Extracellular ATP induces anchorage-independent expression of cyclin A and rescues the transformed phenotype of a ras-resistant mutant cell line.
Anchorage-independent growth is characteristic of neoplastic cells, but the signal transduction pathways that mediate this phenotype are poorly understood. Several important cell cycle events are dependent on cell-substratum adhesion in non-transformed cells, including activation of G1 cyclin-dependent kinases and expression of cyclin A; the adhesion requirement of these events is abrogated in Ras-transformed cells. The ER-1-2 mutant rat fibroblast cell line is: 1) resistant to Ras-mediated, anchorage-independent growth; 2) defective in Ras-mediated, adhesion-independent expression of cyclin A, but not adhesion-independent activation of cyclin-dependent kinases; and 3) rescued for Ras-induced, anchorage-independent growth by ectopic expression of cyclin A. We report here that extracellular ATP induces adhesion-independent expression of cyclin A and rescues growth in soft agar by ER-1-2 cells that express Ras. ADP, AMP and the non-hydrolyzable analog adenosine 5'-(beta, gamma-iminodiphosphate) are also effective, but adenosine is not. Adenine nucleotide-induced growth in soft agar is inhibited by reactive blue 2, an antagonist of some P2 purinoceptors. ATP does not induce adhesion-independent expression of cyclin A in ER-1-2 or control rat fibroblasts that do not express Ras, indicating a requirement for additional Ras-regulated signals for expression of this gene; one such signal may lead to phosphorylation of the retinoblastoma protein, pRB, and related proteins. These results suggest that extracellular ATP could play a role in the multistage carcinogenic process in vivo.
Yang
J J
JJ
Department of Biochemistry, Mount Sinai School of Medicine, New York, New York 10029, USA.
Krauss
R S
RS
D000227:Adenine Nucleotides / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000362:Agar; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D016213:Cyclins / Q000096:biosynthesis*; D011905:Genes, ras; D016296:Mutagenesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D014227:Triazines / Q000494:pharmacology; D018631:ras Proteins / Q000096:biosynthesis*
D000227:Adenine Nucleotides; D016213:Cyclins; D011500:Protein Synthesis Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D014227:Triazines; C012842:Cibacron Blue F 3GA; D000255:Adenosine Triphosphate; D000362:Agar; D018631:ras Proteins; D000241:Adenosine