Figure 6.

Lung tumor cell-specific retention of compounds 2 and 2a (PS 2 and PS 2a). Co-cultures of primary lung squamous carcinoma cells and CSFE-labeled stromal fibroblasts were incubated for 4 h with culture medium containing 3.2 µM PS 2 or PS 2a followed by 6 and 24 h chase in PS-free medium. The culture-associated fluorescence was recorded at the times indicated by microscopy.