Division of Molecular and Cellular Biology, Sunnybrook Research Institute, Toronto, ON, Canada.
Breast Cancer Res Treat. 2011 Apr;126(2):373-84. doi: 10.1007/s10549-010-0921-0. Epub 2010 May 13.
Previously, we have shown that insulin-like growth factor binding protein-7 (IGFBP-7) expression is inversely correlated with disease progression in breast cancer and is associated with poor outcome. To further investigate the role of IGFBP-7 in the growth and metastatic behavior of breast cancer, primary breast tumors and metastatic tumors derived from the same patients were analyzed for IGFBP-7 expression. Immunohistochemical analysis revealed that IGFBP-7 is downregulated in half of the human metastatic breast tumors tested. IGFBP-7 has been linked to suppression of oncogenic pathways and can directly restore cellular senescence in melanomas, leading to their regression. It is possible that breast tumors with metastatic potential have escaped from IGFBP-7-induced suppression by its down-regulation. Twenty-two human primary breast tumor specimens were transplanted into human-bone NOD/SCID mice. One of the two triple negative primary breast tumors was serially xenotransplanted more than five times. Each serial transplant resulted in increased tumor take and rate of growth. Expression of IGFBP-7 was downregulated upon each serial implantation. To investigate the role of IGFBP-7 in breast tumor suppression, IGFBP-7 was overexpressed in the triple negative MDA-MB-468 human breast cancer line by stable transfection of a pSec-tag2-IGFBP-7 vector. The parental MDA-MB-468 breast cancer cells expressed extremely low levels of endogenous IGFBP-7. The production of IGFBP-7 protein by the MDA-MB-468 cells stably transfected with IGFBP-7 was confirmed by immunoblotting with anti-IGFBP-7 antibody. Ectopic overexpression of IGFBP-7 significantly reduced the growth of the IGFBP-7 transfected MDA-MB-468 cells compared to the parental MDA-MB-468 cells. We also assessed the role of IGFBP-7 on cell migration, a key determinant of malignant progression and metastasis. When parental MDA-MB-468 cells were treated with various amounts of conditioned medium derived from the IGFBP-7 overexpressing cell line, a significant difference in cell migration rate was observed between untreated and treated cells. IGFBP-7 strongly suppressed the phosphorylation of the mitogen-activated protein kinases (MAPK) ERK-1/2, suggesting that IGFBP-7 mediates its anti-proliferative effects through negative feedback signaling. Levels of phospho-ERK-1/2 were higher in the parental MDA-MB-468 than in IGFBP-7-expressing cells derived from it. When injected subcutaneously into NOD/SCID mice, the increased expression of IGFBP-7 in the MDA-MB-468 transfected cells reduced the rate of tumor growth in comparison to the parental MDA-MB-468 controls. These results suggest that the growth of breast cancer could be prevented by the forced expression of IGFBP-7 protein.
先前，我们已经表明胰岛素样生长因子结合蛋白-7（IGFBP-7）的表达与乳腺癌的疾病进展呈负相关，并与不良预后相关。为了进一步研究 IGFBP-7 在乳腺癌生长和转移行为中的作用，我们分析了来自同一患者的原发性乳腺癌肿瘤和转移性肿瘤中 IGFBP-7 的表达。免疫组织化学分析显示，在测试的一半人类转移性乳腺癌中，IGFBP-7 下调。IGFBP-7 与抑制致癌途径有关，并可直接恢复黑色素瘤中的细胞衰老，导致其消退。具有转移潜力的乳腺癌可能已经通过其下调而逃脱了 IGFBP-7 诱导的抑制。将 22 个人类原发性乳腺癌标本移植到人类骨 NOD/SCID 小鼠中。两种三阴性原发性乳腺癌中有一个进行了超过五次的连续异种移植。每次连续移植都会导致肿瘤摄取和生长率增加。每次连续植入时，IGFBP-7 的表达都下调。为了研究 IGFBP-7 在乳腺癌抑制中的作用，我们通过稳定转染 pSec-tag2-IGFBP-7 载体，在三阴性 MDA-MB-468 人乳腺癌系中过表达 IGFBP-7。亲本 MDA-MB-468 乳腺癌细胞表达极低水平的内源性 IGFBP-7。用抗 IGFBP-7 抗体进行免疫印迹证实，IGFBP-7 转染的 MDA-MB-468 细胞稳定表达 IGFBP-7 蛋白。与亲本 MDA-MB-468 细胞相比，IGFBP-7 的过表达显着降低了 IGFBP-7 转染的 MDA-MB-468 细胞的生长。我们还评估了 IGFBP-7 在细胞迁移中的作用，细胞迁移是恶性进展和转移的关键决定因素。当用来自 IGFBP-7 过表达细胞系的条件培养基处理亲本 MDA-MB-468 细胞时，未处理和处理细胞之间观察到细胞迁移率的显着差异。IGFBP-7 强烈抑制丝裂原活化蛋白激酶（MAPK）ERK-1/2 的磷酸化，表明 IGFBP-7 通过负反馈信号传导介导其抗增殖作用。磷酸化 ERK-1/2 的水平在亲本 MDA-MB-468 中高于从中衍生的 IGFBP-7 表达细胞。当将其皮下注射到 NOD/SCID 小鼠中时，与亲本 MDA-MB-468 对照相比，MDA-MB-468 转染细胞中 IGFBP-7 的过度表达降低了肿瘤生长速度。这些结果表明，通过强制表达 IGFBP-7 蛋白可以预防乳腺癌的生长。
