Abstract 2361: Pim kinase inhibition alters mRNA splicing in AML cell lines

Abstract

Abstract Oncogenic kinase activity is a common feature of nearly all cancers and kinases are major targets for therapeutic intervention. Pim kinases are deregulated in hematopoietic cancers including Acute Myeloid Leukemia (AML), as well as prostate cancer. While cancer cells can become dependent on Pim activity to sustain proliferation, in normal adult tissues, Pim kinase activity appears to be dispensable. These features make Pim kinases an attractive target for cancer therapy, however, their physiological roles have not been fully characterized. Using the reverse in-gel kinase assay (RIKA), we identified a battery of novel Pim substrates that are involved in mRNA splicing regulation. We hypothesized that Pim family kinases regulate mRNA splicing through phosphorylation of splicing factors. Microarray analysis revealed more than 10,000 splicing changes in AML cells treated with the highly selective small molecule Pim kinase inhibitor AZD1208. Using RT-PCR analysis, multiple AZD1208-induced splicing changes were validated. To discern the mechanisms whereby Pim kinases regulate splicing, we determined whether Pim inhibition alters phosphorylation of serine/arginine-rich (SR) proteins. Inhibition of serine arginine protein kinase (SRPK) activity using a small molecular inhibitor (SRPIN340) reduced SR protein phosphorylation, whereas Pim kinase inhibition did not, suggesting that Pim kinases regulate splicing through an SRPK independent pathway. Comparison of splicing changes in AZD1208 and SRPIN340 treated AML cells demonstrated distinct patterns, providing further evidence of SRPK-independent splicing regulation by Pim kinases. Biomarkers of kinase inhibitor efficacy are critical components of clinical trials. These data suggest that changes in mRNA splicing may serve as a biomarker for assessing patient responsiveness to Pim inhibition therapy. Citation Format: Tejashree A. Joglekar, Xiang Li, Charles J. Bieberich. Pim kinase inhibition alters mRNA splicing in AML cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2361. doi:10.1158/1538-7445.AM2017-2361