Triple-negative breast cancer comprises approximately 15–20% of all breast cancers diagnosed and is nearly twice as common in black women than white women in the United States. We evaluated the effects of two epigenetic-modifying compounds on markers of growth potential in several triple-negative breast cancer cell lines. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor currently used in the treatment of cutaneous T cell lymphoma, was administered to triple-negative breast cancer cells alone or in combination with epigallocatechin-3-gallate (EGCG), a DNA methyltransferase (DNMT) inhibitor isolated from green tea. The compounds affected the expression of oncogenic miR-221/222 and tumor suppressors, p27 and PTEN, in addition to estrogen receptor alpha (ERα). E-cadherin expression was increased while N-cadherin was decreased, indicating a more epithelial phenotype. In addition, the activity of DNMTs was diminished with the treatments, and there was a significant enrichment of AcH3 within the promoter of p27 and PTEN, suggesting a role of epigenetic mechanisms for the aforementioned changes. These results translated to reduced migration of the triple-negative breast cancer cells with the treatments. Together, these findings support the role of SAHA and EGCG in limiting growth and proliferation of breast cancer cells.

Background/Aim: Inhibition of apoptosis is one of the hallmarks of cancer, and anti-apoptotic genes are often targets of genetic and epigenetic alterations. Cellular inhibitor of apoptosis 2 (cIAP2) has a role in degrading caspases by linking them to ubiquitin molecules, and is upregulated in triple-negative breast cancer (TNBC). Previous studies have demonstrated that cIAP2 may play a role in the epithelial-to-mesenchymal transition (EMT). Materials and Methods: Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, was administered to triple-negative breast cancer (TNBC) cells alone or in combination with epigallocatechin-3-gallate (EGCG), a DNA methyltransferase (DNMT) inhibitor isolated from green tea. Results: The compounds were able to decrease the expression of cIAP2 while increasing the expression of pro-apoptotic caspase 7. There were also changes in histone modifications, suggesting a role of epigenetic mechanisms in these changes in expression of cIAP2. These changes resulted in an increase in apoptosis. SAHA and EGCG were also capable of limiting TNBC cell migration across a fibronectin (FN) matrix. Conclusion: SAHA and EGCG reduce the metastatic potential of TNBC by inducing the apoptotic pathway. Hanahan and Weinberg first described the hallmarks of cancer in 2000, which included the inhibition of apoptosis as one of the key factors that drive cancer progression (1). This list was updated in 2011 and included two additional enabling characteristics, one of which was genome instability and mutation that encompasses epigenetic aberrations (2). This enabling characteristic can easily influence the hallmarks of cancer. The apoptotic pathway is a system of checks and balances, utilizing a suite of caspases to promote the process and baculovirus IAP repeat (BIR) proteins to inhibit the process. They are able to do so through linking pro-apoptotic proteins to ubiquitin molecules (3). Dysregulation of these proteins can allow cancer cells to evade apoptosis (4). Cellular inhibitor of apoptosis 2 (cIAP2), which is also known as BIRC3, has been shown to be upregulated in cancers, including triple-negative breast cancer (TNBC). TNBCs are typically more refractory to treatment due to the three silenced targets of hormonal cancer therapy: estrogen receptor alpha (ERα), progesterone receptor, and human epidermal growth factor receptor 2 (HER2). In our previous study, we began to elucidate the anti-cancer effects of suberoylanilide hydroxamic acid (SAHA) and epigallocatechin-3-gallate (EGCG) on TNBC cells through the lens of growth potentiation (5). That study has investigated downstream targets of oncogenic miR-221/222 after treatment with SAHA and EGCG in order to determine their abilities to directly restore expression of p27, PTEN, and ERα. After noting the ability of SAHA and EGCG to decrease the expression of miR-221/222, we aimed to investigate other oncogenes that are upregulated in TNBCs. cIAP2 was one of these genes. Jo et al. have linked cIAP2 to an increase in migration in TNBC...