Matrigel invasion assay of U87 cells pretreated with 100 μM Res and siRNA YKL-40 for 48 h. A. A modified Boyden chamber with a matrigel-precoated membrane filter insert was used to measure in vitro invasiveness. After 24 or 48 h of incubation, cells that invaded through the membrane were stained and representative fields were photographed. Original magnification: 200 ×. B. Invasion was calculated as the ratio of the number of invading cells to total cell numbers in both sides of the membrane. The ratio of invading cells was significantly reduced by Res treatment. Asterisks indicate statistically significant changes (P < 0.01) after Res treatment. Columns represent the average number of invading cells per field of at least 5 fields from 3 independent experiments. Bars indicate SE.