loewen, S.K., Smith, K.M., Ritzel, R.G., Mowles, D.A., Carpenter, P. Chen, X-Z., Karpinski, E., Hyde, R.J., Baldwin, S.A., Cass, C.E. and Young, J.D. Molecular identification and characterization of novel human and mouse concentrative Na+-nucleoside cotransporter proteins (hCNT3 and mCNT3) broadly selective for purine and pyrimidine nucleosides (System cib). J. Biol. Chem 276:2914-2927 (2001).

Baldwin, S.A., Yao, S.Y.M., Hyde, R.J., Ng, A.M.L., Foppolo, S., Barnes, K., Ritzel, M.W.L., Cass, C.E., Young, J.D. Functional characterization of novel human and mouse equilibrative nucleoside transporters (hENT3 and mENT3) located in intracellular membranes. J. Biol. Chem. 280:15880-15887 (2005).

Baldwin, S.A., Yao, S.Y.M., Hyde, R.J., Ng, A.M.L., Foppolo, S., Barnes, K., Ritzel, M.W.L., Cass, C.E., and Young, J.D. Functional characterization of novel human and mouse equilibrative nucleoside transporters (hENT3 and mENT3) located in intracellular membranes. J. Biol. Chem. 280: 15880-15887 (2005)

Barnes, K., Dobrzynski, H., Foppolo, S., Beal, P.R., Tellez, J., Ritzel, M.W.L., Claycomb, W.C., Cass, C.E., Young, J.D., Billeter-Clark, R., Boyett, M.R., and Baldwin, S.A. Distribution and functional characterisation of ENT4, a novel cardiac adenosine transporter activated at acidic pH. Circ. Res. 99: 510-510 (2006).

Transporter Characterization

Visser, F., Vickers, M.F., Ng, A.M.L., Baldwin, S.A., Young, J.D. and Cass, C.E. Mutation of residue 33 of human equilibrative nucleoside transporters 1 and 2 (hENT1 and hENT2) alters sensitivity to inhibition of transport by dilazep and dipyridamole. J. Biol. Chem., 277:395-401 (2002).

Vickers, M.F., Kumar, R., Visser, F., Zhang, J., Charania, J., Raborn, R.T., Baldwin, S.A., Young, J.D. and Cass, C.E. A comparison of the interaction of uridine, cytidine and other pyrimidine nucleoside analogues with recombinant human equilibrative nucleoside transporter 2 (hENT2) produced in Saccharomyces cerevisiae. Biochem. Cell Biol. 80:639-644 (2002).

Zhang, J., Visser, F., Vickers, M.F., Lang, T., Robins, M.J., Nielsen, L.P.C., Nowak, I., Baldwin, S.A., Young, J.D. and Cass, C.E. Uridine binding motifs of human concentrative nucleoside transporters 1 and 3 (hCNT1 and hCNT3) produced in Saccharomyces cerevisiae. Mol. Pharmacol. 64:1512-1520 (2003).

Vickers, M.F., Zhang, J., Visser, F., Tackaberry, T., Robins, M.J., Nielson, L.P.C., Nowak, I., Baldwin, S.A., Young, J.D., and Cass, C.E. Uridine recognition motifs of human equilibrative nucleoside transporters 1 and 2 produced in Saccharomyces cerevisiae. Nucleosides, Nucleotides & Nucleic Acids 23:361-373 (2004).

Damaraju, S., Zhang, J., Visser, J., Tackaberry, T., Dufour, J., Baldwin, S.A., Young, .D. and Cass, C.E. Identification and functional characterization of variants in human concentrative nucleoside transporter 3, hCNT3 (SLC28A3), arising from single nucleotide polymorphisms in coding regions of the hCNT3 gene. Pharmacogenetics. 15:173-182 (2005).

Visser, F., Zhang, J., Raborn, R.T., Baldwin, S.A., Young, J.D., and Cass, C.E. Residue 33 of human equilibrative nucleoside transporter 2 is a functionally important component of both the dipyridamole and nucleoside binding sites. Mol. Pharmacol. 67: 1291-1298 (2005).

Visser, F., Baldwin, S.A., Isaac, R.E., Young, J.D., Cass, C.E. Identification and mutational analysis of amino acid residues involved in dipyridamole interactions with human and Caenorhabditis elegans equilibrative nucleoside transporters. J Biol Chem. 280:11025-11034 (2005).

Zhang, J., Smith, K.M., Tackaberry, T., Visser, F., Robins, M.J., Nielsen, L.P.C., Nowak, I., Karpinski, E., Baldwin, S.A., Young, J.D., Cass, C.E. Uridine Binding and Transportability Determinants of Human Concentrative Nucleoside Transporters. Mol. Pharmacol. 68: 830-839 (2005).

Zhang, J., Tackaberry, T., Ritzel, M.W.L., Raborn, T., Barron, G., Baldwin, S., Young, J.D., and Cass, C.E. Cysteine accessibility analysis of transmembrane domains 11, 12 and 13 of human concentrative nucleoside transporter 3. Biochem. J. 394: 389-398 (2006).

Zhang, J., Smith, K.M., Tackaberry, T., Sun, X., Slugoski, M.D., Robins, M.J., Nielsen, L.P., Nowak, I., Baldwin, S.A., Young, J.D., and Cass, C.E. Characterization of uridine permease, FUI1, of Saccharomyces cerevisiae: the transport mechanism and permeant binding motif. J. Biol. Chem. 281: 28210-28221 (2006).

Visser, F., Sun, L., Damaraju, V., Tackaberry, T., Peng, Y., Robins, M.J., Baldwin, S.A., Young, J.D. and Cass, C.E. Residues 334 and 338 in transmembrane segment 8 of human equilibrative nucleoside transporter 1 are important determinants of inhibitor sensitivity, protein folding and catalytic turnover. J. Biol. Chem. 282:14148-14157 (2007).

Paproski, R.J., Visser, F., Zhang, J., Tackaberry, T., Damaraju, V., Baldwin, S.A., Young, J.D. and Cass, C.E.  Mutation of Trp 29 of human equilibrative nucleoside transporter 1 alters affinity for coronary vasodilator drugs and nucleoside selectivity. Biochem J., 414:291-300 (2008).

Nucleoside Drug Transport

Mackey, J.R., Mani, R.S., Selner, M., Mowles, D., Young, J.D., Belt, J.A., Crawford, C.R., and Cass, C.E. Functional nucleoside transporters are required for gemcitabine influx and cytotoxicity in cancer cell lines. Cancer Res., 58: 4349-4357 (1998).

Mackey, J.M., Yao, S.Y.M., Smith, K.M., Karpinski, E., Baldwin, S.A., Cass, C.E., and Young, J.D. Gemcitabine transport in Xenopus oocytes expressing recombinant plasma membrane mammalian nucleoside transporters. J Natl. Cancer Inst. 91: 1876-1881 (1999).

Graham, K.A., Leithoff, J., Coe, I.R., Mowles, D., Mackey, J.R., Young, J.D., and Cass, C.E. Differential transport of cytosine-containing nucleosides by recombinant concentrative nucleoside transporter protein hCNT1. Nucleosides and Nucleotides, 19: 415-434 (2000).

Yang, T.T., Selner, M., Young, J.D. and Cass, C.E. Acquisition of human concentrative nucleoside transporter 2 (hCNT2) activity by gene transfer confers sensitivity to fluoropyrimidine nucleosides in drug resistant leukemia cells. Molecular Pharmacology 60:1143-1152 (2001).

Gourdeau, H., Clarke, M.L., Ouellet, F., Mowles, D., Selner, M., Richard, A., Lee, N., Mackey, J.R., Young, J.D., Jolivet, J., Lafrenière R.G. and Cass, C.E. Mechanisms of uptake and resistance of troxacitabine, a novel deoxycytidine nucleoside analog, in human leukemic and solid-tumor cell lines. Cancer Research, 61:7217-7224 (2001).

Lang, T.T., Young, J.D. and Cass, C.E. Interactions of nucleoside analogs, caffeine and nicotine with human concentrative nucleoside transporter 1 and 2 stably produced in a transport-defective human cell line. Mol. Pharmacol. 65:925-933 (2004).

Damaraju, V.L., Visser, F., Zhang, J., Mowles, D., Ng, A.M.L., Young, J.D., Jayaram, H.N. and Cass, C.E. Role of human nucleoside transporters in the cellular uptake of inhibitors of IMP dehydrogenase, tiazofurin and benzamide riboside. Mol. Pharmacol. 67:273-279 (2005).

Damaraju, S., Zhang, J., Visser, J., Tackaberry, T., Dufour, J., Baldwin, S.A., Young, J.D. and Cass, C.E. Identification and functional characterization of variants in human concentrative nucleoside transporter 3, hCNT3 (SLC28A3), arising from single nucleotide polymorphisms in coding regions of the hCNT3 gene. Pharmacognenetics & Genomics. 15: 173-182 (2005).

King, K.M., Damaraju, V.L., Vickers, M.F., Yao, S.Y., Lang, T., Tackaberry, T.E., Mowles, D.A., Ng, A.M., Young, J.D. and Cass, C.E. A comparison of the transportability, and its role in cytotoxicity, of 2-chloro-9-(2'-deoxy-2'-fluoro-b-D-arabinofuranosyl) adenine, 2-chloro-2'-deoxyadenosine and 9-b-D-arabinofuranosyl-2-fluoroadenine by recombinant human nucleoside transporters produced in three model expression systems. Mol. Pharmacol. 69: 346-353 (2006).

Clarke, M., Damaraju, V.L., Zhang, J., Mowles, D., Tackaberry, T., Lang, T., Smith, K.M., Young, J., Tomkinson, B., and Cass, C.E. The role of human nucleoside transporters in cellular uptake of 4'-thio-b-D-arabinofuranosylcytosine and b-D-arabinosylcytosine. Mol Pharmacol. 70: 303-310 (2006).

Cai, J., Damaraju, V.L., Groulx, N., Mowles, D., Kuzman, M., Berendt, R.C., Sawyer, M.B. and Cass, C.E.  Two distinct molecular mechanisms underlying cytarabine resistance in human leukemic cells.  Cancer Res.  68:2349-2357 (2008).

Damaraju, D., Damaraju, V.L., Brun, M., Mowles, D., Kuzman, M., Berendt, R.C., Sawyer, M.B. and Cass, C.E.  Malignant mesothelioma evaluation of nucleoside analog antimetabolite drugs and contribution of membrande transport processes.  Biochem. Pharmacol.  75:1901-1911 (2008).

paproski, R.J., Ng., A.M.L., Yao, S.Y.M., Graham, K., Peng, Y., Robins, M.J., Young, J.D. and Cass, C.E.  The role of human nucleoside transporters in uptake of 3'doxy-3'fluorothymidine.  Mol. Pharmacol.  74:1372-1380 (2008).

Clinical Research/Translational Studies

Jennings, L.L., Hao, C., Cabrita, M.A., Vickers, M.F., Baldwin, S.A., Young, J.D. and Cass, C.E. Distinct regional distribution of human equilibrative nucleoside transporter proteins 1 and 2 (hENT1 and hENT2) in the central nervous system. Neuropharmacology 40:722-731, (2001).

Mackey, J.R., Jennings, L.L., Clarke, M.L., Santos, C.L., Dabbagh, L., Vsianska, M., Koski, S.L., Coupland, R.W., Baldwin, S.A., Young, J.D. and Cass, C.E. Immunohistochemical variation of human equilibrative nucleoside transporter 1 (hENT1) protein in primary breast cancers. Clinical Cancer Research 8:110-116, (2002).

Reiman T., Graham, K.A., Wong, J., Belch, A.R., Coupland, R., Young, J.D., Cass, C.E., and Mackey JR Mechanisms of resistance to nucleoside analogue chemotherapy in mantle cell lymphoma: a molecular case study. Leukemia Sep 16:1886-1887, (2002).

Reiman, T., Clarke, M.L., Dabbagh, L., Vsianska, M., Coupland, R.W., Belch, A.R. Baldwin, S.A., Young, J.D., Cass, C.E. and Mackey, J.R. Differential expression of human equilibrative nucleoside transporter 1 (hENT1) protein in the Reed-Sternberg cells of Hodgkin’s Disease. Leukemia & Lymphoma 44:1435 - 1440 (2002).

Spratlin, J., Sangha, R., Glubrecht, D., Dabbagh, L., Young, J.D., Dumontet, C., Cass, C.E., Lai, R. and Mackey, J.R. The Absence of Human Equilibrative Nucleoside Transporter 1 is Associated with Reduced Survival in Patients with Gemcitabine Treated Pancreas Adenocarcinoma. Clin Cancer Res. 10: 6956-6961 (2004).

Mackey, J.R., Galmarini, C.M., Graham, K.A., Joy, A.A., Delmer, A., Dabbagh, L., Glubrecht, D., Jewell, L.D., Lai, R., Lang, T., Young, J.D., Binet, J.L., Cass, C.E. and Dumontet, C. Quantitative analysis of nucleoside transporter and metabolism gene expression in chronic lymphocytic leukemia (CLL) – Identification of fludarabine-sensitive and insensitive populations. Blood. 105: 767-774 (2005).

Chow L., Lai R., Dabbagh L., Mydan L.J., Belch A., Young J.D., Cass, C.E., Mackey J.R. Analysis of Human Equilibrative Nucleoside Transporter 1 (hENT1). protein in non-Hodgkins Lymphoma by immunohistochemistry. Modern Pathol. 18: 558-564 (2005).

Seve, P., Mackey, J.R., Isaac, S., Tredan, O., Souquet, P.J., Perol, M., Cass, C.E., Dumontet, C. cN-II expression predicts survival in patients receiving gemcitabine for advanced non-small cell lung cancer. Lung Cancer. 49 (3): 363-370 (2005).

Damaraju, V.L., Elwi, A.N., Hunter, C., Carpenter, P., Santos, C., Barron, G.M., Sun, X.J., Young, J.D., Mackey, J.R., Sawyer, M.B., and Cass, C.E. Localization of broadly selective equilibrative and concentrative nucleoside transporters, hENT1 and hENT3, in human kidney. Amer. J. Physiol.- Renal Physiol. 293:F200-F211 (2007).

Santini, D., Perrone, G., Vincenzi, B., Lai, R., Cass, C., Alloni, R., Rabitti, C., Antonori, A., Vecchio, F., Magistrelli, P., Coppola, R., Mackey, J.R. and Tonini, G.  Human Equilibrative Nucleoside Transporter 1 (hENT1) protein is associated with short survival in resected ampullary cancer.  Annals in Oncol.  19:724-728 (2008).

Lai, R., Bartlett, N., Mackey, J., Jung, S.H., Johnson, J.L., Cook, J.R., Jones, D., Cass, C., Young, J., Said, J., Cheson, B. and His, E.  High expression of nucleoside transporter protein hENT1 in Reed-Sternberg cells is associated with treatment failure in relapsed/refractory Hodgkin lymphoma patients treated with gemcitabine, vinorelbine, and liposomal doxorubicin - A CALGB 58904 correlative study.  Leukemia and Lymphoma.  9:1202-1205 (2008).

Tsang, R.Y., Santos, C., Ghosh, S., Dabbagh, L., King, K., Young, J., Cass, C.E., Mackey, J.R. and Lai, R. Immunohistochemistry for human concentrative nucleoside transporter 3 protein predicts fludarabine sensitivity in chronic lymphocytic leukemia. Mod. Pathol. Epub ahead of print, PMID: 18604194, July 4, 2008.

Farrell, J., Elsaleh, H., Garcia, M., Lai, R., Ammar, A., Regine, W., Abrams, R., Benson, A., Macdonald, J., Cass, C., Dicker, A. and Mackey, J. Human equilibrative nucleoside transporter 1 levels predict response to gecitabine in patients with pancreatic cancer. Gastroenterology. Epub ahead of print, PMID: 18992248, Oct. 7, 2008.

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