Tumor-derived exosomes confer antigen-specific immunosuppression in a murine delayed-type hypersensitivity model

Exosomes are endosome-derived small membrane vesicles that are secreted by most cell types including tumor cells. Tumor-derived exosomes usually contain tumor antigens and have been used as a source of tumor antigens to stimulate anti-tumor immune responses. However, many reports also suggest that tumor-derived exosomes can facilitate tumor immune evasion through different mechanisms, most of which are antigen-independent. In the present study we used a mouse model of delayed-type hypersensitivity (DTH) and demonstrated that local administration of tumor-derived exosomes carrying the model antigen chicken ovalbumin (OVA) resulted in the suppression of DTH response in an antigen-specific manner. Analysis of exosome trafficking demonstrated that following local injection, tumor-derived exosomes were internalized by CD11c+ cells and transported to the draining LN. Exosome-mediated DTH suppression is associated with increased mRNA levels of TGF-β1 and IL-4 in the draining LN. The tumor-derived exosomes examined were also found to inhibit DC maturation. Taken together, our results suggest a role for tumor-derived exosomes in inducing tumor antigen-specific immunosuppression, possibly by modulating the function of APCs. © 2011 Yang et al

Rab27a and Rab27b control different steps of the exosome secretion pathway

Exosomes are secreted membrane vesicles that share structural and biochemical characteristics with intraluminal vesicles of multivesicular endosomes (MVEs). Exosomes could be involved in intercellular communication and in the pathogenesis of infectious and degenerative diseases. The molecular mechanisms of exosome biogenesis and secretion are, however, poorly understood. Using an RNA interference (RNAi) screen, we identified five Rab GTPases that promote exosome secretion in HeLa cells. Among these, Rab27a and Rab27b were found to function in MVE docking at the plasma membrane. The size of MVEs was strongly increased by Rab27a silencing, whereas MVEs were redistributed towards the perinuclear region upon Rab27b silencing. Thus, the two Rab27 isoforms have different roles in the exosomal pathway. In addition, silencing two known Rab27 effectors, Slp4 (also known as SYTL4, synaptotagmin-like 4) and Slac2b (also known as EXPH5, exophilin 5), inhibited exosome secretion and phenocopied silencing of Rab27a and Rab27b, respectively. Our results therefore strengthen the link between MVEs and exosomes, and introduce ways of manipulating exosome secretion in vivo

Effect of the chemokine receptor CXCR7 on proliferation of carcinoma cells in vitro and in vivo

The chemokine CXCL12/SDF-1 and its receptor CXCR4 have been implicated in invasion, survival and proliferation of carcinoma cells. Recently, CXCR7 was identified as a second receptor for CXCL12. We observed that CXCL12 promoted proliferation of CT26 colon and KEP1 mammary carcinoma cells, and this was blocked when CXCR7 was downregulated by ‘intrakines' or RNAi, but not by CXCR4 inhibitors. The K1R mutant of CXCL12, which acts as a CXCR4 antagonist, also promoted proliferation through CXCR7 and is therefore a selective CXCR7 agonist. The effect of CXCR7 was not due to reduced apoptosis, and CXCR7 mediated chemotaxis of the carcinoma cells towards CXCL12. These results differ from those in a previous report on other carcinoma cells. We conclude that CXCL12 can be a potent growth factor for carcinoma cells by acting on CXCR7. Nevertheless, we observed no effect of complete and stable CXCR7 suppression on the growth of s.c. tumours or lung metastases of KEP1 and CT26 cells. A CXCR7 inhibitor has been reported to reduce growth of other tumours. Our results indicate that this inhibitor may not be applicable to therapy of all carcinomas

Is there an orthographic boost for ambiguous words during their processing?

The present study explores the issue of why ambiguous words are recognized faster than unambiguous ones during word recognition. To this end we contrasted two different hypotheses: the semantic feedback hypothesis (Hino and Lupker in J Exp Psychol Hum Percept Perform 22:1331-1356, 1996. https://doi.org/10.1037/0096-1523.22.6.1331 ), and the hypothesis proposed by Borowsky and Masson (J Exp Psychol Learn Mem Cognit 22:63-85, 1996. https://doi.org/10.1037/0278-7393.22.1.63 ). Although both hypotheses agree that ambiguous words benefit during recognition in that they engage more semantic activation, they disagree as to whether or not this greater semantic activation feeds back to the orthographic level, hence speeding up the orthographic coding of ambiguous words. Participants were presented with ambiguous and unambiguous words in two tasks, a lexical decision task (LDT) and a two-alternative forced-choice task (2AFC). We found differences between ambiguous and unambiguous words in both the LDT and the 2AFC tasks. These results suggest that the orthographic coding of ambiguous words is boosted during word processing. This finding lends support to the semantic feedback hypothesis.This research was funded by the Spanish Ministry of Economy and Competitiveness (PSI2015-63525-P) and by the Research Promotion Program of the Universitat Rovira i Virgili (2016PFR-URV-B2-37). This has also been partially supported by the FCT (Foundation for Science and Technology) through the state budget with Reference IF/00784/2013/CP1158/CT0013. The first author also holds a grant from the Universitat Rovira i Virgili (2015PMF-PIPF-16)

Nuclear Localization of CXCR4 Determines Prognosis for Colorectal Cancer Patients

Chemokines and their receptors are implicated in formation of colorectal cancer metastases. Especially CXCR4 is an important factor, determining migration, invasiveness, metastasis and proliferation of colorectal cancer cells. Object of this study was to determine expression of CXCR4 in tumor tissue of colorectal cancer patients and associate CXCR4 expression levels to clinicopathological parameters. Levels of CXCR4 expression of a random cohort of patients, who underwent primary curative resection of a colorectal carcinoma, were retrospectively determined by quantitative real-time RT-PCR and semi-quantitative analyses of immunohistochemical stained paraffin sections. Expression levels were associated to clinicopathological parameters. Using RT-PCR we found that a high expression of CXCR4 in the primary tumor was an independent prognostic factor for a poor disease free survival (p = 0.03, HR: 2.0, CI = 1.1–3.7). Immunohistochemical staining showed that nuclear distribution of CXCR4 in the tumor cells was inversely associated with disease free and overall survival (p = 0.04, HR: 2.6, CI = 1.0–6.2), while expression in the cytoplasm was not associated with prognosis. In conclusion, our study showed that a high expression of nuclear localized CXCR4 in tumor cells is an independent predictor for poor survival for colorectal cancer patients

Expression of SDF-1α and nuclear CXCR4 predicts lymph node metastasis in colorectal cancer

Although stromal cell-derived factor (SDF)-1α and its receptor CXCR4 are experimentally suggested to be involved in tumorigenicity, the clinicopathological significance of their expression in human disease is not fully understood. We examined SDF-1α and CXCR4 expression in colorectal cancers (CRCs) and their related lymph nodes (LNs), and investigated its relationship to clinicopathological features. Specimens of 60 primary CRCs and 27 related LNs were examined immunohistochemically for not only positivity but also immunostaining patterns for SDF-1α and CXCR4. The relationships between clinicopathological features and SDF-1α or CXCR4 expression were then analysed. Stromal cell-derived factor-1α and CXCR4 expression were significantly associated with LN metastasis, tumour stage, and survival of CRC patients. Twenty-nine of 47 CXCR4-positive CRCs (61.7%) showed clear CXCR4 immunoreactivity in the nucleus and a weak signal in the cytoplasm (nuclear type), whereas others showed no nuclear immunoreactivity but a diffuse signal in the cytoplasm and at the plasma membrane (cytomembrane type). Colorectal cancer patients with nuclear CXCR4 expression showed significantly more frequent LN metastasis than did those with cytomembrane expression. Colorectal cancer patients with nuclear CXCR4 expression in the primary lesion frequently had cytomembrane CXCR4-positive tumours in their LNs. In conclusion, expression of SDF-1α and nuclear CXCR4 predicts LN metastasis in CRCs

Therapeutic Effects of Autologous Tumor-Derived Nanovesicles on Melanoma Growth and Metastasis

Cancer vaccines with optimal tumor-associated antigens show promise for anti-tumor immunotherapy. Recently, nano-sized vesicles, such as exosomes derived from tumors, were suggested as potential antigen candidates, although the total yield of exosomes is not sufficient for clinical applications. In the present study, we developed a new vaccine strategy based on nano-sized vesicles derived from primary autologous tumors. Through homogenization and sonication of tumor tissues, we achieved high yields of vesicle-bound antigens. These nanovesicles were enriched with antigenic membrane targets but lacked nuclear autoantigens. Furthermore, these nanovesicles together with adjuvant activated dendritic cells in vitro, and induced effective anti-tumor immune responses in both primary and metastatic melanoma mouse models. Therefore, autologous tumor-derived nanovesicles may represent a novel source of antigens with high-level immunogenicity for use in acellular vaccines without compromising safety. Our strategy is cost-effective and can be applied to patient-specific cancer therapeutic vaccination

CXC receptor-4 mRNA silencing abrogates CXCL12-induced migration of colorectal cancer cells

<p>Abstract</p> <p>Background</p> <p>Interactions between CXCR4 and its ligand CXCL12 have been shown to be involved in cancer progression in colorectal cancer (CRC). We performed a comparative CXCL12/CXCR4 expression analysis and assessed the effect of external CXCL12 stimulation on migration of CRC cells without and with CXCR4 inhibition.</p> <p>Methods</p> <p>Expression of CXCL12/CXCR4 was assessed by quantitative real-time PCR, ELISA and immunohistochemistry in resection specimens of 50 CRC patients as well as in the corresponding normal tissues and in three human CRC cell lines with different metastatic potential (Caco-2, SW480 and HT-29). Migration assays were performed after stimulation with CXCL12 and CXCR4 was inhibited by siRNA and neutralizing antibodies.</p> <p>Results</p> <p>In CRC tissues CXCL12 was significantly down-regulated and CXCR4 was significantly up-regulated compared to the corresponding normal tissues. In cell lines CXCR4 was predominantly expressed in SW480 and less pronounced in HT-29 cells. CXCL12 was only detectable in Caco-2 cells. CXCL12 stimulation had no impact on Caco-2 cells but significantly increased migration of CXCR4 bearing SW480 and HT-29 cells. This effect was significantly abrogated by neutralizing anti-CXCR4 antibody as well as by CXCR4 siRNAs (P < 0.05).</p> <p>Conclusions</p> <p>CXCR4 expression was up-regulated in CRC and CXCL12 stimulation increased migration in CXCR4 bearing cell lines. Migration was inhibited by both neutralizing CXCR4 antibodies and CXCR4 siRNAs. Thus, the expression and functionality of CXCR4 might be associated with the metastatic potential of CRC cells and CXCL12/CXCR4 interactions might therefore constitute a promising target for specific treatment interventions.</p

The Chemokine Receptor CXCR4 Strongly Promotes Neuroblastoma Primary Tumour and Metastatic Growth, but not Invasion

Neuroblastoma (NB) is a heterogeneous, and particularly malignant childhood neoplasm in its higher stages, with a propensity to form metastasis in selected organs, in particular liver and bone marrow, and for which there is still no efficient treatment available beyond surgery. Recent evidence indicates that the CXCR4/CXCL12 chemokine/receptor axis may be involved in promoting NB invasion and metastasis. In this study, we explored the potential role of CXCR4 in the malignant behaviour of NB, using a combination of in vitro functional analyses and in vivo growth and metastasis assessment in an orthotopic NB mouse model. We show here that CXCR4 overexpression in non-metastatic CXCR4-negative NB cells IGR-NB8 and in moderately metastatic, CXCR4 expressing NB cells IGR-N91, strongly increased tumour growth of primary tumours and liver metastases, without altering the frequency or the pattern of metastasis. Moreover shRNA-mediated knock-down experiments confirmed our observations by showing that silencing CXCR4 in NB cells impairs in vitro and almost abrogates in vivo growth. High levels of CXCL12 were detected in the mouse adrenal gland (the primary tumour site), and in the liver suggesting a paracrine effect of host-derived CXCL12 on NB growth. In conclusion, this study reveals a yet unreported NB-specific predominant growth and survival-promoting role of CXCR4, which warrants a critical reconsideration of the role of CXCR4 in the malignant behaviour of NB and other cancers

Coaction of Spheroid-Derived Stem-Like Cells and Endothelial Progenitor Cells Promotes Development of Colon Cancer

Although some studies described the characteristics of colon cancer stem cells (CSCs) and the role of endothelial progenitor cells (EPCs) in neovascularization, it is still controversial whether an interaction exists or not between CSCs and EPCs. In the present study, HCT116 and HT29 sphere models, which are known to be the cells enriching CSCs, were established to investigate the roles of this interaction in development and metastasis of colon cancer. Compared with their parental counterparts, spheroid cells demonstrated higher capacity of invasion, higher tumorigenic and metastatic potential. Then the in vitro and in vivo relationship between CSCs and EPCs were studied by using capillary tube formation assay and xenograft models. Our results showed that spheroid cells could promote the proliferation, migration and tube formation of EPCs through secretion of vascular endothelial growth factor (VEGF). Meanwhile, the EPCs could increase tumorigenic capacity of spheroid cells through angiogenesis. Furthermore, higher microvessel density was detected in the area enriching cancer stem cells in human colon cancer tissue. Our findings indicate that spheroid cells possess the characteristics of cancer stem cells, and the coaction of CSCs and EPCs may play an important role in the development of colon cancer