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• Median age of AML diagnosis is 67 years, and incidence
increases with age
• Five-year survival rate is dismal at 24% and less than 5%
for patients over the age of 60 years
• A high proportion of patients relapse, and one-third of
patients exhibit primary refractory disease
• New treatments are urgently required
Investigating PARP inhibitors for the treatment of
acute myeloid leukaemiaCheenie Nieva1, Lisa Lincz1,2,3, Kathryn Skelding1
1 School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308
2 Hunter Medical Research Institute, New Lambton NSW 2305
3 Hunter Haematology Research Group, Calvary Mater Newcastle Hospital, Waratah NSW 2298
ABBREVIATIONS
AML Acute myeloid leukaemia
PARPi Poly (adenosine diphosphate [ADP]-ribose polymerase
Acute myeloid leukaemia (AML) is the
most common and aggressive acute
leukaemia in adults
Inhibition of PARP is a potential new for
AML
• AML cells with perturbations in DNA repair pathways
exhibit alterations in sensitivity to a range of anti-cancer
agents [1]
• Cells with defective homologous recombination (HR)
repair are very sensitive to a class of drugs called PARP
inhibitors (PARPi) [2]
• PARPi have shown significant clinical efficacy among a
range of solid tumours, including breast, ovarian, lung and
prostate cancers
• Therapeutic potential of PARPi in AML remains relatively
unexplored
• The PARPi olaparib has been demonstrated to induce cell
death as a monotherapy in a panel of AML cell lines and
primary AML patient blasts in vitro [3]
AIM:
To examine the pharmacological efficacy of PARPi in
AML cells, singly and in combination with existing
chemotherapeutics in vitro.
• Treatment with each of the PARPi led to a reduction in cell
viability in a dose-dependent manner in all AML cell lines
examined (THP-1, MV4-11, KG-1, Kasumi-1, BDCM and
AML-193)
• AML cell lines exhibited differing sensitivities to each
PARPi
Figure 1. Cell viability of AML cells 96 h post-treatment with PARPi as single
agents. A panel of AML cells were treated with increasing concentrations (0.002,
0.02, 0.2, 2 and 20 mM) of PARPi (A) veliparib, (B) olaparib, (C) rucaparib and (D)
pamiparib for 96 h and cell viability was determined by resazurin assay. Mean ±
SEM. n=3 in triplicate.
Table 1. The IC50 values for PARPi (mM) as single agents. Mean ± SEM. n=3 in
triplicate.
• This highlights that different AML subtypes may be more
sensitive to treatment with different PARPi
CONCLUSIONS:
• PARPi demonstrate efficacy against AML cell lines as
single agents in vitro
• PARPi potentiates the cytotoxic activity of cytarabine in
vitro, suggesting that administration of PARPi in
combination with cytarabine may provide benefits to
improving AML patient outcomes.
• Further examination of PARPi may be useful
therapeutically as a new strategy for the treatment of
AML.
• Treatment of AML cells with increasing doses of PARPi led
to a reduction in colony formation with the highest dose
• AML cells exhibited varying sensitivities to each PARPi
treatments
METHODS:
CELL VIABILITY ASSAY:
• A panel of 6 AML cell lines were treated with varying
concentrations of the PARPi veliparib, olaparib, rucaparib
and pamiparib, alone or in combination with daunorubin or
cytarabine, for 96 h and cell viability was assessed by
resazurin assay
CLONOGENIC ASSAY:
• A panel of 6 AML cell lines were treated with increasing
concentrations of PARPi and were growth in soft agar for
7 days before staining with 0.5% crystal violet/10%
methanol/PBS for 30 mins to visualise colonies.
CALCULATION OF COMBINATION INDICES:
• Data was quantitatively analysed to ascertain the degree
of drug interaction using the CompuSyn software
(ComboSyn, Inc, Paramus, NJ) which is based on the
combination index (CI) and isobologram equation
methods derived from the median-effect theorem of Chou
and Talalay [4]
AML cells are sensitive to PARPi in vitro
Long-term treatment with PARPi reduce
clonogenicity of AML cells
Table 2. Combination index (CI) values for AML cells treated with a combination
of PARP inhibitors and chemotherapeutics. Combination indices were calculated
using CompuSyn and the values were defined as synergistic if less than 0.9,
additive if between 0.9 and 1.1, and antagonistic if greater than 1.1. Mean ± SEM.
n=3 in duplicate.
Figure 2. Clonogenic assay of AML cell lines treated with increasing doses of
veliparib. Cells were treated with increasing doses (0.002, 0.02, 0.2, 2 and 20 mM)
of PARPi and were grown for 7 days in soft agar. Bar graphs depict the average
number of colonies grown for AML cell lines treated with (A) veliparib, (B) olaparib,
(C) rucaparib and (D) pamiparib. Statistical significance * (p<0.05); ** (p <0.01);
****(p<0.0001). Mean ± SEM. n=3 in triplicate.
• PARPi synergistically or at least additively enhanced the
sensitivity of THP-1, MV4-11, KG-1, and BDCM cells to
cytarabine as evidenced by combination indices of less
than 0.9 or in between 0.9 and 1.1, but mostly antagonised
the effects of cytarabine in Kasumi-1 and AML-193 cells
with combination indices of greater than 1.1 being
observed
AML cells are sensitive to treatment with
PARPi in combination with daunorubicin
and cytarabine in vitro
REFERENCES[1] Pearsall E. A., et al 2018, Curr Drug Targets In press.
[2] McCabe N., et al., 2006, Cancer Research 66: 16
[3] Faraoni I. et al., 2015, Biochim Biophys Acta 1852: 3
[4] T. C., Talalay P., 1984, Adv Enzyme Regul 22
• In the majority of cases (THP-1, KG-1, Kasumi-1 and
BDCM cells) PARPi exerted antagonistic effects with
daunorubicin as evidenced by combination indices of less
than 0.9 being observed, but were mostly synergistic in
MV4-11 and AML-193 cells with combination indices
greater than 1.1
• Concurrent administration of PARPi and daunorubicin or
cytarabine led to a greater reduction in cell viability
compared to treatment with either agents alone