Our previous whole-genome analysis of post-treatment high-grade serous ovarian cancer (HGSC) and breast cancer samples identified a transcriptional fusion between ABCB1 and the upstream gene SLC25A40 associated with up-regulation of ABCB1 expression, while leaving the predicted MDR1 protein unaltered1,2. This evidence concerns the gene ABCB1 and ovarian serous adenocarcinoma.