Functional characterization of biodegradable nanoparticles as antigen delivery system.

BACKGROUND: Peptide based vaccines may suffer from limited stability and inefficient delivery to professional antigen-presenting cells (APCs), such as dendritic cells (DCs). In order to overcome such limitations, several types of biodegradable nanoparticles (NPs) have been developed as carrier system for antigens. The present study describes for the first time the extensive biological characterization of cationic NPs made of poly (D,L-lactide-co-glycolide) (PLGA) and polyethylenimine (PLGA/PEI) as delivery system for protein/peptide antigens, with potential in therapeutic cancer vaccine development. RESULTS: Flow cytometry as well as confocal laser scanning microscopy (CLSM) showed that PLGA/PEI NPs are more readily taken up than PLGA NPs by both human CD14(+) monocytes and mouse Hepa 1-6 hepatoma cell line. No signs of toxicity were observed in either cellular setting. Sequential image acquisition by TEM showed an intracellular apical localization for PLGA NPs and a perinuclear localization for PLGA/PEI NPs. Both NPs showed a clathrin-dependent as well as a caveolin-dependent internalization pathway and, once in the cells, they formed multivesicular endosomes (MVE). Finally, an ex vivo priming experiment showed that PLGA/PEI NPs are comparable to PLGA NPs in delivering a non-self antigen (i.e., ovalbumin - OVA) to immature dendritic cells (imDCs), which matured and induced autologous naïve CD4(+) T cells to differentiate to memory (i.e., central memory and effector memory) cells. Such a differentiation was associated with a Th1 phenotype suggesting a downstream activation and amplification of a CD8(+) T cell cytotoxic response. The same OVA antigen in a soluble form was unable to induce maturation of DCs, indicating that both NP formulations provided an intrinsic adjuvanting effect combined to efficient antigen delivery. CONCLUSIONS: Our study represents the first report on side-by-side comparison of PLGA and PLGA/PEI NPs as strategy for protein antigen delivery. PLGA/PEI NPs are superior for cellular uptake and antigen delivery as compared to PLGA NPs. Such an evidence suggests their great potential value for vaccine development, including therapeutic cancer vaccines.

TGF-ß1 exposure induces epithelial to mesenchymal transition both in CSCs and non-CSCs of the A549 cell line, leading to an increase of migration ability in the CD133+ A549 cell fraction.

Metastasis is the leading cause of death by cancer. Non-small-cell lung cancer (NSCLC) represents nearly 85% of primary malignant lung tumours. Recent researches have demonstrated that epithelial-to-mesenchymal transition (EMT) plays a key role in the early process of metastasis of cancer cells. Transforming growth factor-ß1 (TGF-ß1) is the major inductor of EMT. The aim of this study is to investigate TGF-ß1's effect on cancer stem cells (CSCs) identified as cells positive for CD133, side population (SP) and non-cancer stem cells (non-CSCs) identified as cells negative for CD133, and SP in the A549 cell line. We demonstrate that TGF-ß1 induces EMT in both CSC and non-CSC A549 sublines, upregulating the expression of mesenchymal markers such as vimentin and Slug, and downregulating levels of epithelial markers such as e-cadherin and cytokeratins. CSC and non-CSC A549 sublines undergoing EMT show a strong migration and strong levels of MMP9 except for the CD133(-) cell fraction. OCT4 levels are strongly upregulated in all cell fractions except CD133(-) cells. On the contrary, wound size reveals that TGF-ß1 enhances motility in wild-type A549 as well as CD133(+) and SP(+) cells. For CD133(-) and SP(-) cells, TGF-ß1 exposure does not change the motility. Finally, assessment of growth kinetics reveals major colony-forming efficiency in CD133(+) A549 cells. In particular, SP(+) and SP(-) A549 cells show more efficiency to form colonies than untreated corresponding cells, while for CD133(-) cells no change in colony number was observable after TGF-ß1 exposure. We conclude that it is possible to highlight different cell subpopulations with different grades of stemness. Each population seems to be involved in different biological mechanisms such as stemness maintenance, tumorigenicity, invasion and migration.

The soluble form of urokinase receptor promotes angiogenesis through its Ser88-Arg-Ser-Arg-Tyr9² chemotactic sequence.

BACKGROUND: The urokinase plasminogen activator receptor (u-PAR) focuses the proteolytic activity of the urokinase plasminogen activator (u-PA) on the endothelial cell surface, thus promoting angiogenesis in a protease-dependent manner. The u-PAR may exist in a glycophosphatidylinositol-anchored and in a soluble form (soluble u-PAR [Su-PAR]), both including the chemotactic Ser88 -Arg-Ser-Arg-Tyr9² internal sequence. OBJECTIVE: To investigate whether Su-PAR may trigger endothelial cell signaling leading to new vessel formation through its chemotactic Ser88 -Arg-Ser-Arg-Tyr9² sequence. METHODS AND RESULTS: In this study, the formation of vascular-like structures by human umbilical vein endothelial cells was assessed by using a matrigel basement membrane preparation. First, we found that Su-PAR protein promotes the formation of cord-like structures, and that this ability is retained by the isolated Ser(88) -Arg-Ser-Arg-Tyr9² chemotactic sequence, the maximal effect being reached at 10 nmol L⁻¹ SRSRY peptide (SRSRY). This effect is mediated by the α(v) ß3 vitronectin receptor, is independent of u-PA proteolytic activity, and involves the internalization of the G-protein-coupled formyl-peptide receptor in endothelial cells. Furthermore, exposure of human saphenous vein rings to Su-PAR or SRSRY leads to a remarkable degree of sprouting. Finally, we show that Su-PAR and SRSRY promote a marked response in angioreactors implanted into the dorsal flank of nude mice, retaining 91% and 66%, respectively, of the angiogenic response generated by a mixture of vascular endothelial growth factor and fibroblast growth factor type 2. CONCLUSIONS: Our results show a new protease-independent activity of Su-PAR that stimulates in vivo angiogenesis through its Ser88 -Arg-Ser-Arg-Tyr9² chemotactic sequence.