PHOTODYNAMIC THERAPY DECREASES CANCER COLONIC CELL ADHESIVENESS AND METASTATIC POTENTIAL

Plasma membrane damage induced in various cell targets by hematoporphy rin (HPD) photodynamic therapy (PDT) could modify cancer cell adhesive ness, an important parameter in cancer metastasis. We investigated the effect of HPD or HPD incubation followed by argon laser light on the adhesiveness of progressive (PROb) or regressive (REGb) cancer cells o f the same colonic origin but with a different in vivo metastatic pote ntial. Adhesiveness was studied on plastic or endothelial cell monolay ers (ECM). In the absence of treatment, both PROb and REGb cells adher ed better on plastic than on ECM. HPD alone or HPD-PDT induced toxicit y proportional to the HPD dose. HPD-PDT increased the adhesiveness rat e of both cell lines on plastic and decreased it on ECM. HPD-PDT of EC M increased adhesiveness, but only at HPD doses causing at least 50% c ell death. With HPD treatment alone or HPD-PDT of culture media, there was no significant decrease in cell adhesiveness to ECM. We also stud ied the effect of HPD or HPD incubation followed by argon laser light on the metastatic potential of cancer cells, which was decreased for P ROb with HPD alone or HPD-PDT. Decreased adhesiveness of colonic cance r cells to ECM after HPD-PDT was thus correlated with decreased metast atic potential. REGb cells did not acquire a progressive phenotype eit her in vitro or in vivo after HPD-PDT.