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ABSTRACT: Multiple myeloma (MM) is an incurable B-cell malignancy in which the marrow microenvironment plays a critical role in our inability to cure MM. Marrow stromal cells in the microenvironment support homing, lodging, and growth of MM cells through activation of multiple signaling pathways in both MM and stromal cells. Recently, we identified annexin II (AXII) as a previously unknown factor produced by stromal cells and osteoclasts (OCL) that is involved in OCL formation, HSC and prostate cancer (PCa) homing to the BM as well as mobilization of HSC and PCa cells. AXII expressed on stromal cells supports PCa cell lodgment via the AXII receptor (AXIIR) on PCa cells, but the role of AXII and AXIIR in MM is unknown. In this study, we show that MM cells express AXIIR, that stromal/osteoblast-derived AXII facilitates adhesion of MM cells to stromal cells via AXIIR, and OCL-derived AXII enhances MM cell growth. Finally, we demonstrate that AXII activates the ERK1/2 and AKT pathways in MM cells to enhance MM cell growth. These results demonstrate that AXII and AXIIR play important roles in MM and that targeting the AXII/AXIIR axis may be a novel therapeutic approach for MM.
Blood 02/2012; 119(8):1888-96. · 9.90 Impact Factor
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Sonia D'Souza,
Davide del Prete,
Shunqian Jin,
Quanhong Sun,
Alissa J Huston,
Flavia Esteve Kostov,
Benedicte Sammut,
Chang-Sook Hong,
Judith L Anderson,
Kenneth D Patrene,
Shibing Yu,
Chinavenmeni S Velu,
Guozhi Xiao,
H Leighton Grimes,
G David Roodman,
Deborah L Galson
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ABSTRACT: Protracted inhibition of osteoblast (OB) differentiation characterizes multiple myeloma (MM) bone disease and persists even when patients are in long-term remission. However, the underlying pathophysiology for this prolonged OB suppression is unknown. Therefore, we developed a mouse MM model in which the bone marrow stromal cells (BMSCs) remained unresponsive to OB differentiation signals after removal of MM cells. We found that BMSCs from both MM-bearing mice and MM patients had increased levels of the transcriptional repressor Gfi1 compared with controls and that Gfi1 was a novel transcriptional repressor of the critical OB transcription factor Runx2. Trichostatin-A blocked the effects of Gfi1, suggesting that it induces epigenetic changes in the Runx2 promoter. MM-BMSC cell-cell contact was not required for MM cells to increase Gfi1 and repress Runx2 levels in MC-4 before OBs or naive primary BMSCs, and Gfi1 induction was blocked by anti-TNF-α and anti-IL-7 antibodies. Importantly, BMSCs isolated from Gfi1(-/-) mice were significantly resistant to MM-induced OB suppression. Strikingly, siRNA knockdown of Gfi1 in BMSCs from MM patients significantly restored expression of Runx2 and OB differentiation markers. Thus, Gfi1 may have an important role in prolonged MM-induced OB suppression and provide a new therapeutic target for MM bone disease.
Blood 12/2011; 118(26):6871-80. · 9.90 Impact Factor
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ABSTRACT: HIP/RPL29 is a heparan sulfate (HS) binding protein with diverse activities including modulation of heparanase (HPSE) activity. We examined HIP/RPL29's ability to modulate actions of HS-binding growth factors (HBGFs) in angiogenesis. Between 1 and 2.5 microg/ml (ca. 60-150 nM), HIP/RPL29 inhibited HBGF-stimulated endothelial cell tube formation. Aortic explant outgrowth also was inhibited, but at higher concentrations (40 microg/ml). At this concentration, HIP/RPL29 had no effect on HBGF-stimulated MAPK phosphorylation or VEGF-stimulated receptor-2 phosphorylation at site Y-996. Partial inhibition occurred at VEGF receptor-2 site Y951, associated with cell migration. HBGF displacement from HS-bearing perlecan domain I showed that HIP/RPL29 released 50% of bound HBGF at 20 microg/ml, a dose where endothelial tube formation is inhibited. Similar FGF2 release occurred at pH 5.0 and 7.0, conditions where HPSE is highly and residually active, respectively. We considered that HIP/RPL29 inhibits HPSE-dependent release of HS-bound HBGFs. At pH 5.0, release of soluble HS was inhibited by 64% at concentrations of 5 microg/ml and by 77% at 40 microg/ml, indicating that HIP/RPL29 antagonizes HPSE activity. At concentrations up to 40 microg/ml (ca. 2.5 microM) where angiogenic processes are inhibited, release of FGF2 occurred in the presence of HPSE and HIP/RPL29. The majority of this FGF2 is not bound to soluble HS. Studies of HIP/RPL29 binding to HS indicated that many structural features of HS are important in modulation of HBGF activities. Our findings suggest that inhibition of angiogenic processes by HIP/RPL29 involves attenuation of the formation of soluble, biologically active HBGF:HS complexes that activate HBGF receptors.
Journal of Cellular Biochemistry 12/2008; 105(5):1183-93. · 2.87 Impact Factor
