Dosiologic Study Of Treating Leukemia Nodes With Cyberknife In Vitro

Objective:To explore the effects and mechanism of human chronic myelogenous leukemia(CML)acute transformation phase cell -K562 cell lines damage and repair induced by 6MV-X ray irradiated using different dose in a single irradiation,the time-effect and dose-effect of leukemic cells apoptosis and cell cycle arrest induced by irradiation were investigated.To prove the effects and mechanisms by clinical cases with leukemic nodus which is treated in Cyberknife.Methods:K562 cells were exposed to 6MV X-ray of 0Gy,1Gy,2Gy,3Gy,5Gy,10Gy,15Gy,20Gy respectively.The changes of K562 cell apoptosis and cell cycle progression were quantified by flow cytometry(FCM)after the cells were conjugated with FITC-ANNEXIN V/PI or only PI single stain at the time 2h,24h and 48h post the irradiation.Cells proliferation inhibition was detected by MTT colorimetric assay and colony formation assay.The results of cell damage caused by irradiation and the cell damage repair ability with different dose or time were processed by SPSS12.0 software.Results:1.Cells could be divided into three groups according to dose levels, low-dose group(1～2Gy),mid-dose group(3～5Gy)and high-dose group(10～20Gy).2. Apoptosis could be observed 2h after irradiation in low-dose group cells,arriving apoptotic peak at 24h.At the same time S phase arrest could be found and recovered after 48h.With increase of the radiation dose,the percentage of apoptotic cells was increased(p＜0.05).Cells proliferation and colony formation ability which detected at 2 weeks later were very strong(85%～93%).3.No obvious change of cell apoptotic rate but higher than in low-dose group(p＜0.05)could be observed in mid-dose group(p＞0.05).Temporal S phase arrest displayed at 2h and became G2/M phase arrest after 24h,and G2/M phase accumulation decreased partially after 48h.Cell proliferation inhibition rate increased after 72h and colony formation ability decreased(49%～71%)in this group(p＜0.05).4.Irreversible G2/M phase cell cycle arrest displayed after temporal S phase accumulation in high-dose group.Cell apoptotic rate increased with time extension(p＜0.05)and higher than mid-dose group(p＜0.05).Little cell proliferation and colony formation ability could be detected in this group(0～27%).5.Local control rate of leukemia nodes extra-marrow treated with 6～17Gy/1～3f by Cyberknife was 100%and secondary effect dependent treatment could not be find.Conclusions:1.K562 cell which was irradiated by 1～2Gy X-ray was sublethally damaged,and the damage increased with increase in dose.The damage caused by single irradiation was almost recovered after 48h.2.K562 cell which was irradiated by 3～5Gy X-ray was partially lethally damaged,and the damage increased with increase in dose.The damage was not recovered completely after 48h.3.Almost through ethal damage of K562 cell was observed after being irradiated by 10-～20Gy X-ray,and the damage was constant with increase in dose.The damage was not recovered after 48h.4.It was primarily concluded that treating leukemia nodes with Cyberknife located by PET-CT or MRI scan was safe and effective.