Increased expression of α-SMC actin, a marker of myofibroblasts, was observed at 7 days after exposure to 56Fe. A priming dose of protons prevented the increase in α-SMC actin in response to 56Fe exposure. Western-blot image indicates 4-5 biological repeats in each radiation group. Graphs indicate average ± SEM, n=4-5. Quantification of α-SMC divided by GAPDH for sham-irradiation: 1.43 ± 0.11; for 0.1 Gy protons: 1.86 ± 0.24; for 0.5 Gy 56Fe: 5.51 ± 1.42; for the consecutive exposure group: 1.72 ± 0.23. *p<0.05 compared to sham-irradiated control, ‡p<0.05 compared to proton exposure, §p<0.05 compared to 56Fe exposure.