Therapeutic Vulnerabilities in -Mutant AML Unmasked by Palbociclib.

Int J Mol Sci 2018 Dec 11;19(12). Epub 2018 Dec 11.

Institute of Pharmacology and Toxicology, University of Veterinary Medicine, 1210 Vienna, Austria.

While significant progress has been made in the treatment of acute myeloid leukemia (AML), not all patients can be cured. Mutated in about 1/3 of de novo AML, the FLT3 receptor tyrosine kinase is an attractive target for drug development, activating mutations of the map to the juxtamembrane domain (internal tandem duplications, ITD) or the tyrosine kinase domain (TKD), most frequently at codon D835. While small molecule tyrosine kinase inhibitors (TKI) effectively target ITD mutant forms, those on the TKD are not responsive. Moreover, FLT3 inhibition fails to induce a persistent response in patients due to mutational resistance. More potent compounds with broader inhibitory effects on multiple mutations are highly desirable. We describe a critical role of CDK6 in the survival of ⁺ AML cells as palbociclib induced apoptosis not only in ⁺ cells but also in ⁻D835Y⁺ cells. Antineoplastic effects were also seen in primary patient-derived cells and in a xenograft model, where therapy effectively suppressed tumor formation in vivo at clinically relevant concentrations. In cells with ⁻ITD or -TKD mutations, the CDK6 protein not only affects cell cycle progression but also transcriptionally regulates oncogenic kinases mediating intrinsic drug resistance, including AURORA and AKT-a feature not shared by its homolog CDK4. While AKT and AURORA kinase inhibitors have significant therapeutic potential in AML, single agent activity has not been proven overly effective. We describe synergistic combination effects when applying these drugs together with palbociclib which could be readily translated to patients with AML bearing or ⁻TKD mutations. Targeting synergistically acting vulnerabilities, with CDK6 being the common denominator, may represent a promising strategy to improve AML patient responses and to reduce the incidence of selection of resistance-inducing mutations.

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Source
http://dx.doi.org/10.3390/ijms19123987DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321303PMC
December 2018
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