The role of EVs in NK cell-dependent immuunosurveillance of cancer
Professor Elke Pogge von Strandmann, University of Cologne
Extracellular vesicles (EVs) are important mediators of intercellular communication and act on the adjacent stroma as well as in the periphery. Recently, EVs have been recognized to play a pathophysiological role in various diseases such as cancer.
Tumor cell-derived exosomes (Tex) have been shown to educate non-malignant cells to provide a tumor supporting microenvironment, which helps to circumvent immune detection and elimination. We identified a disease-related mRNA signature in vesicles from malignant B cells (Chronic Lymphocytic leukemia, CLL), which was even pronounced upon toll like receptor engagement used as a milieu-mimics. The transfer of such mRNAs to healthy bystander cells was detectable indicating that CLL-released vesicles spread tumor-milieu instructions within the CLL microenvironment.
However, Tex with anti-tumor, immune-activating properties were described as well, which reflects the complexity of EVs. Activation of the innate immune receptor retinoic acid-inducible gene I (RIG-I) triggered the secretion of EVs from tumor cells, which exert anti-tumor activity in vitro and in vivo. RIG-I-induced EVs exhibited an increased expression of the NKp30-ligand (BAG6, BAT3) on their surface, triggering NK cell-mediated lysis of tumor cells via activation of the cytotoxicity NK cell-receptor NKp30. Moreover, systemic administration of RIG-I-induced tumor-EVs showed a potent anti-tumor activity in a melanoma mouse model in vivo. In conclusion our data establish a new RIG-I and EV-dependent pathway leading to NK cell-mediated tumor cell killing. The role of EVs as messengers affecting NK cell function in health and disease will be discussed.
Analysing the effects of extracellular vesicles on cancer invasion using human myoma tissue derived extracellular matrixes
Professor Tuula Salo, University of Oulu
Translational cancer research has lacked human tissue in vitro models that mimic the natural tumor microenvironment matrix (TMEM). The 3D invasion pattern has been studied with organotypic models composed of rat tail type I collagen combined with mouse tumor derivatives, such as Matrigel®. However, these classical methods that mix matrixes from different species do not accurately mimic the composition of human TME. Our group has developed a 3D invasion assay using human uterine leiomyoma tissue discs. These hypoxic discs contain all essential TME components for in vitro invasion experiments. Both in native and lyophilized forms, these discs promote invasion and growth of the cancer cells - unlike e.g. healthy heart tissue. The invasion efficiency in the myoma discs can be analyzed by determining the degradation of collagen fibers together with histological and immunohistological staining of the tissue sections. Proteome analysis of myoma rinsing media revealed migration-enhancing factors whereas fragments derived from heart tissue rinsing media inhibited cancer migration. Myoma discs fit also for co-culture experiments of various TME cells, such as carcinoma associated fibroblasts, macrophages and inflammatory cells. We have also prepared myogel product from leiomyoma according to the method described for the preparation of Matrigel®. Myogel provides an excellent method for analyzing cancer cell migratory, invasive or adhesive properties, as well as potential chemotherapeutic compounds. Recently, myoma matrixes are used to test the effects of extracellular vesicles for cancer invasion. Thus, myoma discs together with myogel offer a practical human “TMEM mimicking kit” for translational cancer research purposes.
Cancer exosomes establish a prometastatic inflammatory loop by engaging mesencgymal stem cells
Contributory talk given by D. Michiel Pegtel
Metastasis formation and resistance to therapy, for example via STAT3 activation in tumor cells, could be a consequence of driver-mutations in cancerous ‘stem’ cells or of cancer-stroma interactions, but a role for mesenchymal stem stem cells (MSCs) is poorly understood. This talk will discuss how we explored in an in vivo osteosarcoma (OS) model how tumor exosomes may engage MSCs to facilitate tumor progression.
Extracellular vesicles and the pre-metastatic niche: a deadly conversation between prostate tumours and the bone
Contributory talk given by Victoria James
The popular ‘seed and soil’ hypothesis proposes that organ preference patterns of metastasis result from favourable interactions between the metastatic cancer cells (‘seed’) and the organ microenvironment (‘soil’). However, what is less clear is whether primary tumours communicate with secondary sites in advance of tumour cell arrival, to create a ‘pre-metastatic niche’, to enhance tumour-cell colonisation at the most inefficient stage of metastasis. The role of extracellular-vesicles in this communication process remains to be explored.
In order to investigate how the cargo of prostate cancer (PCa) EVs could act to reprogramme the cells of the bone, to potentially create a supportive pre-metastatic niche. We have adapted a novel RNA tracking technique, to trace the route of the RNA cargo from PCa cells via EVs into recipient bone cells (osteoblasts), identifying several osteoblast specific RNAs suggesting PCa cells may selectively target cells of the bone with EV-mediated communication.
Exposure of osteoblasts to PCa-EVs results in phenotypic changes indicative of microenvironment remodelling. Moreover, our data indicates treatment of the extracellular-environment can effectively block the uptake of PCa-EVs resulting in a reversal of the EV-activated osteoblast phenotype.
Lysyl-oxidase and the pre-metastic bone niche
Dr Alison Gartland
Bone is the primary site for many cancer types and can account for up to 80% of cancer-related deaths in certain tumours. Progression from a discrete solid primary tumour to devastating and painful bone metastases is a complex process involving multiple cell types and steps. Recently it has been shown that tumour-derived factors circulate the body exerting effects on ECM remodelling within distant organs, creating pre-metastatic niches. We have recently begun to unravel the role of Lysyl oxidase (LOX), which is critical for pre-metastatic niche formation in soft-tissue, in the bone pre-metastatic niche formation, in particular the early events governing osteolytic lesion formation. Using multiple in vitro and in vivo models, and a large clinical cohort, we show that LOX gene expression is significantly correlated with osteotropism and bone relapse. We show that high expression of LOX in primary breast tumours or systemic delivery of LOX in vivo leads to osteolytic lesion formation, and that silencing or inhibition of LOX activity abrogates this. The enzymatic activity of tumour-secreted LOX affects both osteoclasts and osteoblasts, disrupting normal bone homeostasis leading to bone lesion formation. These changes and lesions occur prior to tumour cell arrival in the bone and act to provide the initial foothold for circulating tumour cells to colonise the niche and form bone metastases. In summary, we have uncovered a novel step in bone metastasis and mechanism of bone homeostatic regulation, opening up new opportunities for therapeutic intervention with important clinical implications.