Changes in actin and E-cadherin expression induced by 5-aminolevulinic acid photodynamic therapy in normal and Ras-transfected human mammary cell lines

Photodynamic therapy (PDT) is an anticancer treatment based on light-induced destruction of photosensitised malignant cells. It has been reported that PDT strongly affects cell–cell and cell-substrate adhesion through the reorganization of some cytoskeletal and adhesion proteins. m of the present work was to study the changes induced by PDT employing aminolevulinic acid (ALA), on the cytoskeleton actin network and E-cadherin expression. We employed the normal mammary HB4a cell line and its tumor counterpart transfected with the oncogene H-Ras, which has been shown to be resistant to PDT. sertion induces per se disorganization of both F-actin and E-cadherin distribution. ALA-PDT induces on HB4a cells a dramatic disorganization of actin stress fibers, resembling normal Ras-transfected cells. After 48 h some features of disorganization remain present. In HB4a-Ras cells, F-actin exhibits signals of photodamage, but distribution is recovered 24 h after treatment. On the other hand, PDT did not impact on E-cadherin distribution, other than a transient disorganization, which was recovered at 24 h. Moreover, E-cadherin disorganization did not favoured cell–cell detachment after PDT of HB4a-Ras cells. but not E-cadherin constitutes in this model an important target of PDT. The fact that some features of microfilament disorganization remain present in HB4a surviving cells but not in Ras-transfected cells, suggests that cytoskeletal structures such as F-actin may be involved in the mechanisms of resistance to PDT.