2--3--dialdehyde-atp and Cell-Transformation--Neoplastic

The P2X7 receptor is an ATP-gated ion channel known for its cytotoxic activity. However, recent evidence suggests a role for P2X7 in cell proliferation. Here, we found that P2X7 exhibits significant growth-promoting effects in vivo. Human embryonic kidney cells expressing P2X7 exhibited a more tumorigenic and anaplastic phenotype than control cells in vivo, and the growth rate and size of these tumors were significantly reduced by intratumoral injection of the P2X7 inhibitor-oxidized ATP. The accelerated growth of P2X7-expressing tumors was characterized by increased proliferation, reduced apoptosis, and a high level of activated transcription factor NFATc1. These tumors also showed a more developed vascular network than control tumors and secreted elevated amounts of VEGF. The growth and neoangiogenesis of P2X7-expressing tumors was blocked by intratumoral injection of the VEGF-blocking antibody Avastin (bevacizumab), pharmacologic P2X7 blockade, or P2X7 silencing in vivo. Immunohistochemistry revealed strong P2X7 positivity in several human cancers. Together, our findings provide direct evidence that P2X7 promotes tumor growth in vivo.

Topics: Adenosine Triphosphate; Animals; Antibodies, Monoclonal, Humanized; Apoptosis; Bevacizumab; Biomarkers, Tumor; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Female; Gene Expression Regulation, Neoplastic; HEK293 Cells; Humans; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Nude; Neoplasms, Experimental; Neovascularization, Pathologic; NFATC Transcription Factors; Receptors, Purinergic P2X7; Vascular Endothelial Growth Factor A

Binding of nucleotides to a specific site of the large T proteins of polyoma and SV40 viruses was demonstrated by covalent affinity labeling with periodate-oxidized [alpha-32P]ATP (oxATP) (Clertant, P., and Cuzin, F. (1982) J. Biol. Chem. 257, 6300-6305). This site appears different from the catalytic site of these proteins for ATP hydrolysis: (i) nucleotide binding and ATPase activities exhibited different ionic requirements and kinetic parameters; (ii) different antibodies directed against the polyoma large T protein either completely inhibited ATPase activity and not affinity labeling, or vice versa; (iii) a truncated form of polyoma large T, with its carboxyl-terminal third deleted, does not bind oxATP but exhibits normal ATPase activity; (iv) conversely, a "super T" SV40 protein, resulting from a duplication within the coding region of large T, was efficiently labeled with oxATP, although it lacks detectable ATPase activity. Cyanogen bromide cleavage after affinity labeling mapped the nucleotide binding site of the polyoma and SV40 large T proteins within a carboxyl-terminal amino acid sequence highly homologous between the two polypeptides. A survey of the phenotypes of the known mutations in these multifunctional proteins suggests that their ATPase and nucleotide-binding activities, although distinct, might both be required to ensure crucial steps in the lytic cycle.

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Affinity Labels; Animals; Antibodies; Antigen-Antibody Complex; Antigens, Polyomavirus Transforming; Antigens, Viral, Tumor; Binding Sites; Cell Line; Cell Transformation, Neoplastic; Cells, Cultured; Chlorocebus aethiops; Kidney; Kinetics; Mice; Polyomavirus; Protein Binding; Protein Kinases; Simian virus 40; Viral Proteins