Inhibition of chemically induced morphological transformation and reversion of the transformed phenotype of ascorbic acid in C3H/10T 1/2 cells.
Inhibition of chemically induced morphological transformation and reversion of the transformed phenotype of ascorbic acid in C3H/10T 1/2 cells.
复制标题
抑制 C3H/10T 1/2 细胞中化学诱导的形态转化和抗坏血酸转化表型的逆转。
作者：
W. Benedict;William L. Wheatley;P. Jones
C3H/10T½ 小鼠胚胎细胞暴露于 3-甲基胆蒽 (MCA) 24 小时。如果在 MCA 暴露后立即添加抗坏血酸，并在此后每天添加，总共 22 天，则每天添加非细胞毒性浓度 1 µg/ml 的抗坏血酸可在实验开始后 42 或 56 天完全阻止转化灶的表达。抗坏血酸也可以在 MCA 处理后 23 天添加，如果保持在培养物中直至培养皿染色，则仍然完全抑制形态转化。
如果来自这些病灶的转化细胞随后每天接受 1 µg/ml 抗坏血酸，则在 MCA 处理后 6 至 8 周继代培养后，约 80% 含有转化病灶的培养物中转化表型的表达也被完全阻断。如果在传代前接触 MCA 后将培养物维持 10 周，则只有 40% 的含有转化灶的培养物恢复正常形态表型。转化细胞向正常形态模式的回复通常似乎是不可逆的，因为在抗坏血酸存在下进行四次传代培养后，抗坏血酸随后可以被去除而不会重新表达形态转化。然而，如果转化细胞最初在没有抗坏血酸的情况下传代培养数次，然后暴露于维生素，则它们会变得难以抵抗抗坏血酸的作用。当比较早期和晚期传代的转化细胞时，抗坏血酸反应的这种变化可能表明这些转化细胞之间存在根本的生物学差异，尽管它们具有相似的形态模式。
目前尚不清楚负责抑制和逆转转化表型的确切机制。然而，转化细胞和非转化细胞之间的细胞毒性差异、抗坏血酸处理的培养物中细胞外基质的产生、脂肪细胞的形成或环2':3'-单磷酸腺苷的增加并未发现与这些效应的产生有关。
C3H/10T½ mouse embryo cells were exposed to 3-methylcholanthrene (MCA) for 24 hr. The daily addition of ascorbic acid at the noncytotoxic concentration of 1 µg/ml completely prevented the expression of transformed foci at 42 or 56 days after the experiment was begun if the ascorbate was added immediately after MCA exposure and daily thereafter for a total of 22 days. Ascorbic acid also could be added as late as 23 days after MCA treatment and still completely inhibit morphological transformation if maintained in the cultures until the dishes were stained.
The expression of the transformed phenotype in approximately 80% of the cultures containing transformed foci was also completely blocked following subculture at 6 to 8 weeks after MCA treatment if the transformed cells from these foci subsequently received ascorbic acid, 1 µg/ml, daily. Only 40% of cultures containing transformed foci returned to a normal morphological phenotype if the cultures were maintained for 10 weeks after MCA exposure before passage. The reversion of transformed cells to a normal morphological pattern often appeared to be irreversible since, after four subcultures in the presence of ascorbate, the ascorbic acid could subsequently be removed without reexpression of the morphological transformation. Transformed cells, however, became refractory to the effect of ascorbic acid if they were initially subcultured several times without ascorbate and then were exposed to the vitamin. This variation in the response to ascorbic acid when comparing early- and late-passaged transformed cells may indicate a fundamental biological difference between these transformed cells although they have a similar morphological pattern.
The exact mechanism(s) responsible for inhibition and reversion of the transformed phenotype is presently unknown. However, differential cytotoxicity between transformed and nontransformed cells, the production of an extracellular matrix in ascorbate-treated cultures, adipocyte formation, or increases in adenosine cyclic 2′:3′-monophosphoric acid were not found to be implicated in producing these effects.