AR and neoplasm: Strikingly, expression of exons was apparent in tumour C-12A but not C-12B due to mRNA splicing events between AR exon 3 and these AR upstream exons (named exons ‘4-ups', ‘5a-ups', ‘5b-ups' and ‘5c-ups' to denote their relative positions within spliced AR-V mRNAs but their normal genomic locations upstream of AR; Fig. 4c,d and Supplementary Fig. 9).