Why are genes expressed in tumours from one allele?
In some cases, there may be a technical explanation of these effects. For example, if a small population of tumour cells were to loose one allele of SERPINB5 and express the other very strongly, then the DNA of a tumour tissue might appear approximately balanced or only marginally imbalanced. If the rest of the tumour and normal cells of the lesion did not express the gene, then the SERPINB5 mRNA of that tissue would derive exclusively from one allele. This is possible, may explain some cases, but the explanation feels a little contrived. Secondly, where we see strong expression from one allele, this may have been activated in each case by changes to the DNA structure of the gene or its control regions. For instance, AEI may arise as a consequence of cis-located, strand-specific chromosome translocation, mutational activation of a promoter, inactivation of a suppressor region, demthylation of the promoter, or polymorphism of a tumour-utilised transcription factor binding site. Again, t
