Study On K562 Cells' Proliferation Inhibition, Apoptosis And Egr-1 Gene Expression Induced By Radiation

In this paper,we studied the proliferation inhibition , differentiation and apoptosis effects of K562 cells induced by 60Co γ ray irradiation .The transcriptional level of Egr-1 gene is also observed .In these ways ,we are trying to determine several factors that may be responsible for K562 cells' loss of proliferation ability after exposure to ionizing radiation.(1) We observed K562 cells' radiosensitivity by cell proliferation curves and 3H-TdR incorporation assay .It was noted that the proliferation inhibition happens at about 2 days after exposure and is positively dose-dependentBy using Giemsa staining method,we found through a microscope that the morphology and some staining properties of k562 cells greatly changed after exposure.The irradiated cells showed some new properties that higher differentiated cells have.The mean total protein of a cell (MTPC)is assayed.The mean total protein ofan irradiated k562 cell is evidently higher than the control.The increased MTPA is believed to be an important differentiating indicator.(2) We studied the K562 cells' apoptosis induced by 60Co γ ray irradiation using an apoptotic kit which is designed to detect the mitochondrial potential change .We found that K562 cells'apoptotic percentage does not show any relation to the dose they received.Yet the apoptotic percentage is highest 6 hours after exposure to 5Gy(lGy/min).(3) The transcriptional level of Egr-1 gene, before and after exposure to ionizing radiation, is assayed by RT-PCR.The change of Egr-1 gene expression is believed to be greatly related to tumor cells' differentiation and apoptosis caused by different inducers.The amplified fragment is a part of the coding data sequence of the Egr-1 mRNA.We found that 0.5 - 1 h after exposure to 5Gy(lGy/min),the transcriptional level of Egr-1 gene rapidly reaches the top.Then it begin to decline. 8h after exposure ,the transcriptional level is below normal.Our research indicates that k562 cells have a relatively high radiosensitivity and their proliferation inhibition are positively related to the does they received.K562 cells' differentiation and apoptosis inducedby expoure to 60Co γ ray are at least partly responsible for their loss ofproliferation ability. Based on this research and other researches related,webelieve that the transient expression of Egr-1 gene may play an importantrole in the process of differentiation and apoptosis induced by 60Co γ rayirradiation.