Simulation of complex DNA damage enhancement and in vitro cell viability validation for Proton-CAT

Proton therapy has advanced rapidly because of its excellent dose conformity. However, its relatively low relative biological effectiveness may limit its therapeutic efficacy for certain tumors. To address this limitation, we previously proposed a nitrogen-targeting Proton-Carbon-Alpha-Therapy (Proton-CAT) enhancement method. In this work, we established a multiscale DNA damage simulation method. The method uses a pre-calculated DNA damage database generated by Geant4-DNA, coupling tissue-scale DNA damage simulations with microscopic DNA damage yields, supplemented by in vitro cell survival experiments, thereby further investigating the physical mechanisms and potential biological effects of Proton-CAT. The simulations' results show that 15N enrichment significantly enhances complex DNA damage induced by high-linear energy transfer particles within tumor regions. Under 30% 15N condition, compared with the tumor region without added 15N, α and 12C particle-induced DSB++ yield increased by 175.19% and 52.94%, respectively. Furthermore, in vitro cell experiments using 15N-glutamine (15N-Gln) as the 15N carrier indicated that high concentrations of 15N-Gln did not bring about significant cytotoxicity. Following 2 Gy irradiation, the cell viability in the 500 μg/ml 15N-Gln-treated group exhibited a net reduction of about 15.41% compared to the control group. The CCK-8 results showed a trend consistent with the simulation predictions, providing preliminary biological evidence for the Proton-CAT enhancement effect. This work provides a theoretical basis and a research framework for the further mechanistic and experimental development of Proton-CAT.