AICAR Induces AMPK-Independent Cell Death in Adult T-Cell Leukemia/Lymphoma and Has Anti-Tumor Activity

Introduction: Adult T-cell leukemia/lymphoma (ATL) is an aggressive T cell leukemia/lymphoma caused by human T-cell lymphotropic virus type I (HTLV-1) and has a poor outcome. Recently, we reported that AMPKα, the catalytic unit of AMP-activated protein kinase (AMPK), is highly expressed in cells from patients with ATL and that an AMPK inhibitor had anti-tumor activity in ATL mice 1. On the other hand, acadesine or 5-aminoimidazole-4-carboxamide riboside (AICAR) is anAMPK activator, and was recently shown to have tumor suppressive effects on B cell chronic lymphocytic leukemia via the activation of AMPK. However, the effect of AICAR on the death of ATL-related cell lines is unknown. This study evaluated the effects of AICAR on death in ATL-related cell lines and its anti-tumor activity. Results: We demonstrated that AICAR inhibited the proliferation of ATL-related cell lines (S1T, MT-1 and MT-2) but not non-HTLV-1-infected Jurkat cells and peripheral blood mononuclear cells from healthy individuals. However, AICAR did not increase the phosphorylation levels of AMPKα. We found that AICAR increased annexin V-positive cell numbers in the sub-G0/G1 phase, and decreased the mitochondrial membrane potential and caspase-3/8/9 activation, which are hallmarks of apoptosis. However, AICAR did not increase the phosphorylation levels of AMPKα. On the other hand, HTLV-1 Tax, an HTLV-1-encoded oncogenic factor, expression did not affect AICAR-induced cell death. Moreover, AICAR induced the expression of death receptors (DR) DR4 and DR5 in vitro. Furthermore, AICAR inhibited the growth and infiltration of S1T cells transplanted subcutaneously in NOD/SCID/gamma mice. Conclusion: This is the first evidence to demonstrate the AMPK-independent effects of AICAR on death in ATL-related cell lines and its anti-tumor activity. Thus, AICAR might be a candidate for the treatment of ATL. Disclosures : No relevant conflicts of interest to declare. 1. Aikawa A, Kozako T, Uchida Y, et al. Cell death induced by dorsomorphin in adult T-cell leukemia/lymphoma is AMPK-independent. Febs j. 2020;287(18):4005-4015.