Tumour exosomal CEMIP protein promotes cancer cell colonization in brain metastasis

The development of effective therapies against brain metastasis is currently hindered by limitations in our understanding of the molecular mechanisms driving it. Here we define the contributions of tumour-secreted exosomes to brain metastatic colonization and demonstrate that pre-conditioning the brain microenvironment with exosomes from brain metastatic cells enhances cancer cell outgrowth. Proteomic analysis identified cell migration-inducing and hyaluronan-binding protein (CEMIP) as elevated in exosomes from brain metastatic but not lung or bone metastatic cells. CEMIP depletion in tumour cells impaired brain metastasis, disrupting invasion and tumour cell association with the brain vasculature, phenotypes rescued by pre-conditioning the brain microenvironment with CEMIP exosomes. Moreover, uptake of CEMIP+ exosomes by brain endothelial and microglial cells induced endothelial cell branching and inflammation in the perivascular niche by upregulating the pro-inflammatory cytokines encoded by Ptgs2, Tnf and Ccl/Cxcl, known to promote brain vascular remodelling and metastasis. CEMIP was elevated in tumour tissues and exosomes from patients with brain metastasis and predicted brain metastasis progression and patient survival. Collectively, our findings suggest that targeting exosomal CEMIP could constitute a future avenue for the prevention and treatment of brain metastasis.

Bioactive Lipids Lysophosphatidic Acid and Sphingosine 1-Phosphate Mediate Breast Cancer Cell Biological Functions Through Distinct Mechanisms

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are structurally related bioactive lipids with growth factor-like activities. LPA and SIP are naturally produced in vivo by blood platelets upon platelet aggregation and at least in vitro by fibroblasts, adipocytes, and multiple types of tumor cells. Breast cancer cells respond to LPA and S1P. However, their specific actions on breast cancer cell biological functions remain unclear. We therefore conducted an in vitro side-by-side study of these two lipids on breast cancer cells. LPA mediates human breast cancer MDA-BO2 cell proliferation, migration, and invasion through activation of a G JERK1/2-dependent signaling pathway, whereas activation of G(alpha i)/PI3K predominates upon S I P stimulation. In MDA-BO2 cells, LPA but not S I P activities were dependent on active type I insulin-like growth factor and epithelial growth factor receptors. LPA and SIP act directly on endothelial cells to induce angiogenesis. We demonstrate that LPA and SIP have indirect angiogenic properties as judged by induced secretion of angiogenic factors by breast cancer cells primed with these lysophospholipids. SIP, but not LPA, controlled the expression of VEGF-A by breast cancer cells, while LPA, but not S1P, controlled the expression of GM-CSF, Gro-alpha, MCP-1, and IL-6. According to the secretion of these paracrine osteoclastic factors, LPA, but not S1P, stimulates breast cancer cell-induced osteoclastogenesis. These findings suggest that, in vivo, LPA and SIP can coordinate their action on tumor and surrounding cells to induce breast cancer progression both at primary and bone metastatic sites.

2009

Molecular profiling and functional analysis of macrophage-derived tumour extracellular vesicles

Tim Beltraminelli

Extracellular vesicles (EVs) are nanosized vesicles released by virtually all cell types. Increasing data suggest that EVs function in the regulation of intercellular communication both in physiological and pathological states. In cancer biology, mounting evidence suggests that cancer cell-derived EVs directly modulate several aspects of tumour progression by acting on both cancer cells and tumour-associated stromal cells. In addition to cancer cells, the tumour microenvironment (TME) also features an intertwined ensemble of recruited host-derived cells. Tumour-associated macrophages (TAMs) often infiltrate tumours in high numbers, thus representing one of the major host-derived cell populations. The involvement of TAMs in cancer progression has been extensively documented. It is well established that according to their polarisation state, TAMs can exert both pro- and anti-tumoural functions. However, under the influence of cancer cell-derived factors TAMs often acquire a phenotype that fosters tumour progression by supporting angiogenesis, metastasis and immunosuppression. While the role of secreted soluble factors contributing to the pro- and anti-tumoural functions of TAMs is well characterised, the molecular composition, properties, and effects of TAM-derived EVs (TAM-EVs) in the TME are poorly understood. In this thesis, I studied TAM-EVs produced in intact mouse tumours. We developed a methodology for the enrichment, quantification, and selective isolation of TAM-EVs produced in the TME. Furthermore, we performed comprehensive proteomic and lipidomic analyses of tumour-derived EVs and identified molecular signatures indicative of a role for TAM-EVs in immune response and lipid metabolism. Whereas source TAMs display a phenotype consistent with immunosuppressive functions, TAM-EVs have a pro-inflammatory and immune-stimulatory molecular signature. Indeed, TAM-EV-enriched preparations promoted T-cell proliferation and activation ex vivo and modulated arachidonic acid metabolism of cancer cells by inhibiting the production of the immunosuppressive PGE2 while favouring the secretion of pro-inflammatory thromboxane. Therefore, TAM-EVs might have the potential to stimulate, rather than limit, anti-tumour immunity. I also showed that while portraying some similarities with EVs of in vitro-polarised macrophages, TAM-EVs isolated from the TME present distinctive molecular profiles, suggesting that simplistic in vitro models do not faithfully recapitulate the complexity of the TME dynamics. Overall, this work emphasises the importance of studying TAM-EVs in their physiological context and identifies a potential role for TAM-EVs in favouring the development of an anti-tumoural immune microenvironment. Findings from this work extend our knowledge of the multifaceted role of TAMs in tumour biology.

EPFL2020

Molecular profiling and functional analysis of macrophage-derived tumour extracellular vesicles

Tim Beltraminelli

EPFL2020