Reversal of the Migratory and Invasive Phenotype of Ras-Transfected Mammary Cells by Photodynamic Therapy Treatment

Abstract

Photodynamic therapy (PDT) is a non-thermal technique for inducing tumour damage followingadministration of a light-activated photosensitizing drug (PS). In a previous work we found that PDTinduces cytoskeleton changes in HB4a-Ras cells (human mammary breast carcinoma HB4a cellstransfected with the RAS oncogene). In the present work we have studied the migratory and invasivefeatures and the expression of proteins related to these processes on HB4a-Ras cells after 3 successivecycles of PDT using different PSs: 5-aminolevulinic acid (ALA), Verteporfin (Verte), mtetrahydroxyphenylchlorin(m-THPC) and Merocyanine 540 (MC). A slight (1.25- to -2 fold) degree ofresistance was acquired in cell populations subjected to the three successive PDT treatments. However,complete cell killing was achieved after a light dose increase.Regardless of the PS employed, all the PDT-treated populations had shorter stress fibres than theuntreated control HB4a-Ras cells, and the number of dorsal stress fibres was decreased in the PDTtreatedpopulations. E-Cadherin distribution, which was already aberrant in HB4a-Ras cells, becameeven more diffuse in the PDT-treated populations, though its expression was increased in some ofthem.The strong migratory and invasive ability of HB4a-Ras cells in vitro was impaired in all the PDTtreatedpopulations, with a behaviour that was similar to the parental non-tumoral HB4a cells.MMP-2 and MMP-9 metalloproteinase activities were also impaired in the PDT-treated populations.The evidence presented herein suggests that the cells surviving PDT would be less metastatic than theinitial population.These findings encourage the use of PDT in combination with other treatments such as intraoperativeor post-surgery therapeutic procedures.