Exploiting oncogene-induced replicative stress for the selective killing of Myc-driven tumors

Genomic Instability Group, Spanish National Cancer Research Centre, Madrid, Spain.
Nature Structural & Molecular Biology (Impact Factor: 13.31). 11/2011; 18(12):1331-5. DOI: 10.1038/nsmb.2189
Source: PubMed


Oncogene-induced replicative stress activates an Atr- and Chk1-dependent response, which has been proposed to be widespread in tumors. We explored whether the presence of replicative stress could be exploited for the selective elimination of cancer cells. To this end, we evaluated the impact of targeting the replicative stress-response on cancer development. In mice (Mus musculus), the reduced levels of Atr found on a mouse model of the Atr-Seckel syndrome completely prevented the development of Myc-induced lymphomas or pancreatic tumors, both of which showed abundant levels of replicative stress. Moreover, Chk1 inhibitors were highly effective in killing Myc-driven lymphomas. By contrast, pancreatic adenocarcinomas initiated by K-Ras(G12V) showed no detectable evidence of replicative stress and were nonresponsive to this therapy. Besides its impact on cancer, Myc overexpression aggravated the phenotypes of Atr-Seckel mice, revealing that oncogenes can modulate the severity of replicative stress-associated diseases.

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Available from: Oskar Fdez-Capetillo, Feb 20, 2015
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    • "Interestingly, certain proliferation-promoting oncogenic events, such as Ras activation and Myc overexpression, render cancer cells sensitive to ATR suppression (Gilad et al., 2010; Murga et al., 2011; Schoppy et al., 2012), leading to the hypothesis that ATR is important for countering the replication stress in cancer cells. Nevertheless, how replication stress can be measured in normal and cancer cells remains elusive. "
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    ABSTRACT: The ATR-Chk1 pathway is critical for DNA damage responses and cell-cycle progression. Chk1 inhibition is more deleterious to cycling cells than ATR inhibition, raising questions about ATR and Chk1 functions in the absence of extrinsic replication stress. Here we show that a key role of ATR in S phase is to coordinate RRM2 accumulation and origin firing. ATR inhibitor (ATRi) induces massive ssDNA accumulation and replication catastrophe in a fraction of early S-phase cells. In other S-phase cells, however, ATRi induces moderate ssDNA and triggers a DNA-PK and Chk1-mediated backup pathway to suppress origin firing. The backup pathway creates a threshold such that ATRi selectively kills cells under high replication stress, whereas Chk1 inhibitor induces cell death at a lower threshold. The levels of ATRi-induced ssDNA correlate with ATRi sensitivity in a panel of cell lines, suggesting that ATRi-induced ssDNA could be predictive of ATRi sensitivity in cancer cells.
    Molecular cell 09/2015; DOI:10.1016/j.molcel.2015.07.029 · 14.02 Impact Factor
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    • "Cells under replicative stress due to oncogene amplification or activation of oncogenic signaling pathways are addicted to Chk1 kinase activity for the completion of a normal S-phase [35, 36]. The sensitivity of neuroblastoma and melanoma cell lines has been suggested to be likely related to oncogenic replicative stress. "
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    ABSTRACT: Background Chk1 inhibitors are currently in clinical trials as putative potentiators of cytotoxic chemotherapy drugs. Chk1 inhibitors may exhibit single agent anti-tumor activity in cancers with underlying DNA repair, DNA damage response or DNA replication defects. Methods Here we describe the cellular effects of the pharmacological inhibition of the checkpoint kinase Chk1 by the novel inhibitor V158411 in triple-negative breast cancer and ovarian cancer. Cytotoxicity, the effect on DNA damage response and cell cycle along with the ability to potentiate gemcitabine and cisplatin cytotoxicity in cultured cells was investigated. Western blotting of proteins involved in DNA repair, checkpoint activation, cell cycle and apoptosis was used to identify potential predictive biomarkers of Chk1 inhibitor sensitivity. Results The Chk1 inhibitors V158411, PF-477736 and AZD7762 potently inhibited the proliferation of triple-negative breast cancer cells as well as ovarian cancer cells, and these cell lines were sensitive compared to ER positive breast and other solid cancer cells lines. Inhibition of Chk1 in these sensitive cell lines induced DNA damage and caspase-3/7 dependent apoptosis. Western blot profiling identified pChk1 (S296) as a predictive biomarker of Chk1 inhibitor sensitivity in ovarian and triple-negative breast cancer and pH2AX (S139) in luminal breast cancer. Conclusions This finding suggests that Chk1 inhibitors either as single agents or in combination chemotherapy represents a viable therapeutic option for the treatment of triple-negative breast cancer. pChk1 (S296) tumor expression levels could serve as a useful biomarker to stratify patients who might benefit from Chk1 inhibitor therapy.
    BMC Cancer 08/2014; 14(1):570. DOI:10.1186/1471-2407-14-570 · 3.36 Impact Factor
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    • "Recent studies have started to identify cancer types sensitive to Chk1 inhibition as single agents; that is, in the absence of a cytotoxic chemotherapeutic drug. RNAi studies have identified neuroblastoma [20] and Fanconi’s Anemia [18] whilst small molecule inhibitor studies have revealed triple-negative breast cancer [24] and an Eμ-myc driven model of lymphoma as potential clinical targets of Chk1 inhibitor therapy [25,26]. Here we further extend this list of cancer types sensitive to Chk1 inhibitors as single agents to include cancers of a hematopoietic origin. "
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    ABSTRACT: Background Chk1 forms a core component of the DNA damage response and small molecule inhibitors are currently being investigated in the clinic as cytotoxic chemotherapy potentiators. Recent evidence suggests that Chk1 inhibitors may demonstrate significant single agent activity in tumors with specific DNA repair defects, a constitutively activated DNA damage response or oncogene induced replicative stress. Methods Growth inhibition induced by the small molecule Chk1 inhibitor V158411 was assessed in a panel of human leukemia and lymphoma cell lines and compared to cancer cell lines derived from solid tumors. The effects on cell cycle and DNA damage response markers were further evaluated. Results Leukemia and lymphoma cell lines were identified as particularly sensitive to the Chk1 inhibitor V158411 (mean GI50 0.17 μM) compared to colon (2.8 μM) or lung (6.9 μM) cancer cell lines. Chk1 inhibition by V158411 in the leukemia and lymphoma cell lines induced DNA fragmentation and cell death that was both caspase dependent and independent, and prevented cells undergoing mitosis. An analysis of in vitro pharmacodynamic markers identified a dose dependent decrease in Chk1 and cyclin B1 protein levels and Cdc2 Thr15 phosphorylation along with a concomitant increase in H2AX phosphorylation at Ser139 following V158411 treatment. Conclusions These data support the further evaluation of Chk1 inhibitors in hematopoietic cancers as single agents as well as in combination with standard of care cytotoxic drugs.
    Molecular Cancer 06/2014; 13(1):147. DOI:10.1186/1476-4598-13-147 · 4.26 Impact Factor
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