Supporting this, analysis of Abcg2, Abcb1a and Abcb1b showed that ‘up-regulation’ correlated with tumour phenotype rather than olaparib resistance, with all three showing higher expression in MSCCs compared to AC(NST)s, suggesting that the upregulation of these genes noted previously was due to the increase in the proportion of MSCCs in olaparib-resistant cohorts. This evidence concerns the gene ABCG2 and neoplasm.