Evaluation of low-dose proton beam radiation efficiency in MIA PaCa-2 pancreatic cancer cell line vitality and H2AX formation

Abstract

Background and objective: The aim of this study was to evaluate the efficiency of proton beam irradiation in pancreatic cancer cell line MIA PaCa-2 and its role in the cell cycle, apoptosis, and formation of histone γH2AX in different reparation times (72-h follow-up). Material and methods: The MIA PaCa-2 pancreatic carcinoma cell line was irradiated with 1.6-Gy proton beam. After irradiation, cell viability was measured colorimetrically, and the cell cycle, apoptosis, and γH2AX expression were evaluated on a FACScan cytometer. Results: Low-dose proton beam irradiation had an effect on the MIA PaCa-2 tumor cell line already 1 h after exposure, but maximal lethality was reached after 72 h postirradiation with a cell viability rate of 24%. The cell cycle went into partial G1/0 arrest, and was released after 72 h. The expression of γH2AX was strong and its levels were significantly elevated as late as 48 h post radiation. The apoptosis levels increased with post radiation incubation time to reach 79% after 72 h. Conclusions: Our data demonstrate that low-doses proton beam irradiation had an effect on MIA PaCa-2 pancreatic carcinoma cell line. Full extent of irradiation had an impact only 24 h postirradiation, triggering DNA arrested cell cycle in G1/0 phase. Formed DNA DSBs were found to be repaired via the NHEJ pathway mechanism within 72 h. Unsuccessful repaired DSBs induced apoptotic cell death. After 72 h reparation processes were completed, and cell cycle was released from arrest in G1/0 phase.

Keywords

• Proton irradiation
• MIA PaCa-2
• Gamma H2AX
• Non-homologous end joining
• Double strand breaks