Mcl-1 as a Therapeutic Target in Acute Myelogenous Leukemia (AML)

The B-cell lymphoma-2 (Bcl-2) family of proteins regulates the intrinsic, or mitochondrial pathway of apoptosis, the final common mechanism of cell death in response to a variety of physiologic and pharmacologic signals, and plays a central role in AML pathogenesis, prognosis and responsiveness to chemotherapy. Traditionally thought to be an important survival factor for multiple myeloma cells, the anti-apoptotic Bcl-2 family protein myeloid cell leukemia-1 (Mcl-1) has recently been shown in preclinical studies to be critical to the development and maintenance of AML, making it an attractive therapeutic target in this disease. Several characteristics, such as its very short half-life, distinguish Mcl-1 from other anti-apoptotic Bcl-2 family members. Additionally, Mcl-1 levels are regulated by a large number of pathways affecting its transcription, translation and degradation. A variety of approaches exploiting these features has been developed to inhibit directly or indirectly the anti-apoptotic function of Mcl-1. Many of these lend themselves well to combination therapies, leading to striking synergism, at least in preclinical models. In this brief review, we highlight some of the more promising strategies targeting Mcl-1 in AML, with a particular emphasis on rational combinations of novel agents.