Development and mechanism of action of the Novel Anti-cancer Drug HNA-2 in Acute Myeloid Leukemia

Abstract

Acute myeloid leukemia (AML) is the most frequent hematological malignancy in adults accounting for 80 percent of cases of acute leukemias. AML is a clinically and genetically heterogeneous disorder of hematopoietic progenitor cells. AML incidence increases with age, and is known to be highly dependent on the patients’ karyotype and is, therefore, one of the most complex types of leukemias. Therapeutic progress in AML is still modest and current treatment is largely based on combination chemotherapy and the appropriate use of stem cell transplantation. Sesquiterpene lactones are plant secondary metabolites well known for their antitumor activities. These latter plant secondary metabolites have a wide range of action depending on their hydrophobicity, alkylating centers, and their molecular geometry. HNA-2 is a derivative of a sesquiterpene lactone isolated from the indigenous Lebanese plant Centaurea ainetensis. This compound exhibits promising anti-cancer properties in a variety of solid and hematologic cancer cell lines, with remarked specificity for leukemic cells while sparing normal peripheral blood mononuclear cells. In this study, we used representative human AML cell lines harboring different genetic mutations and representing several AML karyotypes in order to investigate the mechanism of action of HNA-2 on cell proliferation, cell cycle, and cell death, and identify potential targets through which the drug may be exerting its action. We further assessed the anti-tumor potency of HNA-2 using an AML xenograft mouse model. We showed that the potency of HNA-2 is not only due to its hydrophobicity since it was more potent than synthesized more hydrophobic derivatives. HNA-2 also exerted potent anti-proliferative effects on AML cells while sparing normal peripheral blood mononuclear cells. Cell cycle analysis of HNA-2 treated AML cells showed a sub-G1 accumulation of, presumably representing apoptotic cells, HNA-2-treated AML cells underwent apoptosis as verified by TUNEL assay and PARP protein cleavage. Furthermore, HNA-2 induced massive early DNA damage starting as early as 30 minutes post-treatment. In vivo pilot study demonstrated the potency of HNA-2 to slightly delay tumors appearance in NOD-SCID xenografted mice. However, a toxicity effect of the drug was recorded at high doses and daily administration for one month. Finally, we were able to reproduce a physiological AML xenograft mouse model by injecting THP-1 cells in the circulation of NOD-scid IL2rγnull (NSG) mice for further investigation. In summary, we have shown promising anti-cancer activities of HNA-2 and investigated its mechanism of action using in vitro and in vivo AML studies. These results highlight the favorable use of HNA-2 in AML therapy and encourage its further development.