Investigation of mechanism of connective tissue growth factor (CTGF) as a molecular target against cancer-induced bone destruction

骨吸收在骨转移或癌骨浸润等癌性骨病中起重要作用。我们曾报道过抗结缔组织生长因子（CTGF）抗体可抑制裸鼠骨转移模型的溶骨性病变。提示抑制CTGF可能用于治疗癌症引起的骨疾病。然而，骨钙素骨吸收与CTGF的关系尚不清楚。本研究以CTGF为靶点，通过免疫组织化学方法观察CTGF在体外培养的小鼠骨髓基质细胞和破骨细胞中的表达，并以破骨细胞核周围的胞浆表达为主。CTGF反义寡核苷酸抑制骨细胞凋亡 ...更多信息 在体外牙本质切片上，ST形成，但不抑制成熟骨细胞的骨吸收。AS-CTGF抑制骨髓基质细胞系ST 2中ODF（RANKL）mRNA的表达，但不影响OCIF mRNA的表达。接下来，我们研究了裸鼠皮下植入转染CTGF基因的CHO细胞的骨代谢。尽管CTGF的过度产生，但在裸鼠中未观察到全身性高钙血症。转染后裸鼠的肿瘤生长和体重减轻与未转染的裸鼠无明显差异。通过癌症诱导的骨吸收释放这些生长因子如TGF-β可能调节骨微环境中的生物学事件。TGF-β浓度依赖性地增加人乳腺癌细胞株MDA-231和ST 2细胞CTGF mRNA的表达。提示TGF-β可能作为旁分泌因子调节骨吸收局部CTGF的表达。因此，CTGF可能在局部骨吸收位点发挥重要作用，抑制CTGF表达可能是治疗肿瘤引起的局部骨破坏的有效方法。少

Osteoclastic bone resorption plays an important role on cancer-induced bone disease likes bone metastases or cancer bone invasion. We previously reported that administration of antibody against connective tissue growth factor (CTGF) inhibited osteolytic lesions in nude mice bone metastasis model. It is suggested that inhibition of CTGF has a possibility of therapeutic use for the treatment of the cancer induced bone disease. However, the relationship between osteoclastic bone resorption and CTGF has been still unknown. In the present study, we examined the mechanism of CTGF on osteoclastic bone resorption to know whether we could use CTGF as a molecular target against the cancer-induced bone disease.Immunohistologically, the expression of CTGF protein was observed at bone-marrow stromal cells and osteoclasts, and especially localized at cytoplasm around the nuclei of osteoclasts in murine bone marrow culture system in vitro. CTGF anti-sense oligonucleotide (AS-CTGF) suppressed osteocla … More st formation, but did not inhibit mature osteoclastic bone resorption on dentin slice in vitro. AS-CTGF suppressed the expression of ODF (RANKL) mRNA in bone marrow /stromal cell line ST2, but did not affect the OCIF mRNA expression. Next, we examined the bone metabolism in nude mice subcutaneous implanting CHO cells transfected with CTGF gene. In spite of over-production of CTGF, systemic hypercalcemia was not observed in nude mice. And there is no difference of the tumor growth and body weight loss between the nude mice transfected with the transfectants and non-transfectant.It is well known that many growth factors store in bone matrices. Release of these growth factors like TGF-β by cancer-induced bone resorption probably regulates the biological events in the bone microenvironment. TGF-β dose-dependently increased the expression of CTGF mRNA of not only human breast cancer cells line MDA-231, but also ST2 cell. This indicates that TGF-β might regulate the CTGF expression of local bone resorption sites as paracrine factor. From these results, CTGF may play an important role on the local bone resorption site, and the inhibition of CTGF expression may be useful therapy for local bone destruction induced by cancer. Less