Inhibition of invadopodium formation and melanoma cell invasion by constitutive increase in cytosolic Ca²⁺. (A and B) Representative traces showing the effects of 2 µM thapsigargin (A) and 5 µM A23187 (B) on cytosolic Ca²⁺ (n > 100, from three independent experiments). Arrows indicate addition of 10% FBS and thapsigargin or A23187. (C and D) Effects of thapsigargin and A23187 induced constitutive Ca²⁺ increases on invadopodium formation (C) and Matrigel invasion (D) in WM793 cells. The numbers of cells used for quantitation in C are indicated in the parenthesis. Data presented are means ± SE. Representative results from at least three similar independent experiments are presented. *, P < 0.05; **, P < 0.01. F/F0 is defined as ratio between fluorescence at a given time (F) and fluorescence at time 0 (F0). TG, thapsigargin.