Nrf2-ME-1 axis is associated with 5-FU resistance in gastric cancer cell line

Abstract

The aim of this study was to investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) and key downstream targeting molecule, malic enzyme-1 (ME-1), in the induction of 5-fluorouracil (5-FU) resistance. Resistant MKN-45 (MKN-45/DR) cell line was generated by employing IC50 concentration of the agent followed by a resting cycles. Cell viability and apoptosis were evaluated by MTT assay, DAPI staining and flow cytometry. mRNA expression levels of Nrf2 and ME-1 were measured by qRT-PCR technique. Morphology analysis and combination index calculation were assessed by ImagJ and compuSyn softwares, respectively. The value for IC50 in 5-FU resistant cells increased from 8.81 ± 0.209–142.4 ± 0.060 μM with a considerable morphological changes from round to elongated shape (p = 0.016). Nrf2 and ME-1 expression levels were decreased in resistant cells with a marked increase in MDR1 mRNA level compared to sensitive cells. Combination of Nrf2 inhibitors, luteolin and brusatol had synergistic effects on 5-FU induced cytotoxicity. Moreover, combined incubation of MKN-45/DR cells with these inhibitors, exponentially increased Nrf2 and ME-1 mRNA levels (p < 0.001). Our findings suggest that the combined application of Nrf2 inhibitors, can be considered as a novel strategy to overcome 5-FU resistance in GC patients.