Orostachys japonica Induces Ferroptosis in 5-Fluorouracil-Resistantance Acquired SNU-C5 Colorectal Cancer Cells

Drug resistance is an un-met need in the treatment of colorectal cancer (CRC).Recently, the iron-dependent regulated cell death, ferroptosis, has been emerged as a potential therapeutic strategy for overcoming drug resistance in CRC.As natural products have been tested as promising candidates to induce ferroptosis in CRC, the anti-cancer effects of aqueous extract of Orostachys japonica (OJ) were investigated in 5-fluorouracil (5-FU)-resistance acquired SNU-C5 (SNU-C5/5-FUR) CRC cells in terms of ferroptosis.The cell viability, western blotting, and flow cytometry were used for analysis.OJ showed IC 50 of 280 g/L in vitro.Long-term treatment of OJ (250 mg/kg) effectively induced ferroptosis with decreased GPX4, transferrin receptor, and ferroportin, and increased HMGB1 in SNU-C5/5-FUR cells-xenografted tissues.Short-term treatment of OJ (up to 250 g/mL) did not show effective ferroptosis with slightly increased GPX4, transferrin receptor, and ferritin heavy chain.Co-treatment with ferroptosis inducers (RSL3 and sulfasalazine) or inhibitors (deferoxamine mesylate and ferrostatin-1) did not show any additive or synergistic effects on cell viability of SNU-C5/5-FUR cells.When co-treated with high dose deferoxamine mesylate, OJ further induced apoptosis as well as cell cycle arrest at G2/M phase.The results on ferroptosis in vitro and in vivo were inconsistent in SNU-C5/5-FUR cells, but ferroptosis in vivo indicating that other pathways might be a feasible candidate to induce ferroptosis or ferroptosis-augmented cell death in 5-FU resistant CRCs.