# MonoHER selectively enhances the radiotherapy response in p53 wild-type breast cancer via stabilization of p53

## TL;DR

MonoHER improves the effectiveness of radiation therapy in breast cancers with normal p53 by stabilizing this protein, with minimal impact on normal cells.

## Contribution

MonoHER selectively radiosensitizes p53 wild-type breast cancer cells by directly stabilizing wild-type p53.

## Key findings

- MonoHER combined with radiation increases DNA damage and apoptosis in p53 wild-type breast cancer cells.
- MonoHER directly binds and stabilizes wild-type p53, enhancing its activation.
- MonoHER has minimal effect on p53-mutant cancer and normal mammary cells.

## Abstract

•MonoHER selectively radiosensitizes p53 wild-type breast cancer cells.•MonoHER combined with radiation enhances DNA damage, apoptosis, and ATM/p53 pathway activation.•MonHER directly binds and stabilizes wild-type p53, “priming” cells for irradiation.•MonoHER has minimal effect on p53-mutant cancer and normal mammary cells.

MonoHER selectively radiosensitizes p53 wild-type breast cancer cells.

MonoHER combined with radiation enhances DNA damage, apoptosis, and ATM/p53 pathway activation.

MonHER directly binds and stabilizes wild-type p53, “priming” cells for irradiation.

MonoHER has minimal effect on p53-mutant cancer and normal mammary cells.

Radiotherapy is one of the standard treatments for breast cancer, but its efficacy is limited by tumour radioresistance. Radiosensitizers can improve treatment outcomes. MonoHER, a flavonoid derivative, has shown anticancer potential; however, its role in radiosensitization has not been investigated. Here, we determined the radiosensitizing properties of monoHER in vitro in breast cancer and normal mammary cells.

Breast cancer cells with different p53 status (MCF7, wild-type; T47D, mutant) and normal mammary cells (MCF10A) were treated with monoHER and radiation. Cell viability, clonogenic survival, apoptosis, and γ-H2AX foci were assessed. Western blotting examined ATM/p53 signalling. Interaction of monoHER with p53 was analysed by molecular docking and CETSA.

MonoHER selectively enhanced radiation-induced cytostatic effects in MCF7 (p < 0.01) cells and in T47D (p < 0.05), but had protective effect in MCF10A (p < 0.01) cells. Combined treatment increased apoptosis (p < 0.001) and DNA damage (p = 0.045) in MCF7 cells, accompanied by upregulation of p-ATM (p = 0.011), p-p53 (p = 0.023), and total p53 (p = 026), while in T47D and MCF10A cells, there is no significant difference. Docking and CETSA confirmed direct binding of monoHER to wild-type p53, increasing its thermal stability. MonoHER alone showed minimal cytotoxicity, suggesting a priming rather than direct killing effect.

MonoHER modestly sensitize only p53-proficient breast cancer cells to radiation by stabilizing and activating p53, highlighting its potential as an adjuvant radiosensitizer.