Most chemotherapy for leukemia is limited by its toxicity to both leukemia cells and normal tissue. Ideally, therapy would target bio-molecules which are essential for leukemia stem-cell (LSC) but not normal hematopoietic stem-cell (HSC) survival. We demonstrate that the DNA methyl-transferase enzyme DNMT1 constitutes such an ideal molecular target;in HSC, DNMT1 is necessary for the self-renewal gene repression that must precede lineage-specific differentiation. In contrast, in LSC, DNMT1 is aberrantly recruited to repress pro-differentiation genes, prevent terminal differentiation and maintain dysregulated proliferation. Therefore, intermittent depletion of DNMT1 with non-DNA damaging doses of the cytosine analogue decitabine terminally differentiates LSC but increases self-renewal of HSC. This constitutes a very favorable therapeutic index. In the first aim of this proposal, we translate these observations into clinical practice. Decitabine was originally developed as a DNA-damaging agent. Doses were escalated to maximum tolerated levels in traditional phase I studies. Current regimens of decitabine still employ relatively high doses and drug administration is cycled to allow the patient to recover from toxicity. However, we show that effective DNMT1 depletion can be produced with levels of decitabine that do not damage DNA. Therefore, we propose lowering the dose of decitabine to minimize/avoid DNA damage and toxicity while maintaining DNMT1 depletion. The lack of toxicity will allow weekly, multi-year therapy to sustain the differential effect on LSC and HSC and introduces the possibility of adjuvant, maintenance or cancer prevention applications. We have demonstrated the remarkable clinical effectiveness and tolerability of using decitabine in this way in the treatment of severe sickle cell disease, where decitabine is administered 1-3X/week for multi-year treatment durations 2,3 4.
In Specific Aim 1 of this proposal, we seek proof of concept of this regimen in treating malignancy. We believe the effort described in Aim 1 will be a significant advance in the treatment of malignancy. However, obstacles to realizing the full clinical potential of DNMT1 depletion by decitabine remain: (i) pharmacogenomic variation in cytidine deaminase (CDA), the enzyme which breaks-down decitabine, produces significant inter-individual variation in pharmacokinetics (PK) and pharmacodynamics (PD), compromising the ability to predict clinical effects in response to a specific dose;(ii) because of CDA- mediated drug destruction, decitabine has limited oral bioavailability, a significant impediment to the proposed treatment paradigm of multi-year, chronic therapy;(iii) we show that the major tumor stratagem for resistance to decitabine is CDA-mediated destruction of the drug. Such resistance may be especially likely in the intended chronic low-dose application of decitabine.
In Specific Aim 2, we propose to surmount all three obstacles by combining decitabine with the CDA inhibitor tetrahydrouridine (THU) in a single oral formulation.

Public Health Relevance

We demonstrate that the DNA methyl-transferase enzyme DNMT1 constitutes an ideal molecular target for leukemia therapy;in hematopoietic stem cells, DNMT1 is necessary for the self-renewal gene repression that must precede lineage-specific differentiation. In contrast, in leukemia cells, including models of leukemia stem cells, DNMT1 is aberrantly recruited to repress pro-differentiation genes, prevent terminal differentiation and maintain dysregulated proliferation. This proposal requests support to translate these observations into effective anti-malignancy therapy by optimizing regimen and formulation of the nucleoside analogue decitabine to deplete DNMT1 without causing DNA damage, even in malignant cells that are usually resistant to decitabine or cytosine arabinoside alone.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA138858-02
Application #
7878037
Study Section
Clinical Oncology Study Section (CONC)
Program Officer
Merritt, William D
Project Start
2009-07-01
Project End
2014-05-31
Budget Start
2010-06-01
Budget End
2011-05-31
Support Year
2
Fiscal Year
2010
Total Cost
$329,202
Indirect Cost
Name
Cleveland Clinic Lerner
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
135781701
City
Cleveland
State
OH
Country
United States
Zip Code
44195
Saunthararajah, Yogen; Sekeres, Mikkael; Advani, Anjali et al. (2015) Evaluation of noncytotoxic DNMT1-depleting therapy in patients with myelodysplastic syndromes. J Clin Invest 125:1043-55
Gale, Robert Peter; Hlatky, Lynn; Sachs, Rainer K et al. (2014) Why is there so much therapy-related AML and MDS and so little therapy-related CML? Leuk Res 38:1162-4
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Mahfouz, Reda Z; Jankowska, Ania; Ebrahem, Quteba et al. (2013) Increased CDA expression/activity in males contributes to decreased cytidine analog half-life and likely contributes to worse outcomes with 5-azacytidine or decitabine therapy. Clin Cancer Res 19:938-48
Mahfouz, Reda Z; Koh, Lip Seng; Teo, Marissa et al. (2013) Gender, cytidine deaminase, and 5-aza/decitabine--response. Clin Cancer Res 19:3106-7
Jackson, Robert C; Radivoyevitch, Tomas (2013) Modelling c-Abl Signalling in Activated Neutrophils: the Anti-inflammatory Effect of Seliciclib. Biodiscovery 7:4
Ebrahem, Quteba; Mahfouz, Reda Z; Ng, Kwok Peng et al. (2012) High cytidine deaminase expression in the liver provides sanctuary for cancer cells from decitabine treatment effects. Oncotarget 3:1137-45
Saunthararajah, Yogen; Triozzi, Pierre; Rini, Brian et al. (2012) p53-Independent, normal stem cell sparing epigenetic differentiation therapy for myeloid and other malignancies. Semin Oncol 39:97-108

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