Resveratrol-triggered genetic switches, which can control in vivo tumor-targeted chimeric antigen receptor T-cell (CAR T) therapy, have been developed by ECNU researchers, who demonstrated that the new tools enabled maximized in vivo immunotherapeutic efficacy while minimizing toxicity.
Our group has created the first [resveratrol]-controlled genetic switch enabling us to control CAR T-cell therapy, said principal investigator Haifeng Ye, a professor in the Institute of Biomedical Sciences and School of Life Sciences at ECNU.
Such resveratrol-controlled switches establish the proof of concept for strategies controlling cancer immunotherapies based on the RES-regulated repression and/or induction of therapeutic CAR T cells, the authors reported in the August 2021 issue of Proceedings of the National Academy of Sciences.
CAR T-cell immunotherapy has radically transformed the treatment of some B-cell cancers, by enabling patient-derived T cells to recognize cancer antigens and eliminate tumor cells.
Since the initial approval of CD19-specific CAR T cells for treating B-cell leukemias and lymphomas, numerous CAR T-cell products have emerged, but challenges remain concerning safety and lack of control over engineered cells.
For example, rapid, robust responses afer CAR T-cell infusion can induce immune-mediated side effects, but potent therapeutic effects require robust expansion and activation of sufficient numbers of CAR T cells.
Therefore, it is necessary to develop control systems that can precisely control activation and deactivation of CAR T cells to avoid severe side effects, Ye told BioWorld Science.
Switches have improved CAR T-cell safety and efficacy by regulating CAR expression and controlling T-cell activation, with different systems developed to control engineered T cells in a 'function on/off' mode to mitigate toxicity.
Several user-controlled switches have reportedly eliminated infused T cells from patients showing severe toxicity, but these may not ensure safety against toxicities induced immediately upon cell infusion.
Gene- and cell-based therapies are widely held to represent the next frontier in medicine, but translating promising therapeutic technologies into the clinic is limited by a lack of safe and remotely controllable inducers, said Ye.
We anticipate that biocompatible, controllable genetic switches will allow dynamic interventions in gene- and cell-based precision medicine, so we have focused on developing safe and effective remote-controllable switches for gene/cell-based precision therapy, he said, noting that in this regard, resveratrol is particularly promising.
A dietary stilbenoid, resveratrol has been shown to be a safe inducer compound for genetic switches designed for immunotherapeutic application. It also has beneficial effects against aging, cancer, cardiovascular diseases and inflammation in its own right, making it an ideal trigger molecule for genetic devices designed for therapeutic applications, Ye said.
To enable safer cancer immunotherapy with functional off/on modalities, Ye and his team harnessed resveratrol-responsive activators and repressors to develop a repressible (RESrep) and inducible transgene expression (RESind) switch, respectively.
After optimization, these tools enabled control of CAR expression and CAR-mediated antitumor function in engineered human cells.
We optimized the RES-triggered transgene expression devices with different synthetic transactivators or transrepressors, as well as RES-responsive promotors, notably the TtgR binding sites, said Ye.
Our results demonstrated that T cells engineered with a RES-repressible or -inducible CAR expression (RESrep-CAR or RESind-CAR) could fine-tune CAR expression levels and CAR-mediated cell activation in human primary T cells by adjusting RES concentrations.
The researchers further demonstrated that a RESrep-CAR switch could effectively inhibit T-cell activation upon RES administration in primary T cells and in a xenograf tumor mouse model.
We verified that T cells engineered with RESrep-CAR provide effective and titratable inhibition over T-cell activation by monitoring CAR-mediated cytokine release and tumor cell killing in primary human T cells and in xenograf mouse models, explained Ye.
Our RESrep-CAR device could be used to inhibit infused CAR T-cell activity, potentially preventing toxicity-associated morbidity and mortality when patients are at a high risk for clinical complications in early-stage of CAR T therapy, he said, adding the pattern and extent of functional inhibition achieved by RES highlights its clinical potential.
Additionally, the researchers showed how the RESind-CAR switch could achieve fine-tuned and reversible control over T-cell activation via a RES-titratable mechanism.
We verified that T cells engineered with RESind-CAR provide fine-tuned reversible control over T-cell activation by monitoring CAR-mediated cytokine release and tumor cell killing in primary human T cells and in xenograf mouse models, said Ye.
In practice, use of RESind-CAR in clinical trials could coincide with monitoring cell infusion toxicity responses and real-time CAR T-cell efficacy, enabling ongoing [resveratrol]-mediated CAR T-cell activity adjustment to achieve highly precise, personalized, therapeutic outcomes.
In future, the sensitivity of [resveratrol]-controlled CAR T cells needs to be improved, which we anticipate could be achieved by optimizing the operator sequences and directed protein evolution approaches, or by rational protein design to improve transactivator and/or transrepressor properties, Ye said.
Such switches, he said, could become a safe, robust, and convenient strategy for dynamic control of the therapeutic outputs of future gene- and cell-based precision medicine. (Yang, L. et al. Proc Natl Acad Sci USA (PNAS) 2021, 118:e2106612118)
Paper link: https://doi.org/10.1073/pnas.2106612118