Matrix metalloproteinase processing of PTHrP yields a selective regulator of osteogenesis, PTHrP1-17.

Parathyroid hormone-related protein (PTHrP) is a critical regulator of bone resorption and augments osteolysis in skeletal malignancies. Here we report that the mature PTHrP1-36 hormone is processed by matrix metalloproteinases to yield a stable product, PTHrP1-17. PTHrP1-17 retains the ability to signal through PTH1R to induce calcium flux and ERK phosphorylation but not cyclic AMP production or CREB phosphorylation. Notably, PTHrP1-17 promotes osteoblast migration and mineralization in vitro, and systemic administration of PTHrP1-17 augments ectopic bone formation in vivo. Further, in contrast to PTHrP1-36, PTHrP1-17 does not affect osteoclast formation/function in vitro or in vivo. Finally, immunoprecipitation-mass spectrometry analyses using PTHrP1-17-specific antibodies establish that PTHrP1-17 is indeed generated by cancer cells. Thus, matrix metalloproteinase-directed processing of PTHrP disables the osteolytic functions of the mature hormone to promote osteogenesis, indicating important roles for this circuit in bone remodelling in normal and disease contexts.

A loss of host-derived MMP-7 promotes myeloma growth and osteolytic bone disease in vivo.

Matrix metalloproteinases (MMPs) play a critical role in cancer pathogenesis, including tumor growth and osteolysis within the bone marrow microenvironment. However, the anti-tumor effects of MMPs are poorly understood, yet have significant implications for the therapeutic potential of targeting MMPs. Host derived MMP-7 has previously been shown to support the growth of bone metastatic breast and prostate cancer. In contrast and underscoring the complexity of MMP biology, here we identified a tumor-suppressive role for host MMP-7 in the progression of multiple myeloma in vivo. An increase in tumor burden and osteolytic bone disease was observed in myeloma-bearing MMP-7 deficient mice, as compared to wild-type controls. We observed that systemic MMP-7 activity was reduced in tumor-bearing mice and, in patients with multiple myeloma this reduced activity was concomitant with increased levels of the endogenous MMP inhibitor, tissue inhibitor of metalloproteinases-1 (TIMP-1). Our studies have identified an unexpected tumour-suppressive role for host-derived MMP-7 in myeloma bone disease in vivo, and highlight the importance of elucidating the effect of individual MMPs in a disease-specific context.

Re-calculating! Navigating through the osteosarcoma treatment roadblock.

The survival rates for patients with osteosarcoma have remained almost static for the past three decades. Current standard of care therapy includes chemotherapies such as doxorubicin, cisplatin, and methotrexate along with complete surgical resection and surgery with or without ifosfamide and etoposide for relapse, though outcomes are hoped to be improved through clinical trials. Additionally, increased understanding of the genetics, signaling pathways and microenvironmental factors driving the disease have led to the identification of promising agents and potential paths towards translation of an exciting array of novel targeted therapies. Here, we review the mechanism of action of these emerging therapies and how, with clinical translation, they can potentially improve the survival rates for osteosarcoma patients in the near future.

Dissecting the multiple myeloma-bone microenvironment reveals new therapeutic opportunities.

Multiple myeloma is a plasma cell skeletal malignancy. While therapeutic agents such as bortezomib and lenalidomide have significantly improved overall survival, the disease is currently incurable with the emergence of drug resistance limiting the efficacy of chemotherapeutic strategies. Failure to cure the disease is in part due to the underlying genetic heterogeneity of the cancer. Myeloma progression is critically dependent on the surrounding microenvironment. Defining the interactions between myeloma cells and the more genetically stable hematopoietic and mesenchymal components of the bone microenvironment is critical for the development of new therapeutic targets. In this review, we discuss recent advances in our understanding of how microenvironmental elements contribute to myeloma progression and, therapeutically, how those elements can or are currently being targeted in a bid to eradicate the disease.

The role of matrilysin (MMP-7) in leukaemia cell invasion.

The matrix metalloproteinases (MMPs) are important in tumour cell invasion and metastasis in many common cancers. However, relatively few studies have investigated the role of MMPs and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), in leukaemia cell invasion. This study examined two leukaemia cell lines, K562 and HL-60 and showed that the K562 cell line was four times more invasive than the HL-60 cell line. The expression of MMP-2, matrilysin (MMP-7), MMP-9. TIMP-1, TIMP-2 and TIMP-3 was analysed. Both cell lines produced similar amounts of MMP-2, MMP-9 and TIMP-2. The K562 cells expressed more TIMP-1 than the HL-60 cells and neither cell line expressed TIMP-3. Interestingly, only the K562 cells expressed matrilysin suggesting a potential role for matrilysin in leukaemia cell invasion. in vitro invasion assays performed in the presence of a matrilysin blocking antibody showed a 40% reduction in invasive ability. This data suggests that matrilysin plays an important role in leukaemia cell invasion.

Nerve growth factor signaling in caveolae-like domains at the plasma membrane.

Nerve growth factor (NGF) binding to its receptors TrkA and p75(NTR) enhances the survival, differentiation, and maintenance of neurons. Recent studies have suggested that NGF receptor activation may occur in caveolae or caveolae-like membranes (CLM). This is an intriguing possibility because caveolae have been shown to contain many of the signaling intermediates in the TrkA signaling cascade. To examine the membrane localization of TrkA and p75(NTR), we isolated caveolae from 3T3-TrkA-p75 cells and CLM from PC12 cells. Immunoblot analysis showed that TrkA and p75(NTR) were enriched about 13- and 25-fold, respectively, in caveolae and CLM. Binding and cross-linking studies demonstrated that the NGF binding to both TrkA and p75(NTR) was considerably enriched in CLM and that about 90% of high affinity binding to TrkA was present in CLM. When PC12 cells were treated with NGF, virtually all activated (i.e. tyrosine phosphorylated) TrkA was found in the CLM. Remarkably, in NGF-treated cells, it was only in CLM that activated TrkA was coimmunoprecipitated with phosphorylated Shc and PLCgamma. These results document a signaling role for TrkA in CLM and suggest that both TrkA and p75(NTR) signaling are initiated from these membranes.

Characterization of Nonmicrobiological Paper Mill Deposits by Simultaneous TG-IR-MS.

The problem of deposits and their identification is one of the most persistent ones facing paper mills. Materials other than fibers accumulate in closed water circulation systems and may appear as impurities in pulp and paper or can contaminate wires and felts or build up deposits at various points in the mills. Traditionally, chromatographic and spectroscopic methods have been employed in the analysis of deposits and other pulp and paper process impurities. Simultaneous thermogravimetry-infrared-mass spectrometric (TG-IR-MS) analysis is a relatively new technique which, when applied to the analysis of mill deposits, provides a rapid means of identifying the source of these contaminants.

Treatment with desmopressin acetate in routine coronary artery bypass surgery to improve postoperative hemostasis.

Desmopressin acetate (DDAVP) has been shown to decrease blood loss and transfusions in complex cardiac operations with long extracorporeal times. Its use in routine cardiac valve operations has been shown not to be beneficial, but its role in routine coronary artery bypass grafting operations has not been defined. We examined the effect of DDAVP in a prospective study of 60 patients undergoing uncomplicated primary coronary artery bypass grafting operations. Thirty consecutive patients received DDAVP (0.3 micrograms/kg) after cardiopulmonary bypass and were compared with 30 consecutive patients who did not receive DDAVP. No significant differences were seen in 12-hour mediastinal blood loss (465 +/- 207 ml with DDAVP versus 511 +/- 221 ml without DDAVP) or 12-24-hour mediastinal blood loss (236 +/- 127 ml with DDAVP versus 260 +/- 112 ml without DDAVP). Transfusion of blood products were similar for both groups. Platelet aggregometry at intraoperative and postoperative time points using ADP, collagen, and ristocetin was not significantly different from baseline values in either group. In a subgroup of patients with poor initial ristocetin-induced platelet aggregometry, a significant increase (p less than 0.05) in ristocetin-induced platelet aggregometry was seen postoperatively only in those patients who had received DDAVP. A decrease in blood loss and transfusions, however, was not demonstrable. In those patients who had been on aspirin or nonsteroidal anti-inflammatory drugs preoperatively, DDAVP did not improve mediastinal blood loss or transfusion needs.(ABSTRACT TRUNCATED AT 250 WORDS)