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Prion protein modulates many cellular functions including the secretion of trophic factors by astrocytes. Some of these factors are found in exosomes, which are formed within multivesicular bodies (MVBs) and secreted into the extracellular space to modulate cell-cell communication. The mechanisms underlying exosome biogenesis were not completely deciphered. Here, we demonstrate that primary cultures of astrocytes and fibroblasts from prnp-null mice secreted lower levels of exosomes than wild-type cells. Furthermore, prnp-null astrocytes exhibited reduced MVB formation and increased autophagosome formation. The reconstitution of PRNP expression at the cell membrane restored exosome secretion in PRNP-deficient astrocytes, whereas macroautophagy/autophagy inhibition via BECN1 depletion reestablished exosome release in these cells. Moreover, the PRNP octapeptide repeat domain was necessary to promote exosome secretion and to impair the formation of the CAV1-dependent ATG12-ATG5 cytoplasmic complex that drives autophagosome formation. Accordingly, higher levels of CAV1 were found in lipid raft domains instead of in the cytoplasm in prnp-null cells. Collectively, these findings demonstrate that PRNP supports CAV1-suppressed autophagy to protect MVBs from sequestration into phagophores, thus facilitating exosome secretion.

Proliferation of neural crest (NC) stem cells and their subsequent differentiation into different neural cell types are key early events in the development of the peripheral nervous system. Soluble growth factors present at the sites where NC cells migrate are critical to the development of NC derivatives in each part of the body. In the present study, we further investigate the effect of microenvironmental factors on quail trunk NC development. We show for the first time that EGF induces differentiation of NC to the neuronal and melanocytic phenotypes, while fibroblast growth factor 2 (FGF2) promotes NC differentiation to Schwann cells. In the presence of both EGF and FGF2, the neuronal differentiation predominates. Our results suggest that FGF2 stimulates gliogenesis, while EGF promotes melanogenesis and neurogenesis. The combination of both growth factors stimulates neurogenesis. These findings suggest that these two growth factors may play an important role in the fate decision of NC progenitors and in the development of the peripheral nervous system.

Colorectal cancer (CRC) is one of the most frequently diagnosed malignancies. The generation of conventional treatments has improved, but approximately 50 % of patients with CRC who undergo potentially curative surgery ultimately relapse and die, usually as a consequence of metastatic disease. Our previous findings showed that engagement of the cellular prion protein (PrP(C)) to its ligand HSP70/90 heat shock organizing protein (HOP) induces proliferation of glioblastomas. In addition, PrP(C) has been described as an important modulator of colorectal tumor growth. Here, we investigated the biological relevance of the PrP(C)-HOP interaction in CRC cells. We demonstrate that HOP induced the migration and invasion of CRC cell lines in a PrP(C)-dependent manner and that phosphorylation of the ERK1/2 pathway is a downstream mediator of these effects. Additionally, we show that a HOP peptide with the ability to bind PrP(C) and abolish the PrP(C)-HOP interaction inhibited the migration and invasion of CRC cells. Together, these data indicate that the disruption of the PrP(C)-HOP complex could be a potential therapeutic target for modulating the migratory and invasive cellular properties that lead to metastatic CRC.

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The colorectal cancer is one of the most common types of cancer in the world. Previous results from our group and others revealed the Cellular Prion Protein (PrPC) as a possible therapeutic target in glioblastomas and ovarian tumors. Its activity depends on the interaction with the secreted form of the Stress Inducible Protein 1 (STI1), also known as HSP70/90 Heat Shock Organizing Protein (HOP). In the present work, we aimed to understand the mechanism by which PrPC-STI1/HOP complex can influence the aggressiveness of colorectal tumor cell lines. Cell migration and invasion assays were performed using recombinant STI1/HOP as a chemical attractant in boyden chambers coated with matrigel. The results showed that when stimulated with recombinant STI1/HOP, cells exhibited higher migration and invasion potentials than non-stimulated cells or those that were stimulated with STI1/HOP deletion mutant for the PrPC binding domain (STI1Δ230-245). Moreover, migration and invasion mediated by STI1/HOP were blocked by a STI1/HOP peptide (230-245), which mimics STI1/HOP binding site to PrPC, as well as by a neutralizing anti-PrPC antibody. To confirm the importance of PrPC-STI1/HOP complex in tumor progression and metastasis we generated a stable PrPC-knockdown colorectal adenocarcinoma cell line (WIDr). These cells showed a decreased invasion upon recombinant STI1/HOP stimulus, suggesting an important role of PrPC-STI1/HOP complex in the invasion process. In addition, as ERK signaling pathway has been related to invasion, we evaluated the ERK1/2 phosphorylation pattern in WIDr wild-type cells and their PrPC knockdown (KD) counterpart. Cells where PrPC was impaired showed a reduction in ERK1/2 phosphorylation when compared to those expressing the former protein. Experiments are under way to evaluate if these lower ERK1/2 levels are associated with decreased migration in PrPC-KD cells. In conclusion, our findings pointed that the disruption of PrPC-STI1/HOP complex could be a therapeutic target in colorectal adenocarcinoma. Supported by São Paulo Research Foundation (FAPESP) Citation Format: Tonielli S. Lacerda, Marcos Vinicius S. Dias, Fernanda S. Giudice, Bianca Luise Teixeira, Vilma Regina Martins. The control of migration and invasion processes in colorectal adenocarcinoma is modulated by prion protein and its ligand STI1/HOP. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5101. doi:10.1158/1538-7445.AM2015-5101

Non-healing skin wounds remain a challenge in the healthcare system. In this sense, it is suggested that the secretome of mesenchymal stromal cells (MSCs) can be effective as a therapeutic strategy for regenerative medicine. Therefore, this systematic review aimed to determine the effects of treatment with secretome derived from MSCs on the healing of skin wounds in preclinical model of rodents (mice and rats). Studies were systematically retrieved from six databases and grey literature that provided 1172 records, of which 25 met the inclusion criteria for qualitative analysis. Results revealed substantial heterogeneity among studies concerning experimental designs and methodologies, resulting in a high risk of bias. Together, the selected studies reported that treatment improved wound healing by (I) accelerating wound closure and improving skin repair quality; (II) reducing inflammation by decreasing the number of cells and inflammatory cytokines, accompanied by polarization of the M2 macrophage; (III) complete re-epithelialization and epidermal reorganization; (IV) neovascularization promoted by proliferation of endothelial cells (CD34+) and increased levels of pro-angiogenic mediators; (V) better scar quality promoted by increased expression of collagen types I and III, as well as improved deposition and remodeling of collagen fibers. In conclusion, despite the need for alignment of methodological protocols and transparent reports in future studies, results show that the secretome of MSCs from different tissue sources corresponds to a promising tool of regenerative medicine for the treatment of skin wounds.