Vascular endothelial growth factor mediates intracrine survival in human breast carcinoma cells through internally expressed VEGFR1/FLT1.
Vascular endothelial growth factor mediates intracrine survival in human breast carcinoma cells through internally expressed VEGFR1/FLT1.
复制标题
DOI：
10.1371/journal.pmed.0040186
复制
发表时间：
2007-06
期刊：
影响因子：
15.8
通讯作者：
Avraham S
中科院分区：
文献类型：
--
作者：
Lee TH;Seng S;Sekine M;Hinton C;Fu Y;Avraham HK;Avraham S
虽然血管内皮生长因子（VEGF）在乳腺肿瘤中的表达与乳腺癌发病机制中的不良预后相关，但VEGF受体VEGFR1（也称为FLT1）和VEGFR2（也称为KDR或FLK1）以及神经匹林1 （NRP1）在乳腺癌中的表达、定位和功能仍存在争议。我们研究了VEGF及其受体在乳腺癌细胞中的表达和功能。我们观察到VEGFR1表达丰富，VEGFR2表达低，NRP1表达变化。与对照细胞相比，转染反义VEGF cDNA或siVEGF （VEGF靶向小干扰RNA）的MDA-MB-231和MCF-7乳腺癌细胞显示VEGF表达显著降低，凋亡增加。此外，通过siRNA特异性靶向敲低VEGFR1表达（siVEGFR1）可通过下调蛋白激酶B （AKT）磷酸化而显著降低乳腺癌细胞的存活，而靶向敲低VEGFR2或NRP1表达对乳腺癌细胞的存活无影响。由于VEGFR1特异性配体胎盘生长因子（PGF）并没有像预期的那样抑制siVEGF诱导的乳腺癌细胞凋亡，而且VEGFR1抗体对这些细胞的存活也没有影响，因此我们检测了VEGFR1的定位。VEGFR1主要在MDA-MB-231和MCF-7乳腺癌细胞中内部表达。具体来说，VEGFR1被发现与lamin A/C共定位，在乳腺癌细胞系和原发性乳腺癌肿瘤中主要在核膜中表达。用siVEGFR1处理的乳腺癌细胞显示VEGFR1表达水平显著降低，核膜中缺乏VEGFR1表达。据我们所知，这项研究首次提供了乳腺癌细胞中独特的生存系统的证据，其中VEGF可以通过与VEGFR1的结合作为内部自分泌（内分泌）生存因子。这些结果可能导致基于抑制血管生成的肿瘤治疗策略的改进。Shalom Avraham及其同事的研究为乳腺癌细胞的生存系统提供了证据，其中VEGF通过与VEGFR1的结合作为一种内部自分泌生存因子。八分之一的女性会在一生中患上乳腺癌。这些妇女中的大多数在确诊后还能活很多年，许多人已经治愈了癌症。然而，有时，尽管肿瘤学家的努力，癌症还是无情地生长并在身体周围扩散（转移）。被称为预后因素的肿瘤特征可以指示这种扩散是否可能发生。已经转移的大肿瘤的预后比局限于乳房的小肿瘤差。肿瘤内特定蛋白的表达也提供了预后信息。一种与预后不良相关的蛋白是血管内皮生长因子（VEGF）。VEGF刺激血管生成——新血管的生长。小肿瘤从现有的血管中获得生长所需的营养，但大肿瘤需要组织自己的血液供应。在某种程度上，它们是通过分泌VEGF来做到这一点的。这种化合物与内皮细胞（血管内壁细胞）表面的蛋白质（受体）结合，然后向细胞发送信号，指示其制造新的血管。血管生成抑制剂，包括阻断VEGF受体活性的分子，正在开发用于治疗癌症。一些乳腺癌细胞系（从乳腺癌中分离出来并在实验室培养的细胞）产生VEGF和VEGF受体（VEGFR1、VEGFR2和neuropilin 1 [NRP1]）。但是，尽管一些研究报道了乳腺肿瘤中VEGFR1的表达与预后不良之间的关联，但其他研究未发现乳腺肿瘤中VEGFR1的表达。因此，VEGF受体在乳腺癌中的作用尚不清楚。在这项研究中，研究人员分析了VEGF及其受体在乳腺癌细胞中的表达和功能，以探讨VEGF是否以及如何帮助这些细胞存活。研究人员首先检测了几种人类乳腺癌细胞系中VEGF受体的表达。它们均表达VEGFR1，部分表达NRP1，但VEGFR2表达普遍较低。然后，他们研究了VEGF及其受体在两种人类乳腺癌细胞系（MDA-MB-231和MCF-7）中的功能。在这两种细胞系中，阻断VEGF或VEGFR1的表达（而不是其他两种受体）通过刺激称为细胞凋亡的特定细胞死亡过程来降低细胞存活率。出乎意料的是，在培养物中加入VEGF并没有逆转阻断VEGF表达的效果，这一结果表明VEGF和VEGFR1并不通过作用于细胞表面来影响乳腺癌细胞的存活。因此，当研究人员检查VEGFR1在细胞中发生的位置时，他们发现它在乳腺癌细胞系细胞核周围的膜上，而不是在细胞表面；一些原发性乳腺肿瘤和正常乳腺组织具有相同的定位模式。最后，研究人员表明，在细胞表面作用的VEGF抑制剂并不影响乳腺癌细胞系的存活。这些发现表明，VEGF以一种独特的方式帮助乳腺癌细胞存活：通过与细胞内的VEGFR1结合。换句话说，虽然VEGF通常作为旁分泌生长因子（由一个细胞释放并影响另一个细胞），但在乳腺癌细胞中，它可能作为内部自分泌（内分泌）生存因子，影响产生它的细胞。这些发现需要在更多细胞系和原发性乳腺癌中得到证实，但可能对乳腺癌的治疗具有重要意义。作用于细胞内的VEGF和VEGFR1抑制剂（小分子药物）可能比作用于细胞表面的抑制剂（例如，与受体结合的蛋白质）更有效地阻止乳腺癌的生长，因为内部作用的抑制剂可能既直接杀死肿瘤又具有抗血管生成作用，而外部作用的抑制剂只能产生第二种效果。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0040186访问这些网站。美国国家癌症研究所关于乳腺癌患者和专业人员的信息（英语和西班牙语）和血管生成（英语和西班牙语）MedlinePlus关于乳腺癌患者的百科全书信息（英语和西班牙语）CancerQuest，来自埃默里大学关于癌症生物学和血管生成和血管生成抑制剂的信息（几种语言）维基百科关于VEGF的页面(注：维基百科是一个免费的在线百科全书，任何人都可以编辑；有多种语言版本)
While vascular endothelial growth factor (VEGF) expression in breast tumors has been correlated with a poor outcome in the pathogenesis of breast cancer, the expression, localization, and function of VEGF receptors VEGFR1 (also known as FLT1) and VEGFR2 (also known as KDR or FLK1), as well as neuropilin 1 (NRP1), in breast cancer are controversial. We investigated the expression and function of VEGF and VEGF receptors in breast cancer cells. We observed that VEGFR1 expression was abundant, VEGFR2 expression was low, and NRP1 expression was variable. MDA-MB-231 and MCF-7 breast cancer cells, transfected with antisense VEGF cDNA or with siVEGF (VEGF-targeted small interfering RNA), showed a significant reduction in VEGF expression and increased apoptosis as compared to the control cells. Additionally, specifically targeted knockdown of VEGFR1 expression by siRNA (siVEGFR1) significantly decreased the survival of breast cancer cells through down-regulation of protein kinase B (AKT) phosphorylation, while targeted knockdown of VEGFR2 or NRP1 expression had no effect on the survival of these cancer cells. Since a VEGFR1-specific ligand, placenta growth factor (PGF), did not, as expected, inhibit the breast cancer cell apoptosis induced by siVEGF, and since VEGFR1 antibody also had no effects on the survival of these cells, we examined VEGFR1 localization. VEGFR1 was predominantly expressed internally in MDA-MB-231 and MCF-7 breast cancer cells. Specifically, VEGFR1 was found to be colocalized with lamin A/C and was expressed mainly in the nuclear envelope in breast cancer cell lines and primary breast cancer tumors. Breast cancer cells treated with siVEGFR1 showed significantly decreased VEGFR1 expression levels and a lack of VEGFR1 expression in the nuclear envelope. This study provides, to our knowledge for the first time, evidence of a unique survival system in breast cancer cells by which VEGF can act as an internal autocrine (intracrine) survival factor through its binding to VEGFR1. These results may lead to an improved strategy for tumor therapy based on the inhibition of angiogenesis. Shalom Avraham and colleagues' study provides evidence of a survival system in breast cancer cells by which VEGF acts as an internal autocrine survival factor through its binding to VEGFR1. One woman in eight will develop breast cancer during her lifetime. Most of these women live for many years after their diagnosis and many are cured of their cancer. However, sometimes the cancer grows inexorably and spreads (metastasizes) around the body despite the efforts of oncologists. Characteristics of the tumor known as prognostic factors can indicate whether this spreading is likely to happen. Large tumors that have metastasized have a poorer prognosis than small tumors that are confined to the breast. The expression of specific proteins within the tumor also provides prognostic information. One protein whose expression is associated with a poor prognosis is vascular endothelial growth factor (VEGF). VEGF stimulates angiogenesis—the growth of new blood vessels. Small tumors get the nutrients needed for their growth from existing blood vessels but large tumors need to organize their own blood supply. They do this, in part, by secreting VEGF. This compound binds to proteins (receptors) on the surface of endothelial cells (the cells lining blood vessels), which then send a signal into the cell instructing it to make new blood vessels. Angiogenesis inhibitors, including molecules that block the activity of VEGF receptors, are being developed for the treatment of cancer. Some breast cancer cell lines (cells isolated from breast cancers and grown in the laboratory) make VEGF and VEGF receptors (VEGFR1, VEGFR2, and neuropilin 1 [NRP1]). But, although some studies have reported an association between VEGFR1 expression in breast tumors and a poor prognosis, other studies have found no expression of VEGFR1 in breast tumors. Consequently, the role of VEGF receptors in breast cancer is unclear. In this study, the researchers analyzed the expression and function of VEGF and its receptors in breast cancer cells to investigate whether and how VEGF helps these cells to survive. The researchers first examined the expression of VEGF receptors in several human breast cancer cell lines. All of them expressed VEGFR1, some expressed NRP1, but VEGFR2 expression was universally low. They then investigated the function of VEGF and its receptors in two human breast cancer cell lines (MDA-MB-231 and MCF-7). In both cell lines, blocking the expression of VEGF or of VEGFR1 (but not of the other two receptors) reduced cell survival by stimulating a specific process of cell death called apoptosis. Unexpectedly, adding VEGF to the cultures did not reverse the effect of blocking VEGF expression, a result that suggests that VEGF and VEGFR1 do not affect breast cancer cell survival by acting at the cell surface. Accordingly, when the researchers examined where VEGFR1 occurs in the cell, they found it on the membranes around the nucleus of the breast cancer cell lines and not on the cell surface; several primary breast tumors and normal breast tissue had the same localization pattern. Finally, the researchers showed that inhibitors of VEGF action that act at the cell surface did not affect the survival of the breast cancer cell lines. These findings suggest that VEGF helps breast cancer cells to survive in a unique way: by binding to VEGFR1 inside the cell. In other words, whereas VEGF normally acts as a paracrine growth factor (it is released by one cell and affects another cell), in breast cancer cells it might act as an internal autocrine (intracrine) survival factor, a factor that affects the cells in which it is produced. These findings need confirming in more cell lines and in primary breast cancers but could have important implications for the treatment of breast cancer. Inhibitors of VEGF and VEGFR1 that act inside the cell (small molecule drugs) might block breast cancer growth more effectively than inhibitors that act at the cell surface (for example, proteins that bind to the receptor), because internally acting inhibitors might both kill the tumor directly and have antiangiogenic effects, whereas externally acting inhibitors could only have the second effect. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040186. US National Cancer Institute information for patients and professionals on breast cancer (in English and Spanish) and on angiogenesis (in English and Spanish) MedlinePlus Encyclopedia information for patients on breast cancer (in English and Spanish) CancerQuest, information from Emory University on cancer biology and on angiogenesis and angiogenesis inhibitors (in several languages) Wikipedia pages on VEGF (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
登录
查看更多内容
影响因子：
3.3
作者：
Nakopoulou, L;Stefanaki, K;Louvrou, A
通讯作者：
Louvrou, A
影响因子：
64.8
作者：
Gerber, HP;Malik, AK;Ferrara, N
通讯作者：
Ferrara, N
DOI：
10.1016/s1357-2725(01)00019-x
发表时间：
2001-04-01
影响因子：
4
作者：
Huang, K;Andersson, C;Claesson-Welsh, L
通讯作者：
Claesson-Welsh, L
影响因子：
6.5
作者：
Graells, J;Vinyals, A;Fabra, A
通讯作者：
Fabra, A
影响因子：
64.8
作者：
KIM, KJ;LI, B;FERRARA, N
通讯作者：
FERRARA, N