Collectively, BMPs play bidirectional and paradoxical effects on cancer development and invasion both at the molecular and cellular levels, in which the dysregulation of both the canonical and non-canonical SMAD pathways, including PI3K/AKT, MAPK/ERK, NF-κB, and STAT3 pathways, produces absolutely opposite influences on cell proliferation, apoptosis, migration, and invasion by affecting tumor EMT, generation and amplification of CSCs, and angiogenesis development. This evidence concerns the gene CLN5 and cancer.