Brain metastases are frequent in patients with advanced
breast cancer and are associated with poor prognosis. However, unique molecular
biomarkers have not yet been established. We hypothesized that microRNA-20b (miR-20b) plays a role in
breast cancer brain
metastasis. Our study cohort comprised of eleven
breast cancer patients with brain
metastasis and nine control patients (age, stage, and follow-up matched) with
breast cancer without brain
metastasis. Cases were reviewed microscopically to select
tumor blocks with >50%
tumor cells,
RNA was extracted from
formalin-fixed
paraffin-embedded (FFPE)
tumor tissue blocks and expression of miR-20b analyzed using qRT-PCR. We further tested the effect of miR-20b overexpression on colony formation and invasion in vitro using MCF-7 and MDA-MB-231 cells. In the patient-derived samples, miR-20b expression was significantly higher in
brain metastases of
breast cancer patients, compared to primary
breast tumors as well as the patients without brain
metastasis. miR-20b also significantly induced the colony formation and invasiveness of
breast cancer cells. Further, miR-20b levels were observed to be high in brain-metastasizing cells, compared to bone-metastasizing cells. Together, our findings suggest a novel role of miR-20b in
breast cancer brain
metastasis that warrants further investigation for its potential to be developed as prognostic and/or therapeutic target.