Oncogenic BCR-ABL1 tyrosine kinase transforms hematopoietic stem cells (HSCs) to leukemia stem cells (LSCs) to induce chronic myeloid leukemia in chronic phase (CML-CP) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL). CML-CP may progress to more advanced accelerated phase (CML-AP), and subsequently to a very aggressive blast phase (CML-BP). Most CML/Ph+ALL patients are currently treated with tyrosine kinase inhibitors (TKis) such as imatinib, dasatinib and nilotinib. However, it is unlikely that TKis will ?cure? CML/Ph+ALL patients due to the presence of TKi-refractory cells (e.g., quiescent LSCs), TKi-resistant cells (e.g., proliferating LSCs carrying BCR-ABL1 kinase T315I mutant) and LSCs carrying additional somatic mutations. Therefore, novel treatment modalities are needed to eradicate TKi-refractory/resistant CML/Ph+ALL cells in the responding patients and to treat patients who do not respond favorably to TKis. CML/Ph+ALL cells accumulate more DNA double strand breaks (DSBs), the most lethal DNA lesions, than normal counterparts. Leukemia cells can tolerate high numbers of DSBs because the repair mechanisms are altered and hyper-activated. Therefore, CML/Ph+ALL cells are ?addicted? to these pathways to survive pro-apoptotic challenge from high numbers of lethal DSBs. There are critical differences between DSB repair in normal and BCR-ABL1 leukemia cells. Proliferating LSCs usually employ RAD52-dependent DSB repairs and PARP1 ?dependent alternative non-homologous end-joining (Alt-NHEJ), whereas normal counterparts use BRCA1/2-mediated homologous recombination (HR) and DNA-PKcs ?dependent NHEJ (D-NHEJ). Quiescent LSCs use PARP1-mediated Alt-NHEJ instead of DNA-PKcs ?dependent D-NHEJ, which is predominant in normal quiescent HSCs. Research supported by previous award demonstrated that genetic and pharmacological targeting of PARP1 and/or RAD52 exerted synthetic lethal effect against BCR-ABL1 ?positive leukemias. However, somatic mutations often detected in CMLs/Ph+ALLs not responding favorably to TKi and/or progressing to more malignant stages can modulate the response to PARP1 and/or RAD52 inhibition. We have discovered that DNA polymerase theta (Pol?, encoded by POLQ) plays a vital role in microhomology-mediated end-joining (MMEJ), a branch of Alt-NHEJ. Our preliminary data indicate that Pol? is essential for BCR-ABL1 ?mediated leukemogenesis and that targeting of Pol? eliminated CML/Ph+ALL cells.
Aim #1 is designed to determine if/how BCR-ABL1 ?mediated signaling modifies Pol? to regulate its biological activities and to pinpoint the role of Pol? in CML and Ph+ALL stem cells.
Aim #2 will optimize Pol? inhibitor (Pol?i) to be suitable for in vivo use.
Aim #3 is focused on genetic and pharmacological targeting of Pol? and/or PARP1 and RAD52 against TKi-naive and TKi-treated CMLs/Ph+ALLs in in vitro conditions mimicking peripheral blood and bone marrow microenvironment and also in vivo in humanized immunodeficient mice bearing primary leukemia xenografts.

Public Health Relevance

Although tyrosine kinase inhibitors (TKis) such as imatinib revolutionized the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) and chronic myeloid leukemia (CML), the TKis will not eradicate leukemia in majority of patients. We propose to test completely novel anti- Ph+ALL/CML approach involving targeting the DNA polymerase theta to induce ?synthetic lethality? in leukemia stem cells, while sparing normal counterparts. Our findings may have broad application to treat other tumors displaying specific defects in DNA repair mechanisms.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Klauzinska, Malgorzata
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Temple University
Schools of Medicine
United States
Zip Code
Caruso, Lisa B; Martin, Kayla A; Lauretti, Elisabetta et al. (2018) Poly(ADP-ribose) Polymerase 1, PARP1, modifies EZH2 and inhibits EZH2 histone methyltransferase activity after DNA damage. Oncotarget 9:10585-10605
Maifrede, Silvia; Nieborowska-Skorska, Margaret; Sullivan-Reed, Katherine et al. (2018) Tyrosine kinase inhibitor-induced defects in DNA repair sensitize FLT3(ITD)-positive leukemia cells to PARP1 inhibitors. Blood 132:67-77
Nieborowska-Skorska, Margaret; Maifrede, Silvia; Ye, Min et al. (2018) Non-NAD-like PARP1 inhibitor enhanced synthetic lethal effect of NAD-like PARP inhibitors against BRCA1-deficient leukemia. Leuk Lymphoma :1-4
Podszywalow-Bartnicka, Paulina; Maifrede, Silvia; Le, Bac Viet et al. (2018) PARP1 inhibitor eliminated imatinib-refractory chronic myeloid leukemia cells in bone marrow microenvironment conditions. Leuk Lymphoma :1-3
Sullivan-Reed, Katherine; Bolton-Gillespie, Elisabeth; Dasgupta, Yashodhara et al. (2018) Simultaneous Targeting of PARP1 and RAD52 Triggers Dual Synthetic Lethality in BRCA-Deficient Tumor Cells. Cell Rep 23:3127-3136
Maifrede, Silvia; Martin, Kayla; Podszywalow-Bartnicka, Paulina et al. (2017) IGH/MYC Translocation Associates with BRCA2 Deficiency and Synthetic Lethality to PARP1 Inhibitors. Mol Cancer Res 15:967-972
Nieborowska-Skorska, Margaret; Sullivan, Katherine; Dasgupta, Yashodhara et al. (2017) Gene expression and mutation-guided synthetic lethality eradicates proliferating and quiescent leukemia cells. J Clin Invest 127:2392-2406
Maifrede, Silvia; Martinez, Esteban; Nieborowska-Skorska, Margaret et al. (2017) MLL-AF9 leukemias are sensitive to PARP1 inhibitors combined with cytotoxic drugs. Blood Adv 1:1467-1472
Czy?, Ma?gorzata; Toma, Monika; Gajos-Michniewicz, Anna et al. (2016) PARP1 inhibitor olaparib (Lynparza) exerts synthetic lethal effect against ligase 4-deficient melanomas. Oncotarget 7:75551-75560
Huang, Fei; Goyal, Nadish; Sullivan, Katherine et al. (2016) Targeting BRCA1- and BRCA2-deficient cells with RAD52 small molecule inhibitors. Nucleic Acids Res 44:4189-99

Showing the most recent 10 out of 12 publications