K17 is required for tumor cell growth and cell invasion. (A) A431 cells stably expressing SCR or KRT17 shRNA were grown in soft agar, and phase-contrast images of colonies were taken after 3 wk. Bar, 1 cm. (B) Colony numbers from A were quantitated using ImageJ, and data from seven experimental repeats (each performed in triplicate) were normalized to SCR shRNA and are represented as mean ± SEM (error bars). *, P < 0.05. (C) A431 cells stably expressing SCR or KRT17 shRNA were subjected to a Matrigel invasion assay with or without 10 ng/ml EGF as a chemoattractant for 48 h. Nuclei of invaded cells were stained with propidium iodide and imaged under a fluorescent microscope. Bar, 100 µm. (D) The numbers of invaded cells from C were quantitated using ImageJ, and data from three experimental repeats (each performed in triplicate) are represented as mean ± SEM (error bars). *, P < 0.009.