# Liposomal Vitamin C as a Modulator of the Efficacy of Ceralasertib Therapy in Ovarian Cancer

## TL;DR

Liposomal vitamin C combined with ceralasertib increases DNA damage and cell death in ovarian cancer cells through ferroptosis and replication stress.

## Contribution

A novel combinatorial therapy using liposomal vitamin C and an ATR inhibitor enhances ovarian cancer treatment efficacy.

## Key findings

- Combining liposomal vitamin C with ceralasertib increases cytotoxicity in ovarian cancer cells.
- The treatment activates ferroptosis and causes DNA double-strand breaks via ATR pathway inhibition.
- Liposomal vitamin C protects during therapy while promoting ROS and lipid peroxidation.

## Abstract

Clinical evidence suggests that vitamin C (VitC) may enhance the efficacy of cancer chemotherapy. However, its high oxidating and reducing activity results in low stability in physiological fluids, which may compromise its supportive role in cancer therapies. VitC stability improves when located in a region where water activity is reduced and exposure to a limited amount of ferrous ions. This can be achieved when VitC is encapsulated in liposomes. Here, we present a novel combinatorial effect of a liposomal formulation of vitamin C (LVC, liposomal VitC) and an ataxia-telangiectasia and Rad3-related (ATR) kinase inhibitor (ATRi, ceralasertib) on cancer cells. The cytotoxic effects of vitamin C, LVC and ATRi were evaluated using spectrophotometric and spectrofluorimetric assays, flow cytometry and Western blot. Lipid peroxidation was assessed via fluorescence microscopy and quantified by spectrofluorimetric assays. DNA damage was examined by Western blot. The combination has higher efficacy than ceralasertib alone in genetically diverse ovarian cancer cell lines. LVC offers protective effects when used as an adjuvant during anticancer therapy. We found that the inhibition of the ATR pathway in the presence of LVC results in increased intracellular calcium levels, elevated lipid peroxidation, and higher Fe2+ concentrations. The upregulation of ROS, together with the increased expression of long-chain-fatty-acid—CoA ligase 4 (ACSL4) following co-treatment with ATRi and LVC, indicates the activation of ferroptotic pathways. The formation of DNA double-strand breaks suggests replication fork collapse. Our findings demonstrates that this synthetic targeted therapy, combining a novel liposomal formulation of VitC with an ATR inhibitor, not only enhances DNA damage and the cytotoxic efficacy of ceralasertib but also effectively drives ovarian cancer cells toward cell death.