Fumitremorgin C (12α-Fumitremorgin C) is a mycotoxin and inhibits ABCG2/BRCP.

Multidrug resistance (MDR) presents a significant challenge in cancer chemotherapy, but Fumitremorgin C has shown remarkable efficacy in counteracting this problem by increasing drug accumulation in multidrug-selected cell lines. Specifically, it enhances the effectiveness of doxorubicin, mitoxantrone, and topotecan by reversing mitoxantrone resistance up to 114-fold and doxorubicin resistance 3-fold in MCF-7/mtxR cells. Additionally, in S1M1-3.2 cells, Fumitremorgin C substantially boosts the toxicity of these drugs, demonstrating a 26-fold increase for doxorubicin, 93-fold for mitoxantrone, and 24-fold for topotecan. However, it does not mitigate drug resistance in cells with high levels of Pgp or MRP expression [1]. Notably, Fumitremorgin C virtually eliminates resistance mediated by BCRP in vitro, making it a valuable pharmacological tool for investigating the expression and molecular functionality of this transporter. Furthermore, it significantly raises the toxicity of mitoxantrone and topotecan in vector-transfected MCF-7 cells by 2.5–5.6 fold and reduces the IC50 of topotecan in BCRP-overexpressing cells to levels even lower than those in untreated vector-transfected cells [2].