Clave E, Carosella E D, Gluckman E, Dubray B, Socié G
Unité de Recherche sur la Biologie des Cellules Souches, Hôpital Saint-Louis, Paris, France.
Int J Radiat Oncol Biol Phys. 1996 Jul 1;35(4):709-19. doi: 10.1016/0360-3016(96)00137-x.
Better understanding of radiation-induced effects on the hematopoietic system is important in both the context of therapeutic intervention and accidental exposure. However, direct study of these effects on the hematopoietic stem cell pool is hampered by the small number of accessible cells. We, thus, studied radiation-induced effects on the KG1a stem cell line.
We confirmed and extended the immunophenotype of KG1a with monoclonal antibodies, established a radiation survival curve, and quantified mRNAs by Northern blotting 30 min after 1, 2, and 3 Gy of ionizing radiation (IR) and followed for up to 48 h after a 3 Gy dose. Cell cycle status and apoptosis were assessed by fluorescent-activated cell sorter (FACS) analysis, cell morphology, and DNA fragmentation.
KG1a was found to be CD34+, CD7+, Thy1 low, CD38 low, lineage negative (neg), C-KITneg and HLA-DRneg, a phenotype consistent with a primitive hematopoietic origin. This immunophenotype was not altered by x-ray irradiation. The D0 value was 1.75 Gy. We showed a time-dependent variation of c-jun mRNA expression with an early and transient dose-dependent induction followed by a second increase at 24 and 48 h: a biphasic dose-dependent variation of bcl-2 expression 30 min after irradiation with a reduction of mRNA level at 1 Gy, and a normalization at higher doses and stable levels of mRNA for c-fos, c-myc, G-CSF, GM-CSF, IL-6, TNF-alpha, TGF-beta, and MIP-1 alpha genes. Cell cycle analysis showed the absence of G1/S phase arrest, a point consistent with the absence of detection of P53 mRNA by Northern blot analysis. The dose-dependent G2/M phase arrest was not followed by significant apoptotic cell death.
Taken together, this data indicates that radiation-induced cell death of KG1a, a cell line that has a relatively high D0 value, does not seem to be the result of the apoptotic pathway but occurs subsequent to a G2/M phase arrest.
在治疗干预和意外辐射暴露的背景下，更好地理解辐射对造血系统的影响都非常重要。然而，由于可获取的细胞数量较少，对造血干细胞池的这些影响的直接研究受到阻碍。因此，我们研究了辐射对KG1a干细胞系的影响。
我们用单克隆抗体确认并扩展了KG1a的免疫表型，建立了辐射存活曲线，并在1、2和3 Gy的电离辐射（IR）后30分钟通过Northern印迹法对mRNA进行定量，并在3 Gy剂量后跟踪长达48小时。通过荧光激活细胞分选仪（FACS）分析、细胞形态学和DNA片段化评估细胞周期状态和凋亡。
发现KG1a为CD34 +、CD7 +、Thy1低、CD38低、谱系阴性（neg）、C-KITneg和HLA-DRneg，该表型与原始造血起源一致。这种免疫表型未因X射线照射而改变。D0值为1.75 Gy。我们显示c-jun mRNA表达随时间变化，早期有短暂的剂量依赖性诱导，随后在24和48小时出现第二次增加；照射后30分钟bcl-2表达呈双相剂量依赖性变化，1 Gy时mRNA水平降低，更高剂量时恢复正常，c-fos、c-myc、G-CSF、GM-CSF、IL-6、TNF-α、TGF-β和MIP-1α基因的mRNA水平稳定。细胞周期分析显示不存在G1/S期阻滞，这一点与Northern印迹分析未检测到P53 mRNA一致。剂量依赖性的G2/M期阻滞之后没有明显的凋亡细胞死亡。
综上所述，这些数据表明，具有相对较高D0值的KG1a细胞系的辐射诱导细胞死亡似乎不是凋亡途径的结果，而是发生在G2/M期阻滞之后。
