Discovery of first-in-class reversible dual small molecule inhibitors against G9a and DNMTs in hematological malignancies.

The indisputable role of epigenetics in cancer and the fact that epigenetic alterations can be reversed have favoured development of epigenetic drugs. In this study, we design and synthesize potent novel, selective and reversible chemical probes that simultaneously inhibit the G9a and DNMTs methyltransferase activity. In vitro treatment of haematological neoplasia (acute myeloid leukaemia-AML, acute lymphoblastic leukaemia-ALL and diffuse large B-cell lymphoma-DLBCL) with the lead compound CM-272, inhibits cell proliferation and promotes apoptosis, inducing interferon-stimulated genes and immunogenic cell death. CM-272 significantly prolongs survival of AML, ALL and DLBCL xenogeneic models. Our results represent the discovery of first-in-class dual inhibitors of G9a/DNMTs and establish this chemical series as a promising therapeutic tool for unmet needs in haematological tumours.

Thrombospondin-1 Mimetic Agonist Peptides Induce Selective Death in Tumor Cells: Design, Synthesis, and Structure-Activity Relationship Studies.

Thrombospondin-1 (TSP-1) is a glycoprotein considered as a key actor within the tumor microenvironment. Its binding to CD47, a cell surface receptor, triggers programmed cell death. Previous studies allowed the identification of 4N1K decapeptide derived from the TSP-1/CD47 binding epitope. Here, we demonstrate that this peptide is able to induce selective apoptosis of various cancer cell lines while sparing normal cells. A structure-activity relationship study led to the design of the first serum stable TSP-1 mimetic agonist peptide able to trigger selective programmed cell death (PCD) of at least lung, breast, and colorectal cancer cells. Altogether, these results will be of valuable interest for further investigation in the design of potent CD47 agonist peptides, opening new perspectives for the development of original anticancer therapies.

The asymmetric binding of PGC-1α to the ERRα and ERRγ nuclear receptor homodimers involves a similar recognition mechanism.

BACKGROUND: PGC-1α is a crucial regulator of cellular metabolism and energy homeostasis that functionally acts together with the estrogen-related receptors (ERRα and ERRγ) in the regulation of mitochondrial and metabolic gene networks. Dimerization of the ERRs is a pre-requisite for interactions with PGC-1α and other coactivators, eventually leading to transactivation. It was suggested recently (Devarakonda et al) that PGC-1α binds in a strikingly different manner to ERRγ ligand-binding domains (LBDs) compared to its mode of binding to ERRα and other nuclear receptors (NRs), where it interacts directly with the two ERRγ homodimer subunits. METHODS/PRINCIPAL FINDINGS: Here, we show that PGC-1α receptor interacting domain (RID) binds in an almost identical manner to ERRα and ERRγ homodimers. Microscale thermophoresis demonstrated that the interactions between PGC-1α RID and ERR LBDs involve a single receptor subunit through high-affinity, ERR-specific L3 and low-affinity L2 interactions. NMR studies further defined the limits of PGC-1α RID that interacts with ERRs. Consistent with these findings, the solution structures of PGC-1α/ERRα LBDs and PGC-1α/ERRγ LBDs complexes share an identical architecture with an asymmetric binding of PGC-1α to homodimeric ERR. CONCLUSIONS/SIGNIFICANCE: These studies provide the molecular determinants for the specificity of interactions between PGC-1α and the ERRs, whereby negative cooperativity prevails in the binding of the coactivators to these receptors. Our work indicates that allosteric regulation may be a general mechanism controlling the binding of the coactivators to homodimers.

Involvement of the DNA repair protein hHR23 in p53 degradation.

The stability of the tumor suppressor protein p53 is regulated via the ubiquitin-proteasome-dependent proteolytic pathway. Like most substrates of this pathway, p53 is modified by the attachment of polyubiquitin chains prior to proteasome-mediated degradation. However, the mechanism(s) involved in the delivery of polyubiquitylated p53 molecules to the proteasome are currently unclear. Here, we show that the human DNA repair protein hHR23 binds to polyubiquitylated p53 via its carboxyl-terminal ubiquitin-associated (Uba) domain shielding p53 from deubiquitylation in vitro and in vivo. In addition, downregulation of hHR23 expression within cells by RNA interference results in accumulation of p53. Since the Ubl domain of hHR23 has been shown to interact with the 26S proteasome, we propose that hHR23 is intrinsically involved in the delivery of polyubiquitylated p53 molecules to the proteasome. In this model, the Uba domain of hHR23 binds to polyubiquitin chains formed on p53 and protects them from deubiquitylation, while the Ubl domain delivers the polyubiquitylated p53 molecules to the proteasome.