The late effects of proton irradiation on cell growth, cell cycle arrest and apoptosis in a human melanoma cell line

The aim of this work is the in vitro study of the late effects of single pr oton irradiation on HTB63 human melanoma cell growth, cell cycle and cell d eath. The experimental conditions were focused on analyzing the effects of irradiation on the periphery of tumour that can be, in clinical practice, c lose to critical organs. Confluent cell monolayers were irradiated with single doses ranging from 1 - 20 Gy, using proton beams having an energy of 22.6 MeV at the target. Ant iproliferative effect of protons, cell cycle analysis and initiation of cel l death, were followed 48 hours after irradiation. The inhibition of melanoma cell growth was observed, especially after singl e application of 12 and 16 Gy. Cell cycle analysis and cell viability have shown the G2/M and G1/G0 arrest of irradiated cells correlating with the in crease of the applied dose. The flow cytometric analysis has shown presence of apoptotic nuclei. These data demonstrate that irradiation with protons, under the chosen experimental conditions, have significant effects on mela noma cell growth inhibition being dose dependent, G2/M cell cycle arrest an d appearance of apoptotic nuclei, even 48 hours after irradiation. The resu lts obtained may help the understanding of the relationship between cell pr oliferation, death and cell cycle regulation of melanomas after proton irra diation.