An unusual DNA binding compound, S23906, induces mitotic catastrophe in cultured human cells

Cancer cells that survive checkpoint adaptation contain micronuclei that harbor damaged DNA

“…By cisplatin treatment, WI-38 cells arrest largely in G1 and few cells expressed cyclin B1 protein, which would be critical for activation of Cdk1 and entry into mitosis. There are numerous genetic and experimental examples of how inhibition of Chk1 protein leads to entry into mitosis 45,46 or micronuclei formation. 42 It is noteworthy, however, that the simplest approach such as re-introducing functional p53 in a cancer cell line does not prevent mitotic catastrophe, or likely checkpoint adaptation.…”

Characterization of novel Checkpoint kinase 1 inhibitors by in vitro assays and in human cancer cells treated with topoisomerase inhibitors

“…We also demonstrated that Chk1 was active, as shown by Chk1 phosphorylation on Ser345, which is the site phosphorylated by the upstream kinases ATM and ATR (Capasso et al, 2002;Zhao and Piwnica-Worms, 2001). A wide range of genotoxic compounds, including novel synthetic molecules are recognized by cells and activate histone H2AX and Chk1 (Cahuzac et al, 2010). Under conditions of genotoxicity, including those induced by topoisomerase I inhibition, cells will arrest in G2 phase of the cell cycle (Shao et al, 1997).…”

“…Chk1 is activated in cells that have been treated with genotoxic cancer drugs, including camptothecin derivatives (Cliby et al, 2002;Eastman et al, 2002), gemcitabine (Morgan et al, 2005), cisplatin (Zhao and Piwnica-Worms, 2001), etoposide (Cliby et al, 2002) and alkylating agents (Cahuzac et al, 2010). Because Chk1 activity is part of the cellular response to anti-cancer drugs, it suggests that inactivation of Chk1 might provide a clinical benefit.…”

“…Chk1 was present in the phosphorylated form by 24 h of camptothecin or SN38 treatment but not in untreated cells. By immunofluorescence microscopy, we demonstrated that after 24 h of CPT or SN38 treatment, cells were positive for histone gamma-H2AX, which is a marker of damaged DNA (Cahuzac et al, 2010;Paull et al, 2000) (Fig. 6B).…”

“…After several washes, the membranes were treated with horseradish peroxidase-coupled anti-mouse IgG (1:2000) for ECL detection (Amersham). To detect damaged DNA, HT-29 cells were cultivated on glass coverslips, treated with camptothecin for 24 h and processed for immunofluorescence microscopy as previously described (Cahuzac et al, 2010). Observations were made on a Zeiss microscope equipped with a digital camera and Axiovision software.…”