Liu Shuqian, Stromberg Arnold, Tai Hsin-Hsiung, Moscow Jeffrey A
Department of Pediatrics, College of Medicine, University of Kentucky, Lexington, Kentucky, USA.
Mol Cancer Res. 2004 Aug;2(8):477-87.
In previous studies, we have shown that RNA levels of the thiamine transporter THTR2 were down-regulated in breast cancer tumors in comparison with normal tissues and that THTR2-mediated increases in thiamine uptake activity contributed to increased apoptosis after exposure to ionizing radiation. To further understand the biological effects of the alteration of THTR2 expression, we conducted a DNA microarray study of gene expression in THTR2-transfected breast cancer cells and found that, in addition to increased expression of THTR2 attributable to the transgene, three other genes were up-regulated >2.5-fold in the transfected cells: cytochrome P450 isoform CYP4B1, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), and transcription factor CRIP1. In addition, two genes were confirmed to be down-regulated in THTR2-transfected cells: trefoil factor 1 (TFF1) and Rho-GDP dissociation inhibitor (RGDI). Up-regulation of 15-PGDH and CYP4B1 expression was observed in other breast cancer cell lines transfected with THTR2, and down-regulation was observed after suppression of THTR2 with siRNA vectors. To determine the role of exogenous thiamine in the expression of these genes, we analyzed THTR2-transfected breast cancer cells grown in thiamine-depleted medium by quantitative reverse transcription-PCR and showed that three of these five genes showed evidence of regulation by exogenous thiamine in a manner concordant with the effects of THTR2 overexpression. One of the genes up-regulated by THTR2 transfection was down-regulated by thiamine depletion (CYP4B1), and two genes with decreased expression in THTR2-transfected breast cancer cells were up-regulated by thiamine depletion (TFF1 and RGDI). In summary, these studies show unexpected relationships between thiamine metabolism and genes that may be involved in the oncogenesis of breast and lung cancer.
在先前的研究中，我们已经表明，与正常组织相比，硫胺素转运体THTR2的RNA水平在乳腺癌肿瘤中下调，并且THTR2介导的硫胺素摄取活性增加有助于在暴露于电离辐射后增加细胞凋亡。为了进一步了解THTR2表达改变的生物学效应，我们对THTR2转染的乳腺癌细胞进行了基因表达的DNA微阵列研究，发现除了由于转基因导致的THTR2表达增加外，转染细胞中另外三个基因上调了2.5倍以上：细胞色素P450同工型CYP4B1、15-羟基前列腺素脱氢酶（15-PGDH）和转录因子CRIP1。此外，两个基因在THTR2转染的细胞中被证实下调：三叶因子1（TFF1）和Rho-GDP解离抑制剂（RGDI）。在用THTR2转染的其他乳腺癌细胞系中观察到15-PGDH和CYP4B1表达上调，在用siRNA载体抑制THTR2后观察到下调。为了确定外源性硫胺素在这些基因表达中的作用，我们通过定量逆转录PCR分析了在硫胺素缺乏培养基中生长的THTR2转染的乳腺癌细胞，结果表明这五个基因中的三个显示出受外源性硫胺素调节的证据，其方式与THTR2过表达的影响一致。通过THTR2转染上调的一个基因在硫胺素缺乏时下调（CYP4B1），而在THTR2转染的乳腺癌细胞中表达降低的两个基因在硫胺素缺乏时上调（TFF1和RGDI）。总之，这些研究表明硫胺素代谢与可能参与乳腺癌和肺癌肿瘤发生的基因之间存在意想不到的关系。
