Retraction: miR-661 expression in SNAI1-induced epithelial to mesenchymal transition contributes to breast cancer cell invasion by targeting Nectin-1 and StarD10 messengers.

At the request of the University of Luxembourg and following an external investigation, the Editor and Publisher have agreed to retract this paper owing to unreliable data.

miR-661 expression in SNAI1-induced epithelial to mesenchymal transition contributes to breast cancer cell invasion by targeting Nectin-1 and StarD10 messengers.

Epithelial to mesenchymal transition (EMT) is a key step toward metastasis. MCF7 breast cancer cells conditionally expressing the EMT master regulator SNAI1 were used to identify early expressed microRNAs (miRNAs) and their targets that may contribute to the EMT process. Potential targets of miRNAs were identified by matching lists of in silico predicted targets and of inversely expressed mRNAs. MiRNAs were ranked based on the number of predicted hits, highlighting miR-661, a miRNA with so far no reported role in EMT. MiR-661 was found required for efficient invasion of breast cancer cells by destabilizing two of its predicted mRNA targets, the cell-cell adhesion protein Nectin-1 and the lipid transferase StarD10, resulting, in turn, in the downregulation of epithelial markers. Reexpression of Nectin-1 or StarD10 lacking the 3'-untranslated region counteracted SNAI1-induced invasion. Importantly, analysis of public transcriptomic data from a cohort of 295 well-characterized breast tumor specimen revealed that expression of StarD10 is highly associated with markers of luminal subtypes whereas its loss negatively correlated with the EMT-related, basal-like subtype. Collectively, our non-a priori approach revealed a nonpredicted link between SNAI1-triggered EMT and the down-regulation of Nectin-1 and StarD10 through the up-regulation of miR-661, which may contribute to the invasion of breast cancer cells and poor disease outcome.

Intracellular routing and inhibitory activity of oligonucleopeptides containing a KDEL motif.

On internalization, oligonucleotides (ODN) remain mostly sequestered in endocytic compartments. To increase their delivery into the cytosol and/or nucleus, which contain their targets, we attempted to guide them into compartments containing the KDEL receptor. Antisense ODN, phosphodiester protected at both ends, that are complementary to the AUG initiation site of gagHIV-1 mRNA (odn) were linked to a peptide ending with the Lys-Asp-Glu-Leu (KDEL) motif in a carboxyl-terminal position (odn-p-KDEL) or with the Lys-Asp-Glu-Ala (odn-p-KDEA) as a control. The effect of odn substitution with a peptide was examined with regard to its accumulation, subcellular location, and activity in HepG2 cells. Although odn-p-KDEL was internalized 4-fold less than the corresponding peptide-free odn, it was 5-fold more efficient in inhibiting gagHIV-1 gene expression in HepG2 cells. The internalization of odn-p-KDEA was as low as that of odn-p-KDEL, but its biological activity was lower, close to that of the peptide-free odn. On endocytosis at 37 degrees, both conjugates as well as the peptide-free odn were found in a neutral environment. However, the substitution of an odn with a KDEL motif altered its intracellular trafficking; most of the odn-p-KDEL was found in the endoplasmic reticulum and in the intermediate compartment as identified by colabeling with either anti-ERGIC-53 or anti-KDEL receptor antibodies. Conversely, odn-p-KDEA and peptide-free odn were localized in vesicular compartments not labeled with these antibodies. In addition, pulse-chase experiments showed that odn-p-KDEL and odn-p-KDEA had a lower efflux than peptide-free odn. Therefore, the large increase in efficiency was due to the KDEL motif.

Synthesis and antiviral activity of peptide-oligonucleotide conjugates prepared by using N alpha-(bromoacetyl)peptides.

Antisense oligonucleotides represent an interesting tool for selective inhibition of gene expression. In order to direct oligonucleotides to specific compartments within the cell, we have investigated the possibility of coupling them to a signal peptide Lys-Asp-Glu-Leu (KDEL). This sequence should be able to convey oligonucleotides to the endoplasmic reticulum and from there to the cytosol and the nucleus where their targets are located. On this basis we prepared peptide-oligonucleotide conjugates by coupling, in a single step, a Nalpha-bromoacetyl peptide with an oligonucleotide bearing a thiol group, through a thioether bond. This paper deals with the definition of the optimal pH and temperature conditions leading to an efficient synthesis of peptide-oligonucleotide conjugates: the reaction was quantitative at pH 7.5 within few hours. This method was first set up using a 5',3'-modified dodecanucleotide and a (bromoacetyl)pentapeptide as a conjugation model. Then a 5',3'-modified pentacosanucleotide, complementary to the translation initiation region of the gag mRNA of HIV, was coupled to a (bromoacetyl)dodecapeptide containing a KDEL signal sequence. The anti-HIV activity of the pentacosanucleotide was compared with that of pentacosanucleotide-dodecapeptide conjugates linked through either a thioether bond or a disulfide bridge. The conjugate with a thioether bond has a higher antiviral activity than the peptide-free oligonucleotide and the conjugate linked via a disulfide bond.