Involvement of chemokine receptor 4/stromal cell-derived factor 1 system during osteosarcoma tumor progression.

Despite intensive chemotherapy and surgery treatment, lung and bone metastasis develop in about 30% of patients with osteosarcoma. Mechanisms for this preferential metastatic behavior are largely unknown. We investigated the role of the chemokine receptor 4 (CXCR4)/stromal cell-derived factor 1 (SDF-1) system to drive the homing of osteosarcoma cells. We analyzed the expression of the CXCR4 and SDF-1 proteins on several osteosarcoma cell lines and the effects of SDF-1 on migration, adhesion, and proliferation of these cancer cells. In vitro assays showed that the migration of osteosarcoma cells expressing CXCR4 receptor follows an SDF-1 gradient and that their adhesion to endothelial and bone marrow stromal cells is promoted by SDF-1 treatment. Moreover, the production of matrix metalloproteinase-9 is increased after SDF-1 exposure. We finally proved in a mouse model our hypothesis of the CXCR4/SDF-1 axis involvement in the metastatic process of osteosarcoma cells. Development of lung metastasis after injection of osteosarcoma cells was prevented by the administration of a CXCR4 inhibitor, the T134 peptide. These data show a possible explanation for the preferential osteosarcoma metastatic development into the lung, where SDF-1 concentration is high, and suggest that molecular strategies aimed at inhibiting the CXCR4/SDF-1 pathway, such as small-molecule inhibitors or anti-CXCR4 antibodies, might prevent the dissemination of osteosarcoma cells.

Expression of the c-ErbB-2/HER2 proto-oncogene in normal hematopoietic cells.

The HER2/c-ErbB-2 proto-oncogene is overexpressed in 25-30% of human breast cancers. We previously reported the c-ErbB-2 transcript in mononuclear cells (MNC) from bone marrow (BM), peripheral blood (PB), and mobilized PB (MPB). Here, we describe extensively the expression pattern of c-ErbB-2 mRNA and protein in normal adult hematopoietic tissue and cord blood (CB)-derived cells. Quantitative reverse transcriptase-polymerase chain reaction shows that the c-ErbB-2 transcript is expressed in hematopoietic cells at low levels if compared with normal epithelial and breast cancer cells. The c-ErbB-2 protein was detected predominantly in MNC from PB and CB by Western blot analysis. Flow cytometry revealed that CD15+, CD14+, and glycophorin A+ subpopulations express c-ErbB-2 protein, whereas lymphocytes are c-ErbB-2-negative. The c-ErbB-2 expression is higher in CB MNC. More than 90% of BM- and MPB-derived CD34+ progenitors are c-ErbB-2-negative; by contrast, 5-40% of CB-derived CD34+ progenitors express c-ErbB-2. We found that c-ErbB-2 protein is up-regulated during cell-cycle recruitment of progenitor cells. Similarly, it increases in mature, hematopoietic proliferating cells. This study reports the first evidence that the c-ErbB-2 receptor is correlated to the proliferating state of hematopoietic cells. Studies in progress aim to clarify the role of c-ErbB-2 in regulation of this process in hematopoietic tissues.

Fast but durable megakaryocyte repopulation and platelet production in NOD/SCID mice transplanted with ex-vivo expanded human cord blood CD34+ cells.

We have previously established a stroma-free culture with Flt-3 ligand (FL), stem cell factor (SCF), and thrombopoietin (TPO) that allows the maintenance and the expansion for several weeks of a cord blood (CB) CD34+ cell population capable of multilineage and long-lasting hematopoietic repopulation in non-obese diabetic/ severe combined immunodeficient (NOD/SCID) mice. In this work the kinetics of megakarocyte (Mk)-engraftment that is often poor and delayed in CB transplantation, and human platelet (HuPlt) generation in NOD/SCID mice of baseline CD34+ cells (b34+), and of CD34+ cells reisolated after a 4-week expansion with FL+SCF+TPO (4w34+) were compared. With b34+ cells Mk-engraftment was first seen at week 3 (CD41+: 0.4%); 4w34+ cells allowed a more rapid Mk-engraftment (at weeks 2 and 3 the CD41+ cells were 0.3% and 0.8%). Circulating HuPlts were first seen at weeks 2 and 1, respectively. Mk-engraftment levels of b34+ and 4w34+ cells 6-8 weeks after transplantation were similar (12 +/- 3.5 versus 15 +/- 5% CD45+; 1.3 +/- 0.5 versus 1.8 +/- 0.5% CD41+ cells). Also serial transplant experiments were performed with expanded and reselected CB cells. In secondary and tertiary recipients the Mk population was detected with bone marrow fluorescence-activated cell sorter analysis; these experiments indicate the effective long-term repopulation of expanded cells. Selected CD34+ cells after a 4-week expansion with FL+SCF+TPO are more efficient in Mk engraftment than the same number of unmanipulated cells.