Mechanisms of Action and Overcoming Obstacles in Solid Tumours with Chimeric Antigen Receptor (CAR) T-Cell Therapy

A revolutionary method in oncological immunotherapy is chimeric antigen receptor T-cell (CAR-T) therapy, which involves isolating a patient's own T cells, genetically reprogramming them ex vivo to express synthetic antigen-binding receptors, and then reinfusing them to produce targeted anti-tumor cytotoxicity. The molecular and translational understanding of how CAR-T cells identify and destroy cancerous cells is summarised in this article, and explains why their clinical impact diverges markedly between haematologic cancers and solid tumour settings. The standard manufacturing pipeline encompasses leukapheresis, viral-mediated gene transfer encoding an antigen-recognition domain generated from antibodies combined with T-cell activation and co-stimulatory signalling modules, ex vivo expansion, lymphodepleting conditioning, and patient reinfusion. Once reintroduced, engineered cells proliferate and detect desired antigens by a process outside of the predominant histocompatibility complex (MHC). Tumour cell destruction proceeds through multiple cytotoxic routes, including perforingranzyme-mediated apoptosis, Fas/Fas ligand death signalling, and inflammatory cytokine secretion that recruits and amplifies endogenous immune responses. The highest therapeutic returns are documented in B-cell haematologic cancers, with up to 90% of relapsed or refractory instances of acute lymphoblastic leukaemia experiencing full remission with CD19-directed treatment. In solid tumour contexts—encompassing colorectal, pancreatic, breast, ovarian, and primary brain cancers such as glioblastoma—therapeutic outcomes remain limited by physical stromal barriers, inadequate T-cell trafficking, antigen heterogeneity, and profoundly immunosuppressive microenvironments driven by myeloid cells and inhibitory cytokines. Emerging strategies include multi-antigen targeting constructs, resistance engineering against immunosuppressive signalling, intratumoral delivery routes, sophisticated CAR architectures, allogeneic off-the-shelf platforms, CRISPR-based gene editing, and CAR-macrophage technologies. Combination regimens incorporating immune checkpoint blockade, nanotechnology-assisted delivery, proton irradiation to enhance mesothelin expression, and oncolytic viral co-therapy are collectively aimed at expanding CAR-mediated cellular immunotherapy well beyond its current haematologic scope