Flp-In™ Cell Lines are designed for rapid generation of stable cell lines that express a protein of interest from a Flp-In™ expression vector. These cells contain a single stably integrated FRT site at a transcriptionally active genomic locus. Targeted integration of a Flp-In™ expression vector ensures high-level expression of your gene of interest. There are six Flp-In™ Cell Lines available for the generation of isogenic stable cell lines and a Flp-In™ T-REx™ Cell Line for the generation of tetracycline-regulated stable cell lines. Flp-In™-CV-1, Flp-In™-293, Flp-In™-BHK, Flp-In™-Jurkat, and Flp-In™-3T3 Cell Lines were created by transfecting the parent cell lines with pFRT/lacZeo and selecting for stable Zeocin™- resistant clones. The Flp-In™-CHO Cell Line was created by transfecting CHO cells with pFRT/lacZeo2 and selecting for Zeocin™-resistant clones. The Flp-In™ T-REx™-293 Cell Line contains pFRT/lacZeo and pcDNA™6/TR (from the T-REx™ System) stably integrated. Co-transfection of the Flp-In™ Cell Lines with a Flp-In™ expression vector and the Flp recombinase vector, pOG44, results in targeted integration of the expression vector to the same locus in every cell, ensuring homogeneous levels of gene expression.

Choosing your Flp-In™ Vector/Cell Line Combination
The Flp-In™-CV-1, Flp-In™-293, Flp-In™-CHO, and Flp-In™-Jurkat Cell Lines (Figure 1) work well with Flp-In™ vectors that express a gene from the CMV promoter (pcDNA™5/FRT, pcDNA5/FRT/V5-His-TOPO™, and pSecTag/FRT/V5-His-TOPO™). Flp-In™-BHK and Flp-In™-3T3 cells tend to down regulate the CMV promoter. Therefore, it is recommended that the Flp-In™ vectors containing the EF-1α promoter (pEF5/FRT/V5-DEST™ and pEF5/FRT/V5-D-TOPO™) be used with these cell lines.