ROLE OF RANKL IN OSTEOLYTIC BONE METASTASIS OF MALIGNANT TUMOR

乳腺癌经常与溶骨性骨转移有关，破骨细胞在骨破坏中起主要作用。最近，破骨细胞分化因子(RANKL)被认为是造血前体细胞形成和维持破骨细胞的先决条件。将人乳腺癌细胞(MCF-7)接种于裸鼠额部，以阐明乳腺癌破骨细胞形成和骨破坏的机制。用原位杂交和TRAP染色分析RANKL和PTHrP基因的表达及破骨细胞的形成。早期，骨表面的梭形基质细胞和成骨细胞表达RANKL，然后在骨膜表面诱导大量破骨细胞。移植三周后，癌细胞迁移到被侵蚀的骨表面，在那里它们在凋亡中幸存下来。在所有阶段，RANKL的表达仅限于基质/成骨细胞，而PTHrP仅限于MCF-7乳腺癌细胞。另一方面，在移植了不产生PTHrP的癌细胞的小鼠中，既没有观察到诱导破骨细胞，也没有观察到癌细胞的浸润性生长。此外，体外培养的MC3T3-E1小鼠成骨细胞系经PTHrP处理后，RANKL基因表达增强，转录活性增强。因此，PTHrP通过反式激活基质/成骨细胞上的RANKL基因来诱导破骨细胞性骨吸收，为产生PTHrP的癌细胞提供了有利于生存的骨微环境。我们在各种国际和国内会议上公布了我们的数据，并在学术期刊上发表了科学论文。

Breast cancer is frequently associated with osteolytic bone metastasis, where osteoclasts play a major role in bone destruction. Recently, osteoclast differentiation factor (RANKL) has been identified as a prerequisite for the formation and maintenance of osteoclasts from haematopoietic precursors. To elucidate the mechanism of osteoclastogenesis and bone destruction in bone-residing breast cancer, human breast cancer cells (MCF-7) were injected into the forehead of nude mice. The expression of RANKL and PTHrP mRNA, and osteoclastogenesis were analysed by in situ hybridization and TRAP staining. At early stages, spindle-shaped stromal cells and osteoblasts on the bone surface expressed RANKL, then numerous osteoclasts were induced on the periosteal bone surface. Three weeks after the transplantation, cancer cells migrated onto the eroded bone surface, where they survived apoptosis. At all stages, RANKL expression was confined to the stromal/osteoblastic cells, whereas PTHrP was confined to the MCF-7 breast cancer cells. On the other hand, neither induction of osteoclasts nor infiltrative growth of cancer cells was observed in mice transplanted with PTHrP-non producing cancer cells. Moreover, in vitro treatment with PTHrP resulted in increased RANKL mRNA expression and transcription activity in the MC3T3-E1 mouse osteoblastic cell line. Thus PTHrP induces osteoclastic bone resorption through the transactivation of the RANKL gene on stromal/osteoblastic cells, affording a bone microenvironment conducive to the survival of PTHrP-producing cancer cells.We have presented our data at various international as well as domestic meeting, and published scientific papers for academic journals.