The well-accepted notion that gene amplification contributes to increased expression still remains, after all these years, a reasonable but unproven assumption.

"Gene amplification causes overexpression" is a longstanding and well-accepted concept in cancer genetics. However, raking the whole literature, we find only statistical analyses showing a positive correlation between gene copy number and expression level, but do not find convincing experimental corroboration for this notion, for most of the amplified oncogenes in cancers. Since an association does not need to be an actual causal relation, in our opinion, this widespread notion still remains a reasonable but unproven assumption awaiting experimental verification.