XIAP and idiopathic pulmonary fibrosis: Conversely, IPF patients with lung fibroblasts showed resistance to FasL-induced apoptosis [11,45], which was highly correlated with the downregulation of Fas expression and increased expression of multiple apoptosis-regulating genes, including Bcl-2, XIAP, cFLIPL, and PTPN13 [12,47,48,49].