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Genetic engineering is an important tool for redirecting the function of various types of immune cells and their use for therapeutic purpose. Although NK cells have many beneficial therapeutic features, genetic engineering of immune cells for targeted therapy focuses mostly on T cells. One of the major obstacles for NK cell immunotherapy is the lack of an efficient method for gene transfer. Lentiviral vectors have been proven to be a safe tool for genetic engineering, however lentiviral transduction is inefficient for NK cells. We show in this study that lentiviral vectors pseudotyped with a modified baboon envelope glycoprotein can transduce NK cells 20-fold or higher in comparison to VSV-G pseudotyped lentiviral vector. When we investigated the mechanism of transduction, we found that activated NK cells expressed baboon envelope receptor ASCT-2. Further analysis revealed that only a subset of NK cells could be expanded and transduced with an expression profile of NK56bright, CD16dim, TRAILhigh, and CX3CR1neg. Using CD19-CAR, we could show that CD19 redirected NK cells efficiently and specifically kill cell lines expressing CD19. Taken together, the results from this study will be important for future genetic modification and for redirecting of NK cell function for therapeutic purpose.

Background: The follicle-stimulating hormone (FSH)-receptor (FSHR) has been reported to be an attractive target for antibody therapy in human cancer. However, divergent immunohistochemical (IHC) findings have been reported for FSHR expression in tumor tissues, which could be due to the specificity of the antibodies used. Methods: Three frequently used antibodies (sc-7798, sc-13935, and FSHR323) were validated for their suitability in an immunohistochemical study for FSHR expression in different tissues. As quality control, two potential therapeutic anti-hFSHR Ylanthia® antibodies (Y010913, Y010916) were used. The specificity criteria for selection of antibodies were binding to native hFSHR of different sources, and no binding to non-related proteins. The ability of antibodies to stain the paraffin-embedded Flp-In Chinese hamster ovary (CHO)/FSHR cells was tested after application of different epitope retrieval methods. Results: From the five tested anti-hFSHR antibodies, only Y010913, Y010916, and FSHR323 showed specific binding to native, cell-presented hFSHR. Since Ylanthia® antibodies were selected to specifically recognize native FSHR, as required for a potential therapeutic antibody candidate, FSHR323 was the only antibody to detect the receptor in IHC/histochemical settings on transfected cells, and at markedly lower, physiological concentrations (ex., in Sertoli cells of human testes). The pattern of FSH323 staining noticed for ovarian, prostatic, and renal adenocarcinomas indicated that FSHR was expressed mainly in the peripheral tumor blood vessels. Conclusion: Of all published IHC antibodies tested, only antibody FSHR323 proved suitable for target validation of hFSHR in an IHC setting for cancer. Our studies could not confirm the previously reported FSHR overexpression in ovarian and prostate cancer cells. Instead, specific overexpression in peripheral tumor blood vessels could be confirmed after thorough validation of the antibodies used.