Isolation and initial characterization of human glioblastoma cells resistant to photodynamic therapy.

Glioblastoma is the most severe form of brain cancer. Despite multimodal therapy combining surgery, radiotherapy and chemotherapy, prognosis of patients is dismal. It has been observed that the surgical resection guided by photosensitizer fluorescence followed by photodynamic therapy (PDT) prolongs the average survival in patients with glioblastoma. The main problem with all oncological treatments, including PDT, is the presence of resistant cells. The objective of this study was to isolate and perform an initial characterization of human glioblastoma cells resistant to PDT employing methyl-5-aminolevulinic acid. We obtained resistant cells from the T98 G cell line. Resistant populations accumulated less photosensitizer, formed spheroids of higher number of cells, had higher tumorigenic capacity, and expressed higher mRNA levels of fibroblastic growth factor receptor (FGFR), epidermal growth factor receptor (EGFR) and β-platelet-derived growth factor receptor (βPDGFR) than parental cells. The studies of glioblastoma resistance to PDT would help to better understand the causes of tumor recurrence after PDT and to develop new therapeutic proposals in this field of oncology.