INTRODUCTION The discovery of the role of HDACs within cancer has promoted the synthesis of inhibitors to HDACs which show a targeted action within the cancer cells. The primary role of HDACs is the regulation of the formation of heterochromatin. It deacetylates the histones and enables the chromatin to attain a more compact form. Some HDAC enzymes also target non histone proteins like NFB and p53. The targeted action of HDAC inhibitors can be understood well with the help of Vorinostat which selectively targets the HDACs belonging to classes I and II. MC1568 is another inhibitor which inhibits the action of HDACs belonging to classes IIa and IIb. SELECTIVE ACTION OF MC1568 ON HDACs BELONGING TO CLASS II ALTERS CELLULAR DIFFERENTIATION A detailed analysis shows that HDACs belonging to class II, play a primary role in regulating the process of differentiation. They are involved in the processes of myogenesis (formation of myocytes), neuronal differentiation (formation of nerve cells) and osteogenesis. HDACs belonging to class IIa compete with p300 (which acts as histone acetyl transferase), for its binding site on MEF2. It ultimately modulates the differentiation of myocytes. HDAC6 which belongs to the class IIb of HDACs performs a unique function which is increasing the acetylation of tubulin protein. This ultimately affects the motility of the cell. Nuclear receptors are involved in the regulation of the transcription of ESR1, PPAR and RAR. HDACs belonging to class II inhibit the process of differentiation instigated by nuclear receptors. MC1568 inhibits class II HDACs under in vitro and in vivo conditions and hence stimulates the process of differentiation. It interferes with the NR-RAR/ PPAR involved differentiation pathways. Within F9 cells it checks the differentiation of endodermal cells. MC1568 helps in understanding the specific roles of HDACs belonging to class II [1]. MC1568 HELPS IN UNDERSTANDING THE MECHANISM BEHIND THE TNF RELATED APOPTOSIS Chronic leukemia within lymphocytes offers a strong resistance to TRAIL stimulated apoptosis process. Molecular basis behind this resistance is not clear; however inhibitors which can sensitize the cells to TRAIL will prove to be efficient in stimulating the process of apoptosis within these lymphocytes. To asses its efficiency in restoring apoptosis within CLL cells, MC1568 was administered along with Entinostat. These two inhibitors specifically target the HDACs belonging to class II and did not stimulate the process of apoptois stimulated by the cleavage of caspase-3 or PARP. Instead inhibitors which target the action of HDACs belonging to class I (especially HDAC1 and HDAC2) are proved to be more efficient in stimulating TRAIL induced apoptosis. Inhibition of HDAC8 or HDAC3 played no role in stimulating apoptosis [2]. MC1568 HELPS IN RESEARCH MC1568 is obtained from the compound library of hydroxamate derivatives. MC1568 shows tissue specific action and represses the function of MEF2 under in vivo conditions. It inhibits the action of HDAC5 and 4 within the skeletal muscles [3]. MC1568 stimulates the hyperacetylation of Cx43 at N-lysine residues. Hence it can prove to be efficient in restoring the cardiac function [4]. CONCLUSION It is a specific inhibitor of HDACs belonging to class II and stimulates the process of differentiation. This molecule has helped in analyzing the role of HDAC class II enzymes. REFERENCES 1. Nebbioso A, Bugge A, et al. HDACs class II-selective inhibition alters nuclear receptor-dependent differentiation. J Mol Endocrinol 2010 Oct 1; 45: 219-228. 2. Inoue S, Mai A, et al. Inhibition of Histone Deacetylase Class I but not Class II Is Critical for the Sensitization of Leukemic Cells to Tumor Necrosis Factorâ€Related Apoptosis-Inducing Ligandâ€Induced Apoptosis. Cancer Res 2006 July 1; 66: 6785. 3. Nebbioso A, Manzo F, et al. Selective class II HDAC inhibitors impair myogenesis by modulating the stability and activity of HDACâ€MEF2 complexes. EMBO Rep 2009 July; 10(7): 776â€782. 4. Colussia C, Rosatib J, et al. N-lysine acetylation determines dissociation from GAP junctions and lateralization of connexin 43 in normal and dystrophic heart. PNAS 2011 Feb15; 108(7): 2795-2800. Related Posts: LBH589 - REACTIVATES THE EXPRESSION OF SILENCED ER LAQ824 (NVP-LAQ824) †SHOWS VARIED EFFECTS IN DIFFERENT TUMORS
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