CHIR-124

419, 91

MDA-MB-435 cells are implanted in the mammary fat pad of 8- to 10-week-old female immunodeficient mice.

0-2350 nM, dependent on cell types

CHIR-124 is dissolved in dimethyl sulfoxide and stored in aliquots at -20 C.

CHIR-124 is a quinolone-based small molecule that is structurally unrelated to other known inhibitors of Chk1. CHIR-124 interacts synergistically with topoisomerase poisons (e.g., Camptothecin or SN-38) in causing growth inhibition in a variety of cancer cell lines, including breast carcinoma (MDA-MB-231 and MDA-MB-435) and colon carcinoma (SW-620 and Colo205), all of which contains the mutant p53 gene. CHIR-124 abrogates the SN-38-induced S and G2-M checkpoints and potentiates apoptosis in MDA-MD-435 breast cancer cells. The abrogation of the G2-Mcheckpoint and induction of apoptosis by CHIR-124 are enhanced by the loss of p53. [1], CHIR-124 also potently targets other kinases such as PDGFR and Flt3 with IC50 of 6.6 nM and 5.8 nM, respectively. [2]

48 hours

MDA-MB-231, MDA-MB-435, SW-620, and COLO 205 cells in log-phase are plated into 96-well microplates. CHIR-124 is serially diluted in the presence of six different concentrations of Camptothecin or 0 nM camptothecin. Camptothecin is also serially diluted in the absence of CHIR-124. CHIR-124 is added to cells in 96-well dishes and incubated at 37 C for 48 hours. Each treatment condition is done in triplicate. Cell proliferation was monitored by the 3-(4, 5-dimethylthiazol-2-yl)-5- (3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), inner salt assay. MTS inner salt is added to the microplates, which are incubated for another 3 hours, and absorbance at 490 nm is read on a plate reader. The concentrations of each drug in the combinations required to produce 50% inhibition are plotted to generate the isoboles. Isobologram analysis of drug interaction is based the equation of Loewe additivity (1= D A /IC50, A + DB/IC50, B), where IC50, A and IC50, B are the concentrations of drugs to result in 50% inhibition for each drug alone, and DA and DB are concentrations of each drug in the combination that yield 50% overall inhibition. A diagonal line indicating Loewe additivity is included in each graph. Data points that fall below the line indicate synergy, whereas those that fall above the line will indicate antagonism.

CHIR-124 is a novel and potent Chk1 inhibitor with IC50 of 0.3 nM in a cell-free assay. It shows 2, 000-fold selectivity against Chk2, 500- to 5, 000-fold less activity against CDK2/4 and Cdc2.