HDAC3 is linked to cell cycle machinery in MiaPaCa2 cells by regulating transcription of skp2

Nuclear receptor corepressor complexes in cancer: mechanism, function and regulation

Nuclear receptor corepressor (NCoR) and silencing mediator for retinoid and thyroid hormone receptors (SMRT) function as corepressors for diverse transcription factors including nuclear receptors such as estrogen receptors and androgen receptors. Deregulated functions of NCoR and SMRT have been observed in many types of cancers and leukemias. NCoR and SMRT directly bind to transcription factors and nucleate the formation of stable complexes that include histone deacetylase 3, transducin b-like protein 1/TBL1-related protein 1, and G-protein pathway suppressor 2. These NCoR/SMRT-interacting proteins also show deregulated functions in cancers. In this review, we summarize the literature on the mechanism, regulation, and function of the core components of NCoR/SMRT complexes in the context of their involvement in cancers and leukemias. While the current studies support the view that the corepressors are promising targets for cancer treatment, elucidation of the mechanisms of corepressors involved in individual types of cancers is likely required for effective therapy.

Acetylation as a transcriptional control mechanism-HDACs and HATs in pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant tumors with a dismal prognosis. Although our understanding of the carcinogenesis of the disease increases continuously, no effective conservative therapeutic strategies exist. Therefore, novel targets have to be defined at the experimental level. Histone deacetylases (HDACs), especially the class I isoenzymes HDAC1, 2, and 3, are highly expressed in PDAC.

CONCLUSION

This article summarizes the expression and functions of HDAC isoenzymes in PDAC, with a special focus on their promoter-specific mode of action. Although we have gained some molecular insight into the HDAC function in PDAC, less is known about the relevance of histone acetyltransferases (HATs) in PDAC. As an example, we will summarize function of the HAT p300, for which promoter-specific functions were described recently. Increasing the molecular insights into the functions of the acetylating and deacetylating machineries in PDAC are important, since this will lead to novel rationally based therapeutic strategies in the future.

Synthesis and biological evaluation of triazol-4-ylphenyl-bearing histone deacetylase inhibitors as anticancer agents

Our triazole-based histone deacetylase inhibitor (HDACI), octanedioic acid hydroxyamide[3-(1-phenyl-1H-[1,2,3]triazol-4-yl)phenyl]amide (4a), suppresses pancreatic cancer cell growth in vitro with the lowest IC(50) value of 20 nM against MiaPaca-2 cell. In this study, we continued our efforts to develop triazol-4-ylphenyl bearing hydroxamate analogues by embellishing the terminal phenyl ring of 4a with different substituents. The isoform inhibitory profile of these hydroxamate analogues was similar to those of 4a. All of these triazol-4-ylphenyl bearing hydroxamates are pan-HDACIs like SAHA. Moreover, compounds 4h and 11a were found to be very effective inhibitors of cancer cell growth in the HupT3 (IC(50) = 50 nM) and MiaPaca-2 (IC(50) = 40 nM) cancer cell lines, respectively. Compound 4a was found to reactivate the expression of CDK inhibitor proteins and to suppress pancreatic cancer cell growth in vivo. Taken together, these data further support the value of the triazol-4-ylphenyl bearing hydroxamates in identifying potential pancreatic cancer therapies.

Targeting histone deacetylases in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a median survival below 6 months and a 5-year survival rate below 1%. Effective therapies for locally advanced or metastatic tumours are missing and curatively resected patients relapse in over 80% of the cases. Although histone deacetylases (HDACs) are involved in the control of proliferation, apoptosis, differentiation, migration and angiogenesis of cancer cells, knowledge about the expression patterns and functions of individual HDAC isoenzymes in pancreatic cancer is sparse. This review summarizes the roles of HDACs as novel therapeutic targets and the molecular mode of action of HDAC-inhibitors (HDACI) in PDACs. Success of HDACI in clinical settings will depend on an increased knowledge of HDAC functions as well as on a better understanding of the mode of action of HDACI. Pre-clinical experimental data that constitute the basis for rational therapeutic strategies to treat PDAC are described here. Translating these rational-based therapies into the clinic will finally increase our chance to establish an effective HDACI-containing combination therapy effective against PDAC.

New insights into the functions and regulation of the transcriptional corepressors SMRT and N-CoR

Corepressors are large proteins that facilitate transcriptional repression through recruitment of histone-modifying enzymes. Two major corepressors, SMRT (silencing mediator for retinoid and thyroid hormone receptors) and N-CoR (nuclear receptor corepressor), have been shown to mediate repression associated with nuclear receptors and a myriad of other transcription factors. This review will focus on recent studies on these proteins, including newly discovered physiological roles of the corepressors, their modes of regulation, their roles in antiestrogen-resistant breast cancer and their functions during the cell cycle.