Despite being a precursor, pro-TNF also exhibits biological activities; for instance, the homolog of pro-TNF, Eiger, induces apoptosis in compound eyes of Drosophila by activating the c-Jun N-terminal kinases (JNKs) signaling pathway (Igaki et al., 2002), and concentric cardiac hypertrophy occurs in transgenic mice with up-regulated pro-TNF expression (Dibbs et al., 2003). Here, TNF is linked to cardiac hypertrophy.