Pim kinase inhibitor co-treatment decreases alternative non-homologous end-joining DNA repair and genomic instability induced by topoisomerase 2 inhibitors in cells with FLT3 internal tandem duplication

• Published in: Oncotarget Vol. 12; no. 18; pp. 1763 - 1779
• Main Authors: Scarpa, Mario, Kapoor, Shivani, Tvedte, Eric S, Doshi, Kshama A, Zou, Ying S, Singh, Prerna, Lee, Jonelle K, Chatterjee, Aditi, Ali, Moaath K Mustafa, Bromley, Robin E, Hotopp, Julie C Dunning, Rassool, Feyruz V, Baer, Maria R
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 31-08-2021
• Subjects: Research Paper; FLT3 internal tandem duplication; Pim kinase; alternative non-homologous end-joining DNA repair; genomic instability; topoisomerase 2 inhibitors
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.28042

Acute myeloid leukemia (AML) with fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) relapses with new chromosome abnormalities following chemotherapy, implicating genomic instability. Error-prone alternative non-homologous end-joining (Alt-NHEJ) DNA double-strand break (DSB) repair is upregulated in FLT3-ITD-expresssing cells, driven by c-Myc. The serine/threonine kinase Pim-1 is upregulated downstream of FLT3-ITD, and inhibiting Pim increases topoisomerase 2 (TOP2) inhibitor chemotherapy drug induction of DNA DSBs and apoptosis. We hypothesized that Pim inhibition increases DNA DSBs by downregulating Alt-NHEJ, also decreasing genomic instability. Alt-NHEJ activity, measured with a green fluorescent reporter construct, increased in FLT3-ITD-transfected Ba/F3-ITD cells treated with TOP2 inhibitors, and this increase was abrogated by Pim kinase inhibitor AZD1208 co-treatment. TOP2 inhibitor and AZD1208 co-treatment downregulated cellular and nuclear expression of c-Myc and Alt-NHEJ repair pathway proteins DNA polymerase θ, DNA ligase 3 and XRCC1 in FLT3-ITD cell lines and AML patient blasts. ALT-NHEJ protein downregulation was preceded by c-Myc downregulation, inhibited by c-Myc overexpression and induced by c-Myc knockdown or inhibition. TOP2 inhibitor treatment increased chromosome breaks in metaphase spreads in FLT3-ITD-expressing cells, and AZD1208 co-treatment abrogated these increases. Thus Pim kinase inhibitor co-treatment both enhances TOP2 inhibitor cytotoxicity and decreases TOP2 inhibitor-induced genomic instability in cells with FLT3-ITD.