Investigation into the interplay between cancer cells and their associated fibroblasts in malignant pleural mesothelioma: therapeutic implications

Malignant pleural mesothelioma (MPM) is a highly aggressive malignancy with a median survival of 12 months following diagnosis. The UK is amongst the leading countries for mesothelioma-caused mortality and the standard-of-care for the disease has not been improved for nearly two decades. A main contributor to poor disease outcome is the extensive associated fibrosis which hinders treatment success and gradually causes loss of respiratory function. Hence, targeting this process in addition to tumour cell viability may be of great therapeutic benefit. This study investigated the interplay between mesothelioma cells and their associated fibroblasts (CAFs), the main contributor to the fibrotic process, using a variety of proteomics profiling approaches. This revealed SRC, PDGFR and VEGFR along with the PI3K/mTOR signalling cascade as key intracellular mediators of the cross-talk between MPM cancer cells and CAFs. Extracellularly, the identified secreted cytokines and growth factors promote angiogenesis (ANGPT2, END), extracellular matrix (ECM) remodelling (BSG, MMPs, LOX2), propagation of the pro-fibrotic signalling (PDGFA, VEGFA, OPN, FGFs, IL-17A) and TME immunosuppression (CXCL12, MIF, M-CFS, MCP1, VEGFA, TGFβ). Last, but not least, analysis of components of the CAF-derived ECM highlighted the released molecules and mechanisms CAFs employ to promote tumourigenesis according to the requirements of the TME, particularly through regulation of the bioavailability of TGFβ and PDGF in the TME. Based on these combined proteomics data, a panel of 14 small-molecule inhibitors against selected identified targets was assembled and their efficiency in targeting the viability of 3D MPM/CAF spheroid co-cultures and the fibrotic response tested. Drugs were tested both as single agents and in 1 to 1 combinations. Our results show that combination of the mTOR inhibitor Vistusertib with either the SRC inhibitor Saracatinib or the tyrosine kinase inhibitor Cediranib was more potent than the current standard-of-care for MPM, Cisplatin/Pemetrexed. Additionally, unlike the latter combination, the Vistusertib-based combinations prevented CAF-induced drug resistance in 3D culture. In short, the findings of this thesis propose novel cytotoxic and anti-fibrotic therapeutic strategies for MPM.Open Acces

Crosstalk with lung fibroblasts shapes the growth and therapeutic response of mesothelioma cells.

Mesothelioma is an aggressive cancer of the mesothelial layer associated with an extensive fibrotic response. The latter is in large part mediated by cancer-associated fibroblasts which mediate tumour progression and poor prognosis. However, understanding of the crosstalk between cancer cells and fibroblasts in this disease is mostly lacking. Here, using co-cultures of patient-derived mesothelioma cell lines and lung fibroblasts, we demonstrate that fibroblast activation is a self-propagated process producing a fibrotic extracellular matrix (ECM) and triggering drug resistance in mesothelioma cells. Following characterisation of mesothelioma cells/fibroblasts signalling crosstalk, we identify several FDA-approved targeted therapies as far more potent than standard-of-care Cisplatin/Pemetrexed in ECM-embedded co-culture spheroid models. In particular, the SRC family kinase inhibitor, Saracatinib, extends overall survival well beyond standard-of-care in a mesothelioma genetically-engineered mouse model. In short, we lay the foundation for the rational design of novel therapeutic strategies targeting mesothelioma/fibroblast communication for the treatment of mesothelioma patients