Background:
Triple-negative breast cancer (TNBC) is a great threat to global women's health due to its high metastatic potential. Epithelial-to-mesenchymal transition (EMT) is considered as a key event in the process of
metastasis. So the pharmacological targeting of EMT might be a promising strategy in improving the therapeutic efficacy of TNBC. Here, we investigated the effect of
shikonin exerting on EMT and consequently the
metastasis of TNBC cells and its underlying mechanism. Methods: The invasive and migratory capacities of MDA-MB-231 and BT549 cells were tested using transwell invasion and wound healing assay. MiR-17-5p expression was examined by qRT-PCR. MiR-17-5p targeted genes were predicted with different bioinformatic algorithms from four databases (TargetScan, miRanda, PITA and picTar) and further screened by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The differential expressions of predicted genes and their correlations with miR-17-5p were identified in
breast cancer patients based on The
Cancer Genome Atlas (TCGA) database. The interaction between
phosphatase and
tensin homolog deleted on chromosome ten (PTEN) and miR-17-5p was analyzed by
luciferase reporter assay. The overexpression vector and
small interfering RNA were constructed to investigate the role PTEN played in
metastasis and EMT regulation. The expressions of EMT markers,
protein kinase B (Akt) and phospho-Akt (p-Akt) were evaluated by western blot. Results:
Shikonin suppressed the migration and invasion of MDA-MB-231 and BT549 cells and meanwhile the corresponding alterations of EMT
biomarkers were observed in
shikonin treated MDA-MB-231 cells.
Shikonin inhibited the expression of miR-17-5p, which was upregulated in
breast cancer. The 3'-untranslated region (3'-UTR) of PTEN was found to be direct binding target of miR-17-5p by
luciferase reporter assays. PTEN functioned as a suppressor both in the
metastasis and EMT of TNBC cells. Moreover, Akt and p-Akt (Ser473) were involved in the process of inhibition in
cancer cell migration, invasion and EMT by
shikonin. Conclusions:
Shikonin inhibits migration and invasion of TNBC cells by suppressing EMT via miR-17-5p/PTEN/Akt pathway. This suggests
shikonin as a promising therapeutic agent to counteract
metastasis in the TNBC patients.