Identification of Preferred Chemotherapeutics for Combining with a CHK1 Inhibitor

Abstract

Here we report that GNE-783, a novel checkpoint kinase-1 (CHK1) inhibitor, enhances the activity of gemcitabine by disabling the S-and G 2 cell-cycle checkpoints following DNA damage. Using a focused library of 51 DNA-damaging agents, we undertook a systematic screen using three different cell lines to determine which chemotherapeutics have their activity enhanced when combined with GNE-783. We found that GNE-783 was most effective at enhancing activity of antimetabolite-based DNA-damaging agents; however, there was a surprisingly wide range of activity within each class of agents. We, next, selected six different therapeutic agents and screened these in combination with GNE-783 across a panel of cell lines. This revealed a preference for enhanced chemopotentiation of select agents within tumor types, as, for instance, GNE-783 preferentially enhanced the activity of temozolomide only in melanoma cell lines. Additionally, although p53 mutant status was important for the overall response to combinations with some agents; our data indicate that this alone was insufficient to predict synergy. We finally compared the ability of a structurally related CHK1 inhibitor, GNE-900, to enhance the in vivo activity of gemcitabine, CPT-11, and temozolomide in xenograft models. GNE-900 significantly enhanced activity of only gemcitabine in vivo, suggesting that strong chemopotentiation in vitro can translate into chemopotentiation in vivo. In conclusion, our results show that selection of an appropriate agent to combine with a CHK1 inhibitor needs to be carefully evaluated in the context of the genetic background and tumor type in which it will be used. Mol Cancer Ther; 12(11); 2285-95. Ó2013 AACR.

γH2AX and Chk1 phosphorylation as predictive pharmacodynamic biomarkers of Chk1 inhibitor-chemotherapy combination treatments

“…V158411 potentiated the cytotoxicity of a range of chemotherapeutic agents in the p53 mutant colon carcinoma cell lines HT29 and Colo205 growing anchorage dependently, anchorage independently or as multi-cellular tumor spheroids (Figure 1A and 1B). The p53 mutant HT29 colon carcinoma cell line has been extensively used to evaluate the potentiation of cytotoxic chemotherapy by Chk1 inhibitors [19-23] and was therefore used as the main test system for this study. Greater potentiation was observed in both cell lines growing anchorage dependently compared to anchorage independently.…”

“…Previously published studies have observed the greatest potentiation of cytotoxicity by Chk1 inhibitors with the anti-metabolite class of drugs, including gemcitabine [23]. Chk1 activity has been demonstrated to be critical for not only the DNA damage response checkpoint but also for replication fork stabilization, replication origin firing and homologous recombination.…”

Targeting cancer with kinase inhibitors

“…For instance, several factors that have been implicated in conferring resistance to MAPK pathway therapeutics fall within the PI3K pathway (Figure 3). These events include the mutation of PIK3CA, loss of the PTEN and INPP4B tumor suppressors, in premature entry into mitosis with damaged DNA and subsequent mitotic catastrophe and cell death (97,98). Kinase inhibitors can also be used to mitigate the effects of cytotoxic agents on rapidly proliferating normal tissue.…”

Re-purposing clinical kinase inhibitors to enhance chemosensitivity by overriding checkpoints

“…Clearly these are important factors that can dictate tumor growth and affecting these processes could contribute to the efficacy observed. 36 Our studies used gemcitabine because it is a major modality of treatment for pancreatic cancer patients. However, we believe that the choice of which chemotherapy to be used along with bosutinib or Bos-I should be explored further.…”