Then, they were assayed for cytotoxicity in vitro against nine human tumor cell lines [57], namely, epidermoid carcinoma of the nasopharynx (KB), P-gp-expressing epidermoid carcinoma of the masopharynx (KB-VIN), osteosarcoma (Hos), melanoma (SKMEL-2), ileocecal carcinoma (HCT-8), breast cancer (MCF-7), lung carcinoma (A-549), glioblastoma (U87-MG), and ovarian cancer (1A9) cell lines. Here, PGP is linked to breast cancer.