It is almost common sense that local amplification of gene increase the its mRNA expression . I recently heard that large scale SCNA (such as arm-level amplification) does not increase the mRNA expression level of gene within the region. I did some analysis (SCNA is determined by SNP array and NGS, mRNA expression is measured by RNA-Seq) and found that this is indeed the case. I further did some research and did not found any explanations. it seems like a common acknowledgement. Is there any technical bias or biological explanation that I am missing here? Or is it something that has not have a answer yet?