Larsson O, Barrios C, Latham C, Ruiz J, Zetterberg A, Zickert P, Wejde J
Department of Tumor Pathology, Karolinska Institutet, Stockholm, Sweden.
Cancer Res. 1989 Oct 15;49(20):5605-10.
The basal level of the gene expression and the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase was higher in SV40-transformed human fibroblasts (90-VA VI) than in normal ones (HDF). In both these cell types mevinolin (25 microM) caused an 85-90% depression of HMG CoA reductase activity and of the incorporation of [3H]acetate into sterols. In HDF this was coupled to an efficient block of cell growth, whereas the growth of 90-VA VI was only slightly reduced by mevinolin. In HDF, mevinolin (25 microM) also abolished essentially all dilichol synthesis, as measured by incorporation of [3H]acetate. In contrast, dolichol synthesis remained unaltered, or was increased, in mevinolin-treated 90-VA VI. We suggest that these different responses of dolichol synthesis may depend on different substrate affinities of the rate-limiting enzyme in the dolichol pathway. However, if 90-VA VI was treated with 25-hydroxycholesterol (25-OH), an alternative inhibitor of HMG CoA reductase, the cellular growth as well as dolichol synthesis was significantly decreased. Since the inhibitory effect of 25OH on HMG CoA reductase activity did not exceed that of mevinolin, it seems that 25-OH, besides HMG CoA reductase, inhibits steps distal to HMG CoA reductase. This notion was further supported by the finding that addition of mevalonate did not prevent the 25-OH-induced growth inhibition. However, if dolichol was added along with 25-OH, the block was partially prevented, indicating that a critical level of de novo synthesis of dolichol for cellular growth.
SV40 转化的人成纤维细胞（90-VA VI）中基因表达的基础水平和 3-羟基-3-甲基戊二酰辅酶 A（HMG CoA）还原酶的活性高于正常成纤维细胞（HDF）。在这两种细胞类型中，美伐他汀（25 μM）可使 HMG CoA 还原酶活性以及[3H]乙酸掺入固醇的量降低 85-90%。在 HDF 中，这与细胞生长的有效阻滞相关，而美伐他汀仅轻微降低 90-VA VI 的生长。在 HDF 中，美伐他汀（25 μM）也基本消除了所有的二萜醇合成，这通过[3H]乙酸掺入来测定。相反，在美伐他汀处理的 90-VA VI 中，二萜醇合成保持不变或增加。我们认为二萜醇合成的这些不同反应可能取决于二萜醇途径中限速酶的不同底物亲和力。然而，如果用 25-羟基胆固醇（25-OH）处理 90-VA VI，这是 HMG CoA 还原酶的另一种抑制剂，则细胞生长以及二萜醇合成均显著降低。由于 25-OH 对 HMG CoA 还原酶活性的抑制作用不超过美伐他汀，似乎 25-OH 除了抑制 HMG CoA 还原酶外，还抑制 HMG CoA 还原酶下游的步骤。这一观点得到以下发现的进一步支持：添加甲羟戊酸并不能阻止 25-OH 诱导的生长抑制。然而，如果在添加 25-OH 的同时添加二萜醇，则阻滞被部分阻止，表明二萜醇的从头合成达到关键水平对细胞生长是必需的。
