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, including using transgenic mice and retroviral infection strategies.

We have developedtwo lines oftransgenic 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.  These 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.  DNA methylation analyses show that DNA methylation patterns and consequent gene expression are altered in the double transgenic tumors.  The Emu-Myc transgenic system shows a crucial dependence on DNA methylation.  We are also testing the hypothesis that truncated DNMT3B isoforms regulate DNA methylation within human cancers, with a particular focus on neuroblastoma in conjunction with Susan Cohn and her laboratory.
In addition to the presence of 5-methylcytosine, we now recognize the existence of 5-hydroxymethylcytosine in mammalian DNA, whose function is unknown currently.  In collaboration with the He Laboratory (Department of Chemistry), we have developed a chemical labeling method to detect 5-hydroxymethylcytosine.  We are in the process of identifying sites of 5-hydroxymethylcytosine in murine and human tumor samples, with a focus on myeloid malignancies and brain tumors, with the goal to define the functional significance of this epigenetic alteration.

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).
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).

Zhou, Y., Goodenbour, J.M., Godley, L.A., Wickrema, A., and Pan, T.  High levels of tRNA abundance and alteration of tRNA charging by bortezomib in multiple myeloma.  Biochem. Biophys. Res. Comm. 385: 160-164 (2009).

Steensma, D.P., Baer, M., Slack, J., Buckstein, R., Godley, L.A., Garcia-Manero, G., Albitar, M., Larsen, J.S., Arora, S., Cullen, M., and Kantarjian, H.M.  Multi-center study of decitabine administered daily for 5 days every 4 weeks to adults with myelodysplastic syndromes: The ADOPT (alternative dosing for outpatient treatment) Trial.  J Clin. Oncol. 27: 3842-3848 (2009).

Godley, L.A., Njiaju, U.O., Green, M., Weiner, H., Lin, S., Odenike, O., Stock, W., Rich, E.S., Artz, A., van Besien, K., Daugherty, C.K., White, C., Ridgeway, J., Zhang, Y., Le Beau, M.M., and Larson, R.A., Treatment of therapy-related myeloid neoplasms with high-dose cytarabine/mitoxantrone followed by hematopoietic stem cell transplantation.  Leuk Lymphoma 51: 995-1006 (2010).

Shah, M.Y., Vasanthakumar, A., Barnes, N.Y., Figueroa, M.E., Kamp, A., Hendrick, C., Ostler, K.R., Davis, E.M., Lin, S., Anastasi, J., Le Beau, M.M., Moskowitz, I., Melnick, A., Pytel, P., and Godley, L.A. DNMT3B7, a truncated DNMT3B isoform expressed in human tumors, disrupts embryonic development and accelerates lymphomagenesis. Cancer Research 70: 5840-5850 (2010).

Yang, Q., Tian, Y., Ostler, K.R., Chlenski, A., Guerrero, L., Salwen, H.R., Godley, L.A., and Cohn, S.L.  Epigenetic alterations differ in phenotypically distinct human neuroblastoma cell lines.  BioMed Central Cancer 10: 286-296 (2010).

Churpek, J.E., Garcia, J.S., Madzo, J., Jackson, S., Onel, K., and Godley, L.A. Identification and molecular characterization of a novel 3’ mutation in RUNX1 in a family with Familial Platelet Disorder. Leuk Lymphoma 51: 1931-1935 (2010).

Figueroa, M.E., Abdel-Wahab, O., Lu, C., Ward, P.S., Patel, J., Shih, A., Li, Y., Bhagwat, N., Vasanthakumar, A., Fernandez, H.F., Tallman, M.S., Sun, Z., Wolniak, K., Peeters, J.K., Liu, W., Choe, S.E., Fantin, V.R., Paietta, E., Lowenberg, B., Licht, J.D., Godley, L.A., Delwel, R., Valk, P.J.M., Thompson, C.B., Levine, R.L., and Melnick, A.  IDH1 and IDH2 mutations result in a hypermethylation phenotype, disrupt TET2 function, and impair hematopoietic differentiation.  Cancer Cell 18: 553-567, 2010.

Song, C.-X., Szulwach, K.E., Fu, Y., Dai, Q., Yi, C., Li, X., Chen, C.-H., Zhang, W., Jian, X., Wang, J., Zhang, L., Looney, T.J., Zhang, B., Godley, L.A., Hicks, L.M., Lahn, B.T., and He, C. Selective labeling of 5-Hydroxymethylcytosine in genomic DNA from cell lines and murine tissues.  Nature Biotech, epub Dec 12, 2010.