Estrogen regulates vascular endothelial growth permeability factor expression in 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors
Estrogen regulates vascular endothelial growth permeability factor expression in 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors
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DOI：
10.1210/en.137.12.5589
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发表时间：
1996-12-01
期刊：
影响因子：
4.8
通讯作者：
Brodie, A
中科院分区：
文献类型：
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作者：
Nakamura, J;Savinov, A;Brodie, A
血管内皮生长/通透性因子（VEG/PF）在一些正常组织中表达，并且在广泛的肿瘤中以高水平表达。这种生长因子被认为是血管生成的关键介质。最近的研究表明，雌二醇（E2）可刺激大鼠子宫VEG/PF mRNA的表达。本研究以7，12-二甲基苯并蒽（DMBA）诱导的大鼠乳腺肿瘤模型为研究对象，观察了VEG/PF在乳腺组织中的表达，以及VEG/PF是否受E（2）的调节。用VEG/PF引物通过RT-PCR扩增来自肿瘤提取物的VEG/PF mRNA，并产生两种主要产物，其大小对应于VEG/PF 164和120的预期产物。在某些情况下，还生成了大小与VEG/PF 188预期大小相对应的第三产物。从等量的正常乳腺组织、大鼠脑或肝脏的RNA中没有产生这样的PCR产物。免疫细胞化学检测肿瘤上皮细胞表达VEG/PF。我们开发了一种ELISA测定法来测量VEG/PF蛋白浓度，发现正常乳腺（1.3 +/- 0.11 ng/mg蛋白）和肿瘤（4.44 +/- 0.66）之间的差异为4倍（P < 0.01）。卵巢切除后24 h，给予E（2）5 μ g/rat，sc，2 h内肿瘤组织RT-PCR产物表达明显增强，6- 8h达高峰，48 h后下降。注射E（2）后8-12 h，VEG/PF浓度也升高。当大鼠间隔24 h两次注射芳香化酶抑制剂4-羟基雄烯二酮（4-OHA 10 mg/rat sc）以降低雌激素浓度时，低水平的RT-PCR产物至少维持96 h。在单次注射4-OHA后，RT-PCR产物保持较低水平，直到36 h，此时出现与血浆E（2）水平升高相对应的增加。4-OHA处理后2 h注射E（2），RT-PCR产物在6- 8h内升高。然而，VEG/PF浓度无显著变化。VEG/PF蛋白浓度增加，随后mRNA水平增加4-6小时。因此，似乎E（2）引起乳腺肿瘤中VEG/PF表达的快速诱导，这与在正常子宫中观察到的相似。这些发现表明，雌激素作为乳腺肿瘤促进剂的一种机制是通过刺激VEG/PF，导致肿瘤血管生成和/或微血管通透性增加，从而允许肿瘤细胞迁移。
Vascular endothelial growth/permeability factor (VEG/PF) is expressed in some normal tissues and at high levels in a wide range of tumors. This growth factor is believed to be a key mediator of angiogenesis. Recent reports have shown that VEG/PF mRNA in the normal rat uterus is stimulated by estradiol (E(2)). In this study, we investigated the expression of VEG/PF in the mammary gland and 7,12-dimethylbenz(a)anthracene (DMBA)-induced, hormone-dependent mammary tumor of the rat model, and also whether VEG/PF is regulated by E(2). VEG/PF mRNA from tumor extracts was amplified by RT-PCR with VEG/PF primers and generated two main products which corresponded in size to those expected for VEG/PF 164 and 120. In some cases, a third product corresponding in size to that expected for VEG/PF 188 was also generated. No such PCR products were generated from equal amount of RNA from normal mammary tissue, rat brain, or liver. Using immunocytochemistry, VEG/PF expression was detected in the epithelial cells of the tumors. We developed an ELISA assay to measure VEG/PF protein concentrations and found a 4-fold difference between normal mammary glands (1.3 +/- 0.11 ng/mg protein) and tumors (4.44 +/- 0.66) (P < 0.01). E(2) treatment (5 mu g/rat, sc) of rats 24 h after ovariectomy, greatly enhanced the expression of RT-PCR products in tumors within 2 h, which reached a maximum at 6-8 h but declined by 48 h. VEG/PF concentrations were also increased 8-12 h after E(2) injection. When rats were given two injections of aromatase inhibitor 4-hydroxyandrostenedione (4-OHA 10 mg/rat sc) 24 h apart, to reduce estrogen concentrations, a low level of RT-PCR products was maintained for at least 96 h. After a single injection of 4-OHA, RT-PCR products remained low until 36 h when an increase occurred corresponding with a rise in plasma E(2) levels. Injection of E(2) 2 h after 4-OHA treatment, caused a rise in RT-PCR products in 6-8 h. However, there was no significant change in VEG/PF concentrations. An increase in VEG/PF protein concentrations followed the increase in mRNA levels by 4-6 h. Thus, it appears that E(2) causes a rapid induction of VEG/PF expression in mammary tumors that is similar to that observed in the normal uterus. These findings suggest that one mechanism by which estrogen acts as a mammary tumor promotor is by stimulating VEG/PF, leading to increased tumor angiogenesis and/or permeability of the microvessels to allow tumor cell migration.