STUDY OF THE ANTITUMOR MECHANISM OF IMIQUIMOD IN HEMANGIOMA CELLS

Fiama Picco - María del Carmen Martinez - Silvina Gazzaniga

Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires

The topical use of Imiquimod (IQ) is approved for treating some skin pathologies due to its antiviral and antitumor activity. IQ has shown benefits in treating infantile hemangiomas, being a potential alternative to beta blockers, which are associated with concerning side effects in infants. It works by stimulating the immune system but also directly inducing tumor cell death, independently of the immune action. We demonstrated that IQ selectively induces apoptosis in transformed cells compared to normal cells and, at sublethal concentrations, impairs some stages of the angiogenic process in hemangioma cells (HC). Additionally, IQ rapidly disrupts the redox balance in transformed cells, increasing reactive oxygen species (ROS) and significantly impacting enzymatic antioxidant defenses. To further understand the direct IQ-induced cytotoxicity in HC, we evaluated nitrosative stress resulting from intracellular drug accumulation in H5V cells treated with IQ (0-10 μg/mL) for 24 h. Reactive nitrogen species (RNS) were detected using the Griess method. A significant increase was observed in RNS/cell ratio at 10 μg/mL IQ (p<0.05). Considering that RNS and ROS can lead to mitochondrial dysfunction, we evaluated the fluorescent MitoTracker CMXROS tracer in H5V cells treated with IQ (10 μg/mL) for 24 h. A decreased fluorescence and perinuclear mitochondrial concentration were noted. The ultrastructural analyses of mitochondria in H5V cells treated with IQ (10 μg/mL) for 4 h using transmission electron microscopy revealed changes in cristae morphology, mitochondrial size, clustering, and perinuclear localization. In summary, these findings support the direct cytotoxic effect of IQ on transformed HC and its potential use as an adjuvant for therapies for transformed/tumor cell pathologies of the skin.