The expression and function of the killer-specific secretory protein of 37 kDa (Ksp37) in natural killer (NK) cells

Natural killer (NK) cells in the human body play a critical role in immunosurveillance and the control of cancer metastasis, mainly due to their capacity to respond spontaneously to targets without the need for prior antigen exposure. The latter, in junction with reported manageable safety profiles and encouraging signs of efficacy, have posed natural killer cell-based immunotherapies as a promising area of clinical research. Nonetheless, there remain pressing hurdles that need to be addressed, including how to deal with immunosuppressive factors and how to overcome the scarcity of growth factors needed for NK cell proliferation and persistence in-vivo. In this regard, the present project aimed at contributing to a more comprehensive understanding of NK cell biology by means of investigating the yet unknown role of the Killer cell secretory protein of 37kDa (Ksp37). In concrete, the thesis focused on the current data available hinting at a potential involvement of Ksp37 in cell-mediated cytolysis and its stipulated ability to bind FGF2. With this purpose in mind, genetically modified NK-92 cell lines overexpressing Ksp37 were employed as effector cells, whilst Panc-1 cells, both with and without fibroblast growth factor 2 (FGF2) gene knockout, were used as targets. In summary, the cytotoxicity appeared to be intrinsically lower in NK92 cells overexpressing Ksp37. This finding is somewhat unexpected and needs confirmation in further experiments. Notwithstanding, the overexpression models used in the present project render a simple yet reliable fashion to secrete Ksp37 protein into the media. Tool that, in light of the new evidence for the binding of Ksp37 to FGF2 herein discussed, opens up a new path for a more targeted approach to decipher the biological relevance of Ksp37. All in all, this project has provided preliminary evidence for (i) the capacity of Ksp37 to physically interact with FGF2, (ii) the lack of direct cytolytic involvement of Ksp37, and (iii) the suitability of pumpless microfluidic chip systems for studying NK cells in a dynamic 3D context. Insights that carry the potential for bringing forth a better understanding of FGF2 dysregulation in cancer development and perhaps even additional tools to address it.