FUNCTIONAL CIRCADIAN CLOCKS REGULATE CELLULAR SENSITIVITY TO PHOTODYNAMIC THERAPY THROUGH PHOTOSENSITIZER UPTAKE AND REDOX STATUS

SUAREZ, AI; FORNASIER, SJ; GONZALEZ GRAGLIA, MA; WAGNER PM; GUIDO, ME; MIRETTI, M; PRUCCA, CG

Córdoba

Congreso; LXI Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2025

Glioblastoma (GBM) is the most aggressive and deadliest tumor of the central nervous system,originating from glial cells and characterized by its infiltrative capacity and rapid progression.The current treatment follows the Stupp protocol, which involves surgical removal of the tumormass followed by chemo and radiotherapy. Despite treatment, a patient with GBM usuallysurvives around 14 months, highlighting the critical need for new therapeutic strategies.Photodynamic therapy (PDT) represents a promising approach that combines a photosensitizer(PS), light at the excitation wavelength of the PS, and oxygen. Individually harmless, thesecomponents together generate reactive oxygen species, hydroxyl radicals, and singlet oxygen,creating a redox imbalance in cells that leads to cell death. Emerging research has shown thatthe effectiveness of cancer treatments can be affected by the biological clock inherent in eachcell, which coordinates multiple metabolic functions. Disruptions in genes associated with thismolecular clock have been linked to the development of various cancers, including GBM. Giventhe complex link between the biological clock and cancer cell growth, combiningchronopharmacology with existing treatments like PDT could improve therapy outcomes. Inthis study, we explore the novel combination of PDT and chronotherapy in GBM cells, usingPSs from the phthalocyanine family (ZnPc and ClAlPc) and 5-aminolevulinic acid (5-ALA), thelatter being an FDA-approved PS precursor. Initial characterization of clock genes Bmal1 andPer1 confirmed the presence of a functional molecular clock in GBM cells. Phototoxicity assaysin dexamethasone-synchronized cells, with photosensitizers (PS) administered at differentpost-synchronization times, revealed a time-dependent variation in cell viability after PDT.These findings suggest that the timing of PS administration has a critical influence on PDTefficacy. Periodicity analysis using mathematical algorithms (JTK, ARS, and RAIN) showed thateach PS displayed a distinct oscillatory profile. Uptake assays with ZnPc further revealed aphase shift compared to cell viability, suggesting decreased PS incorporation during periods ofincreased resistance. Finally, evaluating cellular redox status through ROS and NRF2measurements indicates increased detoxification activity at times associated with greaterresistance to 5-ALA PDT. This study represents a pioneering effort to explore the potential ofcombining PDT and chronopharmacology in the treatment of glioblastoma, offering hope foran improved prognosis for those affected by this devastating tumor.