Development of c-Met targeted chimeric antigen receptor T-cell immunotherapy for malignant pleural mesothelioma

Abstract

Malignant pleural mesothelioma (MPM) is an incurable cancer that commonly presents at an advanced stage. Although surgery, chemotherapy and radiotherapy treatment may be used, median survival from diagnosis is less than 12 months. Consequently, new therapeutic approaches are essential. Chimeric antigen receptors (CARs) are fusion molecules that couple the HLA-independent binding of a cell surface target to the delivery of a tailored T-cell activating signal. The receptor tyrosine kinase c-Met is overexpressed in >80% of MPM making it an attractive candidate for CAR T-cell immunotherapy. To target c-Met, three candidate CARs were developed named N28z, M28z and cM28z. All contained a CD28/CD3ζ endodomain fused to one of three stabilised peptides based on the N and K1 domains of hepatocyte growth factor, which is the only natural ligand for c-Met. Specificity and functionality of c-Met re-targeted CAR+ T-cells was confirmed by co-cultivation with c-Met-expressing NIH 3T3 and MPM cell lines. This was indicated by target-dependent cytotoxicity and enhanced cytokine release (IL-2 and IFN-γ), when compared to appropriate controls. Anti-tumour activity of all three candidate CARs could be further enhanced by pre-treatment of tumour cells with poorly cytotoxic doses of chemotherapy (cisplatin and pemetrexed) or by co-incubation with the PD-1 blocker, pembrolizumab. No differences between function of the three candidate CARs were evident in these studies. To evaluate in vivo anti-tumour activity, an intraperitoneal MPM xenograft model was established that was amenable to monitoring using bioluminescence imaging. Candidate c-Met re-targeted CARs were coexpressed with the chimeric cytokine receptor, 4αβ, enabling IL-4 mediated, selective enrichment of CAR+ T-cells. In mice with an established tumour burden, I found that cM28z/4αβ+ T-cells were superior to other c-Met re-targeted or control T-cells in eliciting sustained disease control. Together, these findings demonstrate proof of concept for the utility of c-Met re-targeted CAR+ T-cells to recognise and destroy mesothelioma tumour cells.

Date of Award	2016
Original language	English
Awarding Institution	King's College London
Supervisor	John Maher (Supervisor) & James Spicer (Supervisor)