Molecular and cellular basis for the anti-proliferative effects of the HDAC inhibitor LAQ824.
We have developed a cinnamic hydroxamic class of histone deacetylase inhibitors of which a prototype was designated as NVP-LAQ824. NVP-LAQ824, inhibits histone deacetylase enzymatic activities in vitro and transcriptionally activated the p21 promoter in reporter gene assays. When tested on a variety of solid tumour cell lines, NVP-LAQ824 exhibited selective anti-proliferative effects, inducing cell growth inhibition in some, while inducing cell death in others. To induce cell death, a minimum of 16 h exposure to NVP-LAQ824 is required. Flow cytometry studies revealed that both tumour cell lines and normal diploid fibroblasts arrested in the G2/M phase of the cell cycle after compound treatment. However, an increased sub-G1 population at 48 h (reminiscent of apoptotic cells) was only observed in the cancer cell lines. Annexin V staining data confirmed that NVP-LAQ824 induced apoptosis in tumour cells, but not in normal cells. To relate HDAC inhibition to the anti-proliferative effects of NVP-LAQ824, expression of HDAC 1 was inhibited using antisense and this was sufficient to activate p21 expression, hypophosphorylate Rb and inhibit cell growth. Furthermore, tumour cells treated with NVP-LAQ824 caused acetylation of HSP90 and degradation of its cargo oncoproteins. Finally, NVP-LAQ824 exhibited antitumour effects in a xenograft animal model. To determine if NVP-LAQ824 inhibited histone deacetylases in vivo, tumours treated with the drug were immunoblotted with an antibody specific for acetylated histones H3 and H4 and the results indicated increased histone H3 and 114 acetylation levels in NVP-LAQ824 treated cancer cells. Together, our data indicated that the activity of NVP-LAQ824 was consistent with its intended mechanism of action. This novel HDAC inhibitor is currently in clinical trials as an anticancer agent.
Atadja
Peter
P
Department of Oncology Molecular and Cellular Biology, Novartis Institutes for Biomedical Research, East Hanover, NJ 07936, USA.
Hsu
Meier
M
Kwon
Paul
P
Trogani
Nancy
N
Bhalla
Kapil
K
Remiszewski
Stacy
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D011401:Promoter Regions, Genetic; D014407:Tumor Cells, Cultured
C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C477361:LAQ824