CAR T-cell immunotherapy of MET-expressing malignant mesothelioma

Abstract

Mesothelioma is an incurable cancer for which effective therapies are required. Aberrant MET expression is prevalent in mesothelioma, although targeting using small molecule-based therapeutics has proven disappointing. Chimeric antigen receptors (CARs) couple the HLA-independent binding of a cell surface target to the delivery of a tailored T-cell activating signal. Here, we evaluated the anti-tumor activity of MET re-targeted CAR T-cells against mesothelioma. Using immunohistochemistry, MET was detected in 67% of malignant pleural mesotheliomas, most frequently of epithelioid or biphasic subtype. The presence of MET did not influence patient survival. Candidate MET-specific CARs were engineered in which a CD28+CD3ζ endodomain was fused to one of 3 peptides derived from the N and K1 domains of hepatocyte growth factor (HGF), which represents the minimum MET binding element present in this growth factor. Using an NIH3T3-based artificial antigen-presenting cell system, we found that all 3 candidate CARs demonstrated high specificity for MET. By contrast, these CARs did not mediate T-cell activation upon engagement of other HGF binding partners, namely CD44v6 or heparan sulfate proteoglycans, including Syndecan-1. NK1-targeted CARs demonstrated broadly similar potency, indicated by destruction of MET-expressing mesothelioma cell lines, accompanied by cytokine release. anti-tumor activity was demonstrated following intraperitoneal delivery to mice with an established mesothelioma xenograft. Progressive tumor regression occurred without weight loss or other clinical indicators of toxicity. These data confirm the frequent expression of MET in malignant pleural mesothelioma and demonstrate that this can be targeted effectively and safely using a CAR T-cell immunotherapeutic strategy.

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…Smaller moieties such as oligopeptides were also demonstrated to be adequate scaffold for the binding portion of CARs [175]. Additionally, synthetic proteins termed DARPins (designed ankyrin repeat proteins) can also be engineered to serve as CAR targeting moieties.…”

HGF/MET and the Immune System: Relevance for Cancer Immunotherapy

“…Another MET-targeted immunotherapy approach that has already been tested in preclinical mesothelioma models is the MET chimeric antigen receptor (CAR) T-cell immunotherapy [ 84 ]. CAR T-cell therapy is an innovative treatment consisting of the genetic modification of patient’s T-cells that makes them able to kill specific cancer cells.…”

“…In the study of Thayaparan et al, T-cells have been engineered to express HGF as a chimeric antigen to target MET-expressing cancer cells [ 84 ]. The efficacy of this approach was confirmed both in vitro and in vivo: a consistent level of cancer cell killing and tumor regression was detected in all models, and it was also accompanied by the release of IFN-gamma and IL-2 from MET-targeted CAR-T-cells, confirming that cancer cell death was immune-mediated.…”

Programming CAR-T cells to kill cancer

“…Conversely, a disadvantage of using scFv-binding domains is their tendency for oligomerization, which can lead to tonic signalling and T-cell exhaustion 17 . Alternative binding domains have been used in preclinical studies, including receptors 18 , ligands 19 , cytokines 20,21 , DARPins (designed ankyrin repeat proteins) 22 , adnectins 23 , Fc receptor fragments 24 , nanobodies 25 , peptides 26 and variable lymphocyte receptors 27 . The relative efficacy, safety and immunogenicity of these alternative binders have not yet been fully investigated and are the focus of substantial ongoing work.…”