An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Endowing chimeric antigen receptor (CAR) T cells with additional potent functionalities holds strong potential for improving their antitumor activity. However, because potency could be deleterious without control, these additional features need to be tightly regulated. Immune pathways offer a wide array of tightly regulated genes that can be repurposed to express potent functionalities in a highly controlled manner. Here, we explore this concept by repurposing TCR, CD25 and PD1, three major players of the T cell activation pathway. We insert the CAR into the TCRα gene (TRAC CAR ), and IL-12P70 into either IL2Rα or PDCD1 genes. This process results in transient, antigen concentration-dependent IL-12P70 secretion, increases TRAC CAR T cell cytotoxicity and extends survival of tumor-bearing mice. This gene network repurposing strategy can be extended to other cellular pathways, thus paving the way for generating smart CAR T cells able to integrate biological inputs and to translate them into therapeutic outputs in a highly regulated manner.

A key to the success of chimeric antigen receptor (CAR) T-cell based therapies greatly rely on the capacity to identify and target antigens with expression restrained to tumor cells. Here we present a strategy to generate CAR T-cells that are only effective locally (tumor tissue), potentially also increasing the choice of targetable antigens. By fusing an oxygen sensitive subdomain of HIF1α to a CAR scaffold, we generated CAR T-cells that are responsive to a hypoxic environment, a hallmark of certain tumors. Along with the development of oxygen-sensitive CAR T-cells, this work also provides a basic framework to use a multi-chain CAR as a platform to create the next generation of smarter self-decision making CAR T-cells.

The ability to control T cells engineered to permanently express chimeric antigen receptors (CARs) is a key feature to improve safety. Here, we describe the development of a new CAR architecture with an integrated switch-on system that permits to control the CAR T-cell function. This system offers the advantage of a transient CAR T-cell for safety while letting open the possibility of multiple cytotoxicity cycles using a small molecule drug.

Adoptive immunotherapy using engineered T-cells has emerged as a powerful approach to treat cancer. The potential of this approach relies on the ability to redirect the specificity of T cells through genetic engineering. Novel specificities in T cells have been typically implemented through the genetic transfer of the so-called chimeric antigen receptors (CARs). CARs are synthetic receptors composed of an extracellular targeting moiety and one or more intracytoplasmic signaling domain derived from lymphocyte activation receptors. Present CAR architectures are designed to combine all relevant domains within a single polypeptide, thereby; they combine advantages of MHC unrestricted target recognition to the potent native effector mechanisms of the T cell. Although adoptive transfer of CAR T cells is proven to be an effective cancer therapy, potential adverse effects such as cytokine release syndrome (CRS) and/or the risk of on-target off-tumor targeting are still a major concern. Synthetic biology applies many of the principles of engineering to the field of biology in order to create biological devices which can ultimately be integrated into increasingly complex systems. Our ability to engineer synthetic systems in primary T-cells that function as Boolean logic gates responding to multiple inputs would benefit adoptive immunotherapy using engineered T-cells. Exogenous or endogenous environmental signal integration by a modular AND gate may represent an important advancement in improving our control of the safety of the CAR T-cell technology. Here, we describe the development of novel CAR designs that integrate new components directly within the CAR architecture to improve our capacity to spatiotemporally control and switch the CAR T-cells functions between on and off states. In particular, we showed that such a system can be engineered to control the CAR through addition of an exogenous small molecule (Rapamycin or synthetic rapalogs) ultimately inducing the cytolytic properties of the engineered T-cell. Alternatively, properties of the tumor microenvironment can also be used as additional endogenous input to the target antigen recognition. We showed that low oxygen levels can be used to trigger the CAR surface presentation, creating a so called "self-decision making" CAR T-cell.

Abstract Adoptive immunotherapy using engineered T-cells has emerged as a powerful approach to treat cancer. The potential of this approach relies on the ability to redirect the specificity of T cells through genetic engineering. Novel specificities in T cells have been typically implemented through the genetic transfer of the so-called chimeric antigen receptors (CARs). CARs are synthetic receptors that associated an extracellular targeting moiety with one or more intracytoplasmic signaling domain derived from lymphocyte activation receptors. Present CAR architectures are designed to combine all relevant domains within a single polypeptide, thereby; they combines advantages of MHC unrestricted target recognition to the potent native effector mechanisms of the T cell. Although adoptive transfer of CAR T cells is proven to be an effective strategy to cancer therapy, potential adverse effects such as Cytokines Release Syndrome (CRS) and/or the risk of on-target off-tumor targeting are still a major concern. To date only suicide mechanisms that can eradicate the engineered T-Cell “at will” or mRNA CAR transfection approaches have been proposed to addresses this safety issue. Here, we describe the development of a small molecule based switch-on technology to control the surface presentation of a chimeric antigen receptor in T-cells. By grafting protein domains that can interact upon addition of a small molecule drug in the hinge domain of the CAR architecture, we are able to turn a T-cell endowed with an engineered CAR from an off-state to an on-state, in term surface presentation as well as for its specific cytolytic properties. This system offers the advantage of a “transient CAR T-cell” for safety while letting open the possibility of multiple cytotoxicity cycles using a small molecule drug. This non-lethal control system of CAR engineered T-cells represents an important advance for the safety of this technology. Citation Format: Alexandre Juillerat, Alan Marechal, Jean-Marie Filhol, Philippe Duchateau, Laurent Poirot. Improved CAR safety by a non-lethal switch to control CAR activity at the T-cell surface membrane. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2307.

A key feature when designing DNA targeting tools and especially nucleases is specificity. The ability to control and tune this important parameter represents an invaluable advance to the development of such molecular scissors. Here, we identified and characterized new non-conventional RVDs (ncRVDs) that possess novel intrinsic targeting specificity features. We further report a strategy to control TALEN targeting based on the exclusion capacities of ncRVDs (discrimination between different nucleotides). By implementing such ncRVDs, we demonstrated in living cells the possibility to efficiently promote TALEN-mediated processing of a target in the HBB locus and alleviate undesired off-site cleavage. We anticipate that this method can greatly benefit to designer nucleases, especially for therapeutic applications and synthetic biology.

Diatoms, a major group of photosynthetic microalgae, have a high biotechnological potential that has not been fully exploited because of the paucity of available genetic tools. Here we demonstrate targeted and stable modifications of the genome of the marine diatom Phaeodactylum tricornutum, using both meganucleases and TALE nucleases. When nuclease-encoding constructs are co-transformed with a selectable marker, high frequencies of genome modifications are readily attained with 56 and 27% of the colonies exhibiting targeted mutagenesis or targeted gene insertion, respectively. The generation of an enhanced lipid-producing strain (45-fold increase in triacylglycerol accumulation) through the disruption of the UDP-glucose pyrophosphorylase gene exemplifies the power of genome engineering to harness diatoms for biofuel production.

A key issue when designing and using DNA-targeting nucleases is specificity. Ideally, an optimal DNA-targeting tool has only one recognition site within a genomic sequence. In practice, however, almost all designer nucleases available today can accommodate one to several mutations within their target site. The ability to predict the specificity of targeting is thus highly desirable. Here, we describe the first comprehensive experimental study focused on the specificity of the four commonly used repeat variable diresidues (RVDs; NI:A, HD:C, NN:G and NG:T) incorporated in transcription activator-like effector nucleases (TALEN). The analysis of > 15 500 unique TALEN/DNA cleavage profiles allowed us to monitor the specificity gradient of the RVDs along a TALEN/DNA binding array and to present a specificity scoring matrix for RVD/nucleotide association. Furthermore, we report that TALEN can only accommodate a relatively small number of position-dependent mismatches while maintaining a detectable activity at endogenous loci in vivo, demonstrating the high specificity of these molecular tools. We thus envision that the results we provide will allow for more deliberate choices of DNA binding arrays and/or DNA targets, extending our engineering capabilities.

Within the past 2 years, transcription activator-like effector (TALE) DNA binding domains have emerged as the new generation of engineerable platform for production of custom DNA binding domains. However, their recently described sensitivity to cytosine methylation represents a major bottleneck for genome engineering applications. Using a combination of biochemical, structural, and cellular approaches, we were able to identify the molecular basis of such sensitivity and propose a simple, drug-free, and universal method to overcome it.