Rice G C, Gray J W, Dean P N, Dewey W C
Cancer Res. 1984 Jun;44(6):2368-76.
We have examined the cell cycle specificity of 45.5 degrees heat-induced toxicity and the induction and expression of thermal tolerance. Ultrapure populations of G1-, S-, and G2-M-phase cells were obtained through sequential centrifugal elutriation and flow cytometric cell sorting of Hoechst 33342-stained cells. We found no interaction of Hoechst 33342 with hyperthermia under staining conditions that gave good cytometric resolution of DNA distributions. Single dose-response survival curves indicated that S phase was the most sensitive to 45.5 degrees hyperthermia (Do = 1.97, 1.26, and 1.95 min for G1, S, and G2-M, respectively). Both S and G2-M phases exhibited a decreased ability from G1 to accumulate sublethal heat lesions as evidenced by decreased heat survival curve shoulders (Dq) = 13.7, 9.51, and 8.39 min for G1, S, and G2-M, respectively). Thermal tolerance, as measured by the decreased inactivation slope of the split-dose treatment, could be induced and expressed in G1, S, and G2-M phases. However, both the magnitude and temporal expression of tolerance were dependent on the position of the cell within the cell cycle at the time of the initial heat treatment. S-phase cells exhibited slightly less thermal tolerance as compared to G1 cells given isosurvival thermal induction doses as measured by the split-dose inactivation rate constants (heated/control = 8.37 and 5.62 for G1 cells at 12 and 24 hr and 7.68 and 5.27 for S-phase cells at 12 and 28 hr). Also, split-dose survival curves for cells heated in G2-M indicated a near total inability to accumulate heat-induced sublethal damage. Simultaneous bivariate (90 degrees light scatter and DNA content) progression analysis of heated replicates indicated that tolerance could probably be expressed in those cells which moved into other cycle compartments following the initial heat treatment. For instance, G1-phase cells preheated for 20 min began progression into normally heat-sensitive S phase between 24 and 28 hr after the heat treatment. This corresponded to approximately the time of maximal thermal tolerance expression. [3H]Thymidine suicide experiments also indicated that the ultimately clonogenic cells began movement into S phase at or near the time of maximal tolerance. In this case then, tolerance expression appeared to supersede the S-phase acute heat sensitivity. Heated S-phase cells began progression into G2-M between 4 and 12 hr, which corresponded temporally to large amounts of tolerance expression4 +
我们研究了45.5摄氏度热诱导毒性的细胞周期特异性以及热耐受性的诱导和表达。通过对经Hoechst 33342染色的细胞进行连续离心淘析和流式细胞术细胞分选，获得了G1期、S期和G2 - M期细胞的超纯群体。我们发现在能给出良好的DNA分布细胞计数分辨率的染色条件下，Hoechst 33342与热疗之间没有相互作用。单剂量反应存活曲线表明，S期对45.5摄氏度热疗最为敏感（G1期、S期和G2 - M期的Do分别为1.97、1.26和1.95分钟）。S期和G2 - M期从G1期开始积累亚致死性热损伤的能力均下降，这可通过热存活曲线的肩宽（Dq）降低得到证明，G1期、S期和G2 - M期的Dq分别为13.7、9.51和8.39分钟。通过分次剂量处理的失活斜率降低来衡量的热耐受性，可在G1期、S期和G2 - M期诱导并表达。然而，耐受性的程度和时间表达均取决于初始热处理时细胞在细胞周期中的位置。与给予等存活热诱导剂量的G1期细胞相比，S期细胞表现出稍低的热耐受性，通过分次剂量失活速率常数测量（对于12小时和24小时的G1期细胞，加热/对照分别为8.37和5.62；对于12小时和28小时的S期细胞，加热/对照分别为7.68和5.27）。此外，在G2 - M期加热的细胞的分次剂量存活曲线表明几乎完全无法积累热诱导的亚致死损伤。对加热复制品进行的同时双变量（90度光散射和DNA含量）进展分析表明，耐受性可能在初始热处理后进入其他细胞周期区室的那些细胞中表达。例如，预热20分钟的G1期细胞在热处理后24至28小时之间开始进入通常对热敏感的S期。这大约对应于热耐受性表达的最大值时间。[3H]胸苷自杀实验还表明，最终具有克隆能力的细胞在最大耐受性时或接近最大耐受性时开始进入S期。在这种情况下，耐受性表达似乎取代了S期的急性热敏感性。加热的S期细胞在4至12小时之间开始进入G2 - M期，这在时间上与大量耐受性表达相对应。
