Cell experiment:

Cells are treated with chemotherapeutic agent and the reversal agents Fumitremorgin C is added to cells (0.1 to 80 /UM). In parallel wells, cells are grown in the presence of the reversal agent alone. Following a 3-day growth period, cells are fixed in 10% trichloroacetic acid for 1 h and washed extensively with water, and cell-associated protein is stained using 0.1% SRB. Excess reagent is removed by washing plates in 5% acetic acid, the dye is solubilized in 10 mM Tris base, and absorbance is determined in a UV Max spectrophotometer at 540 nm. Cell survival is determined relative to control wells[1].

Fumitremorgin C is a potent and selective ABCG2/BRCP inhibitor.

Multidrug resistance (MDR) is a major problem in cancer chemotherapy. Fumitremorgin C is extremely effective in reversing resistance to mitoxantrone, doxorubicin, and topotecan in multidrug-selected cell lines. In MCF-7/mtxR (a mitoxantroneselected cell line), fumitremorgin C reverses mitoxantrone resistance (114-fold) and doxorubicin resistance (3-fold). Fumitremorgin C (5/AM)significantly potentiates the toxicity of mitoxantrone (93-fold), doxorubicin (26-fold), and topotecan (24-fold) in S1M1-3.2 cells. Reversal of resistance is associated with an increase in drug accumulation. Fumitremorgin C does not reverse drug resistance in cells with elevated expression of Pgp or MRP[1]. Fumitremorgin C almost completely reverses resistance mediated by BCRP in vitro and is a pharmacological probe for the expression and molecular action of this transporter. Fumitremorgin C also enhances the toxicity of mitoxantrone and topotecan in vector-transfected MCF-7 cells (2.5–5.6 fold). It reduces the IC50 of topotecan in BCRP-overexpressing cells below that observed in the untreated vector-transfected cells. [2].

References:
[1]. Rabindran SK, et al. Reversal of a novel multidrug resistance mechanism in human colon carcinoma cells by fumitremorgin C. Cancer Res. 1998 Dec 15;58(24):5850-8.
[2]. Rabindran SK, et al. Fumitremorgin C reverses multidrug resistance in cells transfected with the breast cancer resistance protein. Cancer Res. 2000 Jan 1;60(1):47-50.