PHOTOFRIN-INDUCED FLUORESCENCE IN PROGRESSIVE AND REGRESSIVE MURINE COLONIC-CANCER CELLS - CORRELATION WITH CELL PHOTOSENSITIVITY

Microspectrofluorometry and fluorescence imaging were used to investig ate the intracellular fluorescence of two murine colonic cancer cell l ines - a progressive cell line (PROb) and a regressive cell line (REGb ) - incubated with Photofrin. These two cell lines, which were initial ly cloned from the same chemically induced colonic murine cancer, diff er in their metastatic properties and have been considered as models t o mimic the tumoral cell heterogeneity. The fluorescence from cytoplas mic area of cells incubated with Photofrin appeared as a complex emiss ion, with two maxima at 632 and 695 nm assigned to monomer species, an d a poorly resolved band around 665 nm assigned to aggregates. The spe ctral distribution was shown to depend on the incubation time, with an aggregate contribution increasing for extended periods. The amount of Photofrin uptake, as determined from the total fluorescence intensity , was found for PROb to be twice that for REGb. However, the phototoxi cities were quite similar for both cell lines, suggesting that drug co ncentration may not be the only determining factor in photobiological efficiency.