Impact on cell migration and invasion driven by photodynamic therapy on Ras-expressing cells

GUSTAVO CALVO; DANIEL SAENZ; ADRIANA CASAS; MARINA SIMIAN; ROCíO SAMPAYO; LEANDRO MAMONE; PABLO VALLECORSA; ALCIRA BATLLE; GABRIELA DI VENOSA

Córdoba

Congreso; 16th International Congress on Photobiology; 2014

International Union of Photobiology

PDT (Photodynamic therapy), an anticancer treatment, involves the administration of a tumor-localizing PS (photosensitizer) and its activation by visible light, producing short-lived cytotoxic oxygen species, to result primarily in singlet oxygen?induced photodamage. Verte (Verteporfin), ALA (5-aminolaevulinic acid) which induces endogenous Protoporphyrin IX, Foscan (m-THPC) and MC540 (Merocyanine 540) are current clinical PS. 20-30% of tumors express Ras mutations. Since the H-Ras oncogen confers resistance to PDT regardless of the PS, we carried out a series of studies employing the mammary adenocarcinoma cell line HB4a-Ras. We exposed the cells to 1, 2 or 3 PDT treatments employing ALA, Verte, Foscan and MC540, and studied the impact of the treatment on surviving cells. PDT treatment induces a slight resistance upon the third cycle, being the initial and final light lethal doses necessary to induce 50% of cell death: 50 and 120 mJ/cm2 for ALA-PDT; 44 and 77 mJ/cm2 for Verte- PDT; 49 and 117 mJ/cm2 for Foscan-PDT; 17 mJ/cm2 and 24 mJ/cm2 for MC540-PDT. PS incorporation into the cells as well as cell division rate were not modified, but differences in morphology, and increased adhesion become evidenced. The rate of migration (wound assay) and invasion (through Matrigel in transwells) decreased with the number of treatments. ALA, Verte and Foscan ?PDT induced a ten-fold reduction in the invasion degree and MC540-PDT inhibited invasion completely. Matrix metalloproteases 2 and 9 expression was modified, e.g. PDT-MC540 induced 50% decrease after the first PDT cycle. Western blot assays revealed no changes in cadherin expression and â1 integrin, as a consequence of PDT treatments. This study highlights the impact of repetitive PDT decreasing the potential dissemination of tumors and generating scarce resistance thus being an option to be combined with surgery or others treatments.