Preconditioned Endothelial Progenitor Cells Reduce Formation of Melanoma Metastases through SPARC-Driven Cell–Cell Interactions and Endocytosis

Abstract

Tumor progression is associated with the release of signaling substances from the primary tumor into the bloodstream. Tumor-derived cytokines are known to promote the mobilization and the recruitment of cells from the bone marrow, including endothelial progenitor cells (EPC). Here, we examined whether such paracrine influence could also influence the capacity of EPC to interfere with circulating metastatic cells. We therefore consecutively injected EPC prestimulated by tumor-conditioned medium (EPC-CM) and luciferase-expressing B16 melanoma cells to mice. A net decrease in metastases spreading (vs. nonstimulated EPC) led us to carry out a 2-dimensional difference gel electrophoresis (2D-DIGE) proteomic study to identify possible mediators of EPC-driven protection. Among 33 proteins exhibiting significant changes in expression, secreted protein, acidic and rich in cysteine (SPARC) presented the highest induction after EPC exposure to CM. We then showed that contrary to control EPC, SPARC-silenced EPC were not able to reduce the extent of metastases when injected with B16 melanoma cells. Using adhesion tests and the hanging drop assay, we further documented that cell-cell interactions between EPC-CM and melanoma cells were promoted in a SPARC-dependent manner. This interaction led to the engulfment of melanoma cells by EPC-CM, a process prevented by SPARC silencing and mimicked by recombinant SPARC. Finally, we showed that contrary to melanoma cells, the prometastatic human breast cancer cell line MDA-MB231-D3H2 reduced SPARC expression in human EPC and stimulated metastases spreading. Our findings unravel the influence of tumor cells on EPC phenotypes through a SPARC-driven accentuation of macrophagic capacity associated with limitations to metastatic spread. Cancer Res; 71(14); 4748-57. Ó2011 AACR.

Endothelial progenitors promote hepatocarcinoma intrahepatic metastasis through monocyte chemotactic protein-1 induction of microRNA-21

“…Recent studies by Giannoni et al 18 reported that in prostate carcinoma, direct contact between EPCs and mesenchymal tumour cells induces the EphA2/ephrinA1 signalling to elicit a mesenchymal amoeboid transition in tumour cells, allowing them to attain a metastatic advantage. Moreover, EPCs have been shown to promote melanoma metastasis through the secreted protein acidic and rich in cysteine-driven cell-cell interactions and endocytosis 19. In concert with these previous studies, our results indicate that EPCs recruited to the tumour sites may represent a critical component of ‘soil’ to induce phenotypical switch of a non-metastatic tumour towards one with an increased potential for metastasis.…”

Tumour-derived SPARC drives vascular permeability and extravasation through endothelial VCAM1 signalling to promote metastasis

“…Although endothelial cells in the tumour microenvironment are known to produce high levels of SPARC, we found that endothelial-derived SPARC did not influence melanoma cell transmigration, further supporting the notion that tumour-and host-derived SPARC have different biological activities and that the origin of SPARC participates to the complexity of SPARC in metastasis 44,47 .…”

Reducing the serine availability complements the inhibition of the glutamine metabolism to block leukemia cell growth

“…Cells were collected and lysed in with DIGE labelling (DLA) lysis buffer (7 M urea, 2 M thiourea, 4% CHAPS and 30 mM Tris, pH 8.5). Protein labelling with Cy dyes and 2D-electrophoresis were carried out as previously described [ 30 – 32 ]. The 2D-gels were then scanned using a Typhoon FLA 9500 while the images were analysed using the DeCyder software.…”