15th EHA, Barcelona, Spain
ANTI-LEUKEMIC EFFECT OF SODIUM METAARSENITE (KML001) IN ACUTE MYLOGENOUS LEUKEMIA WITH BREAKING-DOWN THE RESISTANCE OF CYTOSINE ARABINOSIDE
Aims. Firstly, to determine the anti-leukemic effect of KML001 in AML, and to compare the efficacy with arsenic trioxide, secondarily, to
investigate the mechanism of anti-leukemic effect of KML001.
Methods. Eleven AML cell lines were used in this study including Ara-C (cytosine arabinoside) resistant HL-60 (HL-60R) cells. AML blasts
were isolated from 4 AML patients (2 M1 and 2 M2 subtypes) after obtaining informed consents. Cellular inhibition was measured by MTT
assay. Expression of molecules was done by western blot. Analysis of cell cycle was used by flow cytometry. Transcriptional expression of
catalytic subunit of telomerase, hTERT, was done by real-time PCR.
Results. KML001 inhibited the cellular proliferation in all AML cell lines and primary AML blasts as well as HL-60R cells in a dose-dependent
manner with IC50 of 5 x 10-8M. While KML001 effectively inhibited cellular proliferation of HL-60 cells (IC50; 5 x 10-8M) as well as HL-60R
cells (IC50; 1 x 10-8M), and its anti-leukemic effect was almost same as Ara-C (IC50; 5 x 10-8M), Ara-C did not inhibit cellular proliferation
in HL-60R as expected. Furthermore, arsenic trioxide was not effective in primary AML blasts and AML cell lines including HL-60 R cells.
KML001 (1 x 10-7M) was induced G1 cell cycle arrest which was associated with decreased expression of cyclin D1, cyclin E1, CDK1
(cdc2p34), CDK4, and CDK6. While KML001 increased the p21 and p27 levels, and enhanced their bindings with CDK4 in HL-60 cells,
the expression of p21 and p27 bound CDK2 was observed in HL-60R cells. Apoptotic molecules of Bcl-2, proform of caspase-3
and caspase-9 were decreased, in contrast, expression of PARP was increased in HL-60 and HL-60R cells treated with KML001. Real-time
PCR with RNA extracted from KML001-treated HL-60 and HL-60R cells showed a significant reduction of catalytic subunit of telomerase,
hTERT, at 12 hr. When treated KML001, DNA damage molecule (γ-H2AX) in HL-60 and HL-60R cells was increased. In addition, KML001
inhibited the activation of STAT1, 3, 5, NF-κB (p65 and p50 subunits), pAKT and PI3K in a time-dependent manner. On the other hand,
activated PTEN was up-regulated.
Summary/conclusions. KML001, sodium metaarsenite, demonstrated anti-leukemic effect via various mechanisms including cell cycle
arrest, induction of apoptosis, and inhibition of JAK/STAT and PI3K pathways. Especially, KML001 might target telomerase with DNA damage.
Furthermore, it is probable that KML001 may overcome the resistance of chemotherapeutic agents. Collectively, KML001 may be a candidate
agent for the treatment of de novo, refractory and relapsed AML.