Correction to "Novel Antiproliferative Chimeric Compounds with Marked Histone Deacetylase Inhibitory Activity".

[This corrects the article DOI: 10.1021/ml5000959.].

Phenylpyrrole-based HDAC inhibitors: synthesis, molecular modeling and biological studies.

AIM: Histone deacetylases (HDACs) regulate the expression and activity of numerous proteins involved in the initiation and progression of cancer. Currently, three hydroxamate-containing HDAC pan-inhibitors have been approved as antitumor agents. RESULTS: We herein present the development of a series of novel phenylpyrrole-based derivatives stemmed from combined computational and medicinal chemistry efforts to rationally modulate HDAC1/6 isoform selectivity. In vitro activity on HDAC1 and HDAC6 isoforms and the effects of selected analogs on histone H3 and α-tubulin acetylation levels were determined. Cell-based data evidenced, for selected compounds, a promising antitumor potential and low toxicity on normal cells. CONCLUSION: The newly developed compounds represent a valuable starting point for the development of novel anticancer agents.

ARHGEF3 controls HDACi-induced differentiation via RhoA-dependent pathways in acute myeloid leukemias.

Altered expression and activity of histone deacetylases (HDACs) have been correlated with tumorigenesis. Inhibitors of HDACs (HDACi) induce acetylation of histone and non-histone proteins affecting gene expression, cell cycle progression, cell migration, terminal differentiation and cell death. Here, we analyzed the regulation of ARHGEF3, a RhoA-specific guanine nucleotide exchange factor, by the HDACi MS275 (entinostat). MS275 is a well-known benzamide-based HDACi, which induces differentiation of the monoblastic-like human histiocytic lymphoma cell line U937 to monocytes/macrophages. Incubation of U937 cells with MS275 resulted in an up regulation of ARHGEF3, followed by a significant enhancement of the marker of macrophage differentiation CD68. ARHGEF3 protein is primarily nuclear, but MS275 treatment rapidly induced its translocation into the cytoplasm. ARHGEF3 cytoplasmic localization is associated with activation of the RhoA/Rho-associated Kinase (ROCK) pathway. In addition to cytoskeletal rearrangements orchestrated by RhoA, we showed that ARHGEF3/RhoA-dependent signals involve activation of SAPK/JNK and then Elk1 transcription factor. Importantly, MS275-induced CD68 expression was blocked by exposure of U937 cells to exoenzyme C3 transferase and Y27632, inhibitors of Rho and ROCK respectively. Moreover, ARHGEF3 silencing prevented RhoA activation leading to a reduction in SAPK/JNK phosphorylation, Elk1 activation and CD68 expression, suggesting a crucial role for ARHGEF3 in myeloid differentiation. Taken together, our results demonstrate that ARHGEF3 modulates acute myeloid leukemia differentiation through activation of RhoA and pathways directly controlled by small GTPase family proteins. The finding that GEF protein modulation by HDAC inhibition impacts on cell differentiation may be important for understanding the antitumor mechanism(s) by which HDACi treatment stimulates differentiation in cancer.

The Jumonji family: past, present and future of histone demethylases in cancer.

The first Jumonji gene was cloned in 1995 by Takeuchi et al. [Takeuchi T, Yamazaki Y, Katoh-Fukui Y, Tsuchiya R, Kondo S, Motoyama J, Higashinakagawa T. Gene trap capture of a novel mouse gene, jumonji, required for neural tube formation. Genes Dev 1995; 9: 1211-22.]. Several genes sharing similar biological features have since been discovered, and are currently grouped into the JMJ family. Interestingly, their deregulation has been associated with cardiac disease, obesity, neurological disorders and cancer. One of the mechanisms underlying their function is gene expression modulation via histone post-translational modifications (PTMs). Increasing evidence of Jumonji deregulation in tumours such as colon, prostate, haematological and breast cancer is continually emerging, hence the need to acquire a better understanding. The Genesapiens.org database of patient arrays allows target expression levels to be investigated in a wide range of cancers, corroborating and extending the role of the JMJ family. Here, we provide an overview of the expression profile and regulation of JMJ family members in cancer, examining the most recent literature in the light of analyses drawn from this database.

Novel antiproliferative chimeric compounds with marked histone deacetylase inhibitory activity.

Given our interest in finding potential antitumor agents and in view of the multifactorial mechanistic nature of cancer, in the present work, taking advantage of the multifunctional ligands approach, new chimeric molecules were designed and synthesized by combining in single chemical entities structural features of SAHA, targeting histone deacetylases (HDACs), with substituted stilbene or terphenyl derivatives previously obtained by us and endowed with antiproliferative and pro-apoptotic activity. The new chimeric derivatives were characterized with respect to their cytotoxic activity and their effects on cell cycle progression on different tumor cell lines, as well as their HDACs inhibition. Among the other, trans -6 showed the most interesting biological profile, as it exhibited a strong pro-apoptotic activity in tumor cell lines in comparison with both of its parent compounds and a marked HDAC inhibition.