Recent data suggests an important role for mutations in the spliceosome machinery, which controls the editing of introns from protein coding transcripts, in the development of hematological malignancies. Understanding how this machinery is regulated in cancer cells may provide leads for design of rational therapeutic targets. We demonstrate that several spliceosome proteins are regulated by the sirtuin class of histone deacetylase inhibitors. HDAC inhibitors (HDACi) have proven preclinical and clinical activity against Hodgkin Lymphoma. HDACs are grouped into four categories with classes I, II, and IV, constituting the zinc-dependent family members and class III comprising the seven known NAD+ dependent members known as sirtuins. Current HDAC inhibitors in clinical use have no activity against the NAD+ sirtuins, thus we have designed lead compound inhibitors. AS4.064, a novel selenium analog of thiobarbituric acid designed in our lab, inhibits sirtuins 1 and 3 in enzymatic studies. We demonstrate that Hodgkin and Acute Lymphoblastic Leukemia lines show decreased proliferation and increased apoptosis when treated with the zinc based HDAC inhibitor SelSA-1 and/or with AS4.064 by viability studies and annexin V studies. We have previously demonstrated an important role for c-Myc inhibition in the activity of HDACi in lymphoid malignancies. The combination of AS4.064 and SelSA-1 showed enhanced inhibition of c-Myc protein levels in L540 cells, while the acetylation of p53 at various lysines is differentially enhanced by single agent versus the combination of the two agents. We show changes in DNA damage response elements such as GADD45 and FOXO3A, telomerase, and several related miRNAs enhanced by the combination of the two agents. Interestingly, time dependent increases in several spliceosome enzymes, were confirmed by RT-PCR, with increased binding of AcH3K9 at the U2AF1 promoter in a ChIP assay, after sirtuin inhibition with AS4.064. Transcription of the metabolic enzyme, IDH2, is altered in cells treated with AS4.064 as well. In summary, the novel SIRT1 inhibitor, AS-64, and the novel HDACi, SelSa-1, show growth inhibitory and pro-apoptotic activity in lymphoid leukemia lines, alone and in combination. Sirtuins may be important regulators the spliceosome machinery, and as such may be of biological and therapeutic importance in the hematologic malignancies.

Citation Format: Kimberly A. Scata, Arun K. Sharma, Dhimant Desai, Shantu Amin, Mark H. Kirschbaum. The novel Sirtuin inhibitor AS4.064 induces apoptosis in lymphoid malignancy lines and regulates transcription of spliceosome components and the metabolic enzyme IDH2. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5140. doi:10.1158/1538-7445.AM2014-5140