The vast preponderance of ACC tumors harbor rearrangements in or near the MYB or MYBL1 loci, leading to overexpression of these oncogenes.

Many MYB antibodies are commercially available. However, researchers should bear in mind that different antibodies may be most appropriate depending on whether they are being used for immunohistochemistry, western blotting or chromatin immunoprecipitation sequencing (ChIP-seq). In addition, each antibody binds to different MYB epitopes. Given that many ACC tumors harbor MYB fusions with breakpoints in exons 8 or higher, antibodies that bind to epitopes in exons 8 or higher may not detect such MYB proteins. Some MYB transcripts in ACC begin at an alternative promoter upstream of exon 2 (Frerich et al., Cancers, 2020), so antibodies binding to exon 1 may not detect such MYB isoforms. Researchers should use MYB antibodies with epitopes in exons 2 through 7 to address these ACC-specific peculiarities. However, keep in mind that antibodies designed against epitopes within MYB’s DNA binding domain may cross-react with MYBL1, as both MYB and MYBL1 share nearly identical sequences within this region.

 Several laboratories have reported success using Sigma’s MYBL1 antibody for western blot analysis. This antibody does not appear to cross-react with MYB. 

Additional efforts to develop better MYB and MYBL1 antibodies are under way.