The anchorage-independent growth of human breast cancer cells is inhibited by ATPγS, but stimulated by adenosine. MDA-MB-231 breast cancer cells were plated on soft agar and were treated with 100 μM ATPγS, 200 μM adenosine, or without for about 2 weeks. Cells growing on soft agar plates were imaged (upper panel) and quantified (lower panel). Data presented as mean ± SEM, n = 3. *, P < 0.05; **, P < 0.01.