Bisphosphonates antagonise bone growth factors' effects on human breast cancer cells survival

Bone tissue constitutes a fertile 'soil' for metastatic tumours, notably breast cancer. High concentrations of growth factors in bone matrix favour cancer cell proliferation and survival, and a vicious cycle settles between bone matrix, osteoclasts and cancer cells. Classically, bisphosphonates interrupt this vicious cycle by inhibiting osteoclast-mediated bone resorption. We and others recently reported that bisphosphonates can also induce human breast cancer cell death in vitro, which could contribute to their beneficial clinical effects. We hypothesised that bisphosphonates could inhibit the favourable effects of 'bone-derived' growth factors, and indeed found that bisphosphonates reduced or abolished the stimulatory effects of growth factors (IGFs, FGF-2) on MCF-7 and T47D cell proliferation and inhibited their protective effects on apoptotic cell death in vitro under serum-free conditions. This could happen through an interaction with growth factors' intracellular phosphorylation transduction pathways, such as ERK1/2-MAPK. In conclusion, we report that bisphosphonates antagonised the stimulatory effects of growth factors on human breast cancer cell survival and reduced their protective effects against apoptotic cell death. Bisphosphonates and growth factors thus appear to be concurrent compounds for tumour cell growth and survival in bone tissue. This could represent a new mechanism of action of bisphosphonates in their protective effects against breast cancer-induced osteolysis.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Influence of ARHGEF3 and RHOA Knockdown on ACTA2 and Other Genes in Osteoblasts and Osteoclasts

Osteoporosis is a common bone disease that has a strong genetic component. Genome-wide linkage studies have identified the chromosomal region 3p14-p22 as a quantitative trait locus for bone mineral density (BMD). We have previously identified associations between variation in two related genes located in 3p14-p22, ARHGEF3 and RHOA, and BMD in women. In this study we performed knockdown of these genes using small interfering RNA (siRNA) in human osteoblast-like and osteoclast-like cells in culture, with subsequent microarray analysis to identify genes differentially regulated from a list of 264 candidate genes. Validation of selected findings was then carried out in additional human cell lines/cultures using quantitative real-time PCR (qRT-PCR). The qRT-PCR results showed significant down-regulation of the ACTA2 gene, encoding the cytoskeletal protein alpha 2 actin, in response to RHOA knockdown in both osteoblast-like (P<0.001) and osteoclast-like cells (P = 0.002). RHOA knockdown also caused up-regulation of the PTH1R gene, encoding the parathyroid hormone 1 receptor, in Saos-2 osteoblast-like cells (P<0.001). Other findings included down-regulation of the TNFRSF11B gene, encoding osteoprotegerin, in response to ARHGEF3 knockdown in the Saos-2 and hFOB 1.19 osteoblast-like cells (P = 0.003– 0.02), and down-regulation of ARHGDIA, encoding the Rho GDP dissociation inhibitor alpha, in response to RHOA knockdown in osteoclast-like cells (P<0.001). These studies identify ARHGEF3 and RHOA as potential regulators of a number of genes in bone cells, including TNFRSF11B, ARHGDIA, PTH1R and ACTA2, with influences on the latter evident in both osteoblast-like and osteoclast-like cells. This adds further evidence to previous studies suggesting a role for the ARHGEF3 and RHOA genes in bone metabolism

Inhibition of Gsk3 beta in cartilage induces steoarthritic features through activation of the canonical Wnt signaling pathway

Objective: In the past years, the canonical Wnt/\u3b2-catenin signaling pathway has emerged as a critical regulator of cartilage development and homeostasis. In this pathway, glycogen synthase kinase-3\u3b2 (GSK3\u3b2) down-regulates transduction of the canonical Wnt signal by promoting degradation of \u3b2-catenin. In this study we wanted to further investigate the role of Gsk3\u3b2 in cartilage maintenance. Design: Therefore, we have treated chondrocytes ex vivo and in vivo with GIN, a selective GSK3\u3b2 inhibitor. Results: In E17.5 fetal mouse metatarsals, GIN treatment resulted in loss of expression of cartilage markers and decreased chondrocyte proliferation from day 1 onward. Late (3. days) effects of GIN included cartilage matrix degradation and increased apoptosis. Prolonged (7. days) GIN treatment resulted in resorption of the metatarsal. These changes were confirmed by microarray analysis showing a decrease in expression of typical chondrocyte markers and induction of expression of proteinases involved in cartilage matrix degradation. An intra-articular injection of GIN in rat knee joints induced nuclear accumulation of \u3b2-catenin in chondrocytes 72. h later. Three intra-articular GIN injections with a 2. days interval were associated with surface fibrillation, a decrease in glycosaminoglycan expression and chondrocyte hypocellularity 6. weeks later. Conclusions: These results suggest that, by down-regulating \u3b2-catenin, Gsk3\u3b2 preserves the chondrocytic phenotype, and is involved in maintenance of the cartilage extracellular matrix. Short term \u3b2-catenin up-regulation in cartilage secondary to Gsk3\u3b2 inhibition may be sufficient to induce osteoarthritis-like features in vivo

Poly(acrylic acid)-block-poly(L-valine): Evaluation of β-sheet formation and its stability using circular dichroism technique

10.1021/bm700491qBiomacromolecules892801-280