TGF-β-Induced TMEPAI Promotes Epithelial–Mesenchymal Transition in Doxorubicin-Treated Triple-Negative Breast Cancer Cells via SMAD3 and PI3K/AKT Pathway Alteration

Abstract 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 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 KEGG pathway enrichment analysis. The differential expressions of predicted genes and their correlations with miR-17-5p were identifed in breast cancer patients based on The Cancer Genome Atlas (TCGA) database. The interaction between 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 matastasis and EMT regulation. The expressions of EMT markers, Akt and p-Akt were evaluated by western blot.Results: Shikonin inhibited the migration and invasion of MDA-MB-231 cells by suppressing EMT. Shikonin suppressed the expression of miR-17-5p, which was upregulated in breast cancer and promoted cancer cell migration, invasion and EMT. The 3’-untranslated region of PTEN was found to be direct binding target of miR-17-5p. PTEN expression increased or decreased in breast cancer cells transfected with miR-17-5p inhibitors or mimics respectively. PTEN functioned as a suppressor both in the metastasis and EMT of TNBC cells. Overexpression or knockdown of PTEN reduced or increased the Akt and p-Akt expression respectively.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.

Download Full-text

Effect of metformin on PARP inhibitors-induced epithelial-mesenchymal transition and PD-L1 expression in triple-negative breast cancer.

Journal of Clinical Oncology ◽

10.1200/jco.2019.37.15_suppl.1063 ◽

2019 ◽

Vol 37 (15_suppl) ◽

pp. 1063-1063 ◽

Cited By ~ 2

Author(s):

Ye Han ◽

Chia-Wei Li

Keyword(s):

Breast Cancer ◽

T Cell ◽

Cancer Cells ◽

Triple Negative Breast Cancer ◽

Breast Cancer Cells ◽

Triple Negative ◽

Epithelial Mesenchymal Transition ◽

Parp Inhibitor ◽

Parp Inhibitors ◽

Mesenchymal Transition

1063 Background: Poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as promising targeted therapies for BRCA-mutated cancers by blocking repair of DNA double-strand breaks. However, resistance to PARP inhibitors have been described in some patients lowering overall response rates. The mechanisms underlying PARP inhibitor (PARPi) resistance are an area of active investigation. Methods: PARPi adaptive resistant clones (MDA-MB-468, MDA-MB-231, HCC1806) were generated in triple-negative breast cancer cell lines. Through morphologic observation and functional analysis, we evaluated epithelial-mesenchymal transition (EMT) and changes in immune checkpoint programmed death-ligand 1 (PD-L1). We also downregulated the expression of PD-L1 by shRNA to study the role of PD-L1 in PARPi resistance. We evaluated the immunology sensitivity to cytotoxic T cell upon PD-L1 change using a murine ex-vivo CD8+ T cell killing assay and a comparison of total killing cells percentage per well. Results: We demonstrated that inhibition of PARP enhances EMT, which induces phosphorylation of Akt at S473. This in turn upregulates the expression of PD-L1 by 2-3 fold in triple-negative breast cancer cells. In addition, PARPi–induced EMT occurred independent of PD-L1 upregulation in triple-negative breast cancer cells. Metformin administration (10µM) was found to reverse EMT by blocking the p-Akt S473 axis through activation of AMPK, resulting in downregulation of PD-L1 expression and sensitizing PARPi-resistant cancer cells to T cell killing. Conclusions: In summary, we identified that induction of EMT is a new mechanism for PARP inhibitor resistance. Metformin was able to reverse EMT and therefore a combination of metformin and PARP inhibitors may be a promising therapeutic strategy to increase the efficacy of PARP inhibitors and tumor sensitivity to T cells.

Download Full-text