Our multi-omics analysis proves that CRC patients’ sample subfractions, expressing a high level of either ABCC4 or ABCG2 followed by a low mRNA level of the second corresponding ABC transporter, are presenting different molecular and physiological functions, even though both transporters present to some extent substrate homology including active transport of irinotecan and its active metabolite SN38 [39]. The gene discussed is ABCG2; the disease is colorectal carcinoma.