Galectin-9 has non-apoptotic cytotoxic activity towards Acute Myeloid Leukemia independent of cytarabine resistance

Abstract

Acute myeloid leukemia (AML) is a malignancy still associated with poor survival rates, among others due to frequent occurrence of therapy-resistant relapse after standard-of-care treatment with cytarabine (AraC). AraC triggers apoptotic cell death, a type of cell death to which AML cells often becomes resistant. Therefore, alternative therapeutic options that trigger a different type of cell death are of particular interest. We previously identified that the glycan-binding protein Galectin-9 (Gal-9) has tumor-selective and non-apoptotic cytotoxicity towards various types of cancer, which depended on autophagy inhibition. Thus, Gal-9 could be of a therapeutic interest for (AraC-resistant) AML. In the current study, we identified that Gal-9 was cytotoxic for AML cells, including for CD34+ patient-derived AML stem cells, but not for healthy cord blood-derived CD34+ stem cells. This Gal-9-mediated cytotoxicity did not rely on apoptosis but negatively associated with autophagic flux. Importantly, both AraC-sensitive and -resistant AML cell lines as well as AML patient samples were sensitive to single agent treatment with Gal-9. Additionally, Gal-9 potentiated the cytotoxic effect of DNA demethylase inhibitor Azacytidine (Aza), a drug that is clinically used for patients that are not eligible for intensive AraC treatment. Thus, Gal-9 is a potential therapeutic agent for the treatment of AML, including AraC resistant AML, by inducing caspase-independent cell death.