Chronic myeloid leukemia in chronic phase (CML-CP) is initiated by t(9;22) encoding for p210BCR-ABL1 tyrosine kinase that transforms hematopoietic stem cells (HSCs). CML-CP is leukemia stem cells (LSCs) - derived disease, but deregulated growth of LSCs-derived leukemia progenitor cells (LPCs) leads to the manifestation of the disease. CML-CP may progress to more advanced accelerated phase (CML-AP), and subsequently to a very aggressive blast phase (CML-BP). Most CML-CP patients are currently treated with tyrosine kinase inhibitors (TKIs) such as imatinib, dasatinib and nilotinib. However, it is unlikely that TKIs will cure CML patients due to the presence of TKI- refractory cells (e.g, quiescent LSCs) and TKI-resistant cells (e.g., proliferating LSCs/LPCs carrying BCR- ABL1 kinase T315I mutant). In addition, population studies revealed that overall only 51% of CML-CP patients respond favorably to TKI treatment. Therefore, novel treatment modalities are needed to eradicate TKI- refractory/resistant CML cells in the responding patients and also to treat patients who do not respond favorably to TKIs. To cure CML these strategies should simultaneously target two fundamentally different leukemia cell populations: TKI-refractory quiescent LSCs and TKI-resistant/refractory proliferating LSCs/LPCs. We found that CML LSCs and LPCs, including quiescent LSCs accumulate 2-4 times more reactive oxygen species (ROS)-induced DNA double strand breaks (DSBs) than normal counterparts (Cramer et al., Cancer Res., 2008; Nieborowska-Skorska et al., Blood, 2012; Bolton-Gillespie et al., Blood, 2013). DSBs are the most lethal DNA lesions. We reported that CML cells can tolerate high numbers of DSBs because two major repair mechanisms, homologous recombination repair (HRR) and non-homologous end-joining (NHEJ) are hyper- activated (Slupianek et al., Mol. Cell, 2001; Oncogene, 2005; DNA Repair, 2006; Cancer Res., 2011; Blood, 2011; Nowicki et al., Blood, 2005). CML cells are addicted to these pathways to survive pro-apoptotic challenge from high numbers of lethal DSBs. However, there are critical differences between DSB repair in normal and CML cells. Proliferating LSCs/LPCs employ RAD52-dependent HRR, in contrast to BRCA1-mediated HRR in normal counterparts. Quiescent LSCs use PARP1-mediated NHEJ instead of DNA-PKcs -dependent NHEJ, which is predominant in normal quiescent HSCs. We will explore these differences to target leukemia-specific DNA repair mechanisms simultaneously in quiescent LSCs and proliferating LSCs/LPCs to achieve dual synthetic lethality, with negligible effect on normal cells and tissues. According to our best knowledge the concept of dual synthetic lethality was not tested before. Dual synthetic lethality will be induced in TKI-treated CML-CP/AP cells by simultaneous targeting of RAD52 and PARP1 using recently identified candidate small molecule inhibitors interrupting key functions of RAD52 and PARP1: RAD52 DNA binding activity and stimulation of PARP1 by histone 4. In addition, using CML-CP -like transgenic mice, Rad52-/-Parp1-/- double knockout mice, mutagenic approach, peptide aptamers, and CML-CP/AP primary cells we will determine if other RAD52 and/or PARP1 activities could be targeted to trigger more efficient dual synthetic lethality simultaneously in TKI-refractory quiescent LSCs and TKI-resistant proliferating LSCs/LPCs. Our long-term plan is to run a clinical trial testing the possibility to eradicate CML-CP/AP by induction of dual synthetic lethality in TKI-treated patients.

Public Health Relevance

Tyrosine kinase inhibitors (TKIs) such as imatinib revolutionized the treatment of chronic myeloid leukemia (CML). However, since TKIs will not eradicate CML in majority of patients who respond favorably to the treatment, there is a growing number of patients with 'dormant' disease. In addition, numerous CML patients do not respond favorably to TKIs. We propose to test completely novel anti-CML approach, which induces 'dual synthetic lethality' in leukemia stem and progenitor cells, while sparing normal counterparts. Our findings may have broad application to treat other tumors displaying specific defects in DNA repair mechanisms.

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National Cancer Institute (NCI)
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Drug Discovery and Molecular Pharmacology Study Section (DMP)
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Kondapaka, Sudhir B
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Temple University
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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

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