Tumor necrosis factor-α (TNF-α) plays a significant role in inflammation and cancer-related apoptosis. We identified a TNF-α-mediated epigenetic mechanism of apoptotic cell death regulation in estrogen receptor-α (ERα)-positive human breast cancer cells. To assess the apoptotic effect of TNF-α, annexin V/ propidium iodide (PI) double staining, cell viability assays, and Western blotting were performed. To elucidate this mechanism, histone deacetylase (HDAC) activity assay and immunoprecipitation (IP) were conducted; the mechanism was subsequently confirmed through chromatin IP (ChIP) assays. Finally, we assessed HDAC3–ERα-mediated apoptotic cell death after TNF-α treatment in ERα-positive human breast cancer (MCF-7) cells via the transcriptional activation of p53 target genes using luciferase assay and quantitative reverse transcription PCR. The TNF-α-induced selective apoptosis in MCF-7 cells was negatively regulated by the HDAC3–ERα complex in a caspase-7-dependent manner. HDAC3 possessed a p53-binding element, thus suppressing the transcriptional activity of its target genes. In contrast, MCF-7 cell treatment with TNF-α led to dissociation of the HDAC3–ERα complex and substitution of the occupancy on the promoter by the p53–p300 complex, thus accelerating p53 target gene expression. In this process, p53 stabilization was accompanied by its acetylation. This study showed that p53-mediated apoptosis in ERα-positive human breast cancer cells was negatively regulated by HDAC3–ERα in a caspase-7-dependent manner. Therefore, these proteins have potential application in therapeutic strategies.

TP53-induced glycolysis and apoptosis regulator (TIGAR) regulates redox homeostasis and provides the intermediates necessary for cell growth by reducing the glycolytic rate. During cellular senescence, cells undergo metabolic rewiring towards the glycolytic pathway, along with the development of the senescence-associated secretory phenotype (SASP), also known as the secretome. We observed that TIGAR expression increased during replicative senescence following the in vitro expansion of human mesenchymal stromal cells (MSCs) and that TIGAR knockout (KO) decreased SASP factors and triggered premature senescence with decelerated progression. Additionally, TIGAR KO impaired flexible lysosomal movement to the perinuclear region and decreased the autophagic flux of MSCs. Research on the mechanism of lysosomal movement revealed that, while native senescent MSCs presented low levels of Ac-α-tubulin (lysine 40) and increased sirtuin 2 (SIRT2) activity compared with those in growing cells, TIGAR KO-MSCs maintained Ac-α-tubulin levels and exhibited decreased SIRT2 activity despite being in a senescent state. The overexpression of SIRT2 reduced Ac-α-tubulin as a protein target of SIRT2 and induced the positioning of lysosomes at the perinuclear region, restoring the cytokine secretion of TIGAR KO-MSCs. Furthermore, TIGAR expression was positively correlated with SIRT2 activity, indicating that TIGAR affects SIRT2 activity partly by modulating the NAD⁺ level. Thus, our study demonstrated that TIGAR provides a foundation that translates the regulation of energy metabolism into lysosome positioning, affecting the secretome for senescence development. Considering the functional value of the cell-secretome in aging-related diseases, these findings suggest the feasibility of TIGAR for the regulation of secretory phenotypes.

Tamoxifen is widely used as a medication for estrogen receptor α (ERα)-positive breast cancer, despite the ~50% incidence of tamoxifen resistance. To overcome such resistance, combining tamoxifen with other agents is considered an effective approach. Here, through in vitro studies with ER-positive MCF7 cells and ER-negative MDA-MB-231 cells, validated by the use of xenograft mice, we investigated the potential of tumor necrosis factor α (TNFα) to enhance tamoxifen sensitivity and identified NCOR1 as a key downstream regulator. TNFα specifically degraded nuclear receptor corepressor 1 (NCOR1) in MCF7 cells. Moreover, knockdown of NCOR1, similar to TNFα treatment, suppressed cancer cell growth and promoted apoptosis only in MCF7 cells and MCF7 xenograft mice through the stabilization of p53, a tumor suppressor protein. Interestingly, NCOR1 knockdown with TNFα treatment increased the occupancy of p53 at the p21 promoter, while decreasing that of ERα. Notably, NCOR1 formed a complex with p53 and ERα, which was disrupted by TNFα. Finally, combinatorial treatment with tamoxifen, TNFα and short–hairpin (sh)-NCOR1 resulted in enhanced suppression of tumor growth in MCF7 xenograft mice compared to single tamoxifen treatment. In conclusion, TNFα promoted tamoxifen sensitivity through the dissociation of the ERα-p53-NCOR1 complex, pointing at NCOR1 as a putative therapeutic target for overcoming tamoxifen resistance in ERα-positive breast cancer.

Transforming growth factor-β1 (TGF-β1) is highly expressed in the tumor microenvironment and known to play a multifunctional role in cancer progression. In addition, TGF-β1 promotes metastasis by inducing epithelial–mesenchymal transition (EMT) in a variety of tumors. Thus, inhibition of TGF-β1 is considered an important strategy in the treatment of cancer. In most tumors, TGF-β1 signal transduction exhibits modified or non-functional characteristics, and TGF-β1 inhibitors have various inhibitory effects on cancer cells. Currently, many studies are being conducted to develop TGF-β1 inhibitors from non-toxic natural compounds. We aimed to develop a new TGF-β1 inhibitor to suppress EMT in cancer cells. As a result, improved chalcone-like chain CTI-82 was identified, and its effect was confirmed in vitro. We showed that CTI-82 blocked TGF-β1-induced EMT by inhibiting the cell migration and metastasis of A549 lung cancer cells. In addition, CTI-82 reduced the TGF-β1-induced phosphorylation of SMAD2/3 and inhibited the expression of various EMT markers. Our results suggest that CTI-82 inhibits tumor growth, migration, and metastasis.

Glioblastoma (GBM) is a highly aggressive and lethal brain tumor characterized by metabolic reprogramming and epigenetic dysregulation. In GBM, the expression levels of Enhancer of Zeste Homolog 2 (EZH2) and dipeptidyl peptidase 4 (DPP4) are inversely correlated, significantly influencing tumor progression. To investigate these reports, the therapeutic potential of digitoxin, a plant-derived bioactive glycoside, was studied in combination with the chemotherapeutic agents temozolomide (TMZ) or romidepsin. We evaluated the EZH2-DPP4 axis and pro-apoptotic signaling using qPCR, western blot, and ELISA. The synergistic effects were assessed through cell viability assays, flow cytometry, and an orthotopic xenograft mouse model utilizing 18F-FDG PET imaging. Digitoxin effectively downregulated EZH2 while restoring DPP4 expression, thereby inhibiting tumor cell growth and enhancing apoptosis. Notably, the combination therapy effectively inhibited tumor progression and reduced tumor burden in vivo, resulting in significantly prolonged survival. Consistent effects were observed in EZH2-knockdown cells, confirming that digitoxin targets the EZH2-DPP4 pathway. These findings suggest that digitoxin acts as a novel epigenetic-regulatory agent, representing a promising integrative medicine and therapeutic strategy to overcome chemoresistance in GBM management.