Neuroglobin overexpression induced by the 17β-Estradiol-Estrogen receptor-α Pathway reduces the sensitivity of MCF-7 Breast cancer cell to paclitaxel

Neuroglobin plays as tumor suppressor by disrupting the stability of GPR35 in colorectal cancer

BACKGROUND

The incidence of colorectal cancer (CRC) has increased in recent years. Identification of accurate tumor markers has become the focus of CRC research. Early and frequent DNA methylation tends to occur in cancer. Thus, identifying accurate methylation biomarkers would improve the efficacy of CRC treatment. Neuroglobin (NGB) is involved in neurological and oncological diseases. However, there are currently no reports on epigenetic regulation involvement of NGB in CRC.

RESULTS

NGB was downregulated or silenced in majority CRC tissues and cell lines. The hypermethylation of NGB was detected in tumor tissue, but no or a very low methylation frequency in normal tissues. Overexpression of NGB induced G2/M phase arrest and apoptosis, suppressed proliferation, migration, invasion in vitro, and inhibited CRC tumor growth and angiogenesis in vivo. Isobaric tag for relative and absolute quantitation (Itraq)-based proteomics identified approximately 40% proteins related to cell-cell adhesion, invasion, and tumor vessel formation in the tumor microenvironment, among which GPR35 was proved critical for NGB-regulated tumor angiogenesis suppression in CRC.

CONCLUSIONS

NGB, an epigenetically silenced factor, inhibits metastasis through the GPR35 in CRC. It is expected to grow into a potential cancer risk assessment factor and a valuable biomarker for early diagnosis and prognosis assessment of CRC.

Resveratrol Analogs and Prodrugs Differently Affect the Survival of Breast Cancer Cells Impairing Estrogen/Estrogen Receptor α/Neuroglobin Pathway

Breast cancer is the first leading tumor in women in terms of incidence worldwide. Seventy percent of cases are estrogen receptor (ER) α-positive. In these malignancies, 17β-estradiol (E2) via ERα increases the levels of neuroglobin (NGB), a compensatory protein that protects cancer cells from stress-induced apoptosis, including chemotherapeutic drug treatment. Our previous data indicate that resveratrol (RSV), a plant-derived polyphenol, prevents E2/ERα-induced NGB accumulation in this cellular context, making E2-dependent breast cancer cells more prone to apoptosis. Unfortunately, RSV is readily metabolized, thus preventing its effectiveness. Here, four different RSV analogs have been developed, and their effect on the ERα/NGB pathway has been compared with RSV conjugated with highly hydrophilic gold nanoparticles as prodrug to evaluate if RSV derivatives maintain the breast cancer cells' susceptibility to the chemotherapeutic drug paclitaxel as the original compound. Results demonstrate that RSV conjugation with gold nanoparticles increases RSV efficacy, with respect to RSV analogues, reducing NGB levels and enhancing the pro-apoptotic action of paclitaxel, even preventing the anti-apoptotic action exerted by E2 treatment on these cells. Overall, RSV conjugation with gold nanoparticles makes this complex a promising agent for medical application in breast cancer treatment.

Neuroglobin: A New Possible Marker of Estrogen-Responsive Breast Cancer

The expression of the α-subtype of Estrogen Receptor (ERα) characterizes most breast cancers (more than 75%), for which endocrine therapy is the mainstay for their treatment. However, a high percentage of ERα+ breast cancers are de novo or acquired resistance to endocrine therapy, and the definition of new targets for improving therapeutic interventions and the prediction of treatment response is demanding. Our previous data identified the ERα/AKT/neuroglobin (NGB) pathway as a common pro-survival process activated in different ERα breast cancer cell lines. However, no in vivo association between the globin and the malignity of breast cancer has yet been done. Here, we evaluated the levels and localization of NGB in ERα+ breast ductal carcinoma tissue of different grades derived from pre-and post-menopausal patients. The results indicate a strong association between NGB accumulation, ERα, AKT activation, and the G3 grade, while no association with the menopausal state has been evidenced. Analyses of the data set (e.g., GOBO) strengthen the idea that NGB accumulation could be linked to tumor cell aggressiveness (high grade) and resistance to treatment. These data support the view that NGB accumulation, mainly related to ER expression and tumor grade, represents a compensatory process, which allows cancer cells to survive in an unfavorable environment.

Proteomic and Bioinformatic Investigation of Altered Pathways in Neuroglobin-Deficient Breast Cancer Cells

Neuroglobin (NGB) is a myoglobin-like monomeric globin that is involved in several processes, displaying a pivotal redox-dependent protective role in neuronal and extra-neuronal cells. NGB remarkably exerts its function upon upregulation by NGB inducers, such as 17β-estradiol (E2) and H₂O₂. However, the molecular bases of NGB’s functions remain undefined, mainly in non-neuronal cancer cells. Human MCF-7 breast cancer cells with a knocked-out (KO) NGB gene obtained using CRISPR/Cas9 technology were analyzed using shotgun label-free quantitative proteomics in comparison with control cells. The differential proteomics experiments were also performed after treatment with E2, H₂O₂, and E2 + H₂O₂. All the runs acquired using liquid chromatography–tandem mass spectrometry were elaborated within the same MaxQuant analysis, leading to the quantification of 1872 proteins in the global proteomic dataset. Then, a differentially regulated protein dataset was obtained for each specific treatment. After the proteomic study, multiple bioinformatics analyses were performed to highlight unbalanced pathways and processes. Here, we report the proteomic and bioinformatic investigations concerning the effects on cellular processes of NGB deficiency and cell treatments. Globally, the main processes that were affected were related to the response to stress, cytoskeleton dynamics, apoptosis, and mitochondria-driven pathways.

Extracellular Neuroglobin as a Stress-Induced Factor Activating Pre-Adaptation Mechanisms against Oxidative Stress and Chemotherapy-Induced Cell Death in Breast Cancer

Components of tumor microenvironment, including tumor and/or stromal cells-derived factors, exert a critical role in breast cancer (BC) progression. Here we evaluated the possible role of neuroglobin (NGB), a monomeric globin that acts as a compensatory protein against oxidative and apoptotic processes, as part of BC microenvironment. The extracellular NGB levels were evaluated by immunofluorescence of BC tissue sections and by Western blot of the culture media of BC cell lines. Moreover, reactive oxygen species (ROS) generation, cell apoptosis, and cell migration were evaluated in different BC cells and non-tumorigenic epithelial mammary cells treated with BC cells (i.e., Michigan Cancer Foundation-7, MCF-7) conditioned culture media and extracellular NGB. Results demonstrate that NGB is a component of BC microenvironment. NGB is released in tumor microenvironment by BC cells only under oxidative stress conditions where it can act as autocrine/paracrine factor able to communicate cell resilience against oxidative stress and chemotherapeutic treatment.

The Network of Angiotensin Receptors in Breast Cancer

The renin-angiotensin system (RAS) is a network of proteins regulating many aspects of human physiology, including cardiovascular, pulmonary, and immune system physiology. The RAS is a complicated network of G-protein coupled receptors (GPCRs) (i.e., AT1R, AT2R, MASR, and MRGD) orchestrating the effects of several hormones (i.e., angiotensin II, angiotensin (1-7), and alamandine) produced by protease-based transmembrane receptors (ACE1 and ACE2). Two signaling axes have been identified in the RAS endocrine system that mediate the proliferative actions of angiotensin II (i.e., the AT1R-based pathway) or the anti-proliferative effects of RAS hormones (i.e., the AT2R-, MAS-, and MRGD-based pathways). Disruption of the balance between these two axes can cause different diseases (e.g., cardiovascular pathologies and the severe acute respiratory syndrome coronavirus 2- (SARS-CoV-2)-based COVID-19 disease). It is now accepted that all the components of the RAS endocrine system are expressed in cancer, including cancer of the breast. Breast cancer (BC) is a multifactorial pathology for which there is a continuous need to identify novel drugs. Here, I reviewed the possible roles of both axes of the RAS endocrine network as potential druggable pathways in BC. Remarkably, the analysis of the current knowledge of the different GPCRs of the RAS molecular system not only confirms that AT1R could be considered a drug target and that its inhibition by losartan and candesartan could be useful in the treatment of BC, but also identifies Mas-related GPCR member D (MRGD) as a druggable protein. Overall, the RAS of GPCRs offers multifaceted opportunities for the development of additional compounds for the treatment of BC.

Divergent Effects of Daidzein and its Metabolites on Estrogen-Induced Survival of Breast Cancer Cells

Although soy consumption is associated with breast cancer prevention, the low bioavailability and the extensive metabolism of soy-active components limit their clinical application. Here, the impact of daidzein (D) and its metabolites on estrogen-dependent anti-apoptotic pathway has been evaluated in breast cancer cells. In estrogen receptor α-positive breast cancer cells treated with D and its metabolites, single or in mixture, ERα activation and Neuroglobin (NGB) levels, an anti-apoptotic estrogen/ERα-inducible protein, were evaluated. Moreover, the apoptotic cascade activation, as well as the cell number after stimulation was assessed in the absence/presence of paclitaxel to determine the compound effects on cell susceptibility to a chemotherapeutic agent. Among the metabolites, only D-4'-sulfate maintains the anti-estrogenic effect of D, reducing the NGB levels and rendering breast cancer cells more prone to the paclitaxel treatment, whereas other metabolites showed estrogen mimetic effects, or even estrogen independent effects. Intriguingly, the co-stimulation of D and gut metabolites strongly reduced D effects. The results highlight the important and complex influence of metabolic transformation on isoflavones physiological effects and demonstrate the need to take biotransformation into account when assessing the potential health benefits of consumption of soy isoflavones in cancer.

Strategies to degrade estrogen receptor α in primary and ESR1 mutant-expressing metastatic breast cancer

With the advent of omic technologies, our understanding of the molecular mechanisms underlying estrogen receptor α (ERα)-expressing breast cancer (BC) progression has grown exponentially. Nevertheless, the most widely used therapy for inhibiting this disease is endocrine therapy (ET) (i.e., aromatase inhibitors, tamoxifen - Tam, faslodex/fulvestrant - FUL). However, in a considerable number of cases, prolonged patient treatment with ET generates the development of resistant tumor cells and, consequently, tumor relapse, which manifests as metastatic disease that is extremely difficult to manage, especially because such metastatic BCs (MBCs) often express ERα mutations (e.g., Y537S, D538G) that confer pronounced growth advantages to tumor cells. Interestingly, ET continues to be the therapy of choice for this neoplasia, which underscores the need to identify novel drugs that could work in primary and MBCs. In this study, we review the approaches that have been undertaken to discover these new anti-ERα compounds, especially considering those focused on evaluating ERα degradation. A literature analysis demonstrated that current strategies for discovering new anti-BC drugs are focusing on the identification either of novel ERα inhibitors, of compounds that inhibit ERα-related pathways or of drugs that influence ERα-unrelated cellular pathways. Several lines of evidence suggest that all of these molecules alter the ERα content and block the proliferation of both primary and MBCs. In turn, we propose to rationalize all these discoveries into the definition of e.m.eral.d.s (i.e., selective modulators of ERα levels and degradation) as a novel supercategory of anti-ERα drugs that function both as modulators of ERα levels and inhibitors of BC cell proliferation.

Potentiation of paclitaxel effect by resveratrol in human breast cancer cells by counteracting the 17β-estradiol/estrogen receptor α/neuroglobin pathway

Neuroglobin (NGB), an antiapoptotic protein upregulated by 17β-estradiol (E2), is part of E2/estrogen receptor α (ERα) pathway pointed to preserve cancer cell survival in presence of microenvironmental stressors including chemotherapeutic drugs. Here, the possibility that resveratrol (Res), an anticancer plant polyphenol, could increase the susceptibility of breast cancer cells to paclitaxel (Pacl) by affecting E2/ERα/NGB pathway has been evaluated. In MCF-7 and T47D (ERα-positive), but not in MDA-MB 231 (ERα-negative) nor in SK-N-BE (ERα and ERβ positive), Res decreases NGB levels interfering with E2/ERα-induced NGB upregulation and with E2-induced ERα and protein kinase B phosphorylation. Although Res treatment does not reduce cell viability by itself, this compound potentiates Pacl proapoptotic effects. Notably, the increase of NGB levels by NGB expression vector transfection prevents Pacl or Res/Pacl effects. Taken together, these findings indicate a new Res-based mechanism that acts on tumor cells impairing the E2/ERα/NGB signaling pathways and increasing cancer cell susceptibility to chemotherapeutic agent.

Beyond the Antioxidant Activity of Dietary Polyphenols in Cancer: the Modulation of Estrogen Receptors (ERs) Signaling

The potential "health benefits" of dietary polyphenols have been ascribed to their direct antioxidant activity and their impact on the regulation of cell and tissue redox balance. However, because of the relative poor bioavailability of many of these compounds, their effects could not be easily explained by the antioxidant action, which may occur only at high circulating and tissue concentrations. Therefore, many efforts have been put forward to clarify the molecular mechanisms underlining the biological effect of polyphenols in physiological and pathological conditions. Polyphenols' bioavailability, metabolism, and their effects on enzyme, membrane, and/or nuclear receptors and intracellular transduction mechanisms may define the overall impact of these compounds on cancer risk and progression, which is still debated and not yet clarified. Polyphenols are able to bind to estrogen receptor α (ERα) and β (ERβ), and therefore induce biological effects in human cells through mimicking or inhibiting the action of endogenous estrogens, even at low concentrations. In this work, the role and effects of food-contained polyphenols in hormone-related cancers will be reviewed, mainly focusing on the different polyphenols' mechanisms of action with particular attention on their estrogen receptor-based effects, and on the consequences of such processes on tumor progression and development.

Nogo-B receptor increases the resistance of estrogen receptor positive breast cancer to paclitaxel

Intrinsic or acquired chemoresistance is a hurdle in oncology. Only 7%-16% of estrogen receptor α (ERα) positive breast cancer cases achieve a pathological complete response (pCR) after neo-adjuvant chemotherapy. Nogo-B receptor (NgBR) is a cell surface receptor that binds farnesylated Ras and promotes Ras translocation to the plasma membrane. Here, we demonstrate NgBR as a potential therapeutic target for ERα positive breast cancer patients to attenuate paclitaxel resistance. NgBR knockdown enhanced paclitaxel-induced cell apoptosis by modulating expression of p53 and survivin in ERα positive breast cancer cells via NgBR-mediated PI3K/Akt and MAPK/ERK signaling pathways. NgBR knockdown attenuated either 17β-estradiol or epidermal growth factor stimulated phosphorylation of ERα at Serine 118 residue. The ChIP-PCR assay further demonstrated that NgBR knockdown decreased ERα binding to the estrogen response element (ERE) of the ERα target gene and increased the binding of p53 to the promoter region of survivin to attenuate survivin transcription. In summary, our data suggest that NgBR expression is essential to promoting ERα positive breast cancer cell resistance to paclitaxel. Findings from this study implicate a novel therapeutic target for treating ERα positive breast cancer in neo-adjuvant/adjuvant chemotherapy.

Dissecting the 17β-estradiol pathways necessary for neuroglobin anti-apoptotic activity in breast cancer

Neuroglobin (NGB) is a relatively recent discovered monomeric heme-protein, which behave in neurons as a sensor of injuring stimuli including oxidative stress, hypoxia, and neurotoxicity. In addition, the anti-apoptotic activity of overexpressed NGB has been reported both in neurons and in cancer cell lines. We recently demonstrated that, NGB functions as a compensatory protein of the steroid hormone 17β-estradiol (E2) protecting cancer cells against the apoptotic death induced by oxidative stress. However, the E2-induced signaling pathways at the root of NGB over-expression and mitochondrial re-localization in breast cancer cells is still elusive. By using a kinase screening library, here, we report that: i) There is a strong positive correlation between NGB and ERα expression and activity in breast cancer cells; ii) The E2-activated phosphatidyl-inositol 3 kinase (PI3K)/protein kinase B (AKT) and protein kinase C (PKC) pathways are necessary to modulate the NGB protein levels; iii) The E2-induced persistent activation of AKT drive NGB to mitochondria; iv) Reactive oxygen species (ROS)-inducing compounds activating rapidly and transiently AKT does not affect the NGB mitochondrial level; and v) High level of NGB into mitochondria are necessary for the pro-survival and anti-apoptotic effect of this globin in cancer cells. As a whole, these results underline the E2 triggered pathways in E2-responsive breast cancer cells that involve NGB as a compensatory protein devoted to cancer cell survival.

Compensatory role of Neuroglobin in nervous and non-nervous cancer cells in response to the nutrient deprivation

Environmental factors or adverse growth conditions that may reduce cell function or viability are considered stress. The cell ability to sense and respond to environmental stresses determine its function and survival destiny. We recently defined Neuroglobin (NGB), a heme-protein, as a compensatory protein in the 17β-Estradiol (E2) anti-apoptotic activity and as a sensor of oxidative stress in both neurons and breast cancer cells. Here, the possibility that NGB levels could represent a pivotal regulator of integrated response of cancer cells to stress has been evaluated. Data obtained in neuroblastoma and in breast cancer cell lines evidence that nutrient deprivation significantly up-regulated NGB levels at different time points. However, the analysis of autophagy activation led to exclude any possible role of stress- or E2-induced NGB in the upstream regulation of general autophagy. However, the over-expression of Flag-NGB in ERα stable transfected HEK-293 cells completely affects nutrient deprivation-induced decrease in cell number. In addition, reported results indicate that modulation of the anti-apoptotic Bcl-2 level may play a key role in the protective NGB function against energetic stress. Overall, these data define a role of NGB as compensatory protein in the cell machinery activated in response to stress and as general stress adaptation marker of cancer cells susceptible to oxidative stress, oxygen and, as demonstrated here for the first time, even to nutrient willingness. Despite the lacking of any direct NGB role on autophagic flux activated by energetic stress, NGB upregulation appears functional in delaying stress-related cell death allowing an appropriate cell response and adaptation to the changing extracellular conditions.

Xenoestrogen regulation of ERα/ERβ balance in hormone-associated cancers

The hormone 17β-estradiol (E2) contributes to body homeostasis maintenance by regulating many different physiological functions in both male and female organs. E2 actions in reproductive and non-reproductive tissues rely on a complex net of nuclear and extra-nuclear signal transduction pathways triggered by at least two estrogen receptor subtypes (ERα and ERβ). Consequently, the de-regulation of E2:ER signaling contributes to the pathogenesis of many diseases including cancer. Among other factors, the ERα/ERβ ratio is considered one of the pivotal mechanisms at the root of E2 action in cancer progression. Remarkably, several natural or synthetic exogenous chemicals, collectively called xenoestrogens, bind to ERs and interfere with their signals and intracellular functions. In this review, the molecular mechanism(s) through which xenoestrogens influence ERα and ERβ intracellular concentrations and the consequences of this influence on E2-related cancer will be discussed.

A high throughput method to study the physiology of E2:ERα signaling in breast cancer cells

17β-estradiol (E2) regulates diverse physiological effects including cell proliferation through the estrogen receptor α (ERα), which as a transcription factor drives gene transcription and as an extra-nuclear localized receptor triggers the membrane-dependent activation of diverse kinase cascades. E2 also modifies ERα intracellular levels via diverse intracellular mechanisms. In this way, the E2-acivated ERα integrates signaling cascades with the modulation of receptor intracellular concentration and with the induction of DNA synthesis and ultimately drives cell proliferation. In turn, E2 signaling deregulation can cause many diseases including breast cancer (BC). Recently, we performed a Western blotting (WB)-based screen to identify novel pathways affecting ERα intracellular levels and BC cell proliferation. However, because WB lacks high throughput potential, a high-content method to detect all aspects of E2:ERα signaling (nuclear and extra-nuclear receptor activity, ERα levels, E2-induced DNA synthesis) is desirable. Here, we set up a rapid way to measure E2:ERα signaling in 96-well plate format. To demonstrate its robustness, we also challenged 4OH-tamoxifen resistant (Tam-Res) BC cells with a library of anti-cancer drugs and identified methotrexate (MTX) as a molecule inducing ERα degradation and preventing BC cell proliferation. Overall, our research provides a high-content technique to study the physiology of E2:ERα signaling in cells and further suggests a possible anti-ERα and anti-proliferative use for MTX in Tam-Res BCs.

Neuroglobin promotes the proliferation and suppresses the apoptosis of glioma cells by activating the PI3K/AKT pathway

Our previous study demonstrated that neuroglobin (Ngb) functions as an independent predictive indicator of the prognosis of patients with glioma and promotes cancer cell growth by suppressing apoptosis. However, the understanding of the mechanisms underlying the survival‑enhancing function of Ngb in glioma is limited. In the present study, KEGG PathwayFinder by gene correlation analysis was performed on the R2: Genomics Analysis and Visualization Platform, which revealed a high association between Ngb and the phosphatidylinositol 3‑kinase (PI3K)/AKT pathway using glioma data (GSE4290) from the Gene Expression Omnibus database. Furthermore, western blotting experiments were performed in U251 and U87 glioma cells, and Ngb knockdown using short hairpin RNA reduced the protein levels of phosphorylated (p)‑AKT, p‑mammalian target of rapamycin (mTOR) and antiapoptotic factor Bcl‑2, and increased the expression of the proapoptotic protein Bcl‑2‑associated X, in U251 cells. In addition, Ngb overexpression promoted the activation of the PI3K/AKT pathway in U87 cells. MK2206, a PI3K/AKT signaling inhibitor, reduced the expression of p‑AKT and increased the levels of apoptosis‑associated proteins, including cleaved poly(ADP‑ribose) polymerase 1 and cleaved caspase‑3/7/8, in Ngb‑overexpressing U87 cells. Furthermore, MK2206 treatment reduced the proliferation and induced the apoptosis of Ngb‑overexpressing U87 cells, as indicated by the results of MTT, colony formation and flow cytometry assays. In addition, insulin‑like growth factor‑1, a PI3K/AKT signaling activator, reversed Ngb knockdown‑induced growth arrest and apoptosis in U251 cells. In conclusion, the results of the present study indicate that Ngb may facilitate a malignant phenotype of glioma cells by activating the PI3K/AKT pathway.

Neuroglobin functions as a prognostic marker and promotes the tumor growth of glioma via suppressing apoptosis

Neuroglobin (Ngb) has been reported to be upregulated by hypoxia and plays an anti-apoptotic function. Previous studies have reported that Ngb is expressed in human glioblastoma cells and up-regulated in hypoxic microregions of glioblastoma tumor xenografts. While, the clinical significance of Ngb and its function in human glioma keep unknown. Ngb expression was analyzed in 86 glioma tissues and 20 normal brain tissues. Results showed that Ngb was significantly overexpressed in glioma tissues compared to normal brain tissues. In addition, increased levels of Ngb also observed in glioma cell lines. Clinicopathological analysis verified that the positive expression of Ngb was associated with histological type and world health organization (WHO) grade of glioma. Moreover, Kaplan-Meier analysis found that Ngb overexpression led to a shorter survival. Multivariate Cox regression analysis demonstrated that Ngb expression was an independent prognostic marker. Further experiments illustrated that Ngb knockdown significantly inhibited proliferation and facilitated apoptosis in U251 cells. In vivo experiments further confirmed that Ngb silencing notably prohibited the tumor growth of glioma in nude mice. While, Ngb overexpression prominently promoted proliferation and suppressed apoptosis in U87 cells. Taken together, this work support the first evidence that Ngb can be potentially used as a promising biomarker and target for novel treatment of human glioma.

Neuroglobin, a Factor Playing for Nerve Cell Survival

Cell death represents the final outcome of several pathological conditions of the central nervous system and available evidence suggests that in both acute injuries and neurodegenerative diseases it is often associated with mitochondrial dysfunction. Thus, the possibility to prevent mitochondrial events involved in cell death might represent efficient tools to limit neuronal damage. In recent years, increased attention has been paid to the endogenous protein neuroglobin, since accumulating evidence showed that its high expression was associated with preserved mitochondrial function and to an increased survival of nerve cells in vitro and in vivo in a variety of experimental models of cell insult. The biological and structural features of neuroglobin and the mitochondria-related mechanisms of neuroglobin-induced neuroprotection will be here briefly discussed. In this respect, the inhibition of the intrinsic pathway of apoptosis emerges as a key neuroprotective effect induced by the protein. These findings could open the possibility to develop efficient neuroglobin-mediated therapeutic strategies aimed at minimizing the neuronal cell death occurring in impacting neurological pathologies like stroke and neurodegenerative diseases.