Novel targeted agents for the treatment of advanced breast cancer

Discovery of a novel hybrid coumarin-hydroxamate conjugate targeting the HDAC1-Sp1-FOSL2 signaling axis for breast cancer therapy

BACKGROUND

Breast cancer is one of the most lethal cancers in women. Despite significant advances in the diagnosis and treatment of breast cancer, many patients still succumb to this disease, and thus, novel effective treatments are urgently needed. Natural product coumarin has been broadly investigated since it reveals various biological properties in the medicinal field. Accumulating evidence indicates that histone deacetylase inhibitors (HDACIs) are promising novel anti-breast cancer agents. However, most current HDACIs exhibit only moderate effects against solid tumors and are associated with severe side effects. Thus, to develop more effective HDACIs for breast cancer therapy, hydroxamate of HDACIs was linked to coumarin core, and coumarin-hydroxamate hybrids were designed and synthesized.

METHODS

A substituted coumarin moiety was incorporated into the classic hydroxamate HDACIs by the pharmacophore fusion strategy. ZN444B was identified by using the HDACI screening kit and cell viability assay. Molecular docking was performed to explore the binding mode of ZN444B with HDAC1. Western blot, immunofluorescent staining, cell viability, colony formation and cell migration and flow cytometry assays were used to analyze the anti-breast cancer effects of ZN444B in vitro. Orthotopic studies in mouse models were applied for preclinical evaluation of efficacy and toxicity in vivo. Proteomic analysis, dual-luciferase reporter assay, chromatin immunoprecipitation, co-immunoprecipitation, immunofluorescent staining assays along with immunohistochemical (IHC) analysis were used to elucidate the molecular basis of the actions of ZN444B.

RESULTS

We synthesized and identified a novel coumarin-hydroxamate conjugate, ZN444B which possesses promising anti-breast cancer activity both in vitro and in vivo. A molecular docking model showed that ZN444B binds to HDAC1 with high affinity. Further mechanistic studies revealed that ZN444B specifically decreases FOS-like antigen 2 (FOSL2) mRNA levels by inhibiting the deacetylase activity of HDAC1 on Sp1 at K703 and abrogates the binding ability of Sp1 to the FOSL2 promoter. Furthermore, FOSL2 expression positively correlates with breast cancer progression and metastasis. Silencing FOSL2 expression decreases the sensitivity of breast cancer cells to ZN444B treatment. In addition, ZN444B shows no systemic toxicity in mice.

CONCLUSIONS

Our findings highlight the potential of FOSL2 as a new biomarker and therapeutic target for breast cancer and that targeting the HDAC1-Sp1-FOSL2 signaling axis with ZN444B may be a promising therapeutic strategy for breast cancer.

The synergistic effect of 2,3,5,4'-Tetrahydroxystilbene-2-O-β-d-glucoside combined with Adriamycin on MCF-7 breast cancer cells

Objective

Breast cancer has been reported to be a serious disease and a threat to women's health. 2,3,5,4'-Tetrahydroxystilbene-2-O-β-d-glucoside (THSG) is a bioactive natural compound originating from Polygonum multiflorum Thunb., which has been shown to possess anti-inflammatory and antitumor properties. Adriamycin (ADM) is a chemotherapy agent used in tumor therapy that is limited by its side effects. However, little is known about the synergistic effect of THSG combined with ADM on breast cancer. This study seeks to investigate the effects of the combination of THSG plus ADM on MCF-7 breast cancer cells and to test the mechanisms involved.

Materials and methods

MTT assay was detected to determine cell viability. Furthermore, cell apoptosis was tested by flow cytometry and TUNEL assay. In addition, protein expression was measured by Western blot analysis.

Results

The individual treatment of THSG and ADM induced cell injury. Moreover, cotreatment further increased it, which the effect may be associated with the elevation of the apoptotic-related protein expression such as Bax/Bcl-2 and cleaved caspase-3/caspase-3. Lastly, our results also show the reduction of vascular endothelial growth factor/phosphatidylinositol 3-kinase/Akt protein expression in the individual or synergistic treatment.

Conclusion

Taken together, cotreatment of THSG and ADM may exert a synergistic reduction of cell injury via the inhibition of vascular endothelial growth factor/phosphatidylinositol 3-kinase/Akt pathway. Thus, THSG might possess potent anti-breast cancer effect with ADM.

FoxM1 is a promising candidate target in the treatment of breast cancer

Forkhead box protein M1(FoxM1) is a member of forkhead superfamily transcription factors. Emerging evidences have progressively contributed to our understanding on a central role of FoxM1 in human cancers. However, perspectives on the function of FoxM1 in breast cancer (BC) remain conflicting, and mostly were from basic research. Here, we explored the expression profile and prognostic values of FoxM1 based on analysis of pooled clinical datasets derived from online accessible databases, including ONCOMINE, Breast Cancer Gene-Expression Miner v4.0, and Kaplan-Meier plotter. It was found that, FoxM1 mRNA expression was significantly higher in breast tumor versus normal control. FoxM1expression profile presented a distinct pattern in different molecular subtypes of BC patients. Higher expression of FoxM1 was correlated to low mRNA expression of estrogen receptor 1 (ESR1), erb-B2 receptor tyrosine kinase 2 (ERBB2), and was inversely associated with the expression of classical luminal regulators forkhead box protein A1 (FoxA1) and GATA binding protein 3 (GATA3). Elevated FoxM1 expression predicted shorter distance metastasis free survival (DMFS) in BC patients, particularly with estrogen receptor (ER) positive and Luminal A, Luminal B subtypes of BC. More interestingly, elevated FoxM1 expression predicted poor survival in breast cancer patients, especially in the ER (+), progesterone receptor (PR) (+) subgroups and BC patients received adjuvant chemotherapy only or treated with tamoxifen only. These results implied that FoxM1 is an essential prognostic factor and promising candidate target in the treatment of breast cancer.

Potential role for mammalian target of rapamycin inhibitors as first-line therapy in hormone receptor-positive advanced breast cancer

Despite advances in cytotoxic chemotherapy and targeted therapies, 5-year survival rates remain low for patients with advanced breast cancer at diagnosis. This highlights the limited effectiveness of current treatment options. An improved understanding of cellular functions associated with the development and progression of breast cancer has resulted in the creation of a number of novel targeted molecular therapies. However, more work is needed to improve outcomes, particularly in the first-line recurrent or metastatic hormone receptor-positive breast cancer setting. The phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (mTOR) pathway is a major intracellular signaling pathway that is often upregulated in breast cancer, and overactivation of this pathway has been associated with primary or developed resistance to endocrine treatment. Clinical data from the Phase III Breast Cancer Trials of Oral Everolimus-2 (BOLERO-2) study of the mTOR inhibitor everolimus combined with exemestane in hormone receptor-positive advanced breast cancer were very promising, highlighting the potential role of mTOR inhibitors in combination with endocrine therapies as a first-line treatment option for these patients. It is hoped that the use of mTOR inhibitors combined with current standard-of-care endocrine therapies, such as aromatase inhibitors, in the first-line advanced breast cancer setting may result in greater antitumor effects and also delay or reverse treatment resistance.

Advances in small-molecule drug discovery for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of poor prognosis, highly invasive and difficult-to-treat breast cancers accounting for approximately 15% of clinical cases. Given the poor outlook and lack of sustained response to conventional therapies, TNBC has been the subject of intense studies on new therapeutic approaches in recent years. The development of targeted cancer therapies, often in combination with established chemotherapy, has been applied to a number of new clinical studies in this setting in recent years. This review will highlight recent therapeutic advances in TNBC, focusing on small-molecule drugs and their associated biological mechanisms of action, and offering the possibility of improved prospects for this patient group in the near future.

Small-molecule inhibitors of the receptor tyrosine kinases: promising tools for targeted cancer therapies

Chemotherapeutic and cytotoxic drugs are widely used in the treatment of cancer. In spite of the improvements in the life quality of patients, their effectiveness is compromised by several disadvantages. This represents a demand for developing new effective strategies with focusing on tumor cells and minimum side effects. Targeted cancer therapies and personalized medicine have been defined as a new type of emerging treatments. Small molecule inhibitors (SMIs) are among the most effective drugs for targeted cancer therapy. The growing number of approved SMIs of receptor tyrosine kinases (RTKs) i.e., tyrosine kinase inhibitors (TKIs) in the clinical oncology imply the increasing attention and application of these therapeutic tools. Most of the current approved RTK-TKIs in preclinical and clinical settings are multi-targeted inhibitors with several side effects. Only a few specific/selective RTK-TKIs have been developed for the treatment of cancer patients. Specific/selective RTK-TKIs have shown less deleterious effects compared to multi-targeted inhibitors. This review intends to highlight the importance of specific/selective TKIs for future development with less side effects and more manageable agents. This article provides an overview of: (1) the characteristics and function of RTKs and TKIs; (2) the recent advances in the improvement of specific/selective RTK-TKIs in preclinical or clinical settings; and (3) emerging RTKs for targeted cancer therapies by TKIs.

Antitumor action of a novel histone deacetylase inhibitor, YF479, in breast cancer

Accumulating evidence demonstrates important roles for histone deacetylase in tumorigenesis (HDACs), highlighting them as attractive targets for antitumor drug development. Histone deactylase inhibitors (HDACIs), which have shown favorable anti-tumor activity with low toxicity in clinical investigations, are a promising class of anticancer therapeutics. Here, we screened our compound library to explore small molecules that possess anti-HDAC activity and identified a novel HDACI, YF479. Suberoylanilide hydroxamic acid (SAHA), which was the first approved HDAC inhibitor for clinical treatment by the FDA, was as positive control in our experiments. We further demonstrated YF479 abated cell viability, suppressed colony formation and tumor cell motility in vitro. To investigate YF479 with superior pharmacodynamic properties, we developed spontaneous and experimental breast cancer animal models. Our results showed YF479 significantly inhibited breast tumor growth and metastasis in vivo. Further study indicated YF479 suppressed both early and end stages of metastatic progression. Subsequent adjuvant chemotherapy animal experiment revealed the elimination of local-regional recurrence (LRR) and distant metastasis by YF479. More important, YF479 remarkably prolonged the survival of tumor-bearing mice. Intriguingly, YF479 displayed more potent anti-tumor activity in vitro and in vivo compared with SAHA. Together, our results suggest that YF479, a novel HDACI, inhibits breast tumor growth, metastasis and recurrence. In light of these results, YF479 may be an effective therapeutic option in clinical trials for patients burdened by breast cancer.

Correlation between PDZK1, Cdc37, Akt and breast cancer malignancy: the role of PDZK1 in cell growth through Akt stabilization by increasing and interacting with Cdc37

PDZ domain containing 1 (PDZK1) is a scaffold protein that plays a role in the fate of several proteins. Estrogen can induce PDZK1 gene expression; however, our recent report showed that PDZK1 expression in the breast cancer cell line MCF-7 is indirect and involves insulin-like growth factor (IGF)-1 receptor function. Such a relationship was established in cell culture systems and human breast cancer tissues. Here we show that overexpression of PDZK1 promoted an increase in cyclin D1 and enhanced anchorage-independent growth of MCF-7 cells in the absence of 17β-estradiol, suggesting that PDZK1 harbors oncogenic activity. Indeed, PDKZ1 overexpression enhanced epidermal growth factor receptor (EGFR)-stimulated MEK/ERK1/2 signaling and IGF-induced Akt phosphorylation. PDZK1 appeared to play this role, in part, by stabilizing the integrity of the growth promoting factors Akt, human epidermal growth factor receptor 2 (Her2/Neu) and EGFR. Increased Akt levels occurred via a decrease in the ubiquitination of the kinase. PDZK1 overexpression was associated with resistance to paclitaxel/5-fluorouracil/etoposide only at low concentrations. Although the increased stability of Akt was sensitive to heat shock protein 90 (HSP90) inhibition, increased levels of the cochaperone cell division cycle 37 (Cdc37), as well as its ability to bind PDZK1, appear to play a larger role in kinase stability. Using human tissue microarrays, we show strong positive correlation between PDZK1, Akt and Cdc37 protein levels, and all correlated with human breast malignancy. There were no positive correlations between PDZK1 and Cdc37 at the mRNA levels, confirming our in vitro studies. These results demonstrate a relationship between PDZK1, Akt and Cdc37, and potentially Her2/Neu and EGFR, in breast cancer, representing a new axis that can be targeted therapeutically to reduce the burden of human breast cancer.

Recent syntheses of PI3K/Akt/mTOR signaling pathway inhibitors

This review focuses on the syntheses of PI3K/Akt/mTOR inhibitors that have been reported outside of the patent literature in the last 5years but is largely centered on synthetic work reported in 2011 and 2012. While focused on syntheses of inhibitors, some information on in vitro and in vivo testing of compounds is also included. Many of these reported compounds are reversible, competitive adenosine triphosphate (ATP) binding inhibitors, so given the structural similarities of many of these compounds to the adenine core, this review presents recent work on inhibitors based on where the synthetic chemistry was started, that is, inhibitor syntheses which started with purines/pyrimidines are followed by inhibitor syntheses which began with pyridines, pyrazines, azoles, and triazines then moves to inhibitors which bear no structural resemblance to adenine: liphagal, wortmannin and quercetin analogs. The review then finishes with a short section on recent syntheses of phosphotidyl inositol (PI) analogs since competitive PI binding inhibitors represent an alternative to the competitive ATP binding inhibitors which have received the most attention.

Synthetic phosphoethanolamine induces cell cycle arrest and apoptosis in human breast cancer MCF-7 cells through the mitochondrial pathway

Phosphoethanolamine (Pho-s) is a compound involved in phospholipid turnover, acting as a substrate for many phospholipids of the cell membranes. In a recent study, we showed that Pho-s has antitumor effect in the several tumor cells. In this study we evaluated the antitumor activity of synthetic Pho-s on MCF-7 breast cancer cells. Here we demonstrate that Pho-s is cytotoxic to MCF-7 cells in a dose-dependent manner, while it is cytotoxic to MCF10 only at higher concentrations. In addition, Pho-s induces a disruption in mitochondrial membrane potential (Δψm). Furthermore, Pho-s induces mitochondria aggregates in the cytoplasm and DNA fragmentation of MCF-7 cells visualized by confocal microscopy. In agreement with the reduction on Δψm, we showed that Pho-s induces apoptosis followed by an increase in cytochrome c expression and capase-3-like activity in MCF-7 cells. Our results demonstrate that Pho-s induces a cell cycle arrest in the G1 phase through an inhibition of cyclin D1 and stimulates p53. An additional highlight of this study is the finding that Pho-s inhibits Bcl-2, inducing apoptosis through the mitochondrial pathway. Taken together, these results show that Pho-s is a promising compound in the fight against cancer.