Santucci M A, Anklesaria P, Laneuville P, Das I J, Sakakeeny M A, FitzGerald T J, Greenberger J S
Department of Radiation Oncology, University of Massachusetts Medical Center, Worcester 01655.
Int J Radiat Oncol Biol Phys. 1993 Aug 1;26(5):831-6. doi: 10.1016/0360-3016(93)90498-k.
The cytogenetic finding of the Ph1+ chromosome and its molecular biologic marker bcr/abl gene rearrangement in cells from patients with chronic myeloid leukemia are associated with a proliferative advantage of the Ph1+ clone in vivo. Although the transition to the acute terminal phase or blastic crisis is often associated with additional cytogenetic abnormalities, the molecular events which correlate the initial cytogenetic lesion with the terminal phase are poorly understood. Defective cellular DNA repair capacity is often associated with chromosomal instability, increased mutation frequency, and biologic alterations.
We, therefore, tested whether the protein product of the bcr/abl translocation (p210) could alter DNA repair after gamma-irradiation of murine cell lines expressing the bcr/abl cDNA.
The 32D cl 3 parent, 32D cl 3 pYN (containing the control vector plasmid) and each of two sources of 32D cl 3 cells expressing p210 bcr/abl cDNA (32D-PC1 cell line and 32D-LG7 subclone) showed a D0 of 1.62, 1.57, 1.16, and 1.27 Gy, respectively. Thus, expression of the p210 bcr/abl product induced a significant (p < 0.05) increase in radiosensitivity at the clinically relevant radiation therapy dose-rate (1.16 Gy/min). The increased radiosensitivity of p210 bcr/abl expressing cells persisted if cells were held before plating in a density-inhibited state for 8 hr after gamma-irradiation, indicating little effect on the repair of potentially lethal gamma-irradiation damage. The IL-3 dependent parent 32D cl 3 cells demonstrated programmed cell death in the absence of growth factor or following gamma-irradiation to 200 cGy. Expression of bcr/abl cDNA in the 32D-PC1 and 32D-LG7 sub clones abrogated IL-3 requirement of these cell lines and inhibited gamma-irradiation induced programmed cell death.
These data suggest a role for bcr/abl p210 in amplifying gamma-irradiation DNA damage or broadly inhibiting DNA repair, conditions that may stimulate further cytogenetic alterations in hematopoietic cells.
慢性髓性白血病患者细胞中Ph1 +染色体的细胞遗传学发现及其分子生物学标志物bcr/abl基因重排与体内Ph1 +克隆的增殖优势相关。虽然向急性终末期或原始细胞危象的转变通常与额外的细胞遗传学异常有关，但将初始细胞遗传学病变与终末期相关联的分子事件却知之甚少。细胞DNA修复能力缺陷常与染色体不稳定、突变频率增加及生物学改变相关。
因此，我们检测了bcr/abl易位的蛋白产物（p210）是否能在表达bcr/abl cDNA的小鼠细胞系经γ射线照射后改变DNA修复。
32D cl 3亲本细胞、32D cl 3 pYN（含对照载体质粒）以及表达p210 bcr/abl cDNA的32D cl 3细胞的两个来源（32D-PC1细胞系和32D-LG7亚克隆）的D0分别为1.62、1.57、1.16和1.27 Gy。因此，在临床相关的放射治疗剂量率（1.16 Gy/min）下，p210 bcr/abl产物的表达诱导了放射敏感性显著（p < 0.05）增加。如果细胞在γ射线照射后以密度抑制状态培养8小时后再接种，表达p210 bcr/abl的细胞的放射敏感性增加仍然存在，这表明对潜在致死性γ射线损伤的修复影响很小。依赖白细胞介素-3的亲本32D cl 3细胞在缺乏生长因子或经200 cGyγ射线照射后表现出程序性细胞死亡。bcr/abl cDNA在32D-PC1和32D-LG7亚克隆中的表达消除了这些细胞系对白细胞介素-3的需求，并抑制了γ射线诱导的程序性细胞死亡。
这些数据表明bcr/abl p210在放大γ射线诱导的DNA损伤或广泛抑制DNA修复中起作用，这些情况可能刺激造血细胞发生进一步的细胞遗传学改变。
