Poly(ADP-ribose) Polymerase 1 Modulates the Lethality of CHK1 Inhibitors in Mammary Tumors

Abstract

The present studies sought to define whether checkpoint kinase 1 (CHK1) inhibitors and poly(ADP-ribose) polymerase 1 (PARP1) inhibitors interact in vitro and in vivo to kill breast cancer cells. PARP1 and CHK1 inhibitors interacted to kill estrogen receptor (ER)ϩ, ERϩ fulvestrant-resistant, HER2ϩ, or triple-negative mammary carcinoma cells in a manner that was not apparently affected by phosphatase and tensin homolog deleted on chromosome 10 functional status. Expression of dominant-negative CHK1 enhanced and overexpression of wild-type CHK1 suppressed the toxicity of PARP1 inhibitors in a dose-dependent fashion. Knockdown of PARP1 enhanced the lethality of CHK1 inhibitors in a dose-dependent fashion. PARP1 and CHK1 inhibitors interacted in vivo both to suppress the growth of large established tumors and to suppress the growth of smaller developing tumors; the combination enhanced animal survival. PARP1 and CHK1 inhibitors profoundly radiosensitized cells in vitro and in vivo. In conclusion, our data demonstrate that the combination of PARP1 and CHK1 inhibitors has antitumor activity in vivo against multiple mammary tumor types and that translation of this approach could prove to be a useful anticancer therapeutic approach.

Identification of DNA Repair Pathways That Affect the Survival of Ovarian Cancer Cells Treated with a Poly(ADP-Ribose) Polymerase Inhibitor in a Novel Drug Combination

“…Fourth, we found that profound Chk1 depletion did not affect ABT-888 sensitivity. This result contrasts with studies showing that Chk1 depletion or inhibition sensitizes tumor cells to PARP inhibition in other experimental systems (McCabe et al, 2006;Mitchell et al, 2010;Tang et al, 2012), thus suggesting that the requirement for Chk1 in PARP-inhibited cells may vary significantly among tumor cell types. Finally, the observation that Chk1 depletion did not influence FdUrd toxicity was unexpected given that Chk1 has been implicated in the regulation of RAD51 and HR (Sørensen et al, 2005), which we showed markedly protect cells from FdUrd.…”

PARP and CHK inhibitors interact to cause DNA damage and cell death in mammary carcinoma cells

“…The CHK1 inhibitor LY2603618 was purchased from Selleckchem. 12,13 penicillin, 100 μg/ml streptomycin and 250 μg/ml amphotericin B) and trypsin-EDTA were purchased from Invitrogen. All the primary antibodies used in the present study were purchased from Cell Signaling Technology.…”

“…12,13,30 The present studies were performed to determine in further detail the biology by which PARP1 inhibitors interact with CHK1 inhibitors to promote breast cancer cell killing. Multiple PARP1 and CHK1 inhibitors interacted in a greater than additive fashion to kill mammary tumor cells.…”

“…[8][9][10][11][12][13] We have repeated our assays using molecular tools to inhibit CHK1 or maintain activation of the ERK1/2 pathway. UCN-01 is an ATP site dependent CHK1 inhibitor, but not a CHK2 inhibitor, and also has inhibitory effects on other protein kinases including PKC isoforms and PDK-1.…”

mTORC1 and DNA‐PKcs as novel molecular determinants of sensitivity to Chk1 inhibition

“…This evidence implicating a role for Chk1 in the cell‐cycle and DNA replication in the absence of exogenous DNA damage suggests combining a Chk1 inhibitor with alternative, molecularly targeted therapeutic agents may be a rational therapeutic option. Synergism with Chk1 inhibitors (UCN‐01, LY2603618 and PF‐477736) or a pan Chk1/Chk2 inhibitor (AZD7762) has so far been observed with MEK inhibitors in glioblastoma (Tang et al., 2012a) and cytokinetically quiescent multiple myeloma (Pei et al., 2011); with PARP inhibitors in breast cancer (Mitchell et al., 2010; Shibata et al., 2011; Tang et al., 2012a); with Src family kinase inhibitors in glioblastoma (Tang et al., 2012b), multiple myeloma (Dai et al., 2008, 2011) and breast cancer (Mitchell et al., 2011); with farnesyl transferase inhibitors in leukaemia and myeloma (Dai et al., 2005); and with the mTOR inhibitor rapamycin in leukaemia (Hahn et al., 2005). Chk1 inhibitors have demonstrated single agent activity in cancers harbouring defects in DNA repair pathways or with high levels of replicative stress including neuroblastoma (Cole et al., 2011), melanoma (Brooks et al., 2013), leukaemia and lymphoma (Bryant et al., 2014b; Ferrao et al., 2012; Murga et al., 2011), breast cancer (Bryant et al., 2014a; Shibata et al., 2011), and cell lines defective in components of the Fanconi's anaemia DNA repair pathway (Chen et al., 2009).…”