ObjectiveTo investigate the effect of expressions of nucleoside transporters subtype (hENT1 and hENT2) on 5-fluorouracil(5-FU) cytotoxicity in breast cancer cell lines(MDA-MB-231, MDA-MB-468, SK-BR-3, MCF-7). MethodsFour breast cancer cell lines were chosen to detect the mRNA expressions of hENT1 and hENT2 by RT-PCR. Cells were incubated in the medium with a serial concentrations of 5-FU from 1.28×104 ng/L to 2.00×108 ng/L for 48 h. Then the cell proliferation in each cell line was measured by MTT assay and the IC50 was evaluated. Results①The mRNA expressions of hENT1 and hENT2 in the MDA-MB-231, MDA-MB-468, or SK-BR-3 cells were significantly higher than thoes in the MCF-7 cells(P < 0.05). The mRNA expression of hENT2 was detected in the MDA-MB-231, MDA-MB-468, or SK-BR-3 cells, not detected in the MCF-7 cells. 2MTT showed that IC50 of 5-FU in the MDAMB-231, MDA-MB-468, or SK-BR-3 cells was significantly lower than that in the MCF-7 cells(P < 0.05). There was no statistical difference of IC50 among the three lines(MDA-MB-231, MDA-MB-468, and SK-BR-3)(P > 0.05).③The three lines(MDA-MB-231, MDA-MB-468, and SK-BR-3) with lower IC50 of 5-FU highly expressed hENTs, and MCF-7 cell with the higher IC50 of 5-FU expressed less hENTs. ConclusionsThe expressions of hENTs in breast cancer cell lines can significantly influence 5-FU cytotoxic effect. It is implicated that the hENTs expressions might be the clue to the choice of nucleoside anticancer drugs in clinic.