Development of an improved mammalian overexpression method for human CD62L.

•We previously developed a glutamine synthetase (GS)-based mammalian recombinant protein expression system with 5–30mg/L yield.•We improved the GS-based method using a single-round in situ amplification to replace the multi-round gene selection and amplification.•The improved method shortens the cell line construction from 4–6month to 2months.•We also developed a MSX resistance assay as an alternative to ELISA for evaluating the expression level of stable recombinant CHO cell lines.