FAS and idiopathic pulmonary fibrosis: It has been shown that Fas overexpression and increased expression of Fas by the cytokines tumor necrosis factor-α and interferon-γ are sufficient to overcome the resistance of IPF fibroblasts to apoptosis.16, 34 Further studies would be needed to determine whether this cytokine-mediated increase in Fas expression is a result of modifications to histones.