Multiple Small Diameter Drillings Increase Femoral Neck Stability Compared with Single Large Diameter Femoral Head Core Decompression Technique for Avascular Necrosis of the Femoral Head.

Femoral head core decompression is an efficacious joint-preserving procedure for treatment of early stage avascular necrosis. However, postoperative fractures have been described which may be related to the decompression technique used. Femoral head decompressions were performed on 12 matched human cadaveric femora comparing large 8mm single bore versus multiple 3mm small drilling techniques. Ultimate failure strength of the femora was tested using a servo-hydraulic material testing system. Ultimate load to failure was compared between the different decompression techniques using two paired ANCOVA linear regression models. Prior to biomechanical testing and after the intervention, volumetric bone mineral density was determined using quantitative computed tomography to account for variation between cadaveric samples and to assess the amount of bone disruption by the core decompression. Core decompression, using the small diameter bore and multiple drilling technique, withstood significantly greater load prior to failure compared with the single large bore technique after adjustment for bone mineral density (p< 0.05). The 8mm single bore technique removed a significantly larger volume of bone compared to the 3mm multiple drilling technique (p< 0.001). However, total fracture energy was similar between the two core decompression techniques. When considering core decompression for the treatment of early stage avascular necrosis, the multiple small bore technique removed less bone volume, thereby potentially leading to higher load to failure.

Quantification of mineralized bone response to prostate cancer by noninvasive in vivo microCT and non-destructive ex vivo microCT and DXA in a mouse model.

BACKGROUND: To compare nondestructive in vivo and ex vivo micro-computed tomography (muCT) and ex vivo dual-energy-X-ray-absorptiometry (DXA) in characterizing mineralized cortical and trabecular bone response to prostate cancer involving the skeleton in a mouse model. METHODOLOGY/PRINCIPAL FINDINGS: In vivo microCT was performed before and 10 weeks after implantation of human prostate cancer cells (MDA-PCa-2b) or vehicle into SCID mouse femora. After resection, femora were imaged by nondestructive ex vivo specimen microCT at three voxel sizes (31 micro, 16 micro, 8 micro) and DXA, and then sectioned for histomorphometric analysis of mineralized bone. Bone mineral density (BMD), trabecular parameters (number, TbN; separation, TbSp; thickness, TbTh) and mineralized bone volume/total bone volume (BV/TV) were compared and correlated among imaging methods and histomorphometry. Statistical tests were considered significant if P<0.05. Ten weeks post inoculation, diaphyseal BMD increased in the femur with tumor compared to the opposite femur by all modalities (p<0.005, n = 11). Diaphyseal BMD by in vivo microCT correlated with ex vivo 31 and 16 microm microCT and histomorphometry BV/TV (r = 0.91-0.94, P<0.001, n = 11). DXA BMD correlated less with bone histomorphometry (r = 0.73, P<0.001, n = 11) and DXA did not distinguish trabeculae from cortex. By in vivo and ex vivo microCT, trabecular BMD decreased (P<0.05, n = 11) as opposed to the cortex. Unlike BMD, trabecular morphologic parameters were threshold-dependent and when using "fixed-optimal-thresholds," all except TbTh demonstrated trabecular loss with tumor and correlated with histomorphometry (r = 0.73-0.90, P<0.05, n = 11). CONCLUSIONS/SIGNIFICANCE: Prostate cancer involving the skeleton can elicit a host bone response that differentially affects the cortex compared to trabeculae and that can be quantified noninvasively in vivo and nondestructively ex vivo.

Androgen receptor-negative human prostate cancer cells induce osteogenesis in mice through FGF9-mediated mechanisms.

In prostate cancer, androgen blockade strategies are commonly used to treat osteoblastic bone metastases. However, responses to these therapies are typically brief, and the mechanism underlying androgen-independent progression is not clear. Here, we established what we believe to be the first human androgen receptor-negative prostate cancer xenografts whose cells induced an osteoblastic reaction in bone and in the subcutis of immunodeficient mice. Accordingly, these cells grew in castrated as well as intact male mice. We identified FGF9 as being overexpressed in the xenografts relative to other bone-derived prostate cancer cells and discovered that FGF9 induced osteoblast proliferation and new bone formation in a bone organ assay. Mice treated with FGF9-neutralizing antibody developed smaller bone tumors and reduced bone formation. Finally, we found positive FGF9 immunostaining in prostate cancer cells in 24 of 56 primary tumors derived from human organ-confined prostate cancer and in 25 of 25 bone metastasis cases studied. Collectively, these results suggest that FGF9 contributes to prostate cancer-induced new bone formation and may participate in the osteoblastic progression of prostate cancer in bone. Androgen receptor-null cells may contribute to the castration-resistant osteoblastic progression of prostate cancer cells in bone and provide a preclinical model for studying therapies that target these cells.

Inhibition of prostate tumor growth and bone remodeling by the vascular targeting agent VEGF121/rGel.

The pathophysiology of tumor growth following skeletal metastases and the poor response of this type of lesion to therapeutic intervention remains incompletely understood. Vascular endothelial growth factor (VEGF)-A and its receptors play a role in both osteoclastogenesis and tumor growth. Systemic (i.v.) treatment of nude mice bearing intrafemoral prostate (PC-3) tumors with the vascular ablative agent VEGF(121)/recombinant gelonin (rGel) strongly inhibited tumor growth. Fifty percent of treated animals had complete regression of bone tumors with no development of lytic bone lesions. Immunohistochemical analysis showed that VEGF(121)/rGel treatment suppressed tumor-mediated osteoclastogenesis in vivo. In vitro treatment of murine osteoclast precursors, both cell line (RAW264.7) and bone marrow-derived monocytes (BMM), revealed that VEGF(121)/rGel was selectively cytotoxic to osteoclast precursor cells rather than mature osteoclasts. VEGF(121)/rGel cytotoxicity was mediated by Flt-1, which was down-regulated during osteoclast differentiation. Analysis by flow cytometry and reverse transcription-PCR showed that both BMM and RAW264.7 cells display high levels of Flt-1 but low levels of Flk-1. Internalization of VEGF(121)/rGel into osteoclast precursor cells was suppressed by pretreatment with an Flt-1 neutralizing antibody or by placenta growth factor but not with an Flk-1 neutralizing antibody. Thus, VEGF(121)/rGel inhibits osteoclast maturation in vivo and it seems that this process is important in the resulting suppression of skeletal osteolytic lesions. This is a novel and unique mechanism of action for this class of agents and suggests a potentially new approach for treatment or prevention of tumor growth in bone.

High efficacy of docetaxel with and without androgen deprivation and estramustine in preclinical models of advanced prostate cancer.

BACKGROUND: To assess the activity of docetaxel in combination with hormonal therapy in preclinical models of prostate cancer. MATERIALS AND METHODS: Since prostate cancer has a predilection for the bone, we assessed the antitumor activity of docetaxel in in vivo models of both bone metastasis and localized prostate cancer, using MDA PCa 2b and PC3 cells in SCID mice. RESULTS: Dramatic antitumor efficacy was observed regardless of whether the tumor cells were implanted in the prostate or in the bone. Antitumor activity was also evident in both osteolytic and osteoblastic lesions. Reasoning that docetaxel efficacy might be enhanced if it were to be used earlier in the course of the disease, we studied the sequence of docetaxel and androgen ablation (part of standard treatment for early-stage prostate cancer) in the MDA PCa 2b xenograft model. The activity was similar whether docetaxel and androgen ablation were used alone, simultaneously, or in sequence, indicating a lack of synergism or antagonism. Finally, we studied the combination of docetaxel and estramustine on androgen-sensitive and androgen-independent cell lines in vitro and in vivo. Estramustine did not increase the activity of docetaxel in these models. CONCLUSION: These results provide a strong preclinical rationale for the clinical development of docetaxel for the treatment of both locally advanced and disseminated prostate cancer.

Prostate cancer cells-osteoblast interaction shifts expression of growth/survival-related genes in prostate cancer and reduces expression of osteoprotegerin in osteoblasts.

PURPOSE: Prostate cancer specifically metastasizes to bone where it leads to bone formation. We previously reported that coculturing MDA PCa 2b prostate cancer cells with primary mouse osteoblasts (PMOs) induced PMO proliferation and differentiation. An osteoblastic reaction was also observed in vivo after injection of MDA PCa 2b cells into the bones of severe combined immunodeficient disease mice. The aim of this study was to identify the sequence of events that leads to these osteoblastic lesions in vivo and, using this in vitro model, to define the contributions of various genes and cellular pathways in the pathophysiology of osteoblastic bone metastases of prostate cancer. EXPERIMENTAL DESIGN AND RESULTS: We show histological evidence of de novo bone formation as early as 2 weeks after injection of MDA PCa 2b cells in the bone of severe combined immunodeficient disease mice. In vitro, we show that PMOs induce MDA PCa 2b proliferation, suggesting a synergistic paracrine loop between these cells and PMOs. Endothelin (ET)-1, which is a mitogen for several cell types, is produced by all prostate cancer cell lines tested, and Atrasentan, an antagonist of ET-1 receptor A, partially reversed PMO proliferation induced by MDA PCa 2b cells. ET-1 is known to be comitogenic with a number of growth factors, including insulin-like growth factor (IGF)-I. In this study, we report that IGF-binding protein (IGFBP)-3 transcripts (that regulate levels of free IGF) are down-regulated in prostate cancer cells cocultured with PMO, whereas prostate-specific antigen (a protease known to cleave IGFBP-3) is detected in the 150-400 ng/ml range. Accordingly, IGFBP-3 has antiproliferative effects in PMOs, which were attenuated in our in vitro system. Taken together, our studies also implicate the IGF axis to play a role in this model of bone metastases. Secondly, the transcript level of mouse double minute 2 (a protein that regulate p53) was increased in prostate cancer cells grown with PMOs. The p53-dependent and -independent oncogenic activities of mouse double minute 2 suggest that osteoblasts induce a survival advantage in prostate cancer cells. Lastly, we show that expression of osteoprotegerin is decreased and of receptor activator of nuclear factor-kappaB ligand is increased in PMOs cultured in the presence of MDA PCa 2b cells, two events associated with osteoclast activation and bone resorption. CONCLUSIONS: Our results provide evidence that multiple and distinct molecular events affecting both bone formation and bone resorption concur to the increase bone mass in prostate cancer bone metastases. These data also provide a rationale for developing therapeutic strategies designed to target these molecular changes.

The association of p21((WAF-1/CIP1)) with progression to androgen-independent prostate cancer.

The molecular events leading to progression toward androgen-independent prostate cancer (AIPC) are not fully understood. The p21((WAF-1/CIP1)) (p21) gene has been identified as a key factor for the regulation of cell growth. The expression of p21 was examined by immunohistochemical studies in 105 prostate cancer samples: (a) 7 of 30 (23%) androgen-dependent tumors; and (b) 36 of 75 (48%) androgen-independent tumors stained positive for p21 (P < 0.02). No association was found between p21 expression and p53, bcl-2, and the androgen receptor protein expression in bone metastases of patients with AIPC, whereas there was a significant association with a high Ki-67 index (P < 0.05). In 4 of 43 (9%) cases, tumors displayed a p53-negative, bcl-2-negative, and p21-positive phenotype. A xenograft mouse model of prostate cancer using the androgen-responsive MDA PCa 2b prostate cancer cell line was used to study p21 expression after androgen deprivation and at relapse. Androgen deprivation reduced p21 expression to undetectable levels after 14 days. Tumor relapse, defining AIPC, was associated with increased expression of p21 to levels comparable with those found before castration. In this model, p21 expression at relapse was also correlated with a high Ki-67 index. In conclusion, p21 expression is associated with the progression to AIPC. A possible explanation involves a paracrine effect of p21 mediated by the release of mitogenic and antiapoptotic factors. Another explanation involves the regulation of p21 expression by the androgen receptor, which also suggests that p21 may have antiapoptotic function in prostate cancer.