STAT3-survivin signaling mediates a poor response to radiotherapy in HER2-positive breast cancers

Targeting the STAT3 oncogenic pathway: Cancer immunotherapy and drug repurposing

Immune effector cells in the microenvironment tend to be depleted or remodeled, unable to perform normal functions, and even promote the malignant characterization of tumors, resulting in the formation of immunosuppressive microenvironments. The strategy of reversing immunosuppressive microenvironment has been widely used to enhance the tumor immunotherapy effect. Signal transducer and activator of transcription 3 (STAT3) was found to be a crucial regulator of immunosuppressive microenvironment formation and activation as well as a factor, stimulating tumor cell proliferation, survival, invasiveness and metastasis. Therefore, regulating the immune microenvironment by targeting the STAT3 oncogenic pathway might be a new cancer therapy strategy. This review discusses the pleiotropic effects of STAT3 on immune cell populations that are critical for tumorigenesis, and introduces the novel strategies targeting STAT3 oncogenic pathway for cancer immunotherapy. Lastly, we summarize the conventional drugs used in new STAT3-targeting anti-tumor applications.

N-acetylglucosamine-bearing polymers mimicking O-GlcNAc-modified proteins elicit anti-fibrotic activities in myofibroblasts and activated stellate cells

O-linked β-N-acetylglucosamine (O-GlcNAc)-modified proteins are post-translationally modified with GlcNAc conjugated to serine and threonine residues. This modification is associated with various physiological functions such as serine and threonine phosphorylation and Notch signaling. Here, we demonstrated that O-GlcNAc-modified proteins leaked from dead cells and GlcNAc-bearing polymers mimicking the multivalent GlcNAc moiety of these proteins induced anti-fibrotic activities, such as the suppression of α-smooth muscle actin and collagen and the induction of matrix metalloprotease 1 in myofibroblasts. We have previously reported that O-GlcNAc-modified proteins and GlcNAc-bearing polymers could interact with cell surface vimentin and desmin. In the current study, it was demonstrated that a multivalent GlcNAc moiety structure of these molecules activated PI3K/Akt and p38MAPK pathway and elicited these anti-fibrotic activities in myofibroblasts by interacting with cell surface vimentin. Since the interaction of O-GlcNAc-modified proteins with desmin was observed in the fibrotic liver of carbon tetrachloride-treated mice via an in situ proximity ligation assay, it was assumed that the activated stellate cells could bind to the O-GlcNAc-modified proteins from the damaged hepatocytes. In addition, the administration of anti-O-GlcNAc antibody to inhibit the interaction exacerbated liver fibrosis in the mice. Moreover, administration of the GlcNAc-bearing polymers into carbon tetrachloride-treated mice could ameliorate liver fibrosis. Thus, O-GlcNAc-modified proteins leaked from dead cells can interact with myofibroblasts and activated stellate cells and function as fibrosis suppressors. Moreover, we anticipate that GlcNAc-bearing polymers mimicking O-GlcNAc-modified proteins will be applied as novel therapeutic tools for fibrosis.

The role of radiotherapy in HER2+ early-stage breast cancer patients after breast-conserving surgery

Background

Due to radioresistance, some HER2+ patients may gain limited benefit from radiotherapy (RT) after breast-conserving surgery (BCS). This study aimed to develop an individualized nomogram to identify early-stage HER2+ patients who could omit RT after BCS.

Methods

The data of HER2+ patients with T0-2N0M0 breast cancer after BCS between 2010 and 2015 were extracted from Surveillance, Epidemiology, and End Results (SEER). Based on the independent prognostic factors determined by the Cox analysis in patients without RT after propensity score matching (PSM), the nomogram and risk stratification model were constructed, and then the prognosis of patients with and without RT was compared in each stratified group.

Results

A total of 10799 early-stage HER2+ patients after BCS were included. Baseline characteristics were similar between groups after PSM. Multivariate Cox analysis indicated that RT could improve overall survival (OS) (HR: 0.45, P<0.001) and breast cancer-specific survival (BCSS) (HR: 0.53, P<0.001). Age, marital status, tumor location, tumor size, and chemotherapy were identified by multivariate Cox analysis in patients without RT and were incorporated into a well-validated nomogram. The risk stratification model based on the nomogram indicated that RT was associated with improved OS (HR 0.40, P< 0.001) and BCSS (HR 0.39, P< 0.001) in the high-risk group but not in the low-risk group [OS: HR 1.04, P = 0.94; BCSS: HR 1.06, P = 0.93].

Conclusion

RT could significantly improve the OS and BCSS of HER2+ early-stage breast cancer patients after BCS on the whole. For high-risk patients, RT is an essential component of cancer therapy. However, the omission of radiotherapy may be considered for low-risk HER2+ early-stage patients. Further validation and improvement of the nomogram by prospective study or randomized controlled trials are warranted.

Radiotherapeutic Strategies to Overcome Resistance of Breast Cancer Brain Metastases by Considering Immunogenic Aspects of Cancer Stem Cells

Breast cancer is the most diagnosed cancer in women, and symptomatic brain metastases (BCBMs) occur in 15-20% of metastatic breast cancer cases. Despite technological advances in radiation therapy (RT), the prognosis of patients is limited. This has been attributed to radioresistant breast cancer stem cells (BCSCs), among other factors. The aim of this review article is to summarize the evidence of cancer-stem-cell-mediated radioresistance in brain metastases of breast cancer from radiobiologic and radiation oncologic perspectives to allow for the better interpretability of preclinical and clinical evidence and to facilitate its translation into new therapeutic strategies. To this end, the etiology of brain metastasis in breast cancer, its radiotherapeutic treatment options, resistance mechanisms in BCSCs, and effects of molecularly targeted therapies in combination with radiotherapy involving immune checkpoint inhibitors are described and classified. This is considered in the context of the central nervous system (CNS) as a particular metastatic niche involving the blood-brain barrier and the CNS immune system. The compilation of this existing knowledge serves to identify possible synergistic effects between systemic molecularly targeted therapies and ionizing radiation (IR) by considering both BCSCs' relevant resistance mechanisms and effects on normal tissue of the CNS.

STAT family of transcription factors in breast cancer: Pathogenesis and therapeutic opportunities and challenges

Breast cancer is the most commonly diagnosed cancer and second-leading cause of cancer deaths in women. Breast cancer stem cells (BCSCs) promote metastasis and therapeutic resistance contributing to tumor relapse. Through activating genes important for BCSCs, transcription factors contribute to breast cancer metastasis and therapeutic resistance, including the signal transducer and activator of transcription (STAT) family of transcription factors. The STAT family consists of six major isoforms, STAT1, STAT2, STAT3, STAT4, STAT5, and STAT6. Canonical STAT signaling is activated by the binding of an extracellular ligand to a cell-surface receptor followed by STAT phosphorylation, leading to STAT nuclear translocation and transactivation of target genes. It is important to note that STAT transcription factors exhibit diverse effects in breast cancer; some are either pro- or anti-tumorigenic while others maintain dual, context-dependent roles. Among the STAT transcription factors, STAT3 is the most widely studied STAT protein in breast cancer for its critical roles in promoting BCSCs, breast cancer cell proliferation, invasion, angiogenesis, metastasis, and immune evasion. Consequently, there have been substantial efforts in developing cancer therapeutics to target breast cancer with dysregulated STAT3 signaling. In this comprehensive review, we will summarize the diverse roles that each STAT family member plays in breast cancer pathobiology, as well as, the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators in the context of breast cancer treatment.

Survivin in Breast Cancer: A Review

Breast cancer is the most frequently diagnosed cancer in women and ranks second among causes for cancer-related death in women. Gene technology has led to the recognition that breast cancer is a heterogeneous disease composed of different biological subtypes, and genetic profiling enables the response to chemotherapy to be predicted. This fact emphasizes the importance of selecting sensitive diagnostic and prognostic markers in the early disease stage and more efficient targeted treatments for this disease. One such prognostic marker appears to be survivin. Many studies have shown that survivin is strongly expressed in different types of cancers. Its overexpression has been demonstrated in breast cancer, and high activity of the survivin gene has been associated with a poor prognosis and worse survival rates.

Identification of an Immune-Related Prognostic Risk Model in Glioblastoma

Background: Glioblastoma (GBM) is the most common and malignant type of brain tumor. A large number of studies have shown that the immunotherapy of tumors is effective, but the immunotherapy effect of GBM is not poor. Thus, further research on the immune-related hub genes of GBM is extremely important.

Methods: The GBM highly correlated gene clusters were screened out by differential expression, mutation analysis, and weighted gene co-expression network analysis (WGCNA). Least absolute shrinkage and selection operator (LASSO) and proportional hazards model (COX) regressions were implemented to construct prognostic risk models. Survival, receiver operating characteristic (ROC) curve, and compound difference analyses of tumor mutation burden were used to further verify the prognostic risk model. Then, we predicted GBM patient responses to immunotherapy using the ESTIMATE algorithm, GSEA, and Tumor Immune Dysfunction and Exclusion (TIDE) algorithm.

Results: A total of 834 immune-related differentially expressed genes (DEGs) were identified. The five hub genes (STAT3, SEMA4F, GREM2, MDK, and SREBF1) were identified as the prognostic risk model (PRM) screened out by WGCNA and LASSO analysis of DEGs. In addition, the PRM has a significant positive correlation with immune cell infiltration of the tumor microenvironment (TME) and expression of critical immune checkpoints, indicating that the poor prognosis of patients is due to TIDE.

Conclusion: We constructed the PRM composed of five hub genes, which provided a new strategy for developing tumor immunotherapy.

STAT3 as a target for sensitizing prostate cancer cells to irradiation

Radioresistance of prostate cancer (PCa) is a major factor leading to local failure of radiotherapy. STAT3 is an oncogenic protein that was recently found to be activated in PCa tumors. This study aimed to investigate the radiosensitization effect of targeting STAT3 in PCa tumors. Here, the radiosensitization effect of STAT3 blockade was investigated by clonogenic assay, flow cytometry and western blot analysis in human PCa cells in vitro and in vivo. We demonstrated that STAT3 blockade with a STAT3 inhibitor or siRNA increased the radiosensitivity of PCa cells and that radiation together with STAT3 blockade induced more apoptosis and double-strand breaks (DSBs) than radiation alone in LNCaP cells. In addition, radiation induced STAT3 activation and survivin expression in PCa cells, which was inhibited by STAT3 blockade. Transfection with survivin cDNA attenuated the radiosensitization effect of STAT3 blockade. These effects were further confirmed by in vivo studies, which showed that the STAT3 inhibitor enhanced the treatment efficacy of radiation on LNCaP xenografts with decreased STAT3 activation and survivin expression. These findings suggest that STAT3 blockade radiosensitizes PCa cells through regulation of survivin. Thus, our study has revealed STAT3 as a potential sensitizer for irradiation in PCa cells. Its clinical application as an adjuvant in radiotherapy of PCa should be explored in the future.

Factors and molecular mechanisms of radiation resistance in cancer cells

PURPOSE

The aim of this work is to review the published studies on radiation resistance mechanisms and molecular markers involved in different tumors. The revision has been focused in the last 5 years (2016-2021).

CONCLUSIONS

Radioresistance is a cause of concern as it causes failure of radiation therapy and subsequent tumor relapse. Combination chemotherapy and radiation therapy are clinically successful in treating many types of tumors. Despite continued improvements in cancer treatment, locoregional recurrence or metastatic spread continues to occur in a high proportion of patients after being treated with radiation therapy or combination treatments. There is strong evidence that cancer stem cells contribute to radiation resistance, contributing to treatment failure. The mechanisms of radiation resistance in different tumors are not fully understood. A better understanding of cancer stem cells and the associated signaling pathways that regulate radiation resistance will open up new strategies for treating cancer by radiation therapy. Radiation can damage malignant cells mainly by the induction of DNA double strand breaks. However, in some tumors appear resistant cells that repopulate the tumor following therapy leading over time to the failure of the treatment. Native mechanisms and induced pathways, are the cause of radiation resistance. It has been described that numerous molecular markers acting through numerous mechanisms of action involved in radiation resistance, such as apoptosis resistance, alterations of cell growth, proliferation and DNA repair, hypoxia, increase in invasiveness and migration capacity, cell cycle alterations and expression of heat shock proteins, among others. Therefore, resistance to radiation is a multifactorial phenomenon that, in different cell types, it occurs through different regulatory mechanisms in which different molecules intervene. Resistance can be acquired by altering different regulatory pathways in different tumors. The knowledge of radiation resistance markers could help in the classification and treatment of patients with more aggressive tumors.

Radiotherapy and radiosensitization in breast cancer: Molecular targets and clinical applications

Relatively poor survival outcomes are observed in advanced or metastatic breast cancer, where local control of the primary or metastatic disease may be achieved by surgical resection, local ablative and radiation therapies. Radioresistance, poses a major challenge in achieving durable oncologic outcomes, mandating development of novel management strategies. Although multimodality approaches that combine radiotherapy with chemotherapy, or systemic agents, are utilized for radiosensitization and treatment of various malignancies, this approach has not yet found its clinical application in breast cancer. Some agents for breast cancer treatment can serve as radiosensitizers, creating an opportunity to enhance effects of radiation while providing systemic disease control. Hence, combination of radiotherapy with radiosensitizing agents have the potential to improve oncologic outcomes in advanced or metastatic breast cancer. This review discusses molecular targets for radiosensitization and novel systemic agents that have potential for clinical use as radiosensitizers in breast cancer.

Anthelminthic niclosamide inhibits tumor growth and invasion in cisplatin-resistant human epidermal growth factor receptor 2-positive breast cancer

Chemotherapy-resistant breast cancer displays aggressive clinical behavior, is poorly differentiated and is associated with the occurrence of epithelial-mesenchymal transition and the presence of cancer stem cells. The anthelmintic drug niclosamide has been shown to have numerous clinical applications in the treatment of malignant tumors, in addition to its traditional use in tapeworm disease. Our previous study demonstrated that niclosamide had an antiproliferative effect and could inhibit the stem-like phenotype of the breast cancer cells, suggesting that it might have the potential to be used in the treatment of triple-negative breast cancer. However, the specific function and underlying mechanism of action of niclosamide in chemoresistant human epidermal growth factor receptor 2 (HER2)-positive breast cancer remain unknown. The present study aimed to determine whether niclosamide can inhibit cell proliferation, invasion and epithelial-to-mesenchymal transition, as well as the stem-like phenotype in cisplatin-resistant HER2-positive breast cancer. Alamar Blue and Annexin V/7-AAD staining, mammosphere formation and Transwell assays were performed to assess the viability, apoptosis, stem-like phenotype and invasion ability of breast cancer cell lines, respectively. Signaling molecule expression was detected via western blotting and a xenograft model was used to verify the inhibitory effect of niclosamide in vivo. The results from the present study demonstrated that niclosamide inhibited the resistance of HER2-positive breast cancer to cisplatin both in vitro and in vivo. Furthermore, niclosamide combined with cisplatin could inhibit breast cancer cell invasion, epithelial-mesenchymal transition and cell stemness. The inhibitory effect of niclosamide was mediated by apoptosis induction and Bcl-2 downregulation. Taken together, the results of the present study suggested that niclosamide combined with cisplatin may be considered as a novel treatment for chemoresistant HER2-positive breast cancer.

STAT3 inhibitor in combination with irradiation significantly inhibits cell viability, cell migration, invasion and tumorsphere growth of human medulloblastoma cells

Persistent activation of signal transducer and activator of transcription 3 (STAT3) is frequently reported in cancers and plays important roles in tumor progression. Therefore, directly targeting persistent STAT3 signaling is an attractive cancer therapeutic strategy. The aim of this study is to test the inhibitory efficacy of novel STAT3 small molecule inhibitors, LLY17 and LLL12B, in combination with irradiation in human medulloblastoma cells. Both LLY17 and LLL12B inhibit the IL-6-induced and persistent STAT3 phosphorylation in human medulloblastoma cells. Irradiation using 4 Gy alone exhibits some inhibitory effects on medulloblastoma cell viability, and these effects are further enhanced by combining with either STAT3 inhibitor. Irradiation alone also shows certain inhibitory effects on medulloblastoma cell migration and invasion and the combination of LLY17 or LLL12B with irradiation further demonstrates greater inhibitory effects than monotherapy. STAT3 inhibitor alone or irradiation alone exhibits some suppression of medulloblastoma tumorsphere growth, and the combination of LLY17 or LLL12B and irradiation exhibits greater suppression of tumorsphere growth than monotherapy. Combining either STAT3 inhibitor with irradiation reduces the expression of STAT3 downstream targets, Cyclin D1 and Survivin, and induces apoptosis in medulloblastoma cells. These results support that combination of a potent STAT3 inhibitor such as LLY17 or LLL12B with irradiation is an effective and novel therapeutic approach for medulloblastoma.

Radiation Resistance: A Matter of Transcription Factors

Currently, radiation therapy is one of the standard therapies for cancer treatment. Since the first applications, the field of radiotherapy has constantly improved, both in imaging technologies and from a dose-painting point of view. Despite this, the mechanisms of resistance are still a great problem to overcome. Therefore, a more detailed understanding of these molecular mechanisms will allow researchers to develop new therapeutic strategies to eradicate cancer effectively. This review focuses on different transcription factors activated in response to radiotherapy and, unfortunately, involved in cancer cells’ survival. In particular, ionizing radiations trigger the activation of the immune modulators STAT3 and NF-κB, which contribute to the development of radiation resistance through the up-regulation of anti-apoptotic genes, the promotion of proliferation, the alteration of the cell cycle, and the induction of genes responsible for the Epithelial to Mesenchymal Transition (EMT). Moreover, the ROS-dependent damaging effects of radiation therapy are hampered by the induction of antioxidant enzymes by NF-κB, NRF2, and HIF-1. This protective process results in a reduced effectiveness of the treatment, whose mechanism of action relies mainly on the generation of free oxygen radicals. Furthermore, the previously mentioned transcription factors are also involved in the maintenance of stemness in Cancer Stem Cells (CSCs), a subset of tumor cells that are intrinsically resistant to anti-cancer therapies. Therefore, combining standard treatments with new therapeutic strategies targeted against these transcription factors may be a promising opportunity to avoid resistance and thus tumor relapse.

Coordinated regulation of immune contexture: crosstalk between STAT3 and immune cells during breast cancer progression

Recent insights into the molecular and cellular mechanisms underlying cancer development have revealed the tumor microenvironment (TME) immune cells to functionally affect the development and progression of breast cancer. However, insufficient evidence of TME immune modulators limit the clinical application of immunotherapy for advanced and metastatic breast cancers. Intercellular STAT3 activation of immune cells plays a central role in breast cancer TME immunosuppression and distant metastasis. Accumulating evidence suggests that targeting STAT3 and/or in combination with radiotherapy may enhance anti-cancer immune responses and rescue the systemic immunologic microenvironment in breast cancer. Indeed, apart from its oncogenic role in tumor cells, the functions of STAT3 in TME of breast cancer involve multiple types of immunosuppression and is associated with tumor cell metastasis. In this review, we summarize the available information on the functions of STAT3-related immune cells in TME of breast cancer, as well as the specific upstream and downstream targets. Additionally, we provide insights about the potential immunosuppression mechanisms of each type of evaluated immune cells. Video abstract.

[Concomitant radiotherapy and trastuzumab: Rational and clinical implications]

The HER2 receptor (Human Epidermal Growth Receptor 2) is a transmembrane receptor with tyrosine kinase activity that is over-expressed in 25-30 % of breast carcinomas. Its activation is associated with an exaggeration of cell proliferation with an increase in repair capacity resulting in increased radioresistance. On cardiac tissues, HER2 receptor activation plays a cardio-protective role. Trastuzumab, the first anti-HER2 drug used to treat patients with breast cancer overexpressing HER2 receptor , inhibits the cascade of reactions resulting in the proliferation of tumor cells, thus restoring cellular radiosensitivity. However, the combination of Trastuzumab with radiation therapy also removes HER2 receptor cardio-protective role on myocardial cells which increases the risk of cardiotoxicity. Thus, the concomitant association of these two modalities has long been a subject of controversy. Recent advances in radiation therapy technology and early detection of cardiac injury may limit the cardiotoxicity of this combination. Through this review, we developed the biological basis and the benefit-risk of concomitant combination of radiotherapy and Trastuzumab in adjuvant treatment of breast cancers overexpressing HER2 and we discuss the modalities of its optimization.

IL-32 Promotes the Radiosensitivity of Esophageal Squamous Cell Carcinoma Cell through STAT3 Pathway

OBJECTIVE

This study is set out to determine the relationship between IL-32 and radiosensitivity of esophageal squamous cell carcinoma (ESCC).

METHODS

Western blot was adopted for measuring IL-32 expression in Eca-109 and TE-10 cells. Eca-109 and TE-10 cells with interference or overexpression of IL-32 were treated with the presence or absence of X-ray irradiation. Then, the use of CCK8 assay was to detect proliferation ability, and effects of IL-32 expression on radiosensitivity of ESCC were tested by colony formation assay. The cell apoptosis was detected using flow cytometry. STAT3 and p-STAT expression, and apoptotic protein Bax were detected by western blot.

RESULTS

Colony formation assay and CCK8 assay showed that compared with the NC group without treatment, the growth of the ESCC cells, that is Eca-109 and TE-10, was significantly inhibited in the OE+IR group with highly expressed IL-32 and irradiation. In flow cytometry analysis, in Eca-109 and TE-10 cells, highly expressed IL-32 combined with irradiation significantly increased apoptosis compared with the control group. Highly expressed IL-32 has a synergistic effect with irradiation, inhibiting STAT3 and p-STAT3 expression and increasing apoptotic protein Bax expression.

CONCLUSION

IL-32 can improve the radiosensitivity of ESCC cells by inhibiting the STAT3 pathway. Therefore, IL-32 can be used as a new therapeutic target to provide a new attempt for radiotherapy of ESCC.

Role of crosstalk between STAT3 and mTOR signaling in driving sensitivity to chemotherapy in osteosarcoma cell lines

Osteosarcoma (OS) is a malignant bone neoplasm, mostly occurring in pediatric patients. OS is characterized by a highly aggressive and metastatically active tumor. Chemotherapy followed by surgical excision is the treatment of choice but is often associated with both chemoresistance and relapse. Hence, it is important to develop further understanding of OS pathogenesis and identify potential therapeutic targets. Both the signal transducer and activator of transcription 3 (STAT3) and mammalian target of rapamycin (mTOR) have been implicated in OS pathogenesis. Crosstalk between mTOR and STAT3 signaling has been shown to regulate hypoxia-induced angiogenesis in other diseases. In this study, we determined using OS cell lines if there is a crosstalk between these two pathways and how that impacts sensitivity to treatment with Rapamycin. OS cell lines exhibited differential sensitivity to mTOR inhibitor Rapamycin. Evaluation of phosphorylated STAT3 showed that in Rapamycin-sensitive 143B cells, the inhibitor decreased phosphorylation of STAT3 at Y705, but not at S727 whereas, in Rapamycin-resistant U2OS cells, the inhibitor decreased S727 phosphorylation but not Y705. However, knockdown of STAT3 in U2OS cells made them sensitive to Rapamycin. Immunofluorescence (IF) analysis showed that mTOR is constitutively activated in the 143B cells but is suppressed in the U2OS cells, indicating that this might be their reason for being resistant to Rapamycin. Both cell lines were sensitive to treatment with the STAT3 inhibitor Napabucasin (NP). Treatment with NP inhibited STAT3 activation at Y705 and additionally inhibited mTOR activation, indicating crosstalk between STAT3 and mTOR signaling pathways. Rapamycin could effectively prevent lung metastasis in an orthotropic OS mice model using 143B cells. However, Rapamycin could not inhibit lung metastasis in mice injected with U2OS cells. The STAT3 inhibitor NP attenuated lung metastasis with the U2OS cells. Our results thus established yet undefined crosstalk of STAT3 and mTOR signaling pathways in OS and highlight the possibility of using mTOR inhibitors for treatment in patients with OS.

HER2-positive breast cancer that resists therapeutic drugs and ionizing radiation releases sphingomyelin-based molecules to circulating blood serum

Breast cancer is the second most common cancer in the world based on incidence, reaching more than 2 million new cases in 2018, while continuing to increase. Invasive ductal carcinoma is the most common type of this cancer, making up approximately 70-80% of all breast cancer diagnoses. In particular, the type of breast cancer overexpressing human epidermal growth factor receptor 2 (HER2) has potential of strong proliferation, migration and invasion and early treatment is necessary. The authors identified and studied a single patient displaying complete therapeutic resistance to monoclonal anti-HER2 antibody therapy, chemotherapy and radiotherapy. A patient who exhibited resistance to postoperative adjuvant therapy after mastectomy was selected from HER2-positive breast cancer, and this patient had the grade of T_4bN_2aM₀, Stage IIIB. The patient samples, blood serum and cancer tissue, were analyzed by metabolome and immunostaining technique, respectively. The characteristics of peripheral blood serum and solid tumor were investigated, aiming to find new serum biomarker(s) using the metabolomics technique. A correlation between the appearance of HER2-positive cancer tissue and serum concentration of the sphingomyelin family was found. In addition, HER2-positive tumor tissue in both the primary and recurrent cancer express the sphingomyelinase. These results suggest that sphingomyelins from this cancer tissue leads to therapy resistance, induction of invasion and strong proliferation.

STAT3, the Challenge for Chemotherapeutic and Radiotherapeutic Efficacy

Chemoradiotherapy is one of the most effective and extensively used strategies for cancer treatment. Signal transducer and activator of transcription 3 (STAT3) regulates vital biological processes, such as cell proliferation and cell growth. It is constitutively activated in various cancers and limits the application of chemoradiotherapy. Accumulating evidence suggests that STAT3 regulates resistance to chemotherapy and radiotherapy and thereby impairs therapeutic efficacy by mediating its feedback loop and several target genes. The alternative splicing product STAT3β is often identified as a dominant-negative regulator, but it enhances sensitivity to chemotherapy and offers a new and challenging approach to reverse therapeutic resistance. We focus here on exploring the role of STAT3 in resistance to receptor tyrosine kinase (RTK) inhibitors and radiotherapy, outlining the potential of targeting STAT3 to overcome chemo(radio)resistance for improving clinical outcomes, and evaluating the importance of STAT3β as a potential therapeutic approach to overcomes chemo(radio)resistance. In this review, we discuss some new insights into the effect of STAT3 and its subtype STAT3β on chemoradiotherapy sensitivity, and we explore how these insights influence clinical treatment and drug development for cancer.

Diagnosis and Treatment of Bone Metastases in Breast Cancer: Radiotherapy, Local Approach and Systemic Therapy in a Guide for Clinicians

The standard care for metastatic breast cancer (MBC) is systemic therapies with imbrication of focal treatment for symptoms. Recently, thanks to implementation of radiological and metabolic exams and development of new target therapies, oligometastatic and oligoprogressive settings are even more common-paving the way to a paradigm change of focal treatments role. In fact, according to immunophenotype, radiotherapy can be considered with radical intent in these settings of patients. The aim of this literature review is to analyze available clinical data on prognosis of bone metastases from breast cancer and benefits of available treatments for developing a practical guide for clinicians.

Radiation with STAT3 Blockade Triggers Dendritic Cell-T cell Interactions in the Glioma Microenvironment and Therapeutic Efficacy

PURPOSE

Patients with central nervous system (CNS) tumors are typically treated with radiotherapy, but this is not curative and results in the upregulation of phosphorylated STAT3 (p-STAT3), which drives invasion, angiogenesis, and immune suppression. Therefore, we investigated the combined effect of an inhibitor of STAT3 and whole-brain radiotherapy (WBRT) in a murine model of glioma.

EXPERIMENTAL DESIGN

C57BL/6 mice underwent intracerebral implantation of GL261 glioma cells, WBRT, and treatment with WP1066, a blood-brain barrier-penetrant inhibitor of the STAT3 pathway, or the two in combination. The role of the immune system was evaluated using tumor rechallenge strategies, immune-incompetent backgrounds, immunofluorescence, immune phenotyping of tumor-infiltrating immune cells (via flow cytometry), and NanoString gene expression analysis of 770 immune-related genes from immune cells, including those directly isolated from the tumor microenvironment.

RESULTS

The combination of WP1066 and WBRT resulted in long-term survivors and enhanced median survival time relative to monotherapy in the GL261 glioma model (combination vs. control P < 0.0001). Immunologic memory appeared to be induced, because mice were protected during subsequent tumor rechallenge. The therapeutic effect of the combination was completely lost in immune-incompetent animals. NanoString analysis and immunofluorescence revealed immunologic reprograming in the CNS tumor microenvironment specifically affecting dendritic cell antigen presentation and T-cell effector functions.

CONCLUSIONS

This study indicates that the combination of STAT3 inhibition and WBRT enhances the therapeutic effect against gliomas in the CNS by inducing dendritic cell and T-cell interactions in the CNS tumor.

Genetic alterations of epithelial polarity genes are associated with loss of polarity in invasive breast cancer

Breast cancer remains a leading cause of cancer-related death for women. The stepwise development of breast cancer through preinvasive to invasive disease is associated with progressive disruption of cellular and tissue organization. Apical-basal polarity is thought to be a barrier to breast cancer development, but the extent and potential mechanisms that contribute to disrupted polarity are incompletely understood. To investigate the cell polarity status of invasive breast cancers, we performed multiplex imaging of polarity markers on tissue cores from 432 patients from a spectrum of grades, stages and molecular subtypes. Apical-basal cell polarity was lost in 100% of cells in all cases studied, indicating that loss of epithelial polarity may be a universal feature of invasive breast cancer. We then analyzed genomic events from the TCGA dataset for an 18-gene set of core polarity genes. Coamplification of polarity genes with established breast oncogenes was found, which is consistent with functional cooperation within signaling amplicons. Gene-expression levels of several polarity genes were significantly associated with survival, and protein localization of Par6 correlated with higher grade, nodal metastasis and molecular subtype. Finally, multiple hotspot mutations in protein-protein interaction domains critical for cell polarity were identified. Our data indicate that genomic events likely contribute to pervasive disruption of epithelial polarity observed in invasive breast cancer.

Epigenetic inhibition of the tumor suppressor ARHI by light at night-induced circadian melatonin disruption mediates STAT3-driven paclitaxel resistance in breast cancer

Disruption of circadian time structure and suppression of circadian nocturnal melatonin (MLT) production by exposure to dim light at night (dLAN), as occurs with night shift work and/or disturbed sleep-wake cycles, is associated with a significantly increased risk of breast cancer and resistance to tamoxifen and doxorubicin. Melatonin inhibition of human breast cancer chemoresistance involves mechanisms including suppression of tumor metabolism and inhibition of kinases and transcription factors which are often activated in drug-resistant breast cancer. Signal transducer and activator of transcription 3 (STAT3), frequently overexpressed and activated in paclitaxel (PTX)-resistant breast cancer, promotes the expression of DNA methyltransferase one (DNMT1) to epigenetically suppress the transcription of tumor suppressor Aplasia Ras homolog one (ARHI) which can sequester STAT3 in the cytoplasm to block PTX resistance. We demonstrate that breast tumor xenografts in rats exposed to dLAN and circadian MLT disrupted express elevated levels of phosphorylated and acetylated STAT3, increased DNMT1, but reduced sirtuin 1 (SIRT1) and ARHI. Furthermore, MLT and/or SIRT1 administration blocked/reversed interleukin 6 (IL-6)-induced acetylation of STAT3 and its methylation of ARH1 to increase ARH1 mRNA expression in MCF-7 breast cancer cells. Finally, analyses of the I-SPY 1 trial demonstrate that elevated MT₁ receptor expression is significantly correlated with pathologic complete response following neo-adjuvant therapy in breast cancer patients. This is the first study to demonstrate circadian disruption of MLT by dLAN driving intrinsic resistance to PTX via epigenetic mechanisms increasing STAT3 expression and that MLT administration can reestablish sensitivity of breast tumors to PTX and drive tumor regression.

Tumor grade and molecular subtypes on local control in breast cancer radiotherapy: Does fractionation really matter? A retrospective control study group

The aim of this current study was to assess whether the tumour grade and molecular subtypes have influenced local control in the whole breast hypofractionated radiotherapy (HRT) over standard radiotherapy (SRT) in early breast node negative cancer patients by a retrospective control group study.

Data of 215 patients treated with hypofractionated radiotherapy at our institution from 2008 to 2011 were prospectively collected and then compared with 215 pts treated with SRT in a control group study. The local relapse free survival (LRFS) in both arms was compared on the basis of variables defined by tumour grade (Nottingham Grading System), and Molecular subtypes. Kaplan-Meier method was applied to estimate the LRFS in both groups. Chi-squared and univariate Cox proportional hazards model were conducted for all variables in both groups to assess the impact on local control. Statistical significance was assumed at P < .05. Statistical significant variables at univariate analysis were then included in multivariate Cox proportional hazards model. The median follow up duration was 9.5 years (7–13 yrs); the Kaplan Meyer 8 year LRFS did not reach any statistical significant difference between the two groups (P = . 836). At univariate Cox analysis tumour grade 3 was significantly related to local relapse only in the SRT group (P = .041) while, among molecular subtypes, no differences were found for all groups; for Her2 + noL no difference was found (P = .233). Multivariate analysis confirmed Her2 non-luminal subtype as an independent variable for local relapse regardless the fractionation arm (P = .045). Breast cancer subtypes show a different radiosensitivity, which is independent by fractionation.

Key microRNAs in the biology of breast cancer; emerging evidence in the last decade

microRNAs (miRNAs) are a family of small noncoding RNAs that play a pivotal role in the regulation of main biological and physiological processes, including cell cycle regulation, proliferation, differentiation, apoptosis, stem cell maintenance, and organ development. Dysregulation of these tiny molecules has been related to different human diseases, such as cancer. It has been estimated that more than 50% of these noncoding RNA sequences are placed on fragile sites or cancer-associated genomic regions. After the discovery of the first specific miRNA signatures in breast cancer, many studies focused on the involvement of these small RNAs in the pathophysiology of breast tumors and their possible clinical implications as reliable prognostic biomarkers or as a new therapeutic approach. Therefore, the present review will focus on the recent findings on the involvement of miRNAs in the biology of breast cancer associated with their clinical implications.

HER2 in stemness and epithelial-mesenchymal plasticity of breast cancer

Breast cancer had been the first non-hematologic malignancy where sub-types based on molecular characterization had entered clinical practice. HER2 over-expression, due to either gene amplification or protein up-regulation, defines one of these sub-types and is clinically exploited by addition of HER2-targeted treatments to the regimens of treatment. Nevertheless, in many occasions HER2-positive cancers are resistant or become refractory to these therapies. Several mechanisms, such as activation of alternative pathways or loss of expression of the receptor in cancer cells, have been proposed as the cause of these therapeutic failures. Cancer stem cells (CSCs, alternatively called tumor-initiating cells) comprise a small percentage of the tumor cells, but are capable of reconstituting and propagating tumors due to their superior intrinsic capacity for regeneration, survival and resistance to therapies. CSCs possess circuits enabling epigenetic plasticity which endow them with the ability to alternate between epithelial and mesenchymal states. This paper will discuss the expression and regulation of HER2 in CSCs of the different sub-types of breast cancer and relationships of the receptor with both the circuits of stemness and epithelial-mesenchymal plasticity. Therapeutic repercussions of the relationship of HER2-initiated signaling with stemness networks will also be proposed.

Inhibition of STAT3 blocks protein synthesis and tumor metastasis in osteosarcoma cells

BACKGROUND

Osteosarcoma is the most common bone cancer. Despite advances, molecular mechanisms associated with osteosarcoma have not been fully understood. Hence, an effective treatment for osteosarcoma has yet to be developed. Even though signal transducer and activator of transcription3 (STAT3) has been implicated, its role in pathogenesis of osteosarcoma is not fully determined. In this study, we investigated the antitumor effect of napabucasin (NP) (BBI608), an inhibitor of STAT3 on osteosarcoma in vitro and in vivo and studied the underlying molecular mechanism.

METHODS

Cell viability, colony formation, apoptosis, tumor growth and metastasis assays were performed to examine the effect of NP on osteosarcoma in vitro and in vivo. Real-time RT-PCR, western analysis, immunofluorescence and reporter assays were used to monitor the expression and activity of proteins and underlying molecular pathways. Protein synthesis, co-immunoprecipitation and CAP binding assays were carried out to understand NP-mediated mechanism of actions in osteosarcoma cells.

RESULTS

Our results show that NP treatment decreases cell viability and induces apoptosis in several osteosarcoma cell lines. NP treatment suppresses both expression and phosphorylation of STAT3 in addition to blocking STAT3-mediated transcription and downstream target proteins in osteosarcoma cells. Furthermore, NP inhibits protein synthesis through regulation of the eukaryotic initiation factor 4E (eIF4E) and eIF4E-binding protein 1 (4E-BP1). NP also inhibits the progression of osteosarcoma tumors and metastasis in vivo in an orthotopic tibial model of osteosarcoma.

CONCLUSIONS

Taken together, our investigation reveals that NP acts through a novel mechanism and inhibits osteosarcoma growth and metastasis, and could be investigated clinically for treating osteosarcoma patients alone or in combination with other drugs.

Intra-hydrogel culture prevents transformation of mesenchymal stem cells induced by monolayer expansion

In this study, we report that the intra-hydrogel culture system mitigates the transformation of mesenchymal stem cells (MSCs) induced by two-dimensional (2D) expansion. MSCs expanded in monolayer culture prior to encapsulation in collagen hydrogels (group eMSCs-CH) featured impaired stemness in chondrogenesis, comparing with the freshly isolated bone marrow mononuclear cells seeded directly in collagen hydrogels (group fMSCs-CH). The molecular mechanism of the in vitro expansion-triggered damage to MSCs was detected through genome-wide microarray analysis. Results indicated that pathways such as proteoglycans in cancer and pathways in cancer expansion were highly enriched in eMSCs-CH. And multiple up-regulated oncoma-associated genes were verified in eMSCs-CH compared with fMSCs-CH, indicating that expansion in vitro triggered cellular transformation was associated with signaling pathways related to tumorigenicity. Besides, focal adhesion (FA) and mitogen-activated protein kinase (MAPK) signaling pathways were also involved in in vitro expansion, indicating restructuring of the cell architecture. Thus, monolayer expansion in vitro may contribute to vulnerability of MSCs through the regulation of FA and MAPK. This study indicates that intra-hydrogel culture can mitigate the monolayer expansion induced transformation of MSCs and maintain the uniformity of the stem cells, which is a viable in vitro culture system for stem cell therapy.

Potential therapeutic effects of curcumin in gastric cancer

Despite recent advancements in understanding of the biology of gastric cancer, treatment of patients with advanced gastric cancer remains a major problem. Among different type of phytochemicals, curcumin, a welltable -known phytochemical, has been shown to be a promising cancer chemopreventive agent. Pharmacokinetics, safety, and efficacy of curcumin have been evaluated in several clinical trials against numerous diseases, and for the treatment of human cancer. In the present review, we have collected in vitro and in vivo investigations and studied the chemosensitizing and anticancer effects of curcumin against the gastric cancer cells. In summary, curcumin has been found to have efficient chemosensitizing effect and also inhibits viability, proliferation, and migration of gastric cancer cells mainly via cell cycle arrest and induction of apoptosis by both mitochondrial-dependent and -independent pathways.

Astragaloside IV reduces the hypoxia-induced injury in PC-12 cells by inhibiting expression of miR-124

BACKGROUND

Astragalus membranaceus has been clinically used in cerebral ischemia treatment in China and its main component, Astragaloside IV (Ast IV) shows anti-hypoxia activity, but the underlying mechanism has not been clearly clarified. This study was aimed to investigate the effects of Ast IV on hypoxia-induced injury in PC-12 cells as well as the underlying mechanism.

METHODS

Relative miR-124 expression was detected by qRT-PCR. Hic-5 expression was analyzed by qRT-PCR and Western blot. To alter miR-124 and Hic-5 expressions, cells were respectively transfected with miR-124 mimic and pEX-Hic-5. Cell proliferation and apoptosis were measured by BrdU assay and Annexin V-fluorescein isothiocynate (FITC)/propidium iodide (PI) double staining method, respectively. Besides, apoptotic proteins and cell proliferation-associated factors were analyzed by Western blot.

RESULTS

Ast IV alleviated hypoxia-induced injury in PC-12 cells by decreasing apoptosis (P <  0.01). Ast IV inhibited up-regulation of miR-124 induced by hypoxia (P <  0.01). miR-124 mimic impaired the anti-apoptotic effect of Ast IV on PC-12 cells (P <  0.01). Hic-5 expression was significantly down-regulated in miR-124 overexpressed cells (P <  0.001) and Hic-5 overexpression activated Sp1/Survivin signaling pathway (P <  0.001).

CONCLUSION

Ast IV could ameliorate hypoxia-induced injury in PC-12 cells by decreasing miR-124 expression and then up-regulating Hic-5 expression.

Activation of STAT3 and Bcl-2 and reduction of reactive oxygen species (ROS) promote radioresistance in breast cancer and overcome of radioresistance with niclosamide

Radiotherapy significantly improves the therapeutic outcomes and survival of breast cancer patients. However, the acquired resistance to this therapeutic modality is a major clinical challenge. Here we show that ionizing irradiation (IR)-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) at the Tyr705 residue and the induction of reactive oxygen species (ROS) in wild-type and radioresistant MDA-MB-231 and MDA-MB-468 triple-negative breast cancer (TNBC) cell lines. Comparing with radiosensitive parental TNBC cells, significantly low levels of ROS and higher protein levels of phospho-STAT3 and Bcl-2 were observed in TNBC cells with acquired radioresistance. Moreover, knockdown of STAT3 by shRNA sensitized the TNBC cells to IR. Niclosamide, a potent inhibitor of STAT3, overcame the radioresistance in TNBC cells via inhibition of STAT3 and Bcl-2 and induction of ROS. In combination with radiation, niclosamide treatment resulted in significant increase of ROS generation and induction of apoptosis in parental and radioresistant TNBC cells in vitro and TNBC xenograft tumors in vivo. These findings demonstrate that activation of STAT3 and Bcl-2 and reduction of ROS contribute to the development of radioresistance in TNBC, and niclosamide acts as a potent radiosensitizer via inhibiting STAT3 and Bcl-2 and increasing ROS generation in TNBC cells and xenograft tumors. Our findings suggest that niclosamide in combination with irradiation may offer an effective alternative approach for restoring the sensitivity of radioresistant TNBC cells to IR for improved therapeutic efficacy and outcomes.

Oct4 suppresses IR‑induced premature senescence in breast cancer cells through STAT3- and NF‑κB-mediated IL‑24 production

Breast cancer stem cells (BCSCs) are a small subpopulation of breast cancer cells that have been proposed to be a primary cause of failure of therapies, including ionizing radiation (IR). Their embryonic stem-like signature is associated with poor clinical outcome. In the present study, the function of octamer-binding transcription factor 4 (Oct4), an embryonic stem cell factor, in the resistance of BCSCs to IR was investigated. Mammosphere cells exhibited increased expression of stemness-associated genes, including Oct4 and sex-determining region Y-box 2 (Sox2), and were more resistant to IR compared with serum-cultured monolayer cells. IR-resistant MCF7 cells also exhibited significantly increased expression of Oct4. To investigate the possible involvement of Oct4 in IR resistance of breast cancer cells, cells were transfected with Oct4. Ectopic expression of Oct4 increased the clonogenic survival of MCF7 cells following IR, which was reversed by treatment with small interfering RNA (siRNA) targeting Oct4. Oct4 expression decreased phosphorylated histone H2AX (γ-H2AX) focus formation and suppressed IR-induced premature senescence in these cells. Mammosphere, IR-resistant and Oct4-overexpressing MCF7 cells exhibited enhanced phosphorylation of signal transducer and activation of transcription 3 (STAT3) (Tyr⁷⁰⁵) and inhibitor of nuclear factor κB (NF-κB), and blockade of these pathways with siRNA against STAT3 and/or specific inhibitors of STAT3 and NF-κB significantly increased IR-induced senescence. Secretome analysis revealed that Oct4 upregulated interleukin 24 (IL-24) expression through STAT3 and NF-κB signaling, and siRNA against IL-24 increased IR-induced senescence, whereas recombinant human IL-24 suppressed it. The results of the present study indicated that Oct4 confers IR resistance on breast cancer cells by suppressing IR-induced premature senescence through STAT3- and NF-κB-mediated IL-24 production.

Increased levels of LAPTM4B, VEGF and survivin are correlated with tumor progression and poor prognosis in breast cancer patients

Objective

This study explored the relationships among the expression of LAPTM4B, VEGF, and survivin and clinicopathological characteristics and prognosis in breast cancer patients.

Methods

The expression of these three molecules in 110 stage I-III breast cancer patients with clinicopathological and follow-up data was detected via immunohistochemistry. Kaplan-Meier and Cox proportional hazard regression analyses were performed to assess the prognostic significance of these markers in breast cancer. Moreover, expression levels of these markers were evaluated in 5 breast cell lines via Western blot analysis.

Results

LAPTM4B, VEGF, and survivin were over-expressed in breast cancer specimens and highly expressed in MDA-MB-231 cells. VEGF and nuclear survivin expression was significantly correlated with LAPTM4B expression, and high levels of all three were associated with a tumor size >2cm, TNM stage II+III and lymph node metastasis, which had worse impacts on overall survival and progression-free survival in breast cancer patients. A multivariate Cox analysis identified LAPTM4B over-expression as an independent prognostic marker in breast cancer.

Conclusions

These findings suggest that LAPTM4B, VEGF, and nuclear survivin expression are significantly correlated in breast cancer, which may be predictive of prognosis as well as effective therapeutic targets for new anticancer therapies.

Epigenetic mechanism of survivin dysregulation in human cancer

Survivin (coding gene BIRC5) is a dual functional protein acting as a critical inhibitor of apoptosis (IAP) and key regulator of cell cycle progression. It is usually produced in embryonic tissues during development and undetectable in most adult tissues. Overexpression of Survivin frequently occurs in various human cancers and increased Survivin correlates with poor clinic outcome, tumor recurrence, and therapeutic resistance. Because of its selective expression in tumor, but not normal tissues, Survivin has been recognized as an attractive target for cancer treatment. Although several therapeutic approaches targeting Survivin are actively under clinical trials in human cancers, to date no Survivin-targeted therapy has been approved for cancer treatment. Numerous studies have devoted to uncovering the underlying mechanism resulting in Survivin dysregulation at multiple levels, such as transcriptional and post-transcriptional regulation. The current article provides a literature review on the transcriptional and epigenetic regulation of Survivin expression in human cancers. We focus on the impact of DNA methylation and histone modifications, including specific lysine methylation, demethylation, and acetylation on the expression of Survivin. The latest development of epigenetic approaches targeting Survivin for cancer treatment are also discussed.

Breast cancer stem cells in HER2-negative breast cancer cells contribute to HER2-mediated radioresistance and molecular subtype conversion: clinical implications for serum HER2 in recurrent HER2-negative breast cancer

Although it has been proposed that the beneficial effect of HER2-targeted therapy in HER2-negative breast cancer is associated with the molecular subtype conversion, the underlying mechanism and the clinical biomarkers are unclear. Our study showed that breast cancer stem cells (BCSCs) mediated HER2 subtype conversion and radioresistance in HER2-negative breast cancer cells and evaluated serum HER2 as a clinical biomarker for HER2 subtype conversion. We found that the CD44⁺/CD24^–/low BCSCs from HER2-negative breast cancer MCF7 cells overexpressed HER2 and EGFR and showed the radioresistant phenotype. In addition, we showed that trastuzumab treatment sensitized the radioresistant phenotype of the CD44⁺/CD24^–/low cells with decreased levels of HER2 and EGFR, which suggested that HER2-targeted therapy in HER2-negative breast cancer could be useful for targeting BCSCs that overexpress HER2/EGFR. Importantly, our clinical data showed that serial serum HER2 measurement synchronously reflected the disease relapse and the change in tumor burden in some patients who were initially diagnosed as HER2-negative breast cancer, which indicated that serum HER2 could be a clinical biomarker for the evaluation of HER2 subtype conversion in patients with recurrent HER2-negative breast cancer. Therefore, our data have provided in vitro and in vivo evidence for the molecular subtype conversion of HER2-negative breast cancer.

HDAC2 and HDAC5 Up-Regulations Modulate Survivin and miR-125a-5p Expressions and Promote Hormone Therapy Resistance in Estrogen Receptor Positive Breast Cancer Cells

Intrinsic or acquired resistance to hormone therapy is frequently reported in estrogen receptor positive (ER⁺) breast cancer patients. Even though dysregulations of histone deacetylases (HDACs) are known to promote cancer cells survival, the role of different HDACs in the induction of hormone therapy resistance in ER⁺ breast cancer remains unclear. Survivin is a well-known pro-tumor survival molecule and miR-125a-5p is a recently discovered tumor suppressor. In this study, we found that ER⁺, hormone-independent, tamoxifen-resistant MCF7-TamC3 cells exhibit increased expression of HDAC2, HDAC5, and survivin, but show decreased expression of miR-125a-5p, as compared to the parental tamoxifen-sensitive MCF7 breast cancer cells. Molecular down-regulations of HDAC2, HDAC5, and survivin, and ectopic over-expression of miR-125a-5p, increased the sensitivity of MCF7-TamC3 cells to estrogen deprivation and restored the sensitivity to tamoxifen. The same treatments also further increased the sensitivity to estrogen-deprivation in the ER⁺ hormone-dependent ZR-75-1 breast cancer cells in vitro. Kaplan-Meier analysis and receiver operating characteristic curve analysis of expression cohorts of breast tumor showed that high HDAC2 and survivin, and low miR-125a-5p, expression levels correlate with poor relapse-free survival in endocrine therapy and tamoxifen-treated ER⁺ breast cancer patients. Further molecular analysis revealed that HDAC2 and HDAC5 positively modulates the expression of survivin, and negatively regulates the expression miR-125a-5p, in ER⁺ MCF7, MCF7-TamC3, and ZR-75-1 breast cancer cells. These findings indicate that dysregulations of HDAC2 and HDAC5 promote the development of hormone independency and tamoxifen resistance in ERC breast cancer cells in part through expression regulation of survivin and miR-125a-5p.

Cystathionine- γ-lyase promotes process of breast cancer in association with STAT3 signaling pathway

Here we provide evidences to link cystathionine-γ-lyase (CSE) to the development of breast cancer. CSE expression is up-regulated in both breast cancers and breast cancer cell lines and results in proliferation and migration of breast cancer cells. CSE Function in breast cancer depends on the STAT3 signaling pathway, a regulator of critical cell functions including cell growth in a wide variety of human cancer cells via activating the expression of relative genes. STAT3 positively relates to CSE expression. It activates the CSE promoter via a direct binding to the promoter. Moreover, CSE could reversely regulate STAT3 expression and consequently enhance the effect of STAT3 on CSE. Taken together, these data demonstrate for the first time the roles of CSE in breast cancer leading to breast cancer development in association with STAT3 signaling pathway.

MicroRNA-124 enhances response to radiotherapy in human epidermal growth factor receptor 2-positive breast cancer cells by targeting signal transducer and activator of transcription 3

Aim

To determine whether microRNA (miR)-124 enhances the response to radiotherapy in human epidermal growth factor receptor 2 (HER2)-positive breast cancer cells by targeting signal transducer and activator of transcription 3 (Stat3).

Methods

miR-29b expression was measured in 80 pairs of breast tumor samples and adjacent normal tissues collected between January 2013 and July 2014. Activity changes of 50 canonical signaling pathways upon miR-124 overexpression were determined using Cignal Signal Transduction Reporter Array. Target gene of miR-124 was determined using Targetscan and validated by Western blotting and dual-luciferase assay. Cell death rate was assessed by propidium iodide (PI)/ Annexin V staining followed by flow cytometry analysis. Stat3 and miR-124 expression was further measured in 10 relapsed (non-responder) and 10 recurrence-free HER2-positive breast cancer patients.

Results

MiR-124 expression was down-regulated in HER2 positive breast cancers compared with normal tissues, and was negatively associated with tumor size. MiR-124 overexpression in HER2 positive breast cancer cell line SKBR3 significantly reduced the activity of Stat3 signaling pathway compared with control transfection (P < 0.001). Bioinformatic prediction and function assay suggested that miR-124 directly targeted Stat3, which is a key regulator of HER2 expression. MiR-124 overexpression down-regulated Stat3 and potently enhanced cell death upon irradiation. Consistently, chemical inhibitor of Stat3 also sensitized HER2-positive breast cancer cells to irradiation. Moreover, increased Stat3 expression and reduced miR-124 expression were associated with a poor response to radiotherapy in HER2-positive breast cancers.

Conclusions

Weak miR-124 expression might enhance Stat3 expression and radiotherapy resistance in HER2-positive breast cancer cells.