On the other hand, the roles of ABC transporters in drug absorption, distribution, metabolism, and excretion (ADME) or pharmacokinetics (PK) are firmly established (Choi and Yu, 2014; Koehn, 2021), and overexpression of efflux ABC transporters in carcinoma cells confers multidrug resistance (MDR) (Choi and Yu, 2014; Bukowski et al., 2020; Koehn, 2021). Here, ABCG2 is linked to carcinoma.