Dr. Öğr. Üyesi Tolga Sütlü

The two defining themes of our laboratory is gene therapy and cancer immunotherapy. We intend to dwell into the basics and focus on the molecular mechanisms of viral gene delivery, with special reference on innate immune responses against viral vectors. In parallel, we work on both basic and preclinical aspects of genetically modified Natural Killer (NK) cells a in cancer immunotherapy. Examples of research projects carried out in our laboratory are as follows:

Engineering of viral vectors and viral gene delivery processes for efficient genetic modification of human cells under clinically compatible conditions.

Especially in cells of the innate immune system, the success of viral gene delivery has always proven challenging and less efficient than other cells of hematopoietic origin. The major hurdle in gene therapy is the delivery of the gene-of-interest into the cell. When it comes to hijacking cellular defense mechanisms and carrying genetic information into the cell, nature presents us with an evolutionarily perfected carrier: viruses. As with wild-type viruses, intracellular recognition of viral components by pattern recognition receptors is a possible mechanism of cellular response against viral vectors. Inevitably, this would render viral vectors prone to inducing strong innate responses upon target cell infection. It is possible that TLR or RLR mediated detection of viral vector components might activate an anti-viral response, negatively affecting the efficiency of viral gene delivery. In order to test this hypothesis, we have previously attempted to use small molecule inhibitors of TLR and RLR signaling preceding lentiviral transduction, and observed a dramatic increase in gene delivery efficiency.

Introduction of Chimeric Antigen Receptors (CARs) to Natural Killer (NK) cells has so far been the only practical method for targeting NK cells to specific surface antigens. In contrast, T cell receptor (TCR) gene therapy can supply large populations of Cytotoxic T-Lymphocytes (CTL) genetically modified to express a TCR that can also target intracellular antigens. The technique of genetically introducing antigen-specific receptors, such as T cell receptors (TCRs) or chimeric antigen receptors (CARs), to redirect T cell-mediated immunity against tumor-associated antigens (TAAs) has delivered promising clinical results and CAR-T cell therapies have recently received clinical approval.

While CARs do have the ability to direct T and natural killer (NK) cell-mediated cytotoxicity, they are blind to intracellular antigens and can only target cell surface antigens. Alternatively, TCRs allow recognition of epitopes from both intracellular and cell surface antigens via Major Histocompatibility Complex (MHC) presentation. Nevertheless, this has so far only been tested in T cells.

However, a major barrier in the development of safe CTL-TCR therapies exists, wherein the mispairing of endogenous and genetically transferred TCR subunits often leads to formation of TCRs with undesirable off-target specificity. In order to overcome this obstacle and enable specific intracellular antigen targeting, we have tested the use of NK cells for TCR gene transfer. Our results show that gene delivery to induce ectopic expression of TCR α/β chains, along with CD3 subunits, enables the functional expression of an antigen specific TCR complex on NK cells. Most importantly, we demonstrate that introduction of a TCR complex to NK cells enables Major Histocompatibility Complex (MHC)-restricted, antigen-specific killing of tumor cells both in vitro and in vivo. Antigen-specific targeting of NK cells via TCR gene delivery stands out as a unique discovery providing a novel tool in the field of adoptive immunotherapy which can also overcome the major hurdle of “mispairing” in TCR gene therapy.