Date of Award
Doctor of Philosophy
M Mahmun MMH Hossain
James JC Cook, Alexander AA Arnold, Xiaohua XP Peng, Arsenio AP Pacheco
Anticancer Activity, Epigenetics, HDAC Inhibitors, HDACs and HATs, Mechanistic Study, Memory Enhancement
PART I: DEVELOPMENT OF A NOVEL, SMALL-MOLECULE HISTONE DEACETYLASE INHIBITOR THAT ENHANCES SPATIAL MEMORY FORMATION IN MICE
Histone acetylation is a prominent epigenetic modification linked to the memory loss symptoms associated with aging and neurodegenerative disease. The acetylation of histones promotes gene transcription, which is essential to the formation of long-term memories. Thus, compounds that maintain histone acetylation, called histone deacetylase inhibitors (HDACi), are promising therapeutics to treat memory loss associated with aging and neurodegenerative disease. However, the use of existing HDAC inhibitors for the treatment of central nervous system disorders is ruled out due to their poor permeability across the blood-brain barrier and the associated undesirable toxicity. In this project, we aimed to address these shortcomings by developing a new class of disulfide-based compounds inspired by the FDA-approved HDACi romidepsin (FK288, Istodax). The synthesis and purification of several newly designed compounds have been performed, and their biological activities have been evaluated. In our findings, we found that our lead compound, MJM-1, increases overall levels of histone 3 (H3) acetylation and also displays cytotoxicity against prostate cancer cell line (DU 145). Utilizing the maximum tolerable dose determination assay, we observed that MJM-1 has a promising safety profile in mice compared to romidepsin. The pharmacokinetic study of MJM-1 showed that when administered intraperitoneally (i.p.), it crosses the blood-brain barrier (BBB) rapidly and travels to the hippocampus, a critical brain region that is responsible for memory formation. Consistent with this finding, we demonstrate that post-training i.p. administration of MJM-1 enhances hippocampus-dependent spatial, but not object recognition, memory consolidation in male mice. These findings collectively demonstrate that MJM-1 is a promising HDACi with low systemic toxicity and has beneficial effects on memory formation. Thus, MJM-1 represents a potential lead for further optimization as a therapeutic strategy for ameliorating cognitive deficits in aging and neurodegenerative diseases.
PART II: SYNTHESIS AND SAR STUDIES OF NOVEL HDAC INHIBITORS ON PROSTATE CANCER CELL LINE: MECHANISTIC INSIGHTS TOWARDS ANTICANCER ACTIVITY
We discovered that disulfide-based HDAC inhibitor MJM-1 has promising anticancer properties against prostate tumor cell line (DU145). This led us to investigate its structure-activity relationship (SAR) in order to develop more potent HDACi for prostate cancer. Initially, several series of analogs were synthesized based on the structure of MJM-1 by following the typical pharmacophore model. We then assessed the potency of the analogs by analyzing their effects on the viability of prostate cancer cell line (DU145). A number of newly synthesized analogs have been shown to have better antiproliferative activity than MJM-1. This prompted us to examine their biological mechanism of action in the prostate tumor cell. We performed a variety of cell-based bioassays to investigate the mode of action of three lead compounds from three different series. The acetylation level of histone H3 was initially assessed by using immunofluorescence (IF) microscopy, which showed a very high increment of H3 acetylation by all three analogs in a dose-dependent manner. Based on HDAC inhibition assays, it was found that all three analogs inhibited both class I and class II recombinant purified enzymes through the prodrug mechanism, while the degree of inhibitory activity varied between the analogs. Multiple IF-based assays have been conducted to verify whether these analogs induce caspase-mediated apoptosis in cells and the results indicate that all of these analogs cause cell death via this mechanism. Further, we explored their possible involvement in the induction of reactive oxygen species (ROS) generation in both nucleus and cytoplasmic area with a view to understanding the molecular events responsible for their mode of action. Interestingly, all three analogs generated ROS, but the localization of ROS differed between the nucleus and the cytoplasm. Overall, the results suggest that all three lead compounds showed promising antiproliferative effects on prostate cancer cell by increasing the level of H3 acetylation and through the caspase 3/7 mediated apoptotic pathway that concomitantly generates ROS.
Belayet, Jawad Bin, "Part I: Development of a Novel, Small-Molecule Histone Deacetylase Inhibitor That Enhances Spatial Memory Formation in Mice Part II: Synthesis and SAR Studies of Novel HDAC Inhibitors on Prostate Cancer Cell Line: Mechanistic Insights Towards Anticancer Activity" (2022). Theses and Dissertations. 2869.
Available for download on Saturday, May 25, 2024