Figure 6.

Very low concentrations of MTX can enhance PpIX in LNCaP cells. At time zero, LNCaP cells (3 × 10⁵ cells dish⁻¹) were plated on glass cover slips as described in Materials and Methods, and at 24 h, switched to medium containing variable quantities of MTX (0.001–1.0 mg l⁻¹). At 72 h, new medium with 1 mM ALA was added and cells were incubated for 4 h before visualisation of PpIX-specific fluorescence by confocal microscopy. (A–D) Representative images (shown here in grey scale) of PpIX-specific fluorescence in LNCaP cells at the MTX concentrations indicated. (E) Semiquantitative analysis of the relative number of cells that were PpIX-positive (% of total cells), performed as described in Materials and Methods. Bars are the mean±s.d. of three digital images per transfection. (^*) P<0.001; (^**) P<0.0005. The experiment was performed twice with similar results.