Riassunto analitico
Ewing’s sarcoma (ES) is an aggressive tumour representing the second most common malignant bone cancer in children and young adults. Patients with metastases have the worst prognosis. The invasive nature of this tumour is indeed the major reason underlying failure of standard therapeutic approaches. Novel therapies are therefore urgently needed. The tumour-tropic ability of mesenchymal stromal/stem cells (MSCs) offers an alternative where these cells may be used as vehicle of anti-tumour molecules delivery. MSCs are considered as putative cell of origin for ES and display an active role as progenitors of the tumour supportive stroma. To exploit these MSC features, our group developed a therapeutic approach based on MSCs as vehicle of the pro-apoptotic TNF-related apoptosis inducing ligand (TRAIL) molecule showing a robust antitumour activity of TRAIL MSCs against primary localized ES. Nevertheless, the interaction occurring between tumour cells and MSCs still need to be better clarified. Setting up in vitro and in vivo models to study this interaction is a prerequisite for novel approaches where the MSC affinity for the tumour and the retention inside the tumour microenvironment are ameliorated to ultimately increase the therapeutic efficacy.
In the present study, we employed the VITVO50, a novel three-dimensional device by Rigenerand s.r.l., to develop in vivo-like ES metastatic nodules. Setting up a VITVO50-based fluidic circuit we were able to model the process of tissue colonization and creation of metastatic nodules by migrating tumour cells, mimicking in a simplified way what happens in ES patients. MSCs were subsequently introduced in the circuit, and their interaction with tumour nodules on the VITVO50 was evaluated under flow conditions. Colonization and interaction within the dynamic VITVO50 model were investigated by droplet digital PCR (ddPCR). Setting up 2-plex and 3-plex ddPCR-based assays we were able to simultaneously detect both tumour cells and MSCs within the VITVO50. Collectively, the VITVO50 demonstrated to be a manageable and versatile bioreactor to develop in vivo-like tumour nodules and investigate dynamic cell-to-cell interactions with MSCs, as relevant players in cancer progression and as vehicle of anticancer drugs. ddPCR proved to be a sensitive method to analyse colonization and interaction within the dynamic VITVO50 model. The proposed fluidic system could be applied to study tumour-MSC interactions, where the MSC affinity for the tumour has been increased by novel targeting strategies.
In VITVO50 findings were then applied in vivo. An Ewing’s sarcoma metastatic model was established in NSG mice to evaluate the TRAIL MSC capability to home to metastatic sites and their anti-tumour potential by the release of the soluble TRAIL (sTRAIL) molecule. Here, we took advantage of the acquired molecular know how to set up a 4-plex ddPCR assay to investigate the TRAIL MSC fate in vivo, looking at their distribution in mice organs affected by metastases, as well as at their anti-tumour potential. ddPCR data showed that MSCs effectively engraft into the lung and liver of mice and the sTRAIL molecule produced in vivo by TRAIL MSCs was able to significantly reduce the growth of lung metastases.
Collectively, our work highlights how novel ex-vivo models could facilitate the understanding of tumour-stroma interaction to accelerate the progress towards the early clinical phase.
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