 Thus, in order to obtain a "stable" transfection, a gene which confers a significant survival advantage must also be transfected, causing the few cells that did integrate the transfected DNA into their genomes to increase their population as cells that did not integrate the DNA are eliminated.In the case of this study, "grow[th] in increasing concentrations of methotrexate" promoted the survival of stably transfected cells, and diminished the survival of other cells.The Chinese hamster ovary cells that were stably transfected produced significant quantities of Factor IX, which was shown to have substantial coagulant properties, though of a lesser degree than Factor IX produced from human blood