Photodynamic effect of a galactodendritic porphyrin on the cytoskeletal network of human bladder cancer cells

Abstract

PorGal8, a porphyrin conjugated with dendritic galactose units, binds to galectin-1 in bladder cancer cells and induces localized cell death after light activation. Although it has been previously shown that photodynamic treatment (PDT) affects the cytoskeleton of cancer cells, it is still unclear how this change contributes to PDT-induced cell death. In this work, the association between changes in the cytoskeletal constituents and cell death triggered by PDT with PorGal8 was investigated in two bladder cancer cell lines derived from transitional cell carcinoma (UM-UC-3 and HT-1376 cells). Photoactivated PorGal8 did not change [Formula: see text]-tubulin protein levels in UM-UC-3 cells but reduced [Formula: see text]-tubulin in HT-1376 cells. A significant decrease in vimentin protein levels was exhibited in both cell lines 24 hours after irradiation. In the initial post-irradiation stage, both cell lines showed changes in actin filaments, but only recovery was apparent in HT-1376 cells 24 hours after treatment. In cells expressing higher levels of galectin-1 (UM-UC-3), PDT did not significantly affect these protein levels. Interestingly, 24 hours after irradiation, there was a robust increase in galectin-1 levels in HT-1376 cells. A small GTPases family protein, RhoA, involved in the galectin-1 expression, was also evaluated, indicating an increase in HT-1376 cells 24 hours after therapy. Overall, our results bring new insights into the relationship between the phototoxic effects of PorGal8 and the disorganization of the cytoskeleton. Clarifying the mechanisms underlying PDT efficiency might contribute to envisaging new potential therapeutic adjuvants for PDT, acting on the cytoskeleton, to treat resistant cancers.