ESTRO 2022 - Abstract Book

S438

Abstract book

ESTRO 2022

Conclusion Radiotherapy-induced gene expression changes depend strongly on the breast cancer cell line. For HR+/HER2-negative cell lines, radiotherapy seems to induce a low-proliferative HER2-enriched phenotype. This HER2-enriched phenotype seems to be persistent (at least up to 3 weeks after irradiation), while cell proliferation seems to return to the baseline. If confirmed in patients, these findings could open the door to new therapeutic strategies for high-risk HR+/HER2-negative BC, based on the combination of radiotherapy and anti-HER2 drugs.

PD-0488 Caffeic Acid Phenethyl Ester, a natural radiosensitizer for lung adenocarcinomas

È. Prades-Sagarra 1 , R. Biemans 1 , N.G. Lieuwes 1 , P. Lambin 1 , A. Yaromina 1 , L.J. Dubois 1

1 Maastricht University, Precision Medicine - The M lab, Maastricht, The Netherlands

Purpose or Objective Radiotherapy-induced adverse effects are dose limiting factors and therefore narrow the therapeutic window. A novel potential radioprotector, Caffeic Acid Phenethyl Ester (CAPE), has been suggested to widen the therapeutic window by having cytotoxic effects in tumor cells but protecting the normal tissue against radiation. CAPE has been shown to have anti-inflammatory and anti-oxidant effects in normal tissue, while anti-proliferative and pro-apoptotic effects in tumor cells. The aim of this study is therefore to investigate the radiosensitizing effect of CAPE in a panel of lung cancer cell lines in vitro . Materials and Methods Human adenocarcinoma (H1299, H1975, H522, HCC827) and non-adenocarcinoma (H520, H292) NSCLC lines were incubated for 24 hours with increasing doses of CAPE. Viability was assessed using multi-well plate alamarBlue-based viability assays. Clonogenic survival assays were used to assess the radiosensitizing properties of CAPE. Cells were incubated with CAPE (IC 25 and IC 50 ) for 24 hours followed by irradiation with doses up to 6 Gy, and seeded to allow colony formation. Colonies were stained and counted (>50 cells) after 11 to 15 days. Results Treatment with CAPE decreased cell viability in lung cancer cells in a dose-dependent manner. IC 50 values varied between 32 and 88 µM. Clonogenic survival assays showed significant radiosensitization by CAPE in human lung adenocarcinoma cell lines (H1299 p<0.001, H1975 p<0.0001, H522 p<0.0001 for both CAPE concentrations IC 25 and IC 50 ; HCC827 p<0.0001 for