ANPEP and breast cancer: Finally, in order to confirm that Cbz-APN exhibited the highest cytotoxicity to Hela, MCF-7, MDA-MB-231 and MDA-MB-468 breast cancer cells and HeLa and SKOV-3 cervical and ovarian cells, respectively, but was far less cytotoxic to human fibroblasts and RPE-1 cells in 2D cells in culture, we investigated the relative activity of these compounds in 3D cancer cells.