Human melanoma cell lines differ in their capacity to release ADP and aggregate platelets.

In this study we have investigated, using three different human melanoma cell lines (M1Do., M3Da., M4Be.). the varying capacity of melanoma cells to induce platelet aggregation in the presence or absence of inhibitors of ADP or thrombin. The expression levels of different integrins (alpha v, beta 3, alpha v beta 3, alpha IIb, alpha v beta 3) were evaluated by immunoprecipitation, binding and flow cytometry studies. The level of ADP in supernatants of melanoma cells were quantified by ADP bioassay and HPLC. Platelets were irreversibly aggregated by M3Da, as shown by electron microscopy, in contrast to M1Do, which induced a slow reversible aggregation. M4Be. did not induce platelet aggregation. In both cases, with M3Da. or M1Do., apyrase but not PPACK inhibited platelet induced aggregation. An anti-alpha v beta 3 monoclonal antibody (LYP18) or polyclonal antibody inhibited platelet aggregation. A similar number of LYP18 molecules bound to the surface of M1Do., M3Da. and M4Be. cell lines. Biological HPLC assays of ADP present in the supernatant of tumour cell lines showed the highest concentration of ADP to be secreted by M3Da., followed by M1Do., and none detected for M4Be. These results show that differences in in vitro aggregating potential of the three human melanoma cell lines are not related to low integrin expression levels but to their ability to generate ADP. Generation of ADP by human melanoma cells may act as important modulator of melanoma-platelet interactions

Alpha(v)beta3 and alpha(v)beta5 integrin expression in glioma periphery

OBJECTIVE: This study analyzed the expression of integrins alpha(v)beta3 and alpha(v)beta5 in glioma tissue and focused on the periphery of high-grade gliomas. METHODS: The analysis was performed with Western blot, immunohistochemistry, and immunofluorescence, by use of two monoclonal antibodies able to recognize the functional integrin heterodimer. The expression of integrin-related ligands and growth factors also was studied. Sections from the tumor periphery were classified as either tumor periphery (light tumor infiltrate or scant visible cells) or peritumor (heavy tumor infiltration). RESULTS: Our data on glioma tissues demonstrated that both integrins were expressed in glioma cells and vasculature and their expression correlated with the histological grade. Alpha(v)beta3 expression was prominent in astrocytic tumors. Both integrins were markers of tumor vasculature, particularly of endothelial proliferation. A high-grade glioma periphery demonstrated a prominent expression of integrin alpha(v)beta3. Cells demonstrating alpha(v)beta3 positivity were identified as tumor astrocytes and endothelial cells by double imaging. The same cells were surrounded by some alpha(v)beta3 ligands and co-localized fibroblast growth factor 2. Matrix metalloproteinase 2 also was found to be co-localized with alpha(v)beta3 in the same cells. Alpha(v)beta3 expression was more relevant in tumor astrocytes. Alpha(v)beta3 integrin and vascular endothelial growth factor expression increased from the periphery to the tumor center. CONCLUSION: Our data support the role of integrins alpha(v)beta3 and alpha(v)beta5 in glioma-associated angiogenesis. In addition, they suggest a role for integrin alpha(v)beta3 in neoangiogenesis and cell migration in high-grade glioma periphery

O-Acetylation of Sialic Acids is Required for the Survival of Lymphoblasts in Childhood Acute Lymphoblastic leukemia (ALL)

Exploiting the selective affinity of Achatinin-H towards 9-O-acetylneuraminic acid(α2-6)GalNAc, we have demonstrated the presence of 9-O-acetylated sialoglycoproteins (Neu5,9Ac2-GPs) on hematopoietic cells of children suffering from acute lymphoblastic leukemia (ALL), indicative of defective sialylation associated with this disease. The carbohydrate epitope of Neu5,9Ac2-GPsALL was confirmed by using several synthetic sialic acid analogues. They are functionally active signaling molecules as demonstrated by their role in mediating lymphoproliferative responses and consequential increased production of IFN-γ due to specific stimulation of Neu5,9Ac2-GPs on PBMCALL with Achatinin-H. Cells devoid of 9-Oacetylations (9-O-AcSA−) revealed decreased nitric oxide production as compared to 9-O-AcSA+ cells on exposure to IFN-γ. Under this condition, a decrease in viability of 9-OAcSA− cells as compared to 9-O-AcSA+ cells was also observed which was reflected from increased caspase 3 activity and apoptosis suggesting the protective role of this glycotope