<p>Exosomes from
cancer cells are rich sources of biomarkers and may contain elevated levels of
lipids of diagnostic value. 27-Hydroxycholesterol (27-OHC) is associated with proliferation
and metastasis in estrogen receptor positive (ER+) breast cancer. In this study,
we investigated the levels of 27-OHC, and other sidechain-hydroxylated oxysterols
in exosomes. </p>
<p>To study both cytoplasmic
and exosomal oxysterol samples of limited size, we have developed a capillary
liquid chromatography-mass spectrometry platform that outperforms our
previously published systems regarding chromatographic resolution, analysis
time and sensitivity. In the analyzed samples, the quantified level of cytoplasmic
27-OHC using this platform fitted with mRNA levels of 27-OHC’s corresponding
enzyme, CYP27A1.</p>
<p>We find clearly increased
levels of 27-OHC in exosomes (i.e. enrichment) from an ER+ breast cancer cell
line (MCF-7) compared to exosomes derived from an estrogen receptor (ER-) breast
cancer cell line (MDA-MB-231) and other control exosomes (non-cancerous cell
line (HEK293) and human pooled serum). </p>
<p>The exosomal oxysterol
profile did not reflect cytoplasmic oxysterol profiles in the cells of origin; cytoplasmic
27-OHC was low in ER+ MCF-7 cells while high in MDA-MB-231 cells. Other control
cancer cells showed varied cytoplasmic oxysterol levels. Hence, exosome profiling
in cancer cells might provide complementary information with the possibility of
diagnostic value.</p
