[Inhibitory effects of breast cancer cells on proliferation and differentiation of osteoblasts].

BACKGROUND AND OBJECTIVE: The effect of breast cancer cells on the normal function of osteoblasts remains unclear. This study was to investigate the effect of conditioned medium from two types of human breast cancer lines on osteoblastic proliferation, differentiation and mineralization. METHODS: Fetal rat carvarial cells were treated with conditioned medium from MCF-7 estrogen-receptor(ER) positive, or MDA-MB-231 ER negative, breast cancer cells. Proliferation was measured by MTT assay, alkaline phosphatase (ALP) activity was assessed by the p-nitrophenyl phosphate (PNPP) method, and mineralized nodules were confirmed by alizarin red S (ARS) staining and the area of bone nodules was measured to observe the mineralization capacity. RESULTS: When osteoblasts were treated with conditioned medium from MDA-MB-231 or MCF-7, the cells became long and spindle-like, assumed a fibroblastic morphology. Conditioned medium from breast cancer cells inhibited proliferation and differentiation of osteoblasts, compared with those cultured with vehicle control medium. The proliferation inhibition rates of culture with 50% conditioned medium from MDA-MB-231 and MCF-7 cells on osteoblasts were 18.1%, 13.0%, 19.2%, 19.3% and 15.8%, 20.8%, 33.9%, 28.7% on day 1, day 3, day 5, and day 7, respectively (P<0.01). Moreover, incubation with conditioned medium inhibited ALP activity and bone-nodule formation of osteoblasts in a dose-dependent manner. Addition of 50% conditioned medium from MDA-MB-231 and MCF-7 cells inhibited ALP activity by 31.9% and 47.5% (P<0.01), and diminished the area of bone nodules by 89% and 74%, respectively, compared with the vehicle control group. CONCLUSION: Breast cancer cells inhibit proliferation, decrease ALP activity and disrupt the mineralization process of osteoblasts.

[Therapeutic effect of recombinant human parathyroid hormone(1-34) on osteoporosis of ovariectomized rats].

OBJECTIVE: To investigate the therapeutic effect of recombinant human parathyroid hormone(1-34) [rhPTH(1-34)] on osteoporosis of ovariectomized rats. METHODS: The model of osteoporosis was formed after 3 months of ovariectomy with 6-month age of 80 rats. Another 20 rats was control of sham operation. rhPTH(1-34) was subcutaneously injected once daily with 5, 10, 20, 40 micrograms/kg for 3 months. There were 10 rats in each group. The control of therapy included Salmon Calcitonin to 10 rats and Alendronate sodium to 10 rats. The bone weight of dry and ash, bone mineral density, bone biomechanical property, trabecular area, bone mineral deposition and serum alkaline phosphatase, Ca, P and urinary Pyridinoline/creatin (Pyd/Cr) were measured after the end of therapy. RESULTS: When administered to animals as a single subcutaneous injection once daily, rhPTH(1-34) increased obviously bone mass, bone biomechanical property and trabecular area, as well as bone deposition compared with the animals of control group. The bone architecture was ultimately improved by rhPTH(1-34) therapy. CONCLUSIONS: Rats of ovariectomized-induced osteoporosis possess obvious effect of treatment with low dose of rhPTH(1-34) administered once daily.

Modulation of isoflavones on bone-nodule formation in rat calvaria osteoblasts in vitro.

OBJECTIVE: To observe the effects of two main isoflavones, daidzein and genistein on the bone-nodule formation in rat calvaria osteoblasts in vitro. METHODS: Osteoblasts obtained from newborn Sprague-dawley rat calvaria were cultured for several generations. The second generation cells were cultured in Minimum Essential Medium supplemented with ascorbic acid and Na-beta-glycerophosphate for several days, in the presence of daidzein and genistein, with or without the estrogen receptor antagonist ICI 182780. Number of nodules was counted at the end of the incubation period (day 20) by staining with Alizarin Red S calcium stain. The release of osteocalcin, as a marker of osteoblast activity, was also determined on day 7 and day 12 during the incubation period. RESULTS: Compared with the control, the numbers of nodules were both increased by incubation with daidzein and genistein. 17 beta-estradiol was used as a positive control and proved to be a more effective inducer of the increase in bone-nodules formation that daidzein and genistein. The release of osteocalcin into culture media was also increased in the presence of daidzein and genistein, as well as 17 beta-estradiol on day 7 and day 12 (day 12 were higher). The estrogen receptor antagonist ICI 182780 completely blocked the genistein- and 17 beta-estradiol-induced increase of nodule numbers and osteocalcin release in osteoblasts. However, the effects induced by daidzein could not be inhibited by ICI 182780. CONCLUSION: These findings suggest that geinistein can stimulate bone-nodule formation and increase the release of osteocalcin in rat osteoblasts. The effects, like those induced by 17 beta-estradiol, are mediated by the estrogen receptor dependent pathway. Daidzein also can stimulate bone-nodule formation and increase the release of osteocalcin in rat osteoblasts, but it is not, at least not merely, mediated by the estrogen receptor dependent pathway.