The E3 ubiquitin ligase TRIP12 participates in cell cycle progression and chromosome stability.

Several studies have linked the E3 ubiquitin ligase TRIP12 (Thyroid hormone Receptor Interacting Protein 12) to the cell cycle. However, the regulation and the implication of this protein during the cell cycle are largely unknown. In this study, we show that TRIP12 expression is regulated during the cell cycle, which correlates with its nuclear localization. We identify an euchromatin-binding function of TRIP12 mediated by a N-terminal intrinsically disordered region. We demonstrate the functional implication of TRIP12 in the mitotic entry by controlling the duration of DNA replication that is independent from its catalytic activity. We also show the requirement of TRIP12 in the mitotic progression and chromosome stability. Altogether, our findings show that TRIP12 is as a new chromatin-associated protein with several implications in the cell cycle progression and in the maintenance of genome integrity.

Elaboration of a thermosensitive smart biomaterial: From synthesis to the ex vivo bioadhesion evaluation.

Alginate and chitosan are polysaccharides that are widely used in the biomedical field, especially as wound dressings. Controlled bioadhesion is an advanced functionality that offers the potential to reduce injuries due to the stripping-off of the biomaterial. Herein, we report the efficient grafting of poly-N(isopropylacryamide) (PNIPAM), a thermosensitive polymer that exhibits a lower critical solution temperature (LCST) at 32 °C on the alginate/chitosan polyelectrolyte complex (PEC) surface. In vitro studies did not exhibit a cytotoxic effect, and cells adhered preferentially on the LCST on PNIPAM grafted surfaces, as reported in the literature. Ex vivo investigations revealed that the adhesive behavior of the biomaterials was not the same on the liver and pancreas. The effect of the temperature on the bioadhesion to organs was unexpected, as PNIPAM surfaces exhibited higher adhesion at low temperature. The PNIPAM was therefore able to confer PEC matrix thermosensitivity, but due to the application force, interactions between PNIPAM chains and their substrate could influence bioadhesion on tissues.

PNIPAM grafted surfaces through ATRP and RAFT polymerization: Chemistry and bioadhesion.

Biomaterials surface design is critical for the control of materials and biological system interactions. Being regulated by a layer of molecular dimensions, bioadhesion could be effectively tailored by polymer surface grafting. Basically, this surface modification can be controlled by radical polymerization, which is a useful tool for this purpose. The aim of this review is to provide a comprehensive overview of the role of surface characteristics on bioadhesion properties. We place a particular focus on biomaterials functionalized with a brush surface, on presentation of grafting techniques for "grafting to" and "grafting from" strategies and on brush characterization methods. Since atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization are the most frequently used grafting techniques, their main characteristics will be explained. Through the example of poly(N-isopropylacrylamide) (PNIPAM) which is a widely used polymer allowing tuneable cell adhesion, smart surfaces involving PNIPAM will be presented with their main modern applications.

miR-219-1-3p is a negative regulator of the mucin MUC4 expression and is a tumor suppressor in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal cancers in the world with one of the worst outcome. The oncogenic mucin MUC4 has been identified as an actor of pancreatic carcinogenesis as it is involved in many processes regulating pancreatic cancer cell biology. MUC4 is not expressed in healthy pancreas whereas it is expressed very early in pancreatic carcinogenesis. Targeting MUC4 in these early steps may thus appear as a promising strategy to slow-down pancreatic tumorigenesis. miRNA negative regulation of MUC4 could be one mechanism to efficiently downregulate MUC4 gene expression in early pancreatic neoplastic lesions. Using in silico studies, we found two putative binding sites for miR-219-1-3p in the 3'-UTR of MUC4 and showed that miR-219-1-3p expression is downregulated both in PDAC-derived cell lines and human PDAC tissues compared with their normal counterparts. We then showed that miR-219-1-3p negatively regulates MUC4 mucin expression via its direct binding to MUC4 3'-UTR. MiR-219-1-3p overexpression (transient and stable) in pancreatic cancer cell lines induced a decrease of cell proliferation associated with a decrease of cyclin D1 and a decrease of Akt and Erk pathway activation. MiR-219-1-3p overexpression also decreased cell migration. Furthermore, miR-219-1-3p expression was found to be conversely correlated with Muc4 expression in early pancreatic intraepithelial neoplasia lesions of Pdx1-Cre;LSL-Kras(G12D) mice. Most interestingly, in vivo studies showed that miR-219-1-3p injection in xenografted pancreatic tumors in mice decreased both tumor growth and MUC4 mucin expression. Altogether, these results identify miR-219-1-3p as a new negative regulator of MUC4 oncomucin that possesses tumor-suppressor activity in PDAC.

[Regulation of cell proliferation by somatostatin]. / Contrôle de la prolifération cellulaire par la somatostatine.

Somatostatin and its stable analogues (octreotide, lanreotide and vapreotide) exert an antiproliferative effect on various normal and cancerous cells both in vitro and in vivo. This effect results from different mechanisms: an indirect effect by the inhibition of release of growth factors and trophic hormones (GH, IGF-1, insulin, gastrin, EGF), an inhibition of angiogenesis processes (endothelial cell proliferation, VEGF release, monocyte activity), an immunomodulatory effect (lymphocyte proliferation, interleukine or cytokine release, NK activity) and a direct effect on target cells. This direct antiproliferative effect is mediated through specific somatostatin receptors. Among them, sst(1), sst(2), sst(4) and sst(5) have been implicated in vitro in the G1-G0 cell cycle blockade, sst(3) and sst(2) mediating the apoptotic effect of somatostatin. In addition, sst(2) acts as an antioncogene in human pancreatic cancer cells. Coupling to membrane tyrosine phosphatases (SHP-1, SHP-2) is the main transduction pathway involved in the antiproliferative effect mediated by sst receptors. The dissociation observed clinically between a frequent antisecretory response and an inconstant antitumor effect after administration of somatostatin analogues may reflect an absence of expression or coupling of the receptor(s) involved in antiproliferative effect. Moreover, a desensitization or mutation of these receptors may also occur in tumors. All the potential mechanism involved should be elucidated in order to improve or better target the antitumor effect of somatostatin analogues clinically used.

Transcriptional activation of mouse sst2 somatostatin receptor promoter by transforming growth factor-beta. Involvement of Smad4.

The sst2 somatostatin receptor is an inhibitory G protein-coupled receptor, which exhibits anti-tumor properties. Expression of sst2 is lost in most human pancreatic cancers. We have cloned 2090 base pairs corresponding to the genomic DNA region upstream of the mouse sst2 (msst2) translation initiation codon (ATG). Deletion reporter analyses in mouse pituitary AtT-20 and human pancreatic cancer PANC-1, BxPC-3, and Capan-1 cells identify a region from nucleotide -260 to the ATG codon (325 base pairs) showing maximal activity, and a region between nucleotides -2025 and -260 likely to comprise silencer or transcriptional suppressor elements. In PANC-1 and AtT-20 cells, transforming growth factor (TGF)-beta up-regulates msst2 transcription. Transactivation is mediated by Smad4 and Smad3. The cis-acting region responsible for such regulation is comprised between nucleotides -1115 and -972 and includes Sp1 and CAGA-box sequences. Expression of Smad4 in Smad4-deficient Capan-1 and BxPC-3 cells restores TGF-beta-dependent and -independent msst2 transactivation. Expression of Smad4 in BxPC-3 cells reestablishes both endogenous sst2 expression and somatostatin-mediated inhibition of cell growth. These findings demonstrate that msst2 is a new target gene for TGF-beta transcription regulation and underlie the possibility that loss of Smad4 contributes to the lack of sst2 expression in human pancreatic cancer, which in turn may contribute to a stimulation of tumor growth.

Transcription of SST2 somatostatin receptor gene in human pancreatic cancer cells is altered by single nucleotide promoter polymorphism.

BACKGROUND & AIMS: The somatostatin receptor SST2 mediates the antiproliferative effect of stable somatostatin analogues. SST2 gene expression is lost in most human pancreatic carcinomas. We investigated the mechanisms that could be involved in this defect. METHODS: SST2 gene structure was investigated by sequencing and restriction fragment length polymorphism. Characterization of the polymorphism was performed by electrophoretic mobility shift, cross-linking, and transcription assays. RESULTS: No major deletion of the SST2 coding sequence was found in pancreatic carcinoma specimens, but 2 point mutations were frequently detected in the promoter sequence at positions -83 (A-->G) and -57 (C-->G) from the major transcription initiation site. These mutations were present in pancreatic cancer but also in normal pancreatic tissues or leukocytes and thus correspond to a genetic polymorphism. In the 2 human pancreatic cancer cell lines MiaPaCa-2 and AsPC-1, the naturally occurring mutation -57G had no effect on transcription of SST2 gene, whereas -83G mutation reduced it by 60%-70%. We showed that the -83G mutation creates a specific binding site for the nuclear factor I. Cotransfection experiments showed that the nuclear factor I-A1.1 isoform was responsible for SST2 promoter repression. CONCLUSIONS: The -83G polymorphism identified on human SST2 gene promoter is responsible for the specific fixation of nuclear factor I and repression of SST2 transcription in human pancreatic cancer cells. However, its contribution to pancreatic tumorigenesis remains unknown.