Molecular mechanism of bone metastasis in prostate cancer

双膦酸盐已被广泛用于治疗癌症引起的骨骼并发症。最近的研究表明，双膦酸盐促进骨转移部位的癌细胞和破骨细胞的凋亡。在本研究中，为了确定双膦酸盐对前列腺癌细胞的直接影响，我们检测了米诺膦酸盐对前列腺癌细胞生长、凋亡相关蛋白和破骨因子表达的影响。用氨基二膦酸米诺膦酸盐处理PC-3、DU 145和LNCaP细胞。然后观察bcl-2、bax、聚(ADP)-核糖聚合酶（PARP）、caspase-3、核因子- kb配体受体激活剂（RANKL）、骨保护素（OPG）、基质金属蛋白酶-2（MMP-2）、甲状旁腺激素相关蛋白（PTHrP）的增殖、凋亡和表达。米诺膦酸钠能抑制LNCaP、DU145和PC-3细胞的增殖。米诺膦酸钠处理的PC-3细胞DNA断裂，TUNEL细胞核呈阳性。米诺膦酸钠降低DU145和PC-3细胞bax表达，诱导bcl-2表达、caspase-3活性和PARP降解。米诺膦酸钠降低PC-3细胞中RANKL、PTHrP和MMP-2的表达。采用胫骨内注射激素难治性LNCaP-SF细胞形成的小鼠骨肿瘤模型，研究了一种新型双膦酸盐YM-529的抗肿瘤作用。YM-529对骨肿瘤形成的抑制作用呈剂量依赖性，未见新的类骨形成，而对照小鼠肿瘤细胞对骨基质的侵袭作用显著。我们的研究结果表明，双膦酸盐不仅能直接促进前列腺癌细胞的凋亡，还能降低前列腺癌细胞中促破骨基因的表达，有可能成为激素难治性前列腺癌的抗肿瘤药物。

Bisphosphonates are well established for the management of cancer-induced skeletal complications.Recent studies suggest that bisphosphonates promote apoptosis of cancer cells as well as osteoclasts in bone metastatic sites.In the present study, to determine the direct effects of bisphosphonate on prostate cancer cells, we examined the effects of minodronate on prostatic cancer cell growth and the expression of apoptosis related proteins and osteoclastogenic factors.PC-3, DU 145 and LNCaP cells were treated with amino-bisphosphonate minodronate.Then proliferation, apoptosis and expression of bcl-2, bax, poly(ADP)-ribose polymerase(PARP), caspase-3, receptor activator of nuclear factor-kB ligand(RANKL), osteoprotegerin(OPG), matrix metalloproteinases-2(MMP-2), and parathyroid hormone related protein(PTHrP)were assessed. The proliferation of LNCaP, DU145 and PC-3 cells were inhibited by minodronate.DNA fragmentation and TUNEL positive nuclei were observed in minodronate treated PC-3 cells.Minodronate decreased bax expression and induced bcl-2 expression, caspase-3 activity and degradation of PARP in DU145 and PC-3 cells. Minodronate decreased expression of RANKL, PTHrP and MMP-2 in PC-3 cells.Antitumor effect of a new bisphosphonate, YM-529 was tested using a mouse model of bone tumor formation created by intratibial injection of hormone refractory LNCaP-SF cells.Antitumor effect of YM-529 on bone tumor formation was evident in a dose-dependent manner as no new osteoid formation was seen in mice treated with YM-529, while tumor cell invasion into bone matrix was remarkable in control mice.Our results suggest that bisphosphonate not only directly promotes prostate cancer cell apoptosis but also decreases pro-osteoclasfic gene expression in prostate cancer cells, and has the potential of an antitumor agent against hormone refractory prostate cancer.