Novel Hdac Inhibitor Sbak-Gha: Potential Therapuetic Molecule For Lymophocytic Leukaemia

In cancer cells, an imbalance exists between Histone acetylase(HAT) and Histone deacetylase(HDAC) activities and current research focuses actively on seeking competitive HDAC inhibitors (HDACi) for chemotherapeutic intervention.We have designed and synthesized a library of novel HDACi molecules from naturally occurring boswellic acids as an alternate CAP for already validated pharmacophore of suberanilohydroxamic acid (SAHA).Novel HDACi molecules were screened against a panel of cancer cell lines. A lead HDACi i.e.N1-hydroxy-N5-(3-α-hydroxy-11-oxo-24-norurs-12-en-4-yl) glutaramide (SBAK-GHA) having IC50 of 1.5µM against leukaemia HL-60 cell line and 6µM in enzyme based assay was obtained. Further HDACi, isoform evaluation was done for SBAK-GHA and it was found to be HDAC Class 1 Specific, especially against HDAC 2 (IC50 of 200 nM) and HDAC 8(IC50 of 250 nM). Acetylation level of different histone residues on H3 and H4 upon SBAK-GHA treatment in HL-60 cell line was studied by immunoblotting. HDACi, SAHA and Sodium Butyrate (NaB) were used as positive controls to compare acetylation levels of different H3 and H4 residues.SAHA and NaB showed significant increase in H3K9, H3K14, H3K27, H4K5, H4K12, and H4K16 acetylation levels while H3K18 showed mild change in acetylation levels. On the other hand SBAK-GHA showed significant increase in acetylation levels of all the lysine residues of histone H3 and H4 especially H4K16 in comparison to SAHA and NaB. In order to analyse varied expression of cyclins and their corresponding control of different phases of cell cycle, we performed chromatin immunoprecipitation assay (ChIP) and observed acetylation pattern of different histone (H3 and H4) residues regulates cyclins differently. In order to analyse the correlation of acetylation on different H3 and H4 residues and their varied pattern of regulation of cyclins, we next analyzed the effect of SBAK-GHA on different cell cycle events in HL-60 cells and found G1 phase cell cycle arrest at significantly low concentration (1µM).We further observed SBAK-GHA induced apoptosis at lower concentrations while as autophagy was found at higher concentrations. Furthermore,we conducted mitochondrial membrane potential studies of SBAK-GHA in HL-60 cells and observed significant loss in mitochondrial membrane potential. We took our findings from in vitro studies and analysed effect of SBAK-GHA on different in vivo murine models. SBAK-GHA showed significant activity especially against P388 lymphocytic leukemia compared to SAHA and 5-FU. Moreover, SBAK-GHA showed promising activity against Ehrlich Ascites Carcinoma (EAC). In conclusion our findings indicate that our lead molecule of interest have great therapeutic potential singly or in combination, however further mechanism of action needs to be elucidated before taking it from Bench to Bedside. Note: This abstract was not presented at the meeting. Citation Format: Javeed Ahmad Bhat, Mudassier Ahmad, Nawab John Dar, Aashiq Hussain, Rauf Ahmad Najar, Simmi Sharma, Mubashir Javeed Minto, Dilip Manikrao Mondhe, Vaqar M. Adhami, Bhahwal Ali Shah, Neena caplash, Abid Hamid*. Novel HDAC inhibitor SBAK-GHA: potential therapuetic molecule for lymophocytic leukaemia [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 1376. doi:10.1158/1538-7445.AM2017-1376