Park K, Bae H, Heydemann A, Roberts A B, Dotto G P, Sporn M B, Kim S J
Laboratory of Chemoprevention, National Cancer Institute, Bethesda, Maryland 20892.
Cancer Res. 1994 Dec 1;54(23):6087-9.
1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] inhibited DNA synthesis in transformed mouse keratinocytes (Pam212) in a time- and dose-dependent manner as measured by [3H]thymidine incorporation. To investigate the mechanism through which 1,25-(OH)2D3 acts, we examined its effects on Pam212 cells further transformed with the E1A oncogene. Here, we show that transformation of the cells with the E1A oncogene induced resistance to the effects of 1,25-(OH)2D3 on inhibition of growth of Pam212 cells. While 1,25-(OH)2D3 treatment increased the level of expression of vitamin D receptor mRNA 20-fold in parental cells, the E1A-transformed cells failed to express vitamin D receptor mRNA even after treatment with 1,25-(OH)2D3. Transfection of the E1A-transformed cell line with an expression construct encoding the vitamin D receptor restored receptor expression as well as the inhibition of growth by 1,25-(OH)2D3. These results suggest that one of the mechanisms for acquisition of 1,25-(OH)2D3 resistance induced by E1A may involve loss of vitamin D receptor inducibility by 1,25-(OH)2D3.
1,25 - 二羟基维生素D3 [1,25-(OH)2D3] 以时间和剂量依赖性方式抑制转化的小鼠角质形成细胞（Pam212）中的DNA合成，这是通过[3H]胸苷掺入法测定的。为了研究1,25-(OH)2D3发挥作用的机制，我们进一步研究了它对用E1A癌基因进一步转化的Pam212细胞的影响。在此，我们表明用E1A癌基因转化细胞可诱导对1,25-(OH)2D3抑制Pam212细胞生长作用的抗性。虽然1,25-(OH)2D3处理使亲代细胞中维生素D受体mRNA的表达水平增加了20倍，但E1A转化的细胞即使在用1,25-(OH)2D3处理后也未能表达维生素D受体mRNA。用编码维生素D受体的表达构建体转染E1A转化的细胞系可恢复受体表达以及1,25-(OH)2D3对生长的抑制作用。这些结果表明，E1A诱导的1,25-(OH)2D3抗性获得机制之一可能涉及1,25-(OH)2D3诱导的维生素D受体诱导性丧失。
