Suppression of triple-negative breast cancer metastasis by pan-DAC inhibitor panobinostat via inhibition of ZEB family of EMT master regulators

Abstract

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial-to-mesenchymal transition (EMT) is a key contributor in the metastatic process. We previously showed the pan-deacetylase inhibitor LBH589 induces CDH1 expression in TNBC cells, suggesting regulation of EMT. The purpose of this study was to examine the effects of LBH589 on the metastatic qualities of TNBC cells and the role of EMT in this process. A panel of breast cancer cell lines (MCF-7, MDA-MB-231, BT-549), drugged with LBH589, were examined for changes in cell morphology, migration, and invasion in vitro. The effect on in vivo metastasis was examined using immunofluorescent staining of lung sections. EMT gene expression profiling was used to determine LBH589-induced changes in TNBC cells. ZEB overexpression studies were conducted to validate requirement of ZEB in LBH589-mediated proliferation and tumorigenesis. Our results indicate a reversal of EMT by LBH589 as demonstrated by altered morphology and altered gene expression in TNBC. LBH589 was shown to be a more potent inhibitor of EMT than other HDAC inhibitors, SAHA and TMP269. Additionally, we found that LBH589 inhibits metastasis of MDA-MB-231 cells in vivo. These effects of LBH589 were mediated in part by inhibition of ZEB, as overexpression of ZEB1 or ZEB2 mitigated the effects of LBH589 on MDA-MB-231 EMT-associated gene expression, migration, invasion, CDH1 expression, and tumorigenesis. These data indicate therapeutic potential of LBH589 in targeting EMT and metastasis of TNBC.

Histone Deacetylases as New Therapeutic Targets in Triple-negative Breast Cancer: Progress and Promises

“…In a recent study it has been tested whether panobinostat has the ability to inhibit the migration, invasion, and metastasis of MDA-MB-231 and BT-549 cell lines, by suppressing EMT (110). In TNBC cells, panobinostat has been reported to inhibit the expression of genes associated to EMT and to induce the expression of CDH1, while these results were not found in luminal A or basal BC cell lines (106).…”

“…Furthermore, Rhodes et al compared panobinostat to other HDAC inhibitors (SAHA, TMP269) and found that panobinostat has much more potent anti-EMT effects than the other inhibitors (110). In vitro research showed that changes in EMT-related gene expression were associated with the suppression of cell migration and invasion.…”

“…Except for CDH1expression, panobinostat has induced the suppression of multiple predominant pro-EMT genes including ZEB1 and ZEB2. In addition, when investigators forced exogenous expression of ZEB1 or ZEB2, the inhibitory effects of panobinostat on cell migration, invasion, and CDH1 expression were reversed (110).…”

“…However, it is probably the repression of ZEB2 that regulates the effects of panobinostat on tumor genesis, as ZEB1 expression alone was not sufficient to overcome the actions of panobinostat on CDH1 expression (110). To sum up, it is critical to study panobinostat as a novel therapeutic to target the aggressive and metastatic nature of TNBC, as panobinostat is claimed to inhibit both TNBC primary tumor genesis and the metastasis of TNBC cells.…”

PTK6 Inhibition Suppresses Metastases of Triple-Negative Breast Cancer via SNAIL-Dependent E-Cadherin Regulation

“…Cells that have undergone an EMT exhibit enhanced cellular migration, invasion, and survival, which are required for tumor cell dissemination and metastasis formation. In many preclinical models, suppression or reversal of EMT impairs metastatic potential of many tumor cell types (8,9).…”