ABCB1 and cancer: Thirdly, a significant correlation of ERβ expression and multidrug resistance protein families was observed in various other cancer types [25, 26]; our previous analysis of TCGA NSCLC samples also showed a moderate but significant correlation (Spearman’s correlation coefficient 0.33, p<0.01) of ESR2 expression and multidrug resistance protein 1 (MDR1) at the mRNA level, which is a well-known inducer of chemoresistance.