Nkx3.2 Promotes Primary Chondrogenic Differentiation by Upregulating Col2a1 Transcription

Background: The Nkx3.2 transcription factor promotes chondrogenesis by forming a positive regulatory loop with a crucial chondrogenic transcription factor, Sox9. Previous studies have indicated that factors other than Sox9 may promote chondrogenesis directly, but these factors have not been identified. Here, we test the hypothesis that Nkx3.2 promotes chondrogenesis directly by Sox9-independent mechanisms and indirectly by previously characterized Sox9-dependent mechanisms. Methodology/Principal Findings: C3H10T1/2 pluripotent mesenchymal cells were cultured with bone morphogenetic protein 2 (BMP2) to induce endochondral ossification. Overexpression of wild-type Nkx3.2 (WT-Nkx3.2) upregulated glycosaminoglycan (GAG) production and expression of type II collagen a1 (Col2a1) mRNA, and these effects were evident before WT-Nkx3.2-mediated upregulation of Sox9. RNAi-mediated inhibition of Nkx3.2 abolished GAG production and expression of Col2a1 mRNA. Dual luciferase reporter assays revealed that WT-Nkx3.2 upregulated Col2a1 enhancer activity in a dose-dependent manner in C3H10T1/2 cells and also in N1511 chondrocytes. In addition, WT-Nkx3.2 partially restored downregulation of GAG production, Col2 protein expression, and Col2a1 mRNA expression induced by Sox9 RNAi. ChIP assays revealed that Nkx3.2 bound to the Col2a1 enhancer element. Conclusions/Significance: Nkx3.2 promoted primary chondrogenesis by two mechanisms: Direct and Sox9-independen

Simultaneous siRNA Targeting of Src and Downstream Signaling Molecules Inhibit Tumor Formation and Metastasis of a Human Model Breast Cancer Cell Line

Src and signaling molecules downstream of Src, including signal transducer and activator of transcription 3 (Stat3) and cMyc, have been implicated in the development, maintenance and/or progression of several types of human cancers, including breast cancer. Here we report the ability of siRNA-mediated Src knock-down alone, and simultaneous knock-down of Src and Stat3 and/or cMyc to inhibit the neoplastic phenotype of a highly metastatic human model breast cancer cell line, MDA-MB-435S, a widely used model for breast cancer research.Src and its downstream signaling partners were specifically targeted and knocked-down using siRNA. Changes in the growth properties of the cultured cancer cells/tumors were documented using assays that included anchorage-dependent and -independent (in soft agar) cell growth, apoptosis, and both primary and metastatic tumor growth in the mouse tumor model. siRNA-mediated Src knock-down alone, and simultaneous knock-down of Src and Stat3 and/or cMyc inhibited the neoplastic phenotype of a highly metastatic human model breast cancer cell line, MDA-MB-435S. This knock-down resulted in reduced growth in monolayer and soft agar cultures, and a reduced ability to form primary tumors in NOD/SCID mice. In addition, direct intra-tumoral injection of siRNAs targeting these signaling molecules resulted in a substantial inhibition of tumor metastases as well as of primary tumor growth. Simultaneous knock-down of Src and Stat3, and/or Myc exhibited the greatest effects resulting in substantial inhibition of primary tumor growth and metastasis.These findings demonstrate the effectiveness of simultaneous targeting of Src and the downstream signaling partners Stat3 and/or cMyc to inhibit the growth and oncogenic properties of a human cancer cell line. This knowledge may be very useful in the development of future therapeutic approaches involving targeting of specific genes products involved in tumor growth and metastasis

Therapeutic targets for bone metastases in breast cancer

Breast cancer is prone to metastasize to bone. Once metastatic cells are in the bone marrow, they do not, on their own, destroy bone. Instead, they alter the functions of bone-resorbing (osteoclasts) and bone-forming cells (osteoblasts), resulting in skeletal complications that cause pathological fractures and pain. In this review, we describe promising molecular bone-targeted therapies that have arisen from recent advances in our understanding of the pathogenesis of breast cancer bone metastases. These therapies target osteoclasts (receptor activator of nuclear factor kB ligand, integrin αvβ3, c-Src, cathepsin K), osteoblasts (dickkopf-1, activin A, endothelin A) and the bone marrow microenvironment (transforming growth factor β, bone morphogenetic proteins, chemokine CXCL-12 and its receptor CXCR4). The clinical exploitation of these bone-targeted agents will provide oncologists with novel therapeutic strategies for the treatment of skeletal lesions in breast cancer

Interconnected porous hydroxyapatite ceramics for bone tissue engineering

Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the ‘foam-gel’ technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 μm, porosity 75%), which were interconnected by window-like holes (average diameter 40 μm), and also demonstrated adequate compression strength (10–12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field