Expression and activity of vitamin D-metabolizing cytochrome P450s (CYP1α and CYP24) in human nonsmall cell lung carcinomas
Expression and activity of vitamin D-metabolizing cytochrome P450s (CYP1α and CYP24) in human nonsmall cell lung carcinomas
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DOI：
10.1210/en.140.7.3303
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发表时间：
1999-07-01
期刊：
影响因子：
4.8
通讯作者：
Petkovich, M
中科院分区：
文献类型：
--
作者：
Jones, G;Ramshaw, H;Petkovich, M
肾外25-羟基维生素D-3-1 α-羟化酶被认为在与各种类型的肉芽肿性和淋巴增生性疾病以及某些实体瘤相关的高钙血症的发病机制中起主要作用。在本文中，我们描述了细胞色素P450组分的肾外酶从人非小细胞肺癌，SW 900的克隆。肾外Ia-羟化酶的细胞色素P450具有与CYP 1 α（该酶的肾形式）的细胞色素P450组分相同的氨基酸序列，并且似乎是相同基因的产物。CYP1 α：在5个非小细胞肺癌细胞系中的2个（SW 900，SK-Luci-6）中检测了信使RNA（mRNA）和Icr-羟化酶活性。所有五种肺细胞系在相同条件下用相同培养基培养，但五种中只有两种表达la-羟化酶;另外两种（WT-E，Calu-1）表达高水平的α-羟化酶，25-羟基维生素D-3-24-羟化酶，其特异性细胞色素P450组分CYP 24。尽管在基础条件下，肺细胞系SW 900仅表达CYP 1 α并显示出Icr-羟化酶活性，但当用低浓度的1 α，25-二羟基维生素D-3或高浓度的25-羟基维生素D-3处理时，它开始表达CYP 24并显示出24-羟化酶活性。令人惊讶的是，SW 900细胞在维生素D处理后约24小时仍具有可检测的CYP 1 α mRNA，尽管1 α-羟化酶活性不可测量。这些数据与新出现的假设一致，即维生素D通过其活性形式不会直接关闭CYP 1 α mRNA的产生，而是强烈刺激CYP 24，从而掩盖CYP 1 α活性。负责SW 900和SK-Luci-6中CYP 1 α基础表达的因子目前尚不清楚。
Extrarenal 25-hydroxyvitamin D-3-1 alpha-hydroxylase is believed to play a major role in the pathogenesis of hypercalcemia associated with various types of granulomatous and lymphoproliferative diseases and certain solid tumors. In this paper, we describe the cloning of the cytochrome P450 component of the extrarenal enzyme from a human nonsmall cell lung carcinoma, SW 900. The cytochrome P450 for the extrarenal la-hydroxylase has an amino acid sequence identical to that of the cytochrome P450 component of the CYP1 alpha, the renal form of the enzyme, and appears to be a product of the same gene. CYP1 alpha: messenger RNA (mRNA) and Icr-hydroxylase enzyme activity were detected in two (SW 900, SK-Luci-6) of a series of five nonsmall cell lung carcinoma cell lines. All five lung cell lines were cultured with the same medium under the same conditions, but only two of the five expressed la-hydroxylase enzyme; two others (WT-E, Calu-1) expressed high levels of the reciprocally regulated enzyme, 25-hydroxyvitamin D-3-24-hydroxylase, with its specific cytochrome P450 component, CYP24. Although under basal conditions the lung cell line SW 900 expressed only CYP1 alpha and showed Icr-hydroxylase enzyme activity, when treated with small concentrations of 1 alpha,25-dihydroxyvitamin D-3 or high concentrations of 25-hydroxyvitamin D-3, it began to express CYP24 and exhibit 24-hydroxylase enzyme activity. Somewhat surprisingly, SW 900 cells still had detectable CYP1 alpha mRNA some 24 h after vitamin D treatment despite the fact that 1 alpha-hydroxylase enzyme activity was unmeasurable. These data are consistent with the emerging hypothesis that vitamin D through its active form does not directly turn off CYP1 alpha mRNA production but, rather, strongly stimulates CYP24, thereby masking CYP1 alpha activity. The factor(s) responsible for the basal expression of CYP1 alpha in SW 900 and SK-Luci-6 is currently unknown.