Molecular Effects of Indocyanine Green-Photodynamic Therapy on Programmed Cell Death Pathways in T98G and U-118MG Glioblastoma Cells—An RT-qPCR Study

Glioblastoma multiforme (GBM) remains one of the most aggressive primary brain tumors with poor prognosis despite multimodal therapy. Photodynamic therapy (PDT) using indocyanine green (ICG) is an emerging adjuvant approach aimed at eliminating residual tumor cells after resection. While ICG-PDT exerts cytotoxic effects, its impact on molecular pathways regulating programmed cell death in glioma cells is not fully understood. In this study, T98G and U-118MG glioblastoma cells were divided into four groups: untreated control, light-only (10 min broadband irradiation), ICG-only (15 min incubation), and ICG-PDT (15 min ICG + 10 min broadband irradiation). Relative mRNA expression of apoptosis-related genes (BAX, BCL2, CASP3, FAS) and ferroptosis-related genes (GPX4, ACSL4, SLC7A11, GCH1) was quantified 24 h post-treatment by RT-qPCR using the 2−ΔΔCt method. ICG-PDT significantly reduced cell viability to 67.79% ± 3.39% (vs. 86.66% ± 4.33% in control), confirming effective phototoxicity. No statistically significant differences in mRNA levels were observed for any of the investigated genes across the groups (one-way ANOVA and Kruskal–Wallis, all p > 0.05). The largest non-significant deviation was a mild decrease in GPX4 (fold change 0.87) in the ICG-PDT group. Fluctuations in GCH1 were accompanied by high variance, likely reflecting technical noise rather than a true biological trend. The mRNA BAX/BCL2 ratio remained stable (~30) across all conditions. In contrast, the U-118MG line showed greater transcriptional sensitivity, with statistically significant decreases in CASP3 (p = 0.012) and ACSL4 (p = 0.031) expression, along with downward trends in BCL2 and GPX4 following ICG-PDT. ICG-PDT does not induce significant transcriptional changes in the analyzed genes T98G at the 24 h time point under the applied experimental conditions. In U-118MG cells, moderate transcriptional engagement of both apoptotic and ferroptotic routes was observed. Further studies at the protein and functional levels, across multiple time points and models, are warranted to fully elucidate the mechanisms of ICG-PDT in glioblastoma.