ABCB1 and neoplasm: As SLC25A40 was the most common fusion partner, and novel fusions with ABCB1 were mostly found in tumours where an SLC25A40–ABCB1 fusion was also detected, we considered why certain genes became partners to ABCB1. In principle, transcriptional fusion could result in loss of negative regulation of ABCB1 and/or acquisition of a constitutively expressed, stronger promoter in the lineage giving rise to HGSC.