Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of hematological malignancies. The importance of the receptor costimulatory domain for long-term CAR-T cell engraftment and therapeutic efficacy was demonstrated with second-generation CAR-T cells. Fifth generation CAR-T cells are currently in preclinical trials. At the same time, the processes that orchestrate the activation and differentiation of CAR-T cells into a specific phenotype that predisposes them to long-term persistence are not fully understood. This review highlights ongoing research aimed at elucidating the role of CAR domains and T-cell signaling molecules involved in these processes.

Therapy with chimeric antigen receptor (CAR)-T cells has revolutionized the treatment of hematological malignancies. However, their application in solid tumors remains a formidable challenge due to obstacles such as the immunosuppressive tumor microenvironment, tumor heterogeneity, and limited T cell persistence. Although second- and third-generation CAR-T cells have shown restricted efficacy in clinical trials, next-generation strategies—including cytokine-armored CAR-T cells (e.g., IL-15, IL-7/CCL19), logic-gated systems, and localized delivery approaches—demonstrate promising potential to overcome these limitations. This review examines the major barriers impeding CAR-T cell efficacy in solid tumors, evaluates clinical outcomes from conventional CAR constructs, and highlights innovative strategies being tested in recent clinical trials. Key advances discussed include the use of dominant-negative receptors (e.g., TGFβRII) to combat immunosuppression and the co-expression of bispecific T cell engagers (BiTEs) to address antigen escape.

Background. Research in oncology assumes establishment and usage of xenograft animal models, meeting the requirements of humanity and rationality. Although praised as promising field of research, preclinical studies of low-molecular-weight inhibitors, antitumor monoclonal antibodies, vaccines, cellular therapy products, CAR-T cells entail continuous control of tumor growth dynamics. Luciferase detection of bioluminescence requires injection of a reporter substrate. However, injections not only are laborious, time-consuming and expensive, but are also stressful for animals. Thus, a vast variety of new visualization methods is employed, including proteins of the far-red spectrum.Objective. The study aimed to compare detection efficiency of tumor growth dynamics in mice models of cervical cancer, applying a commercially available line of fluorescent red protein derivatives of Katushka clade and Renilla luciferase, that is commonly used in in vivo studies. Design and methods. Xenograft mice models were derived injecting modified HeLa cell line, that expresses fluorescent reporter proteins: Katushka, Katushka2S, TurboRFP, TurboFP650 and Renilla enzyme. Results. Spectral properties and emission wavelength of far-red fluorescent protein Katushka and Katushka2S outlines these markers within RFP derivatives lineage as outstanding instrument for in vivo tumor visualization.Conclusion. Detection of fluorescent far-red reporters Katushka and Katushka2S can be considered as a credible alternative to Renilla luciferase bioluminescence in experimental models in vivo on the part of immunotherapy research.

Chimeric antigen receptor (CAR) T-cell therapy has revolutionised cancer gene therapy, yet its expansion into solid tumours is hindered by a critical vulnerability: the autonomous, “always-on” nature of conventional CAR constructs. This unregulated activity drives severe toxicities, including cytokine release syndrome (CRS) and on-target/off-tumour damage, while constitutive signalling in hostile tumour microenvironments (TMEs) accelerates T-cell exhaustion. Early safety strategies relied on irreversible genetic “kill switches,” which sacrifice the therapeutic cell population entirely. This review traces the conceptual evolution of CAR T-cell controllability from binary elimination towards platforms enabling graded, reversible, and spatiotemporally precise regulation. We examine the transition from calibrated signalling architectures and small-molecule-regulated split-CARs to advanced optogenetic and sonogenetic controllers, detailing the biophysics of photoreceptor pairs and their preclinical efficacy. Furthermore, we explore complementary architectures, including autonomous logic-gated receptors. Finally, we propose that the optimal next-generation CAR T product will integrate calibrated signalling, external control, and context-dependent armouring to achieve truly programmable, safe, and durable cellular immunotherapy.