ABCB1 and cancer: Tumors have also been observed to develop resistance against chemotherapeutics, such as via efflux pumps that remove endocytosed drugs.37 In multidrug-resistant cancer cell lines like NCI/ADR-RES, the ABCB1 gene encoding the P-glycoprotein (Pgp) efflux pump is overexpressed, reducing accumulation of chemotherapeutics like doxorubicin, paclitaxel, etoposide, and irinotecan.38 Novel CPP–NC formulations have been found to circumvent these issues, yielding better prognostic outcomes.