Figure 6.

Counter-selection of cells harboring unwanted auxiliary vector integration. (a) Vector used. (b) Flow cytometric analysis of untransfected Jurkat cells and transfected Jurkat cells that were exposed to puromycin selection. Cells resistant to puromycin are almost uniformly positive for EGFR. (c) B16 colony formation by the indicated cell populations. Top: untransfected cells; middle: transfected cells; bottom: transfected cells that were subjected to negative selection. Numbers indicate input cell numbers times 10^–3. Note that counter-selection against EGFR expression leads to the formation of only few puromycin-resistant colonies. (d) EGFR expression on untransfected cells (left) and transfected and puromycin selected cells (right). The majority of cells surviving puromycin treatment retain EGFR expression.