Non-melanoma skin cancer (NMSC) is the most common type of cancer worldwide, being subdivided in two types: basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). SCC is more aggressive than BCC, triggering severe health and aesthetic complications. Among non-invasive therapies to treat SCC, Photodynamic therapy (PDT) and 5-Fluorouracil (5-FU) are frequently employed in clinic. PDT uses a photosensitizing agent which in the presence of red light produces reactive oxygen species (ROS) causing cell death. 5-FU is a chemotherapeutic drug that inhibits thymidylate synthase, repressing cell cycle. Although satisfactory results are generally obtained, some cells can survive, proliferate and even disseminate, producing tumor relapses. In sense, we aim to study the role of 5-FU resistance development on SCC and BCC, evaluating the efficacy modulation to other therapies, focusing specifically on PDT. To study these processes, we isolated resistant lines to 5-FU of SCC13 and CSZ exposing them to 10 cycles of 72-hour 5-FU (10 μM). The viability assay MTT was used after each treatment to confirm and tested resistances. PpIX accumulation was studied by flow cytometry as well as its localization since it is related with the cell death. ROS production was evaluated measuring the fluorescence intensity after PDT. In addition, After, an evaluation of the PDT resistance was measured by MTT assay and 3D-spheroids. We observed SCC13 5-FU resistant line increased its sensibility to PDT damage showing a higher PpIX localization in membrane and lysosome and ROS production. In BCC, the opposite tendency was shown. As conclusion, 5-FU pretreatment favors the sensibility to PDT damage in 2D and 3D cultures in SCC but lower it in BCC. Although further studies are needed, 5-FU optimizes PDT efficacy in SCC models.

ESDR500 - Photodynamic therapy optimization after 5-Fluorouracil treatment in Squamous Cell Carcinoma

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.