State-of-the-art small interfering RNA (siRNA) therapeutics such as givosiran and fitusiran are constructed from three variable components: a fully-modified RNA core that conveys metabolic stability, ...a targeting moiety that mediates target-cell uptake, and a linker. This structural complexity poses challenges for metabolite characterization and risk assessment after long-term patient exposure. In this study, we show that basic phosphorothioate modification of a siRNA targeting the oncoprotein Lin28B provides a useful increase in metabolic stability, without greatly compromising potency. We found that its stability
in vitro
matched that of nanoparticle-free patisiran in serum and surpassed it in liver tritosome extracts, although it did not reach the stability of the fitusiran siRNA core structure. Liver and kidney were the main sites of accumulation after its subcutaneous administration in mice. Despite the lack of a delivery agent-free antitumor effect, we anticipate our study to be a starting point to develop alternative siRNA scaffolds that can be degraded into naturally-occurring metabolites and help alleviate the aforementioned challenges. Furthermore, Lin28B is a promising target for cancers, and the development of such simplified siRNA analogs, possibly together with novel targeting units, holds potential.
The involvement of the ErbB receptor tyrosine kinases in human cancer, as well as their essential role in a variety of physiological events during normal development, have motivated the interest in ...this receptor family. Approaches taken to block the activity of ErbB receptors in cancer cells have not only proven that they drive in vitro tumor cell proliferation, but have also become clinically relevant for targeting tumors with deregulated ErbB signaling. The mechanisms and downstream effectors through which the ErbB receptors influence processes linked to malignant development, including proliferation, cell survival, angiogenesis, migration, and invasion, are, however, only now becoming apparent. Our particular emphasis in this review will be on how ErbB receptors, in particular ErbB1 and ErbB2, contribute to processes linked to cancer progression. Importantly, in keeping with the emerging theme that ErbB receptors do not function in isolation, we will focus on receptor cooperativity, i.e., ErbB1 cooperates with other classes of receptors, and the ligand-less ErbB2 functions as a heterodimer with other ErbBs.
Mutations and deletions in components of ubiquitin ligase complexes that lead to alterations in protein turnover are important mechanisms in driving tumorigenesis. Here we describe an alternative ...mechanism involving upregulation of the microRNA miR-424 that leads to impaired ubiquitination and degradation of oncogenic transcription factors in prostate cancers. We found that miR-424 targets the E3 ubiquitin ligase COP1 and identified STAT3 as a key substrate of COP1 in promoting tumorigenic and cancer stem-like properties in prostate epithelial cells. Altered protein turnover due to impaired COP1 function led to accumulation and enhanced basal and cytokine-induced activity of STAT3. We further determined that loss of the ETS factor ESE3/EHF is the initial event that triggers the deregulation of the miR-424/COP1/STAT3 axis. COP1 silencing and STAT3 activation were effectively reverted by blocking of miR-424, suggesting a possible strategy to attack this key node of tumorigenesis in ESE3/EHF-deficient tumors. These results establish miR-424 as an oncogenic effector linked to noncanonical activation of STAT3 and as a potential therapeutic target.
A Small-Molecule Inhibitor of Lin28 Roos, Martina; Pradère, Ugo; Ngondo, Richard P ...
ACS chemical biology,
10/2016, Letnik:
11, Številka:
10
Journal Article
Recenzirano
New discoveries in RNA biology underscore a need for chemical tools to clarify their roles in pathophysiological mechanisms. In certain cancers, synthesis of the let-7 microRNA tumor suppressor is ...blocked by an RNA binding protein (RBP) Lin28, which docks onto a conserved sequence in let-7 precursor RNA molecules and prevents their maturation. Thus, the Lin28/let-7 interaction might be an attractive drug target, if not for the well-known difficulty in targeting RNA-protein interactions with drugs. Here, we describe a protein/RNA FRET assay using a GFP-Lin28 donor and a black-hole quencher (BHQ)-labeled let-7 acceptor, a fluorescent protein/quencher combination which is rarely used in screening despite favorable spectral properties. We tested 16 000 molecules and identified N-methyl-N-3-(3-methyl1,2,4triazolo4,3-bpyridazin-6-yl)phenylacetamide, which blocked the Lin28/let-7 interaction, rescued let-7 processing and function in Lin28-expressing cancer cells, induced differentiation of mouse embryonic stem cells, and reduced tumor-sphere formation by 22Rv1 and Huh7 cells. A biotinylated derivative captured Lin28 from cell lysates consistent with an on-target mechanism in cells, though the compound also showed some activity against bromodomains in selectivity assays. The Lin28/let-7 axis is presently of high interest not only for its role as a bistable switch in stem-cell biology but also because of its prominent roles in numerous diseases. We anticipate that much can be learned from the use of this first reported small molecule antagonist of Lin28, including the potential of the Lin28/let-7 interaction as a new drug target for selected cancers. Furthermore, this approach to assay development may be used to identify antagonists of other RBP/RNA interactions suspected to be operative in pathophysiological mechanisms.
A series of novel σ1 receptor ligands with a 4‐(2‐aminoethyl)piperidine scaffold was prepared and biologically evaluated. The underlying concept of our project was the improvement of the lipophilic ...ligand efficiency of previously synthesized potent σ1 ligands. The key steps of the synthesis comprise the conjugate addition of phenylboronic acid at dihydropyridin‐4(1H)‐ones 7, homologation of the ketones 8 and introduction of diverse amino moieties and piperidine N‐substituents. 1‐Methylpiperidines showed particular high σ1 receptor affinity and selectivity over the σ2 subtype, whilst piperidines with a proton, a tosyl moiety or an ethyl moiety exhibited considerably lower σ1 affinity. Molecular dynamics simulations with per‐residue binding free energy deconvolution demonstrated that different interactions of the basic piperidine‐N‐atom and its substituents (or the cyclohexane ring) with the lipophilic binding pocket consisting of Leu105, Thr181, Leu182, Ala185, Leu186, Thr202 and Tyr206 are responsible for the different σ1 receptor affinities. Recorded logD7.4 and calculated clogP values of 4a and 18a indicate low lipophilicity and thus high lipophilic ligand efficiency. Piperidine 4a inhibited the growth of human non‐small cell lung cancer cells A427 to a similar extent as the σ1 antagonist haloperidol. 1‐Methylpiperidines 20a, 21a and 22a showed stronger antiproliferative effects on androgen negative human prostate cancer cells DU145 than the σ1 ligands NE100 and S1RA.
Seven to eight reaction steps led to novel σ1 receptor ligands with a 4‐(2‐aminoethyl)‐2‐phenylpiperidine scaffold. 1‐Methylpiperidine derivatives show high σ1 affinity, considerable selectivity over the σ2 subtype, and an improved Lipophilicity‐corrected Ligand Efficiency (LELP) index. Molecular dynamics simulations with per‐residue binding free energy deconvolution demonstrated that different interactions of the basic piperidine N atom and its substituents with the lipophilic binding pocket are responsible for the different σ1 receptor affinities. 1‐Methylpiperidine derivatives show antiproliferative activity against the human prostate cancer cell line DU145.
Cancer stem cells (CSC) play a significant role in tumor progression, disease recurrence, and treatment failure. Here, we show that the endogenously expressed ETS transcription factor ESE3/EHF ...controls prostate epithelial cell differentiation and stem-like potential. We found that loss of ESE3/EHF induced epithelial-to-mesenchymal transition (EMT), stem-like features, and tumor-initiating and metastatic properties in prostate epithelial cells, and reexpression of ESE3/EHF inhibited the stem-like properties and tumorigenic potential of prostate cancer cells. Mechanistically, ESE3/EHF repressed the expression of key EMT and CSC genes, including TWIST1, ZEB2, BMI1, and POU5F1. Analysis of human tissue microarrays showed that reduced ESE3/EHF expression is an early event in tumorigenesis, frequently occurring independently of other ETS gene alterations. Additional analyses linked loss of ESE3/EHF expression to a distinct group of prostate tumors with distinctive molecular and biologic characteristics, including increased expression of EMT and CSC genes. Low ESE3/EHF expression was also associated with increased biochemical recurrence of prostate cancer and reduced overall survival after prostatectomy. Collectively, our findings define a key role for ESE3/EHF in the development of a subset of prostate tumors and highlight the clinical importance of identifying molecularly defined tumor subgroups.
A series of novel σ
receptor ligands with a 4-(2-aminoethyl)piperidine scaffold was prepared and biologically evaluated. The underlying concept of our project was the improvement of the lipophilic ...ligand efficiency of previously synthesized potent σ
ligands. The key steps of the synthesis comprise the conjugate addition of phenylboronic acid at dihydropyridin-4(1H)-ones 7, homologation of the ketones 8 and introduction of diverse amino moieties and piperidine N-substituents. 1-Methylpiperidines showed particular high σ
receptor affinity and selectivity over the σ
subtype, whilst piperidines with a proton, a tosyl moiety or an ethyl moiety exhibited considerably lower σ
affinity. Molecular dynamics simulations with per-residue binding free energy deconvolution demonstrated that different interactions of the basic piperidine-N-atom and its substituents (or the cyclohexane ring) with the lipophilic binding pocket consisting of Leu105, Thr181, Leu182, Ala185, Leu186, Thr202 and Tyr206 are responsible for the different σ
receptor affinities. Recorded logD
and calculated clogP values of 4a and 18a indicate low lipophilicity and thus high lipophilic ligand efficiency. Piperidine 4a inhibited the growth of human non-small cell lung cancer cells A427 to a similar extent as the σ
antagonist haloperidol. 1-Methylpiperidines 20a, 21a and 22a showed stronger antiproliferative effects on androgen negative human prostate cancer cells DU145 than the σ
ligands NE100 and S1RA.
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