Description
Background: Olaparib (AZD2281, KU0059436) is a selective inhibitor of PARP1 and PARP2 with IC50 of 5 nM and 1 nM, respectively.
Targets
PARP1
PARP2
IC50
5 nM
1 nM
In vitro
Olaparib would act against BRCA1 or BRCA2 mutations. Olaparib is not sensitive to tankyrase-1 (IC50 >1 uM). Olaparib could ablate the PARP-1 activity at concentrations of 30-100 nM in SW620 cells. Olaparib is hypersensitive to BRCA1-deficient cell lines (MDA-MB-463 and HCC1937), compared with BRCA1- and BRCA2-proficient cell lines (Hs578T, MDA-MB-231, and T47D). [1] Olaparib is strongly sensitive to KB2P cells due to suppression of base excision repair by PARP inhibition, which may result in the conversion of single-strand breaks to double-strand breaks during DNA replication, thus activating BRCA2-dependent recombination pathways. [2]
In vivo
Combining with temozolomide, Olaparib (10 mg/kg, p.o.) significantly suppresses tumor growth in SW620 xenografts. [1] Olaparib shows great response to Brca1-/-;p53-/- mammary tumors (50 mg/kg i.p. per day), while no responses to HR-deficient Ecad-/-;p53-/- mammary tumors. Olaparib even does not show dose-limiting toxicity in tumor-bearing mice. [3] Olaparib has been used to treat with BRCA mutated tumors, such as ovarian, breast and prostate cancers. Moreover, Olaparib shows selectively inhibition to ATM (Ataxia Telangiectasia Mutated)-deficient tumor cells, which indicates to be a potential agent for treating ATM mutant lymphoid tumors. [4]
Clinical Trials
Combining with cediranib, Olaparib is currently in Phase I/II study for treatment of recurrent papillary-serous ovarian, fallopian tube or peritoneal cancer or treatment of recurrent triple-negative breast cancer.
Features
Olaparib is one of the first PARP inhibitors.
Protocol(Only for Reference)
Kinase Assay:
FlashPlate assay (96-well screening assay)
To columns 1 through 10, 1 uL of Olaparib (in DMSO) is added, and 1 uL DMSO only is added to the positive (POS) and negative (NEG) control wells (columns 11 and 12, respectively) of a pretreated FlashPlate. PARP-1 is diluted 1:40 in buffer (buffer B: 10% glycerol (v/v), 25 mM HEPES, 12.5 mM MgCl2,50 mM KCl, 1 mM DTT, 0.01% NP-40 (v/v), pH 7.6) and 40 uL added to all 96 wells (final PARP-1 concentration in the assay is ~1 ng/ uL). The plate is sealed and shaken at RT for 15 min. Following this, 10 uL of positive reaction mix (0.2 ng/ uL of double-stranded oligonucleotide [M3/M4] DNA per well, 5 uM of NAD+ final assay concentration, and 0.075 uCi 3H-NAD+ per well) is added to the appropriate wells (columns 1-11). The negative reaction mix, lacking the DNA oligonucleotide, is added to column 12 (with the mean negative control value used as the background). The plate is resealed and shaken for a further 60 min at RT to allow the reaction to continue. Then, 50 uL of ice-cold acetic acid (30%) is added to each well to stop the reaction, and the plate is sealed and shaken for a further 60 min at RT. Tritiated signal bound to the FlashPlate is then determined in counts per minute (CPM) using the TopCount plate reader.
In vitro isolated enzyme assay
PARP-2 activity inhibition uses a variation of the PARP-1 assay in which PARP-2 protein (recombinant) is bound down by a PARP-2 specific antibody in a 96-well white-walled plate. PARP-2 activity is measured following 3H-NAD+ DNA additions. After washing, scintillant is added to measure 3H-incorporated ribosylations. For tankyrase-1, a alpha-Screen assay is developed in which HIS-tagged recombinant TANK-1 protein is incubated with biotinylated NAD+in a 384-well ProxiPlate assay. Alpha beads are added to bind the HIS and biotin tags to create proximity signal, whereas the inhibition of TANK-1 activity is directly proportional to the loss of this signal.
Cell Assay:
Cell lines
Breast cancer cell lines including SW620 colon, A2780 ovarian, HCC1937, Hs578T, MDA-MB-231, MDA-MB-436, and T47D