Osteoblast-Induced Prostate Cancer Cell Migration and Invasion Is Mediated Through TGF-β1/SMAD2 Signal Pathway and Blocked by 17α-Estradiol

Prostate cancer (PCa) is curable if it is diagnosed and treated in localized and regional stage. However, PCa outcome is poor once it has distant metastasis. Approximately 70% to 100% of PCa deaths have bone metastasis, which may be associated with a specific bone microenvironment. In this study, we investigated the effect and molecular mechanism of osteoblast cells on stimulation of PCa cell migration and invasion and examined the effectiveness of 17α-estradiol on blocking osteoblast-induced PCa cell migration and invasion using in vitro cell analysis. PCa cells (PC3, LNCaP and DU145), osteoblast hFOB, kidney CV-1, breast tumor MCF-7 and liver cancer Huh-7 cells (ATCC) were cultured in RMPI-1640 or DMEM media supplemented with or without fetal bovine serum (FBS) at 37 oC in a 5% CO2-humidified incubator. hFOB condition media (HCM) without FBS were collected at different times of hFOB cell culture. Transwell and wound-healing experiments were used to determine PCa cell migration and invasion. Cell migration and invasion in PC3, DU-145 and LNCaP PCa cells were markedly promoted by co-culturing hFOB osteoblast cells or HCM, but not by cells or condition media originated from kidney (CV-1), liver (Huh-7) and breast (MCF-7). Compared to other non-osteoblast cell conditioned media, HCM had much higher levels of several cytokines and chemokines including tumor growth factor (TGF) β1. Both HCM and TGF-β1 produced a dose- and time-dependent induction of PCa cell migration and invasion as well as SMAD2 phosphorylation without altering cell proliferation. These HCM and TGF-β1 effects were inhibited by a specific TGFβ receptor inhibitor, LY2157299, as well as by 17α-estradiol in a dose-dependent manner. Most intriguing, 17α-estradiol significantly inhibited the HCM and TGF-β1-induced PCa cell migration and invasion at very low nanomolar concentrations, presumably mediated through estrogen receptor β. These findings suggest that TGF-β1 is a major factor in mediating hFOB cell stimulation of PCa cell migration and invasion, and 17α-estradiol is a potential agent to block PCa cell bone metastasis, probably through inhibition of TGF-β1/SMAD2 signal pathway.