Evaluation of the Efficacy of Photodynamic Therapy and Cdc42 Inhibitor on Cancer Cells In Vitro

Abstract

Background: Photodynamic therapy (PDT) is a new and promising approach in anticancer treatment. Despite this, usage of this type of treatment is limited, as ICG (photosensitizer) has its own disadvantages - photobleaching and moderate singlet oxygen yeild. The small GTPase Cdc42 is playing an important role in cancer cell adaptation towards oxidative stress and regulation of migration of cells. This study is aiming to evaluate the in vitro antitumor efficacy of photodynamic therapy that is mediated with ICG and combined with the Cdc42 inhibitor CASIN. Methods: Several cell lines were used, NIH-3T3, fibroblasts, and cancer cell lines HT-29, HCT116, HeLA, MCF-7, MDA-MB-231, B16 were used during study. Cells were pretreated with CASIN (5 μM, 16 h), followed by ICG (8–65 μM) and irradiation (745 nm, 40 mW/cm², 3 min). Results: Across tested cell lines, combination of CASIN with ICG-PDT substantially reduced viability beyond what either treatment achieved alone - the exception was MDA-MB-231 (effect was additive). Notably, CASIN pretreatment did not amplify the ROS burst itself, but appeared to lower the cellular tolerance threshold for oxidative damage. Suppression of cancer cell migration was also observed under combination conditions, while NIH-3T3 fibroblast viability remained comparatively unaffected, suggesting a level of tumor selectivity.