Skeletal Localization and Neutralization of the SDF-1(CXCL12)/CXCR4 Axis Blocks Prostate Cancer Metastasis and Growth in Osseous Sites In Vivo

Abstract

To delineate the role of SDF-1 and CXCR4 in metastatic prostate cancer (CaP), positive correlations were established between SDF-1 levels and tumor metastasis. Neutralization of CXCR4 limited the number and the growth of intraosseous metastasis in vivo. Together, these in vivo metastasis data provide critical support that SDF-1/CXCR4 plays a role in skeletal metastasis.Introduction: Previously we determined that the stromal-derived factor-1 (SDF-1)/CXCR4 chemokine axis is activated in prostate cancer (CaP) metastasis to bone. To delineate the role of SDF-1/CXCR4 in CaP, we evaluated SDF-1 levels in a variety of tissues and whether neutralization of SDF-1 prevented metastasis and/or intraosseous growth of CaPs. Materials and Methods: SDF-1 levels were established in various mouse tissues by ELISA, immunohistochemistry, and in situ hybridization. To assess the role of SDF-1/CXCR4 in metastasis, bone metastases were established by administering CaP cells into the left cardiac ventricle of nude animals in the presence or absence of neutralizing CXCR4 antibody. The effect of SDF-1 on intraosseous growth of CaP cells was determined using intratibial injections and anti-CXCR4 antibodies and peptides. Results: There was a positive correlation between the levels of SDF-1 and tissues in which metastatic CaP lesions were observed. SDF-1 levels were highest in the pelvis, tibia, femur, liver, and adrenal/kidneys compared with the lungs, tongue, and eye, suggesting a selective effect. SDF-1 staining was generally low or undetectable in the center of the marrow and in the diaphysis. SDF-1 mRNA was localized to the metaphysis of the long bones nearest to the growth plate where intense expression was observed near the endosteal surfaces covered by osteoblastic and lining cells. Antibody to CXCR4 significantly reduced the total metastatic load compared with IgG control-treated animals. Direct intratibial injection of tumor cells followed by neutralizing CXCR4 antibody or a specific peptide that blocks CXCR4 also decreased the size of the tumors compared with controls. Conclusions: These data provide critical support for a role of SDF-1/CXCR4 in skeletal metastasis. Importantly, these data show that SDF-1/CXCR4 participate in localizing tumors to the bone marrow for prostate cancer.

Stromal cell–derived factor 1/CXCR4 signaling is critical for the recruitment of mesenchymal stem cells to the fracture site during skeletal repair in a mouse model

“…To examine the localization of SDF-1 protein expressed during the acute phase of live bone graft healing, immunohistochemical analysis was performed. The expression of SDF-1 protein was observed at the growth plate and the endosteum (results not shown), as previously reported (32). We also detected high expression of SDF-1 protein at the periosteum of the bone graft on day 2 ( Figure 1B, bottom left).…”

“…To answer this, we performed gene expression and immunohistochemical analysis and observed that the periosteum of the long bones indeed expressed SDF1 mRNA, and that the expression of SDF-1 protein was highly increased in the periosteum of the live grafts, while no remarkable increase was observed either in the periosteum of the host bone or in that of the dead grafts ( Figures 1B and C). It was previously reported that SDF-1 is expressed at the endosteum and the growth plate of normal long bones in adults (32), but a recent study showed that SDF-1 is expressed at the periosteum during embryonic endochondral bone development, and that expression is substantially reduced after birth (38). Combined with these reports, our results may lead to an interesting hypothesis that, in endochondral bone repair, progenitor cells in the periosteum regain the embryonic state and recruit MSCs through the up-regulation of SDF-1 expression, which is consistent with a wellaccepted hypothesis that fracture healing recapitulates normal bone growth.…”

CXCL12/CXCR4 Transactivates HER2 in Lipid Rafts of Prostate Cancer Cells and Promotes Growth of Metastatic Deposits in Bone

“…A recent report further supports the role of CXCL12/CXCR4 in prostate cancer bone metastasis using the intratibial model in which inhibition of CXCR4 function reduced bone tumor growth (4). Experimental manipulation of CXCR4 also affects secondary tumor growth in lymph nodes.…”

“…Furthermore, binding of CXCL12 to CXCR4 has been shown to play a crucial role in site-specific metastasis to lymph nodes, lung, and bone (1). In prostate cancer, we and others showed CXCL12/CXCR4 signaling in tumor cells when in bone tissue (2)(3)(4). We also showed that CXCL12/CXCR4 interaction leads to mitogen-activated protein kinase and phosphoinositide 3-kinase/Akt -mediated MMP-9 expression, migration, and invasion of prostate cancer cells (2).…”

Homing of Cancer Cells to the Bone

“…SDF-1 levels are highest in the pelvis, tibia, femur, liver, and adrenal/ kidneys compared with the lungs, tongue, and eye. Antibody to CXCR4 significantly reduces skeletal metastases [67]. High-density tissue microarrays constructed from clinical samples obtained from a cohort of over 600 patients demonstrates that CXCR4 protein expression is significantly elevated in localized and metastatic cancers [68].…”