In Vitro and in Vivo Effect of Sodium Metaarsenite (KML001) in Non-Hodgkin's Lymphoma

Abstract 1656

Arsenic trioxide has been used for treatment of hematological malignancies including acute promyelocytic leukemia (APL), multiple myeloma. Sodium metaarsenite (NaAs₂O₃: code name KML001) is an orally bio-available arsenic compound with potential anti-cancer activity. However, the effect of KML001 has not been well studied in non-Hodgkin's lymphoma.

The aim of this study is to determine the anti-tumoral effect of KML001 and to investigate the mechanism of anti-tumoral effect of KML001 in malignant lymphoma. KML001 inhibited the cellular proliferation in all lymphoma cell lines as well as JurkatR cells (adriamycin-resistant Jurkat cells) in a dose-dependent manner with IC₅₀ of 5 × 10⁻⁸M. KML001 induced G1 cell cycle arrest which was associated with decreased expression of cyclin B1, cyclin E1, CDK1 (cdc2p34), CDK2, CDK4, and CDK6. KML001- induced p27 was bound to CDK4 and CDK6 in Jurkat cells, and bound to CDK2, CDK4 and CDK6 in JurkatR cells. CDK4 and CDK6 kinase activities were reduced in Jurkat and JurkatR cells. KML001 increased early apoptotic fraction using annexin V-PI staining in a time-dependent manner. In addition, Apoptotic molecules of Bcl-2, Bcl-_XL, Mcl-1, proform of caspase-3, caspase-8, and caspase-9 were decreased; in contrast, expressions of PARP active form and Bax, were increased in Jurkat and JurkatR cells treated with KML001 in a dose-dependent manner. In addition, KML001 inhibited the activation of STAT1, 3, 5, NF-κB (p65 and p50 subunits), pAKT, p-mTOR, p-GSK3 ß in a dose-dependent manner, but p-PTEN was up-regulated in KML001-treated Jurkat and JurkatR cells. In MAP kinase signaling, pERK was down regulated, while pp38 and pJNK were increased in a dose-dependent manner. Real-time PCR with RNA extracted from KML001-treated Jurkat and JurkatR cells showed a reduction of catalytic subunit of telomerase, hTERT, in a time- dependent manner. When treated KML001, DNA damage molecule (p-γ-H₂A_X) was increased in a time-dependent manner, and the telomere length was shorten in Jurkat and JurkatR cells. In vivo anti-tumoral activity of KML001 was confirmed using a xenograft-murine model of human lymphoma cell. Tumor burden was significantly reduced (P < 0.01) for 42 days. Especially, in-vivo anti-tumoral effect of 3.5 mg/Kg KML001 was comparable to that of doxorubicin (2.5 mg/Kg, P < 0.05). Furthermore, three refractory or relapsed malignant lymphoma patients (Diffuse large cell lymphoma, Follicular lymphoma. Mantle cell lymphoma) were treated with 10 mg of KML001 daily, resulting in decrease of lymphoma mass in 4 weeks without severe toxicities.

In summary, KML001(sodium metaarsenite) demonstrated anti-tumoral effect via various mechanisms including cell cycle arrest, induction of apoptosis, and inhibition of JAK/STAT, PI3K and MAPK 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 malignant lymphoma.