Anderson R L, Fong K J, Gabriele T, Lavagnini P, Hahn G M, Evans J W, Waldren C A, Stamato T D, Giaccia A J
Department of Radiation Oncology, Stanford University, California 94305.
Cancer Res. 1991 May 15;51(10):2636-41.
Since mammalian cells vary widely in their intrinsic thermoresistance, we have investigated the genetic basis underlying this phenomenon in human and rodent cell lines. Typically, human cells are considerably more resistant to killing by heat than rodent cell lines. To determine whether the heat-resistant phenotype is dominant or recessive and to locate the chromosome(s) bearing determinants for heat resistance, we have prepared hybrids of heat-resistant human HT1080 cells and heat-sensitive Chinese hamster ovary (CHO) cells to test their response to heat. For both mass hybrid cultures and individual clones, the heat response of the hybrids was similar to that of the CHO parent. Analysis by in situ hybridization revealed the presence of five to 20 human chromosomes per cell in the mass hybrids and four to eight intact chromosomes plus some fragments in individual clones isolated from the hybrid cell population. A similar result was obtained using a different human cell line, AG1522. These data suggest that heat resistance is a recessive trait. Consistent with this conclusion are the results from a study of a fusion of HT1080 to a CHO mutant, BL-10, which was found to be hypersensitive to heat-induced killing. These hybrids had a normal CHO heat response and not the more heat-resistant phenotype of HT1080 cells. Two hybrid clones, H2 and H4, from the HT1080/BL-10 fusion were studied in more detail. Both clones possess similar amounts of Mr 70,000 heat shock protein (HSP70), despite the fact that H4 contains three human chromosomes (Nos. 6, 14, and 21) which carry HSP70 genes while H2 contains only one (chromosome 6). Both hybrid cell lines have the same response to heat. Although we found a wide range of sensitivities to heat, all cell lines contained a similar amount of constitutive HSP70, suggesting that HSP70 levels per se are not the critical determinant of intrinsic heat resistance.
由于哺乳动物细胞的内在耐热性差异很大，我们研究了人类和啮齿动物细胞系中这一现象的遗传基础。通常，人类细胞比啮齿动物细胞系对热杀伤的抵抗力要强得多。为了确定耐热表型是显性还是隐性，并定位携带耐热决定因素的染色体，我们制备了耐热的人类HT1080细胞和热敏性中国仓鼠卵巢（CHO）细胞的杂种，以测试它们对热的反应。对于大量杂种培养物和单个克隆，杂种的热反应与CHO亲本相似。通过原位杂交分析发现，大量杂种中每个细胞存在5至20条人类染色体，从杂种细胞群体中分离出的单个克隆中有4至8条完整染色体以及一些片段。使用不同的人类细胞系AG1522也获得了类似的结果。这些数据表明耐热性是一种隐性性状。与这一结论一致的是一项关于HT1080与CHO突变体BL-10融合的研究结果，该突变体对热诱导杀伤高度敏感。这些杂种具有正常的CHO热反应，而不是HT1080细胞更耐热的表型。对来自HT1080/BL-10融合的两个杂种克隆H2和H4进行了更详细的研究。尽管H4含有三条携带热休克蛋白70（HSP70）基因的人类染色体（6号、14号和21号），而H2仅含有一条（6号染色体），但两个克隆都拥有相似数量的分子量为70,000的热休克蛋白（HSP70）。两种杂种细胞系对热的反应相同。尽管我们发现对热的敏感性范围很广，但所有细胞系都含有相似数量的组成型HSP70，这表明HSP70本身的水平不是内在耐热性的关键决定因素。
