Targeted photodynamic therapy of metastatic melanoma cancer and cancer stem cells

Abstract

Abstract: Metastatic melanoma is highly aggressive and has been recorded by the American Cancer Society as being the most common cause of skin cancer associated deaths (ACS., 2020). Tumours are heterogeneous and encompass various dynamic subpopulations of cells, one of these being cancer stem cells (CSCs). Cancer stem cells have the potential to cause cancer relapse and metastasis, as well as being resistant to multiple forms of therapy (Nguyen et al., 2015). Melanoma CSC populations have been identified and linked to tumor progression, immune-evasive behavior, drug resistance, and metastasis. Intra-tumour heterogeneity, which refers to how different subpopulations inside and between tumor lesions interact, has a significant impact on the tumor's response to pharmacological therapy in melanomas. The present study evaluated the effects of Photodynamic Therapy (PDT) using Aluminum phthalocyanine (AlPcS4Cl) photosensitizer (PS) at 673.2 nm in targeting melanoma cells (A375) and their stem cell population. The use of human malignant melanoma cell cultures (A375 cells, alongside with fibroblast (WS1) cell cultures (normal cells) was employed. These were grown in a complete liquid medium incubated at 37 °C, 5% CO₂ and 85% humidity. Dose response studies were performed on the total cell populations by increasing doses of AlPcS4Cl. Post-irradiation signs of cell death were determined using microscopy, Trypan blue viability, ATP, and LDH assays. The increasing cell death of treated A375 and WS1 cells was directly proportional to increasing dose responses observed. Changes post-irradiation were realized through cell viability testing with significantly increased damaged cells taking up Trypan blue dye. Treatment group cells with a dose of 20 μM AlPcS4Cl indicated 68.25% viability and for a dose of 40 μM, 35% viability. This suggests that PDT is most effective at a higher dose but also harmful to normal cells at a dose of 40 μM. A lower dose range was used for A375 cells which showed a significant decrease in cell viability for a dose of 20 μM, showing only 55.25% viability. The impact of PDT on metastatic melanoma was highlighted through its target specific effects causing morphological changes, dose dependent decreases in ATP, and increased LDH content released due to cytotoxicity. Current treatments have limited...M.Tech. (Biomedical Sciences