Abstract: The invention relates to the field of medicine and genetic engineering, specifically to guide RNAs and DNA fragments and to cell selection methods, which can be used in CRISPR-Cas9 systems for producing lines of natural killer cells with a PD-1 knockout gene and increased production of TRAIL or Fas-ligand proteins. Methods are disclosed for producing modified lines of NK cells: with a PD-1 knockout gene and constitutive Fas-ligand overexpression, with a PD-1 knockout gene and constitutive TRAIL overexpression, and also a method is described for selecting modified NK cells with a PD-1 knockout gene, which is carried out using a zeocin selection marker. The invention makes it possible to produce a high yield of modified lines of NK cells that are highly active in inhibiting the growth of tumour cells.