Introduction/Background Cisplatin-remedial chemotherapy is a widely used treatment for ovarian cancer; however, many patients eventually develop resistance to this conventional therapy, resulting in aggressive tumor recurrence. The molecular mechanisms underlying this resistance remain poorly understood. It has been observed that the accumulation of reactive oxygen species (ROS) occurs during the early stages of 3D culture in ovarian cancer cells, gradually decreasing over time, accompanied by the activation of NOTCH1/HES1 and P38 MAPK signaling pathways. In this study, we sought to unravel the cellular antioxidant systems responsible for maintaining ROS homeostasis, which in turn activate the NOTCH1/HES1 and P38 MAPK signaling pathways and promote platinum resistance in ovarian cancer spheroids.

Methodology 2D and/or 3D cultures of ovarian cancer cell lines and HOSEs assessed anti-oxidant mechanisms against intracellular ROS. HO-1 and MnSOD expressions were analyzed via qPCR and Western blot analysis. The loss-of-function of HO-1 and/or MnSOD genes in 3D-cultured ovarian cancer cells were performed by shRNA-mediated knockdown approach. ROS production was measured using intracellular ROS assay.

Results MnSOD and HO-1 act as prominent cellular antioxidants, mitigating oxidative damage by scavenging excess ROS. In ovarian cancer cells, qPCR and Western blot analysis demonstrated significantly higher expression levels of MnSOD and HO-1 compared to HOSE cells, implying their crucial role in reducing elevated ROS. Intriguingly, 3D-cultured ovarian cancer cells with MnSOD or HO-1 knockdown exhibited a substantial increase in ROS and gradually declined over time. Notably, double-gene knockdown resulted in sustained and intensified ROS production, surpassing single-gene knockdown and control cells. Suppression of NOTCH1 or P38 signaling confirmed the interplay of MnSOD and HO-1 in ROS regulation within ovarian cancer spheroids.

Conclusion This study highlights the significance of MnSOD and HO-1 as the key anti-oxidants in ovarian cancer spheroids for neutralizing ROS in facilitating cancer chemoresistance.

Disclosures All the authors declare no personal or funding interests.