One study found that the levels of 27-OHC in exosomes from ER+ breast cancer cell line (MCF-7) were significantly higher than exosomes derived from estrogen receptor (ER-) breast cancer cell line (MDA-MB-231), other control exosomes (non-cancerous cell line HEK293 and human pooled serum) by employing capillary liquid chromatography-mass spectrometry. This evidence concerns the gene ESR1 and breast cancer.