(a) Effect of 6-thioguanine on the 1.1 kb 5′-flanking region of the PTHrP gene. (b) Effect of 6-thioguanosine on the 1.1 kb 5′-flanking region of the PTHrP gene. (c) Effect of purine on the 1.1 kb 5′-flanking region of the PTHrP gene. (d) Effect of dexamethasone on the 1.1 kb 5′-flanking region of the PTHrP gene. Values in all panels represent means ± SEM (n = 3 per group). Ctrl, control; Untr, MDA-MB-231 cells stably transfected with the 1.1 kb 5′-flanking region/luciferase reporter gene. *P < 0.05.