Lucy Godley, M.D., Ph.D.

The Role of DNMT3B in Mediating the Abnormal Methylation Patterns of Cancer Cells; Defining the Molecular Events that Accompany Unusual Cases of Hematopoietic Malignancies

Research Summary

Epigenetic changes alter chromatin structure, thereby regulating gene transcription.  In normal cells, repetitive DNA is hypermethylated and transcriptionally silent, whereas transcribed gene promoters are undermethylated and associated with open chromatin. Cancer cells are characterized by abnormal DNA methylation.  Repetitive DNA sequences and some gene promoters are hypomethylated and transcriptionally active, whereas many tumor suppressor gene promoters are hypermethylated and transcriptionally inactive.  Work in my laboratory focuses on elucidating mechanisms that control DNA methylation within cancer cells.

Our laboratory has shown that cancer cells exhibit aberrant splicing of the DNMT3B gene, which encodes one of the three DNA methyltransferases.  The aberrant splicing produces DNMT3B transcripts containing premature stop codons, which encode truncated proteins lacking the catalytic domain.  We hypothesize that truncated DNMT3B proteins contribute to the abnormal DNA methylation observed in cancer cells, and we are currently testing this hypothesis through a variety of approaches.

We have developed two lines of transgenic mice that express DNMT3B7, the truncated DNMT3B protein most frequently observed in cancer cells, and these mice exhibit a remarkable phenotype of disrupted embryonic development, the extent of which depends on the number of copies of the transgene.  DNMT3B7 transgenic mice show defects in craniofacial development (cleft palates and asymmetric eye development), heart formation (sub-aortic ventricular septal defects and abnormalities of the great vessels), and in the development of the skeletal and hematopoietic systems. We observe changes in DNA methylation within organs that express the transgene, thus supporting our hypothesis.

Currently, we are testing if the transgenic mice have abnormal function of neural crest cells, since many of the phenotypes that we see are similar to those seen if neural crest cell function is blocked.  We are also transplanting hematopoietic stem cells from these mice to see if they can establish normal bone marrow function.  We are testing molecular models of how the truncated DNMT3B7 protein could alter DNA methylation.  In particular, we are characterizing the interactions between DNMT3B/DNMT3B7 and several exciting interacting proteins.

The DNMT3B7 transgenic animals provide a model by which we can study the molecular mechanism for the DNA methylation alterations seen in cancer cells.  We have crossed them to the Emu-myc transgenic mice, which are predisposed to the development of B cell lymphomas.  DNMT3B7/Emu-myc double transgenic mice develop mediastinal tumors much more frequently and within a narrow time frame compared to Emu-myc single transgenic mice, indicating that DNMT3B7 can alter tumorigenesis.  The mediastinal tumors that develop in the double transgenic animals have more chromosomal abnormalities than single transgenic tumors.  Gene expression profiling indicates that about 200 genes are differentially expressed between tumors of differing genotypes, and there are several blocks of genes that appear to be coordinately regulated.

We are also testing our hypothesis that truncated DNMT3B isoforms regulate DNA methylation within human cancers: neuroblastoma (in conjunction with Susan Cohn and her laboratory) and myeloid leukemias.

Selected Papers

Ostler, K.R., Davis, E.M., Payne, S.L., Patel, B.B., Exposito-Cespedes, J., Le Beau, M.M., and Godley, L.A.  Cancer cells express aberrant DNMT3B transcripts encoding truncated proteins.  Oncogene 26: 5553-5563 (2007).

Pollyea, D.A., Artz, A.S., Stock, W., Daugherty, C., Godley, L., Odenike, O.M., Rich, E., Smith, S.M., Zimmerman, T., Zhang, Y., Huo, D., Larson, R., and van Besien, K.  Outcomes of patients with AML and MDS who relapse or progress after reduced intensity allogeneic hematopoietic cell transplantation.  Bone Marrow Transplant. 40: 1027-1032 (2007).

Hill, B.T., Kondapalli, L., Artz, A., Smith, S.M., Rich, E., Godley, L., Odenike, O., Pursell, K.J., Larson, R.A., Stock, W., and van Besien, K.  Successful allogeneic transplantation of patients with suspected prior invasive mold infection.  Leuk Lymphoma 48: 1799-1805 (2007).

Gordon, M.K., Sher, D., Karrison, T., Kebriaei, P., Chuang, K., Zhang, Y., McDonnell, D., Artz, A., Godley, L., Odenike, O., Rich, E., Michaelis, L., Thirman, M.J., Wickrema, A., van Besien, K., Larson, R.A., and Stock, W.  Successful autologous stem cell collection in patients with chronic myeloid leukemia in complete cytogenetic response, with quantitative measurement of BCR-ABL expression in blood, marrow and apheresis products.  Leuk Lymphoma 49: 531-537 (2008).

Klisovic, R.B., Stock, W., Cataland, S., Klisovic, M.I., Liu, S., Blum, W., Green, M., Odenike, O., Godley, L., Burgt, J.V., Van Laar, E., Cullen, M., Macleod, A.R., Besterman, J.M., Reid, G.K., Byrd, J.C., and Marcucci, G.  A phase I biological study of MG98, an oligodeoxynucleotide antisense to DNA methyltransferases 1, in patients with high-risk myelodysplasia and acute myeloid leukemia.  Clin Cancer Res 14(8): 2444-2449 (2008).

Stock, W., Undevia, S.D., Bivins, C., Ravandi, F., Odenike, O., Faderl, S., Rich, E., Borthakur, G., Godley, L., Verstovsek, S., Artz, A., Wierda, W., Larson, R.A., Zhang, Y., Cortes, J., Ratain, M.J., and Giles, F.J.  A phase I and pharmacokinetic study of XK469R (NSC 698215), a quinoxaline phenoxypropionic acid derivative, in patients with refractory acute leukemia.  Invest New Drugs 26: 331-338 (2008).

Ozer, O., Zhao, Y.D., Ostler, K.R., Akin, C., Anastasi, J., Vardiman, J.W., and Godley, L.A.  The identification and characterization of novel KIT transcripts in aggressive mast cell malignancies and normal CD34+ cells.  Leuk Lymphoma 49: 1567-1577 (2008).

Carbonaro, A., Mohanty, S.K., Huang, H., Godley, L.A., and Sohn, L.L. NanoCytometry:  A label-free technique for performing single-cell screening.  Lab Chip 8: 1478-1485 (2008).

Godley, L.A. and Larson, R.A. Therapy-related myeloid leukemia.  Seminars in Oncol 35: 418-429 (2008).

Fackenthal, J.D. and Godley, L.A. Aberrant RNA splicing and its functional consequences in cancer cells.  Disease Models and Mechanisms 1: 37-42 (2008).

Artz, A.S., Wickrema, A., Dinner, S., Godley, L.A., Kocherginsky, M., Odenike, O., Rich, E.S., Stock, W., Ulaszek, J., Larson, R.A., and van Besien, K.  Pre-treatment C-reactive Protein (CRP) is a Predictor for Outcomes After Reduced Intensity Allogeneic Hematopoietic Cell Transplantation.  Biol Bone Marrow Transpl., in press.

Poiré, X., Artz, A., Larson, R.A., Kline, J., Odenike, O., Rich, E., Godley, L., Stock, W., van Besien, K. Allogeneic Stem Cell Transplantation with alemtuzumab-based conditioning for patients with advanced chronic myelogenous leukemia.  Leuk Lymphoma, in press.