It was found that miR-21 in lung and pancreatic cancer cell-derived exosomes could bind to TLR8 on human muscle cells or TLR7 (homologous to TLR8 in humans) on mouse muscle cells to activate the Jun N-terminal kinase (JNK) pathway and induce apoptosis of muscle cells, thereby causing muscle atrophy [92, 93]. This evidence concerns the gene MAPK8 and familial pancreatic carcinoma.