Trichostatin A enhances estrogen receptor-alpha repression in MCF-7 breast cancer cells under hypoxia

Pharmacological Properties of Trichostatin A, Focusing on the Anticancer Potential: A Comprehensive Review

Trichostatin A (TSA), a natural derivative of dienohydroxamic acid derived from a fungal metabolite, exhibits various biological activities. It exerts antidiabetic activity and reverses high glucose levels caused by the downregulation of brain-derived neurotrophic factor (BDNF) expression in Schwann cells, anti-inflammatory activity by suppressing the expression of various cytokines, and significant antioxidant activity by suppressing oxidative stress through multiple mechanisms. Most importantly, TSA exhibits potent inhibitory activity against different types of cancer through different pathways. The anticancer activity of TSA appeared in many in vitro and in vivo investigations that involved various cell lines and animal models. Indeed, TSA exhibits anticancer properties alone or in combination with other drugs used in chemotherapy. It induces sensitivity of some human cancers toward chemotherapeutical drugs. TSA also exhibits its action on epigenetic modulators involved in cell transformation, and therefore it is considered an epidrug candidate for cancer therapy. Accordingly, this work presents a comprehensive review of the most recent developments in utilizing this natural compound for the prevention, management, and treatment of various diseases, including cancer, along with the multiple mechanisms of action. In addition, this review summarizes the most recent and relevant literature that deals with the use of TSA as a therapeutic agent against various diseases, emphasizing its anticancer potential and the anticancer molecular mechanisms. Moreover, TSA has not been involved in toxicological effects on normal cells. Furthermore, this work highlights the potential utilization of TSA as a complementary or alternative medicine for preventing and treating cancer, alone or in combination with other anticancer drugs.

Anticancer Therapy with HDAC Inhibitors: Mechanism-Based Combination Strategies and Future Perspectives

The increasing knowledge of molecular drivers of tumorigenesis has fueled targeted cancer therapies based on specific inhibitors. Beyond "classic" oncogene inhibitors, epigenetic therapy is an emerging field. Epigenetic alterations can occur at any time during cancer progression, altering the structure of the chromatin, the accessibility for transcription factors and thus the transcription of genes. They rely on post-translational histone modifications, particularly the acetylation of histone lysine residues, and are determined by the inverse action of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Importantly, HDACs are often aberrantly overexpressed, predominantly leading to the transcriptional repression of tumor suppressor genes. Thus, histone deacetylase inhibitors (HDACis) are powerful drugs, with some already approved for certain hematological cancers. Albeit HDACis show activity in solid tumors as well, further refinement and the development of novel drugs are needed. This review describes the capability of HDACis to influence various pathways and, based on this knowledge, gives a comprehensive overview of various preclinical and clinical studies on solid tumors. A particular focus is placed on strategies for achieving higher efficacy by combination therapies, including phosphoinositide 3-kinase (PI3K)-EGFR inhibitors and hormone- or immunotherapy. This also includes new bifunctional inhibitors as well as novel approaches for HDAC degradation via PROteolysis-TArgeting Chimeras (PROTACs).

Co-inhibition of mTORC1, HDAC and ESR1α retards the growth of triple-negative breast cancer and suppresses cancer stem cells

Triple-negative breast cancer (TNBC) is the most refractory subtype of breast cancer. It causes the majority of breast cancer-related deaths, which has been largely associated with the plasticity of tumor cells and persistence of cancer stem cells (CSCs). Conventional chemotherapeutics enrich CSCs and lead to drug resistance and disease relapse. Development of a strategy capable of inhibiting both bulk and CSC populations is an unmet medical need. Inhibitors against estrogen receptor 1, HDACs, or mTOR have been studied in the treatment of TNBC; however, the results are inconsistent. In this work, we found that patient TNBC samples expressed high levels of mTORC1 and HDAC genes in comparison to luminal breast cancer samples. Furthermore, co-inhibition of mTORC1 and HDAC with rapamycin and valproic acid, but neither alone, reproducibly promoted ESR1 expression in TNBC cells. In combination with tamoxifen (inhibiting ESR1), both S6RP phosphorylation and rapamycin-induced 4E-BP1 upregulation in TNBC bulk cells was inhibited. We further showed that fractionated CSCs expressed higher levels of mTORC1 and HDAC than non-CSCs. As a result, co-inhibition of mTORC1, HDAC, and ESR1 was capable of reducing both bulk and CSC subpopulations as well as the conversion of fractionated non-CSC to CSCs in TNBC cells. These observations were partially recapitulated with the cultured tumor fragments from TNBC patients. Furthermore, co-administration of rapamycin, valproic acid, and tamoxifen retarded tumor growth and reduced CD44^high/+/CD24^low/− CSCs in a human TNBC xenograft model and hampered tumorigenesis after secondary transplantation. Since the drugs tested are commonly used in clinic, this study provides a new therapeutic strategy and a strong rationale for clinical evaluation of these combinations for the treatment of patients with TNBC.

Bisphenol A induces COX-2 through the mitogen-activated protein kinase pathway and is associated with levels of inflammation-related markers in elderly populations

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical, and it is one of the highest volume chemicals produced worldwide. Even though several in vivo and in vitro studies showed positive associations of BPA exposure with pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL)-6, the mechanism by which BPA induces inflammation is unclear. We investigated the mechanism by which BPA induces inflammation (expression of inflammation-related genes, changes in oxidative stress, and cell proliferation and migration) and evaluated the effect of BPA exposure on inflammation-related markers in epidemiologic studies using repeat urine and serum samples from elderly subjects. BPA induced COX-2 expression via nuclear translocation of NF-κB and activation of mitogen-activated protein kinase (MAPK) by phosphorylation of ERK1/2 and enhanced the migration of lung cancer A549 and breast cancer MDAMB-231 cells. In two epidemiologic studies, we detected associations of BPA with six inflammation-related markers (WBC, CRP, IL-10, ALT, AST, and γ-GTP levels). Our findings probably suggest that BPA exposure induces inflammation and exacerbates tumorigenesis.

Inhibition of hypoxia-induced cyclooxygenase-2 by Korean Red Ginseng is dependent on peroxisome proliferator-activated receptor gamma

Background

Korean Red Ginseng (KRG) is a traditional herbal medicine made by steaming and drying fresh ginseng. It strengthens the endocrine and immune systems to ameliorate various inflammatory responses. The cyclooxygenase-2 (COX-2)/prostaglandin E2 pathway has important implications for inflammation responses and tumorigenesis. Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor that regulates not only adipogenesis and lipid homeostasis, but also angiogenesis and inflammatory responses.

Methods

The effects of the KRG on inhibition of hypoxia-induced COX-2 via PPARγ in A549 cells were determined by luciferase assay, Western blot, and/or quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The antimigration and invasive effects of KRG were evaluated on A549 cells using migration and matrigel invasion assays.

Results and conclusion

We previously reported that hypoxia-induced COX-2 protein and mRNA levels were suppressed by KRG. This study examines the possibility of PPARγ as a cellular target of KRG for the suppression of hypoxia-induced COX-2. PPARγ protein levels and PPARγ-responsive element (PPRE)-driven reporter activities were increased by KRG. Reduction of hypoxia-induced COX-2 by KRG was abolished by the PPARγ inhibitor GW9662. In addition, the inhibition of PPARγ abolished the effect of KRG on hypoxia-induced cell migration and invasion.

Discussion

Our results show that KRG inhibition of hypoxia-induced COX-2 expression and cell invasion is dependent on PPARγ activation, supporting the therapeutic potential for suppression of inflammation under hypoxia. Further studies are required to demonstrate whether KRG activates directly PPARγ and to identify the constituents responsible for this activity.