Cloning of the molecules associated with bone metastases of cancers and its characterization

(1)转化生长因子-β和胰岛素样生长因子-1在乳腺癌骨转移中的作用在骨组织中存在大量的转化生长因子-β和胰岛素样生长因子-1，因此，这两种主要生长因子可能在生理或病理条件下对骨重建起一定的作用。众所周知，乳腺癌在转移到骨中后会吸收骨。为了探讨IGF-1在骨转移中的作用，我们建立了高表达显性-阴性IGF-1受体的乳腺癌细胞系MDA231，并用动物模型评价了其骨转移效应。我们发现，与亲代MDA231细胞相比，该细胞系的骨转移活性要低得多。接下来，我们评估了转化生长因子-β对MDA231细胞的影响。转化生长因子-β对MDA231细胞的生长影响不大，但明显促进甲状旁腺素的产生，甲状旁腺素是肿瘤骨转移的重要因素之一。另外，转化生长因子-β通过Smad2、Smad3和Smad4激活Smad信号。最后，我们发现Smad4缺陷的乳腺癌细胞株没有显示出向骨转移的能力。这些发现提示转化生长因子-β和胰岛素样生长因子-1在乳腺癌骨转移中起重要作用。(2)双膦酸盐对乳腺癌软组织转移的作用众所周知，双膦酸盐是一种强有力的破骨细胞抑制剂，对骨转移癌有治疗作用。然而，对乳腺癌软组织转移的影响却知之甚少。为了解决这个问题，我们建立了一个系统，在这个系统中我们可以评估骨转移和软组织转移。利用这一系统，我们发现双膦酸盐阻断了骨转移，但刺激了转移到软组织，如肺和肝脏。很可能双膦酸盐对骨骼和软组织有不同的影响。

(1) Role of TGF-beta and IGF-1 in bone metastases of breast cancersIn bone tissues/there are large amount of Transforming growth factor-beta (TGF-beta) and Insulin-like growth factor-1 (IGF-1), it is, therefore, likely that these two major growth factors play some roles in bone remodeling in physiological or pathological conditions. It is well know that breast cancers resorb the bone after metastasizing into bone. To examine the role of IGF-1 in bone metastases, we established the breast cancer cell line MDA231 overexpressing dominant-negative IGF-1 receptor, and assessed its bone-metastatic effects using animal model. We found that the cell line showed much less bone metastatic activity compared with parental MDA231 cells. We next evaluated the effects of TGF-beta on MDA231 cells. TGF-beta had little effects on the growth of MDA231 cells but markedly enhanced the production of PTHrP which is one of the important factor in bone metastases by cancers. In addtion, TGF-beta activates the Smad signaling through Smad2, Smad3 and Smad4. Finally, we found the breast cancer cell line that is deficient in Smad4 showed no ability to metastasize into bone. These finding suggest that important roles of TGF-beta and IGF-1 in bone metastases by breast cancers.(2) The effects of bisphosphonate on soft-tissue metastases of breast cancersIt is well know that bisphosphonate is a powerful inhibitor for osteoclasts and useful to treat the bone metastasized cancers. However, little is know the effects on soft tissue metastases of breast cancers. To address this, we established the system in which we can evaluate the bone metastases as well as soft tissues metastases. Using this system, we found that bisphosphonate blocked the bone metastases but stimulated the metastases into soft tissues such as lung and liver. It is likely that bisphosphonate has distinct effects on bone and soft tissues.