Interaction Between Near-Infrared Radiation and Temozolomide in a Glioblastoma Multiform Cell Line: A Treatment Strategy?

Photodynamic therapy (PDT) is a potential therapeutic modality against cancer, resulting from the interaction of a photosensitizer (PS) and radiation that generates damage to tumor cells. The use of near-infrared radiation (IR-A) is relevant because presents recognized biological effects, such as antioxidant, neuroprotective and antitumor effects. Glioblastoma is the most aggressive central nervous system (CNS) neoplasm with high proliferation and tissue invasion capacity and is resistant to radio and chemotherapy. Here, we evaluated in vitro the possible interaction of temozolomide (TMZ) with IR-A in a glioblastoma cell line (C6) and in a human keratinocyte cell line (HaCat) how non-tumor cell model, in an attempt to search for a new treatment strategy. The effects of TMZ, IR-A and the interaction between TMZ and IR-A was evaluated by viability exclusion with trypan blue. To perform the interaction experiments, we have chosen 10 μM TMZ and 4.5 J/cm2 of IR-A. From this, we evaluated cytotoxicity, cell proliferation, intracellular reactive oxygen species levels (ROS), as well as the process of cell migration and the P-gp and MRP-1 activity. Cell death mainly due to apoptosis, followed by necrosis, decreased cell proliferation, increased ROS levels, decreased cell migration and decreased P-gp and MRP1 activity were observed only when there was interaction between TMZ and IR-A in the C6 cell line. The interaction between TMZ and IR-A was not able to affect cell proliferation in the HaCat non-tumor cell line. Our results suggest that this interaction could be a promising approach and that in the future may serve as an antitumor strategy for PDT application.