Ds2-TryB (23) exhibited a very potent inhibitory effect on breast cancer resistance protein (BCRP), which was accompanied by a strong cytotoxic effect observed on the panel of 19 cancer cell lines, derived from both solid and blood tumors [116], while Tryprostatin A (21) and Tryptostatin B (22) exhibited an only moderate cytotoxic effect on H520, MCF7, and PC-3 cell lines at concentrations of 100 μM. Here, ABCG2 is linked to cancer.