Figure 1.

Histochemical detection of β-gal expression. (A and B) After infection with the retrovirus Gal/Neo and selection with G418, cells were stained in situ with X-Gal to confirm the expression of β-gal. Whereas the majority of cells from individual clones of cell line HCT116 was not stained (A), virtually all cells of HT29 stained intensely blue (B). (C and D) Cells were stained in situ with X-Gal after retroviral infection with Gal/Hyg and selection with hygromycin. Whereas virtually all HT29 cells stained blue (D), the majority of cells from individual clones of HCT116+ch3 were not stained (C). (All ×10.)