COLO 320DM cells (A), CHO DG44 cells (B) and CHO-K1 cells (C) were transfected with IR/MAR-bearing pBM-MycLH or the control IR/MAR-negative pV-MycLH plasmid. CHO DG44 cells were co-transfected with IR/MAR-bearing pΔBN.AR1 and pMycLH plasmids (D, E), or co-transfected with control pSFV-V and pMycLH (D, F) plasmids. After selection of the stable transformant for about one month, gene amplification (A to C, D) and antibody expression (A’ to D’) were examined by FISH and ELISA, respectively. Clones were obtained from the cells shown in D by the limiting dilution in 96 well plates. The wells bearing a single colony were microscopically determined, and the culture liquid was analyzed by ELISA. The horizontal axis of panel E or F corresponds to 43 or 53 clones, respectively.