Coculture-induced PYCARD expression renders KG1a cells sensitive to apoptotic ligands. (A) Gene expression profiling. mRNA isolated from KG1a cells cultured alone or in coculture with HS5 cells was analyzed by quantitative PCR for genes involved in apoptotic signaling pathways. The expression levels of 7 genes, including PYCARD, increased significantly after coculture with HS5 cells. (B) Transfection of KG1a cells with PYCARD-specific siRNA attenuated the TNF-α–induced apoptosis in KG1a cells cocultured with HS5 cells. (C) Western blot analysis of PYCARD expression in KG1a cells, cultured alone or with HS5 cells. Transfection of KG1a cells with PYCARD-specific siRNA significantly attenuated the induction of PYCARD protein. (D) Quantification of the relative pixel intensity of PYCARD compared with β-actin expression in wild-type and siRNA- transfected KG1a cells. Ω indicates P < .01.