Mammalian cells are the most widely used hosts for the production of industrial biopharmaceuticals. However, recombinant cell lines often exhibit low expression and instability during culture period. In order to circumvent such a situation, targeted gene integration is designed to optimize product expression. Crispr/Cas9 technology is a newly developed gene editing tool and has been widely used in animals, plants and mammalian cells. In this work, we described a universal protocol as well as some cases usin...