Reverse phase protein array identifies novel anti-invasion mechanisms of YC-1

Modulation of hypoxia-inducible factor-1 signaling pathways in cancer angiogenesis, invasion, and metastasis by natural compounds: a comprehensive and critical review

Tumor cells employ multiple signaling mediators to escape the hypoxic condition and trigger angiogenesis and metastasis. As a critical orchestrate of tumorigenic conditions, hypoxia-inducible factor-1 (HIF-1) is responsible for stimulating several target genes and dysregulated pathways in tumor invasion and migration. Therefore, targeting HIF-1 pathway and cross-talked mediators seems to be a novel strategy in cancer prevention and treatment. In recent decades, tremendous efforts have been made to develop multi-targeted therapies to modulate several dysregulated pathways in cancer angiogenesis, invasion, and metastasis. In this line, natural compounds have shown a bright future in combating angiogenic and metastatic conditions. Among the natural secondary metabolites, we have evaluated the critical potential of phenolic compounds, terpenes/terpenoids, alkaloids, sulfur compounds, marine- and microbe-derived agents in the attenuation of HIF-1, and interconnected pathways in fighting tumor-associated angiogenesis and invasion. This is the first comprehensive review on natural constituents as potential regulators of HIF-1 and interconnected pathways against cancer angiogenesis and metastasis. This review aims to reshape the previous strategies in cancer prevention and treatment.

Targeting Hypoxia-Inducible Factor-1-Mediated Metastasis for Cancer Therapy

Significance: Hypoxia is emerging as a crucial regulator of the tumor microenvironment; it governs the metastatic potential of multiple primary cancers. It is also potentially involved in the regulation of tumorigenesis, tumor metabolism, and proangiogenic activity. Recent Advances: A wealth of clinical data across a wide range of cancer types has revealed strong correlations between hypoxia or the overexpression of hypoxia-inducible transcription factors and the rates of distant metastases and poor prognoses. Hypoxia-inducible factor (HIF)-1α, one of the key regulatory molecules of the HIF-1 signaling pathways, is involved in multiple crucial steps in the metastatic cascade. Critical Issues: Here, we present recent findings on the roles of the HIF-1 complex in tumor metastasis and highlight the potential of HIF-1α as a target for abrogating tumor metastasis. Moreover, we systematically describe the regulatory role of HIF-1 at each step of the metastatic cascade. Finally, we present the most recent advances in potential pharmacological interventions and the development of specific HIF-1 inhibitors for blocking tumor metastasis. Future Directions: Well-designed clinical trials are urgently needed to validate the anti-metastatic activity of HIF-1 inhibitors discovered in preclinical models. Antioxid. Redox Signal. 34, 1484-1497.

Deciphering nasopharyngeal carcinoma pathogenesis via proteomics

Introduction: Nasopharyngeal carcinoma (NPC) is a distinct head and neck squamous cell carcinoma in its etiological association of Epstein-Barr virus (EBV) infection, hidden anatomical location, remarkable racial and geographical distribution, and high incidence of locoregional recurrence or metastasis. Thanks to the advancements in proteomics in recent decades, more understanding of the disease etiology, carcinogenesis, and progression has been gained, potentially deciphering the molecular characteristics of the malignancy. Areas covered: In this review, we provide an overview of the proteomic aberrations that are likely involved or drive NPC development and progression, focusing on the contributions of major EBV-encoded factors, intercommunication with environment, protein features of high metastasis and therapy resistance, and protein-protein interactions that allow NPC cells to evade immune recognition and elimination. Finally, multistep carcinogenesis and subtypes of NPC from a proteomic perspective are inquired. Expert commentary: Proteomic studies have covered various aspects involved in NPC pathogenesis, yet much remains to be uncovered. Coherent study designs, optimal conditions for obtaining high-quality data, and compelling interpretation are critical in ensuring the emergence of good science out of NPC proteomics. NPC proteogenomics and proteoform analysis are two promising fields to promote the application of the proteomic findings from bench to bedside.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

Models for predicting stage in head and neck squamous cell carcinoma using proteomic data

Head and neck squamous cell carcinoma (HNSCC) that is detected at an advanced stage is associated with much worse patient outcomes than if detected at early stages. This study uses reverse phase protein array (RPPA) data to build predictive models that discriminate between early and advanced stage HNSCC. Individual and ensemble binary classifiers, using filter-based and wrapper-based feature selection, are used to build several models which achieve moderate MCC and AUC values. This study identifies informative protein feature sets which may contribute to an increased understanding of the molecular basis of HNSCC.

Models for Predicting Stage in Head and Neck Squamous Cell Carcinoma Using Proteomic and Transcriptomic Data

Late diagnosis is one of the reasons that head and neck squamous cell carcinoma (HNSCC) patients experience relative five-year survival rates ranging from 40%-66%. The molecular-level differences between early and advanced stage HNSCC may provide insight into therapeutic targets and strategies. Previous bioinformatics studies have shown mixed or limited results in identifying gene and protein markers and in developing models for discriminating between early and advanced stage HNSCC. Thus, we have investigated models for HNSCC stage prediction using RNAseq and reverse phase protein array data from The Cancer Genome Atlas and The Cancer Proteome Atlas. We systematically assessed individual and ensemble binary classifiers, using filter and wrapper feature selection methods, to develop several well-performing models. In particular, integrated models harnessing both data types consistently resulted in better performance. This study identifies informative protein and gene feature sets which may increase understanding of HNSCC progression.

Reverse Phase Protein Arrays-Quantitative Assessment of Multiple Biomarkers in Biopsies for Clinical Use

Reverse Phase Protein Arrays (RPPA) represent a very promising sensitive and precise high-throughput technology for the quantitative measurement of hundreds of signaling proteins in biological and clinical samples. This array format allows quantification of one protein or phosphoprotein in multiple samples under the same experimental conditions at the same time. Moreover, it is suited for signal transduction profiling of small numbers of cultured cells or cells isolated from human biopsies, including formalin fixed and paraffin embedded (FFPE) tissues. Owing to the much easier sample preparation, as compared to mass spectrometry based technologies, and the extraordinary sensitivity for the detection of low-abundance signaling proteins over a large linear range, RPPA have the potential for characterization of deregulated interconnecting protein pathways and networks in limited amounts of sample material in clinical routine settings. Current aspects of RPPA technology, including dilution curves, spotting, controls, signal detection, antibody validation, and calculation of protein levels are addressed.

Prognostic Value of Molecular Markers and Implication for Molecular Targeted Therapies in Nasopharyngeal Carcinoma: An Update in an Era of New Targeted Molecules Development

The aim of the study was to evaluate the prognostic significance of molecular biomarkers which could provide information for more accurate prognostication and development of novel therapeutic strategies for nasopharyngeal carcinoma (NPC). NPC is a unique malignant epithelial carcinoma of head and neck region, with an intimate association with the Epstein-Barr virus (EBV). Currently, the prediction of NPC prognosis is mainly based on the clinical TNM staging; however, NPC patients with the same clinical stage often present different clinical outcomes, suggesting that the TNM stage is insufficient to precisely predict the prognosis of this disease. In this review, we give an overview of the prognostic value of molecular markers in NPC and discuss potential strategies of targeted therapies for treatment of NPC. Molecular biomarkers, which play roles in abnormal proliferation signaling pathways (such as Wnt/β-catenin pathway), intracellular mitogenic signal aberration (such as hypoxia-inducible factor (HIF)-1α), receptor-mediated aberrations (such as vascular endothelial growth factor (VEGF)), tumor suppressors (such as p16 and p27 activity), cell cycle aberrations (such as cyclin D1 and cyclin E), cell adhesion aberrations (such as E-cadherin), apoptosis dysregualtion (such as survivin) and centromere aberration (centromere protein H), are prognostic markers for NPC. Plasma EBV DNA concentrations and EBV-encoded latent membrane proteins are also prognostic markers for NPC. Implication of molecular targeted therapies in NPC was discussed. Such therapies could have potential in combination with different cytotoxic agents to combat and eradicate tumor cells. In order to further improve overall survival for patients with loco-regionally advanced NPC, the development of innovative strategies, including prognostic molecular markers and molecular targeted agents is needed.

YC-1 inhibits proliferation of breast cancer cells by down-regulating EZH2 expression via activation of c-Cbl and ERK

BACKGROUND AND PURPOSE

YC-1 exhibits potent anticancer activity via numerous actions in many cancer cell lines. Hence, we investigated the in vivo antitumour efficacy of YC-1 in an MDA-MB-468 xenograft model and elucidated the mechanism of down-regulation of enhancer of zeste homology 2 (EZH2) by YC-1 in breast cancer cells.

EXPERIMENTAL APPROACH

In YC-1-treated breast cancer cells and tumour specimens from YC-1-treated MDA-MB-468 xenografts, EZH2 expression was analysed by Western blotting. Pharmacological inhibitors and short hairpin RNA-mediated knockdown were applied to identify possible signalling pathways involved in EZH2 down-regulation by YC-1.

KEY RESULTS

YC-1 reduced the viability of breast cancer cells and tumour growth in MDA-MB-468 xenografts. In breast cancer cells, YC-1 down-regulated EZH2 expression in a concentration- and time-dependent manner. Depletion of EZH2 reduced the proliferation and susceptibility of breast cancer cells to YC-1-induced apoptosis. EZH2 expression was suppressed in tumour specimens from YC-1-treated MDA-MB-468 xenograft mice. YC-1 enhanced both the degradation rate and ubiquitination of EZH2. The down-regulation of EZH2 by YC-1 was associated with activation of PKA and Src-Raf-ERK-mediated signalling pathways. Furthermore, depletion of Casitas B-lineage lymphoma (c-Cbl), an E3 ubiquitin ligase, abolished YC-1-induced apoptosis and suppression of EZH2. YC-1 rapidly activated c-Cbl to induce signalling associated with ERK and EZH2.

CONCLUSION AND IMPLICATIONS

We discovered that YC-1 induces apoptosis and inhibits tumour growth of breast cancer cells via down-regulation of EZH2 by activating c-Cbl and ERK. These data suggest that YC-1 is a potential anticancer drug candidate for triple-negative breast cancer.

PAX2 Expression in Ovarian Cancer

PAX2 is one of nine PAX genes that regulate tissue development and cellular differentiation in embryos. However, the functional role of PAX2 in ovarian cancer is not known. Twenty-six ovarian cancer cell lines with different histology origins were screened for PAX2 expression. Two ovarian cancer cell lines: RMUGL (mucinous) and TOV21G (clear cell), with high PAX2 expression were chosen for further study. Knockdown PAX2 expression in these cell lines was achieved by lentiviral shRNAs targeting the PAX2 gene. PAX2 stable knockdown cells were characterized for cell proliferation, migration, apoptosis, protein profiles, and gene expression profiles. The result indicated that these stable PAX2 knockdown cells had reduced cell proliferation and migration. Microarray analysis indicated that several genes involved in growth inhibition and motility, such as G0S2, GREM1, and WFDC1, were up-regulated in PAX2 knockdown cells. On the other hand, over-expressing PAX2 in PAX2-negative ovarian cell lines suppressed their cell proliferation. In summary, PAX2 could have both oncogenic and tumor suppression functions, which might depend on the genetic content of the ovarian cancer cells. Further investigation of PAX2 in tumor suppression and mortality is warranty.

YC-1 exerts inhibitory effects on MDA-MB-468 breast cancer cells by targeting EGFR in vitro and in vivo under normoxic condition

3-(5′-hydroxymethyl-2′-furyl)-1-benzyl indazole (YC-1), the hypoxia-inducible factor-1 alpha (HIF-1α) inhibitor, suppresses tumor proliferation and metastasis by down-regulating HIF-1α expression under hypoxic conditions. Our previous studies demonstrated that YC-1 inhibited breast cancer cell proliferation under normoxic conditions. In the current study, we investigated the targets of YC-1 and mechanism of its action in MDA-MB-468 breast cancer cells. In the in vitro experiments, we found that YC-1 significantly inhibited MDA-MB-468 cell proliferation in normoxia and hypoxia. Under normoxic conditions, YC-1 induced apoptosis of MDA-MB-468 cells and blocked cell cycle in the G₁ phase, and these effects were possibly related to caspase 8, p21, and p27 expression. RT-PCR and Western blotting results showed that YC-1 primarily inhibited HIF-1α at the mRNA and protein levels under hypoxic conditions, but suppressed the expression of epidermal growth factor receptor (EGFR) at the mRNA and protein levels under normoxic conditions. In vivo, YC-1 prolonged survival, increased survival rate, decreased tumor size and metastasis rate, and inhibited tissue EGFR and HIF-1α expression. However, YC-1 exerted no obvious effect on body weight. These results indicate that YC-1 inhibits the proliferation of MDA-MB-468 cells by acting on multiple targets with minimal side effects. Thus, YC-1 is a promising target drug for breast cancer.

Sustained antitumor activity by co-targeting mTOR and the microtubule with temsirolimus/vinblastine combination in hepatocellular carcinoma

The mammalian target of rapamycin (mTOR) and the microtubules are prominent druggable targets for hepatocellular carcinoma (HCC). PI3K/Akt/mTOR activation is associated with resistance to microtubule inhibitors. Here, we hypothesized that co-targeting of mTOR (by mTOR inhibitor temsirolimus) and the microtubule (by microtubule-destabilizing agent vinblastine) would be more efficacious than single targeting in HCC models. In vitro studies showed that effective inhibition of mTOR signaling with temsirolimus alone was able to suppress HCC cell growth in a dose-dependent manner. Among five cell lines tested, Huh7 was the most temsirolimus-sensitive (IC(50)=1.27±0.06μM), while Hep3B was the most temsirolimus-resistant (IC(50)=52.95±17.14μM). We found that co-targeting of mTOR (by temsirolimus) and the microtubule (by vinblastine, at low nM) resulted in marked growth inhibition in Huh7 cells and synergistic growth inhibition in Hep3B cells (achieving maximal growth inhibition of 80-90%), demonstrating potent antitumor activity of this novel combination. In vivo studies showed that temsirolimus treatment alone for 1 week was able to inhibit the growth of Huh7 xenografts. Strikingly, the temsirolimus/vinblastine combination induced a significant and sustained antitumor activity (up to 27 days post-treatment), with effective reduction of tumor vessel density in both Huh7 and Hep3B xenograft models. Mechanistic investigation revealed that this marked antitumor effect was accompanied by specific and concerted down-regulation of several key anti-apoptotic/survival proteins (survivin, Bcl-2, and Mcl-1), which was not observed in single agent treatments. Our findings demonstrated that the potent anti-cancer activity of this co-targeting strategy was indeed mediated in parts by inhibition of these key survival/anti-apoptotic proteins.

Metformin induces G1 cell cycle arrest and inhibits cell proliferation in nasopharyngeal carcinoma cells

It has been reported that metformin, a biguanide derivative widely used in type II diabetic patients, has antitumor activities in some cancers by activation of AMP-activated protein kinase (AMPK). But its role in nasopharyngeal carcinoma (NPC) is not known. Here, we reported for the first time that 1-50 mM of metformin in a dose- and time-dependent manner suppressed cell proliferation and colony formation in NPC cell line, C666-1. Further studies revealed that the protein level of cyclin D1 decreased and the percentage of the cells in G0/G1 phase increased by 5 mM metformin treatment. Metformin also induced the phosphorylation of AMPK (T172) in a time-dependent manner. Mammalian target of rapamycin complex 1 (mTORC1), which is negatively regulated by AMPK and plays a central role in cell growth and proliferation, was inhibited by metformin, as manifested by dephosphorylation of its downstream targets 40S ribosomal S6 kinase 1 (S6K1) (T389), the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) (T37/46) and S6 (S235/236) in C666-1 cells. In a summary, metformin prevents proliferation of C666-1 cells by down-regulating cyclin D1 level and inducing G1 cell cycle arrest. AMPK-mediated inhibition of mTORC1 signaling may be involved in this process.

Targeted therapies in cancer - challenges and chances offered by newly developed techniques for protein analysis in clinical tissues

In recent years, new anticancer therapies have accompanied the classical approaches of surgery and radio- and chemotherapy. These new forms of treatment aim to inhibit specific molecular targets namely altered or deregulated proteins, which offer the possibility of individualized therapies.The specificity and efficiency of these new approaches, however, bring about a number of challenges. First of all, it is essential to specifically identify and quantify protein targets in tumor tissues for the reasonable use of such targeted therapies. Additionally, it has become even more obvious in recent years that the presence of a target protein is not always sufficient to predict the outcome of targeted therapies. The deregulation of downstream signaling molecules might also play an important role in the success of such therapeutic approaches. For these reasons, the analysis of tumor-specific protein expression profiles prior to therapy has been suggested as the most effective way to predict possible therapeutic results. To further elucidate signaling networks underlying cancer development and to identify new targets, it is necessary to implement tools that allow the rapid, precise, inexpensive and simultaneous analysis of many network components while requiring only a small amount of clinical material.Reverse phase protein microarray (RPPA) is a promising technology that meets these requirements while enabling the quantitative measurement of proteins. Together with recently developed protocols for the extraction of proteins from formalin-fixed, paraffin-embedded (FFPE) tissues, RPPA may provide the means to quantify therapeutic targets and diagnostic markers in the near future and reliably screen for new protein targets.With the possibility to quantitatively analyze DNA, RNA and protein from a single FFPE tissue sample, the methods are available for integrated patient profiling at all levels of gene expression, thus allowing optimal patient stratification for individualized therapies.

Reverse phase protein microarrays advance to use in clinical trials

Individualizing cancer therapy for molecular targeted inhibitors requires a new class of molecular profiling technology that can map the functional state of the cancer cell signal pathways containing the drug targets. Reverse phase protein microarrays (RPMA) are a technology platform designed for quantitative, multiplexed analysis of specific phosphorylated, cleaved, or total (phosphorylated and non-phosphorylated) forms of cellular proteins from a limited amount of sample. This class of microarray can be used to interrogate tissue samples, cells, serum, or body fluids. RPMA were previously a research tool; now this technology has graduated to use in research clinical trials with clinical grade sensitivity and precision. In this review we describe the application of RPMA for multiplexed signal pathway analysis in therapeutic monitoring, biomarker discovery, and evaluation of pharmaceutical targets, and conclude with a summary of the technical aspects of RPMA construction and analysis.