BACKGROUND: Platelets take part in repairing the lesions of endothelial damage. To understand the molecular mechanism of this process, we tested the hypothesis that CD154 expressed on activated platelets stimulates proliferation of human endothelial cells. METHODS: The expression levels of CD154 and CD40 on platelets and endothelial cells, respectively, were measured by flow cytometry and confocal microscopy. Function-blocking monoclonal antibody against CD154 was developed after immunization with CD154- transfected L cells. RESULTS: An anti-CD40 agonist antibody and soluble CD154 both induced significant proliferation of endothelial cells. In addition, a function-blocking anti-CD154 antibody inhibited the platelet-induced proliferation of endothelial cells, indicating that the CD154-CD40 pathway is involved in these cellular interactions. An anti-VEGF antibody failed to inhibit the proliferation. This, in addition to the fact that very small amounts of VEGF are released from platelets or endothelial cells, suggests that VEGF does not play an important role in the platelet-stimulated proliferation of endothelial cells. CONCLUSION: Our results indicate that platelets induce proliferation of endothelial cells by CD154-CD40 interactions independently of VEGF.
Blood Platelets ; Endothelial Cells ; Flow Cytometry ; Human Umbilical Vein Endothelial Cells ; Humans ; Immunization ; Microscopy, Confocal ; Vascular Endothelial Growth Factor A

Expression of matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9), which correlates with tumor invasion and metastasis, has been known to be regulated by several intracellular signaling pathways. Since the CD9 membrane protein has been implicated in signal transduction and malignant progression of cancer cells, we examined the functional involvement of CD9 in the regulation of MMP-2 and MMP-9 expression by using stable CD9 transfectant clones of MelJuso human melanoma cells. The CD9 cDNA-transfected cells with elevated CD9 expression displayed increased MMP-2 and decreased MMP-9 expression when compared with the mock transfectant cells. Among several signal pathway inhibitors tested, SB203580 and SP600125, which inhibit p38 MAPK and JNK respectively, completely blocked the CD9-stimulated MMP-2 expression. Phosphorylation levels of p38 MAPK and c-Jun in MelJuso cells were also significantly increased by CD9 transfection. In addition, the down-regulation of p38 MAPK and JNK by siRNA transfection resulted in a decrease in MMP-2 expression by MelJuso cells. Promoter analysis and gel shift assay showed that the CD9-induced MMP-2 expression is mediated by a functional AP-1 site through interactions with AP-1 transcription factors including c-Jun. These results suggest that CD9 induces MMP-2 expression by activating c- Jun through p38 MAPK and JNK signaling pathways in human melanoma cells.
Antigens, CD/*metabolism ; Electrophoretic Mobility Shift Assay ; Enzyme Activation ; Gelatinase A/genetics/*metabolism ; Gelatinase B/metabolism ; Humans ; JNK Mitogen-Activated Protein Kinases/antagonists & inhibitors/genetics/*metabolism ; Melanoma/*metabolism/pathology ; Membrane Glycoproteins/*metabolism ; Promoter Regions (Genetics) ; Proto-Oncogene Proteins c-jun/*metabolism ; RNA, Small Interfering/pharmacology ; Research Support, Non-U.S. Gov't ; *Signal Transduction ; Skin Neoplasms/metabolism/pathology ; Transcription Factor AP-1/metabolism ; Transfection ; p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors/genetics/*metabolism

Treatment-related myelodysplastic syndrome (t-MDS) and acute myelogenous leukemia (t-AML) are now well established as complications of cytotoxic chemotherapy. We experienced a 28-yr-old female patient who developed t-MDS/t-AML with characteristic chromosomal abnormalities including 11q23 chromosomal rearrangement following high-dose chemotherapy with autologous stem cell transplantation (ASCT) for non-Hodgkin's lymphoma. The patient was admitted with bulky abdominal masses of B cell lineage non-Hodgkin's lymphoma. After 2 cycles of systemic chemotherapy of the Vanderbilt regimen, the patient underwent ASCT with high dose chemotherapy of the BEAC regimen. She also received radiation of 48 Gy for the residual periportal lymphadenopathy. The initial cytogenetic analysis of the infused mononuclear cells revealed a normal karyotype. Twenty two months after the ASCT, pancytopenia was noted and her bone marrow aspirate showed dysplastic hemopoiesis with myeloblasts up to 12% of nonerythroid nucleated cells. The patient was diagnosed as t-MDS (refractory anemia with an excess of blasts). Cytogenetic analysis showed complex chromosomal abnormalities including 11q23 rearrangement, which is frequently found in topoisomerase II inhibitor-related hematologic malignancies. Four months later, it was noted that the t-MDS had evolved into an overt t-AML. Cytogenetic analysis showed an evolving pattern with more complex abnormalities. The patient was treated with combination che-motherapy, but her leukemic cells were resistant to the therapy.
Adult ; Antineoplastic Agents, Phytogenic/adverse effects ; Antineoplastic Combined Chemotherapy Protocols/*adverse effects ; B-Lymphocytes/cytology ; Bone Marrow Cells/pathology ; Carmustine/*adverse effects ; Chromosome Aberrations ; Chromosomes, Human, Pair 11 ; Combined Modality Therapy/adverse effects ; Cyclophosphamide/*adverse effects ; Cytarabine/*adverse effects ; Etoposide/*adverse effects ; Female ; Gene Rearrangement ; Hematopoietic Stem Cell Transplantation/*adverse effects ; Humans ; Leukemia, Myeloid, Acute/*etiology/genetics ; Lymphoma, Non-Hodgkin/*therapy ; Myelodysplastic Syndromes/*etiology/genetics ; Neoplasms, Second Primary/*etiology ; Pelvis ; Pregnancy ; Pregnancy Complications, Neoplastic/*therapy ; Transplantation, Autologous