This technology includes an efficient lentiviral vector-based method for gene transfer into NK cells and demonstrates a stable and long-term robust expression of transgenes for the treatment of cancer. High gene transfer rates into primary cells being transduced and the ability to produce high titers of virus particles for large-scale transduction of patient cells are prerequisites for clinical trials. Lentiviral vectors can be produced in high titer and concentrated without compromising their transduction efficiency. Additionally, the described method is cheaper and simpler to apply clinically as it does not require the need for several cumbersome and expensive. The present invention of a highly efficient lentiviral vector-based gene transfer protocol can be used to complement a number of already optimized ex vivo NK cell expansion protocols to generate large numbers of genetically reprogrammed NK cells potentially revolutionizing NK cell based immunotherapeutic approaches by enhancing their antitumor efficacy in patient with cancer.