SLCO and SLC22 Solute Carriers: Establishing Differential Expression Patterns in Human Breast Cancer Cell Lines and Tumour Samples

Abstract Background: The uptake of nutrients essential for cell growth and survival is facilitated by solute carrier (SLC) transporters. The SLCO and SLC22 subfamilies mediate the uptake of substrates relevant to breast cancer (BC), including steroid hormones and anticancer drugs, and accumulating evidence suggests that altered expression of these transporters may affect BC pathogenesis by influencing cell proliferation and anticancer drug resistance. Methods: The differential expression of 11 SLCO and 14 SLC22 transporters was investigated using semi-quantitative and quantitative PCR in MCF-7 and MDA-MB-231 BC cell lines and in human BC tissue samples. Results: 8 SLCO and 10 SLC22 transporters were expressed in at least one cell line. Of these SLCO1B1, SLCO1B3, SLCO3A1, SLC22A1, SLC22A3, SLC22A4 and SLC22A16 showed higher expression in MDA-MB-231 than MCF-7 cells. Conversely, SLCO2A1, SLCO4A1, SLCO4C1, SLCO5A1, SLC22A5 showed higher expression in MCF-7 than MDA-MB-231 cells. In four human breast cancer samples, there was variable expression of the 25 SLC transporters, however, 11 SLCO and 9 SLC22 transporters were detected in at least one sample. Conclusion: BC cells express a variety of SLCs capable of transporting a range of steroid hormones and clinically relevant anticancer drugs, which could implicate them in BC pathogenesis and anti-cancer drug resistance.