14-3-3zeta Cooperates with ErbB2 to promote ductal carcinoma in situ progression to invasive breast cancer by inducing epithelial-mesenchymal transition

WITHDRAWN: MiR-200 family and cancer: Function, regulation and signaling

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Increased 14-3-3ζ expression in the multidrug-resistant leukemia cell line HL-60/VCR as compared to the parental line mediates cell growth and apoptosis in part through modification of gene expression

BACKGROUND

Acute myeloid leukemia (AML) recurrence is largely a result of multidrug resistance (MDR). We aimed to examine the role of 14-3-3ζ in AML chemosensitivity using HL-60 and vincristine-resistant HL-60/VCR cells.

METHODS

The effects of 14-3-3ζ siRNA on the growth and cell cycle progression of HL-60 and HL-60/VCR cells were determined. The effect of 14-3-3ζ siRNA on topotecan (TPT)-induced apoptosis was evaluated by several assays.

RESULTS

Compared to HL-60 cells, HL-60/VCR cells had increased 14-3-3ζ mRNA and protein expression. Increased mdr-1 mRNA as well as mdr-1, Bcl-2 and Mcl-1 protein expression were observed in HL-60/VCR cells. In both HL-60 and HL-60/VCR cells, 14-3-3ζ was observed in the cytoplasm and nuclear compartments. 14-3-3ζ siRNA significantly reduced HL-60 and HL-60/VCR cell growth after 48 h and increased the proportion of cells in the G0/G1 phase. Moreover, 14-3-3ζ siRNA significantly increased the sensitivity of both HL-60 and HL-60/VCR cells to TPT, possibly through the inhibition of Bcl-2, Mcl-1 and mdr-1 protein expression.

CONCLUSIONS

Silencing of 14-3-3ζ increased the sensitivity of both sensitive and resistant HL-60 cells to TPT-induced apoptosis, possibly through altering the expression of apoptosis-associated proteins, suggesting that it may be a potential target for MDR AML.

Transforming potential and matrix stiffness co-regulate confinement sensitivity of tumor cell migration

It is now well established that tumor cell invasion through tissue is strongly regulated by the microstructural and mechanical properties of the extracellular matrix (ECM). However, it remains unclear how these physical microenvironmental inputs are jointly processed with oncogenic lesions to drive invasion. In this study, we address this open question by combining a microfabricated polyacrylamide channel (μPAC) platform that enables independent control of ECM stiffness and confinement with an isogenically-matched breast tumor progression series in which the oncogenes ErbB2 and 14-3-3ζ are overexpressed independently or in tandem. We find that increasing channel confinement and overexpressing ErbB2 both promote cell migration to a similar degree when other parameters are kept constant. In contrast, 14-3-3ζ overexpression slows migration speed, and does so in a fashion that dwarfs effects of ECM confinement and stiffness. We also find that ECM stiffness dramatically enhances cell motility when combined with ErbB2 overexpression, demonstrating that biophysical cues and cell-intrinsic parameters promote cell invasion in an integrative manner. Morphometric analysis of cells inside the μPAC platform reveals that the rapid cell migration induced by narrow channels and ErbB2 overexpression are both accompanied by increased cell polarization. Disruption of this polarization occurs by pharmacological inhibition of Rac GTPase phenocopies 14-3-3ζ overexpression by reducing cell polarization and slowing migration. By systematically measuring migration speed as a function of matrix stiffness and confinement, we also quantify for the first time the sensitivity of migration speed to microchannel properties and transforming potential. These results demonstrate that oncogenic lesions and ECM biophysical properties can synergistically interact to drive invasive migration, and that both inputs may act through common molecular mechanisms to enhance migration speed.

When Good Turns Bad: Regulation of Invasion and Metastasis by ErbB2 Receptor Tyrosine Kinase

Overexpression and activation of ErbB2 receptor tyrosine kinase in breast cancer is strongly linked to an aggressive disease with high potential for invasion and metastasis. In addition to inducing very aggressive, metastatic cancer, ErbB2 activation mediates processes such as increased cancer cell proliferation and survival and is needed for normal physiological activities, such as heart function and development of the nervous system. How does ErbB2 activation make cancer cells invasive and when? Comprehensive understanding of the cellular mechanisms leading to ErbB2-induced malignant processes is necessary for answering these questions. Here we present current knowledge about the invasion-promoting function of ErbB2 and the mechanisms involved in it. Obtaining detailed information about the "bad" behavior of ErbB2 can facilitate development of novel treatments against ErbB2-positive cancers.

14-3-3ζ orchestrates mammary tumor onset and progression via miR-221-mediated cell proliferation

14-3-3ζ is overexpressed in more than 40% of breast cancers, but its pathophysiologic relevance to tumorigenesis has not been established. Here, we show that 14-3-3ζ overexpression is sufficient to induce tumorigenesis in a transgenic mouse model of breast cancer. MMTV-LTR promoter-driven HA-14-3-3ζ transgenic mice (MMTV-HA-14-3-3ζ) developed mammary tumors, whereas control mice did not. Whey acidic protein promoter-driven HA-14-3-3ζ transgenic mice (WAP-HA-14-3-3ζ) developed hyperplastic lesions and showed increased susceptibility to carcinogen-induced tumorigenesis. When crossed with MMTV-neu transgenic mice, 14-3-3ζ.neu transgenic mice exhibited accelerated mammary tumorigenesis and metastasis compared with MMTV-neu mice. Mechanistically, 14-3-3ζ overexpression enhanced MAPK/c-Jun signaling, leading to increased miR-221 transcription, which inhibited p27 CDKI translation and, consequently, promoted cell proliferation. Importantly, this 14-3-3ζ-miR-221-p27 proliferation axis is also functioning in breast tumors in patients and is associated with high-grade cancers. Taken together, our findings show that overexpression of 14-3-3ζ has a causal role in mammary tumorigenesis and progression, acting through miR-221 in cooperation with known oncogenic events to drive neoplastic cell proliferation.

The overexpression of 14-3-3ζ and Hsp27 promotes non–small cell lung cancer progression

BACKGROUND

The 14-3-3ζ protein has been identified as a putative oncoprotein in several cancers, including non–small cell lung cancer (NSCLC). However, the mechanisms underlying its functions have not been well defined.

METHODS

Proteins that interact with 14-3-3ζ were identified through coimmunoprecipitation and mass spectrometry in NSCLC cells. The interaction of 14-3-3ζ with these molecular partners and their roles in the invasiveness and metastasis of NSCLC cells were assayed through specific disruptions in the 14-3-3ζ signaling network. In addition, the clinical implications of this 14-3-3ζ complex were examined in samples from patients with NSCLC.

RESULTS

Among the identified proteins that interacted with 14-3-3ζ, there were 230 proteins in 95-D cells, 181 proteins in 95-C cells, and 203 proteins in A549 cells; and 16 interacting proteins were identified that overlapped between all cell lines. Further studies revealed 14-3-3ζ complexes within the heat shock protein 27 (Hsp27) protein and demonstrated that the interference of Hsp27 or 14-3-3ζ inhibited the invasion and metastasis of NSCLC cells. The invasive and metastatic capabilities of cells with both Hsp27 and 14-3-3ζ interference could be completely restored only by Hsp27 and 14-3-3ζ complementary DNA transfection and not by either agent alone. Clinically, the postoperative 5-year overall survival (OS) in patients who had high expression of both 14-3-3ζ and Hsp27 was significantly lower than the 5-year OS in patients who had low expression of both 14-3-3ζ and Hsp27 (26.5% vs 59.7%, respectively). Multivariate analysis revealed that the combined expression of 14-3-3ζ and Hsp27 was an independent prognostic indicator of OS(P = .036).

CONCLUSIONS

The current data suggest that the combined expression of 14-3-3ζ and Hsp27 may be a biomarker for predicting survival in patients with NSCLC, and this combination may have potential as a therapeutic target for NSCLC.

Next-generation sequencing: a powerful tool for the discovery of molecular markers in breast ductal carcinoma in situ

Mammographic screening leads to frequent biopsies and concomitant overdiagnosis of breast cancer, particularly ductal carcinoma in situ (DCIS). Some DCIS lesions rapidly progress to invasive carcinoma, whereas others remain indolent. Because we cannot yet predict which lesions will not progress, all DCIS is regarded as malignant, and many women are overtreated. Thus, there is a pressing need for a panel of molecular markers in addition to the current clinical and pathological factors to provide prognostic information. Genomic technologies such as microarrays have made major contributions to defining subtypes of breast cancer. Next-generation sequencing (NGS) modalities offer unprecedented depth of expression analysis through revealing transcriptional boundaries, mutations, rare transcripts and alternative splice variants. NGS approaches are just beginning to be applied to DCIS. Here, the authors review the applications and challenges of NGS in discovering novel potential therapeutic targets and candidate biomarkers in the premalignant progression of breast cancer.

14-3-3 proteins modulate the ETS transcription factor ETV1 in prostate cancer

Overexpression of the ETS-related transcription factor ETV1 can initiate neoplastic transformation of the prostate. ETV1 activity is highly regulated by phosphorylation, but the underlying mechanisms are unknown. Here we report that all 14-3-3 proteins, with the exception of the tumor suppressor 14-3-3σ, can bind to ETV1 in a condition manner dictated by its prominent phosphorylation site S216. Non-σ 14-3-3 proteins synergized with ETV1 to activate transcription of its target genes MMP-1 and MMP-7, which regulate extracellular matrix in the prostate tumor microenvironment. S216 mutation or 14-3-3τ downregulation was sufficient to reduce ETV1 protein levels in prostate cancer cells, indicating that non-σ 14-3-3 proteins protect ETV1 from degradation. Notably, S216 mutation also decreased ETV1-dependent migration and invasion in benign prostate cells. Downregulation of 14-3-3τ reduced prostate cancer cell invasion and growth in the same manner as ETV1 attenuation. Finally, we showed that 14-3-3τ and 14-3-3ε were overexpressed in human prostate tumors. Taken together, our results showed that non-σ 14-3-3 proteins are important modulators of ETV1 function that promote prostate tumorigenesis.

Analysis and prediction of pathways in HeLa cells by integrating biological levels of organization with systems-biology approaches

It has recently begun to be considered that cancer is a systemic disease and that it must be studied at every level of complexity using many of the currently available approaches, including high-throughput technologies and bioinformatics. To achieve such understanding in cervical cancer, we collected information on gene, protein and phosphoprotein expression of the HeLa cell line and performed a comprehensive analysis of the different signaling pathways, transcription networks and metabolic events in which they participate. A total expression analysis by RNA-Seq of the HeLa cell line showed that 19,974 genes were transcribed. Of these, 3,360 were over-expressed, and 2,129 under-expressed when compared to the NHEK cell line. A protein-protein interaction network was derived from the over-expressed genes and used to identify central elements and, together with the analysis of over-represented transcription factor motifs, to predict active signaling and regulatory pathways. This was further validated by Metal-Oxide Affinity Chromatography (MOAC) and Tandem Mass Spectrometry (MS/MS) assays which retrieved phosphorylated proteins. The 14-3-3 family members emerge as important regulators in carcinogenesis and as possible clinical targets. We observed that the different over- and under-regulated pathways in cervical cancer could be interrelated through elements that participate in crosstalks, therefore belong to what we term "meta-pathways". Additionally, we highlighted the relations of each one of the differentially represented pathways to one or more of the ten hallmarks of cancer. These features could be maintained in many other types of cancer, regardless of mutations or genomic rearrangements, and favor their robustness, adaptations and the evasion of tissue control. Probably, this could explain why cancer cells are not eliminated by selective pressure and why therapy trials directed against molecular targets are not as effective as expected.

Quantitative proteome analysis of overexpressed Cripto-1 tumor cell reveals 14-3-3γ as a novel biomarker in nasopharyngeal carcinoma

We previously found that Cripto-1 is involved in the tumorigenesis of nasopharyngeal carcinoma (NPC). Here, to identify new NPC related proteins and to investigate the clinicopathological correlations of it in NPC, Cripto-1 over-expressed cell (CNE1/CR1(+)) was established. Two-dimensional difference in gel electrophoresis (2D-DIGE) analysis and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) were used to identify 23 differential proteins in CNE1/CR1(+) and parental cells. Among them, 14-3-3γ showed the potential to be a NPC related protein. 14-3-3γ expression was found in 58.3% (60/103) tumor tissues as detected by IHC, and 69.6% (16/23) NPC fresh tumors expressed higher 14-3-3γ than paired non-cancerous tissues as detected by Western blot. Moreover, 14-3-3γ expression was positively correlated with N classification (p=0.031), distant metastasis (M classification, p=0.018) and clinical stage (p=0.046) of NPC patients. As determined by the Kaplan-Meier method, 14-3-3γ expression in NPC was significantly associated with overall survival (p=0.015). Multivariate analysis also showed that the expression of 14-3-3γ protein was an independent prognostic factor for outcome of NPC. In this study, we identified upregulated 14-3-3γ by 2D-DIGE in CNE1/CR-1(+). We also demonstrated that 14-3-3γ might be a potential biomarker for the prognosis of patients with NPC.

BIOLOGICAL SIGNIFICANCE

We believe that three aspects of this manuscript will make it interesting to general readers of Journal of Proteomics. Firstly, based on our previous report, we further validated that Cripto-1 can promote the proliferation and invasion of nasopharyngeal carcinoma (NPC). In this context, we used 2D-DIGE to identify new NPC related proteins. As a result, 14-3-3γ showed the potential to be a candidate. Secondly, we reported for the first time that the expression level of 14-3-3γ was significantly increased in human NPC patient tissues, and 14-3-3γ overexpression correlated statistically with N classification, distant metastasis, and clinical stage. Our results highlight the clinical significance of 14-3-3γ in NPC. Finally, we found that high 14-3-3γ expression is associated with poor survival in NPC patients. Thus, this study has identified that the 14-3-3γ involves in the carcinogenesis of NPC. Our findings may also provide new insights into understanding the molecular mechanism involved in NPC carcinogenesis and progression, and may lead to the development of new approaches for effective diagnosis and therapy.

14-3-3ε overexpression contributes to epithelial-mesenchymal transition of hepatocellular carcinoma

Background

14-3-3ε is implicated in regulating tumor progression, including hepatocellular carcinoma (HCC). Our earlier study indicated that elevated 14-3-3ε expression is significantly associated with higher risk of metastasis and lower survival rates of HCC patients. However, the molecular mechanisms of how 14-3-3ε regulates HCC tumor metastasis are still unclear.

Methodology and Principal Findings

In this study, we show that increased 14-3-3ε expression induces HCC cell migration and promotes epithelial-mesenchymal transition (EMT), which is determined by the reduction of E-cadherin expression and induction of N-cadherin and vimentin expression. Knockdown with specific siRNA abolished 14-3-3ε-induced cell migration and EMT. Furthermore, 14-3-3ε selectively induced Zeb-1 and Snail expression, and 14-3-3ε-induced cell migration was abrogated by Zeb-1 or Snail siRNA. In addition, the effect of 14-3-3ε-reduced E-cadherin was specifically restored by Zeb-1 siRNA. Positive 14-3-3ε expression was significantly correlated with negative E-cadherin expression, as determined by immunohistochemistry analysis in HCC tumors. Analysis of 14-3-3ε/E-cadherin expression associated with clinicopathological characteristics revealed that the combination of positive 14-3-3ε and negative E-cadherin expression is significantly correlated with higher incidence of HCC metastasis and poor 5-year overall survival. In contrast, patients with positive 14-3-3ε and positive E-cadherin expression had better prognostic outcomes than did those with negative E-cadherin expression.

Significance

Our findings show for the first time that E-cadherin is one of the downstream targets of 14-3-3ε in modulating HCC tumor progression. Thus, 14-3-3ε may act as an important regulator in modulating tumor metastasis by promoting EMT as well as cell migration, and it may serve as a novel prognostic biomarker or therapeutic target for HCC.

Overexpression of YWHAZ relates to tumor cell proliferation and malignant outcome of gastric carcinoma

BACKGROUND

Several studies have demonstrated that YWHAZ (14-3-3ζ), included in the 14-3-3 family of proteins, has been implicated in the initiation and progression of cancers. We tested whether YWHAZ acted as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).

METHODS

We analysed 7 GC cell lines and 141 primary tumours, which were curatively resected in our hospital between 2001 and 2003.

RESULTS

Overexpression of the YWHAZ protein was frequently detected in GC cell lines (six out of seven lines, 85.7%) and primary tumour samples of GC (72 out of 141 cases, 51%), and significantly correlated with larger tumour size, venous and lymphatic invasion, deeper tumour depth, and higher pathological stage and recurrence rate. Patients with YWHAZ-overexpressing tumours had worse overall survival rates than those with non-expressing tumours in both intensity and proportion expression-dependent manner. YWHAZ positivity was independently associated with a worse outcome in multivariate analysis (P=0.0491, hazard ratio 2.3 (1.003-5.304)). Knockdown of YWHAZ expression using several specific siRNAs inhibited the proliferation, migration, and invasion of YWHAZ-overexpressing GC cells. Higher expression of the YWHAZ protein was significantly associated with the lower expression of miR-375 in primary GC tissues (P=0.0047).

CONCLUSION

These findings suggest that YWHAZ has a pivotal role in tumour cell proliferation through its overexpression, and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

Loss of Par3 promotes breast cancer metastasis by compromising cell-cell cohesion

The mechanisms by which tumour cells metastasize and the role that cell polarity proteins play in this process are not well understood. We report that partitioning defective protein 3 (Par3) is dysregulated in metastasis in human breast cancer, and is associated with a higher tumour grade and ErbB2-positive status. Downregulation of Par3 cooperated with ErbB2 to induce cell invasion and metastasis in vivo. Interestingly, the metastatic behaviour was not associated with an overt mesenchymal phenotype. However, loss of Par3 inhibited E-cadherin junction stability, disrupted membrane and actin dynamics at cell-cell junctions and decreased cell-cell cohesion in a manner dependent on the Tiam1/Rac-GTP pathway. Inhibition of this pathway restored E-cadherin junction stability and blocked invasive behaviour of cells lacking Par3, suggesting that loss of Par3 promotes metastatic behaviour of ErbB2-induced tumour epithelial cells by decreasing cell-cell cohesion.

The mitotic kinase Aurora--a promotes distant metastases by inducing epithelial-to-mesenchymal transition in ERα(+) breast cancer cells

In this study, we demonstrate that constitutive activation of Raf-1 oncogenic signaling induces stabilization and accumulation of Aurora-A mitotic kinase that ultimately drives the transition from an epithelial to a highly invasive mesenchymal phenotype in estrogen receptor α-positive (ERα(+)) breast cancer cells. The transition from an epithelial- to a mesenchymal-like phenotype was characterized by reduced expression of ERα, HER-2/Neu overexpression and loss of CD24 surface receptor (CD24(-/low)). Importantly, expression of key epithelial-to-mesenchymal transition (EMT) markers and upregulation of the stemness gene SOX2 was linked to acquisition of stem cell-like properties such as the ability to form mammospheres in vitro and tumor self-renewal in vivo. Moreover, aberrant Aurora-A kinase activity induced phosphorylation and nuclear translocation of SMAD5, indicating a novel interplay between Aurora-A and SMAD5 signaling pathways in the development of EMT, stemness and ultimately tumor progression. Importantly, pharmacological and molecular inhibition of Aurora-A kinase activity restored a CD24(+) epithelial phenotype that was coupled to ERα expression, downregulation of HER-2/Neu, inhibition of EMT and impaired self-renewal ability, resulting in the suppression of distant metastases. Taken together, our findings show for the first time the causal role of Aurora-A kinase in the activation of EMT pathway responsible for the development of distant metastases in ERα(+) breast cancer cells. Moreover, this study has important translational implications because it highlights the mitotic kinase Aurora-A as a novel promising therapeutic target to selectively eliminate highly invasive cancer cells and improve the disease-free and overall survival of ERα(+) breast cancer patients resistant to conventional endocrine therapy.

ErbB2, FoxM1 and 14-3-3ζ prime breast cancer cells for invasion in response to ionizing radiation

ErbB2 is frequently highly expressed in premalignant breast cancers, including ductal carcinoma in situ (DCIS); however, little is known about the signals or pathways it contributes to progression into the invasive/malignant state. Radiotherapy is often used to treat early premalignant lesions regardless of ErbB2 status. Here, we show that clinically relevant doses of ionizing radiation (IR)-induce cellular invasion of ErbB2-expressing breast cancer cells, as well as MCF10A cells overexpressing ErbB2. ErbB2-negative breast cancer cells, such as MCF7 and T47D, do not invade following treatment with IR nor do MCF10A cells overexpressing epidermal growth factor receptor. ErbB2 becomes phosphorylated at tyrosine 877 in a dose- and time- dependent manner following exposure to X-rays, and activates downstream signaling cascades including PI3K/Akt. Inhibition of these pathways, as well as inhibition of reactive oxygen species (ROS) with antioxidants, prevents IR-induced invasion. Activation of ErbB2-dependent signaling results in upregulation of the forkhead family transcription factor, FoxM1, and its transcriptional targets, including matrix metalloproteinase 2 (MMP2). Inhibition of FoxM1 by RNA interference prevented induction of invasion by IR, and overexpression of FoxM1 in MCF10A cells was sufficient to promote IR-induced invasion. Moreover, we found that 14-3-3ζ is also upregulated by IR in cancer cells in a ROS-dependent manner, is required for IR-induced invasion in ErbB2-positive breast cancer cells and together with FoxM1 is sufficient for invasion in ErbB2-negative breast cancer cells. Thus, our data show that IR-mediated activation of ErbB2 and induction of 14-3-3ζ collaborate to regulate FoxM1 and promote invasion of breast cancer cells and furthermore, may serve as therapeutic targets to enhance radiosensitivity of breast cancers.

14-3-3ζ as a predictor of early time to recurrence and distant metastasis in hormone receptor-positive and -negative breast cancers

The 14-3-3ζ gene, on 8q22, is often amplified in breast cancer and encodes a survival factor that interacts with and stabilizes many key signaling proteins. We examined the relationship between the expression of 14-3-3ζ, estrogen receptor α (ERα), and other parameters ( tumor size, grade, nodal status, progesterone receptor, HER2, EGFR, and p53) in matched primary and recurrence tumor tissue and how these factors impact time to recurrence, properties of the recurred tumors, and site of metastasis. In this cohort of over 100 patients, median time to recurrence was 3 years (range 1-17 years). Our analyses of primary tumor microarray cores revealed that 14-3-3ζ status was significantly correlated with tumor grade, size, and ERα. Women with 14-3-3ζ-positive and ERα-negative tumors had the earliest time to recurrence (median 1 yr, p < 0.001, hazard ratio 2.89), while median time to recurrence was 7 years for 14-3-3ζ-negative and ER-positive tumors. Of recurred tumors, 70-75 % were positive for 14-3-3ζ, up from the 45 % positivity of primary tumors. High expression of 14-3-3ζ also correlated with site of recurrence and showed a propensity for distant metastases to lung and chest wall. Multifactor correlation regression analysis revealed 14-3-3ζ to be a non-redundant, independent variable that adds clinical strength in predicting risk for early recurrence in ER-positive and -negative breast cancers, providing information beyond that of all other clinical pathological features examined. Thus, high expression of 14-3-3ζ in the primary tumor was significantly associated with earlier time to recurrence and with distant metastasis. Furthermore, even when the primary breast cancers were negative-low for 14-3-3ζ, the majority acquired increased expression in the recurrence. The findings underscore the detrimental role played by 14-3-3ζ in tumor aggressiveness and suggest that reducing its expression or interfering with its actions might substantially improve the clinical outcome for breast cancer patients.

Quantitative proteomic analysis in metastatic renal cell carcinoma reveals a unique set of proteins with potential prognostic significance

Metastatic renal cell carcinoma (RCC) is one of the most treatment-resistant malignancies, and patients have a dismal prognosis, with a <10% five-year survival rate. The identification of markers that can predict the potential for metastases will have a great effect in improving patient outcomes. In this study, we used differential proteomics with isobaric tags for relative and absolute quantitation (iTRAQ) labeling and LC-MS/MS analysis to identify proteins that are differentially expressed in metastatic and primary RCC. We identified 1256 non-redundant proteins, and 456 of these were quantified. Further analysis identified 29 proteins that were differentially expressed (12 overexpressed and 17 underexpressed) in metastatic and primary RCC. Dysregulated protein expressions of profilin-1 (Pfn1), 14-3-3 zeta/delta (14-3-3ζ), and galectin-1 (Gal-1) were verified on two independent sets of tissues by means of Western blot and immunohistochemical analysis. Hierarchical clustering analysis showed that the protein expression profile specific for metastatic RCC can distinguish between aggressive and non-aggressive RCC. Pathway analysis showed that dysregulated proteins are involved in cellular processes related to tumor progression and metastasis. Furthermore, preliminary analysis using a small set of tumors showed that increased expression of Pfn1 is associated with poor outcome and is a potential prognostic marker in RCC. In addition, 14-3-3ζ and Gal-1 also showed higher expression in tumors with poor prognosis than in those with good prognosis. Dysregulated proteins in metastatic RCC represent potential prognostic markers for kidney cancer patients, and a greater understanding of their involved biological pathways can serve as the foundation of the development of novel targeted therapies for metastatic RCC.

Comprehensive fluorogenic derivatization-liquid chromatography/tandem mass spectrometry proteomic analysis of colorectal cancer cell to identify biomarker candidate

Existing colorectal cancer biomarkers are insufficient for providing a quick and accurate diagnosis, which is critical for a good prognosis. More appropriate biomarkers are thus needed. To identify new colorectal cancer biomarker candidates, we conducted a comprehensive differential proteomic analysis of six cancer cell lines and a normal cell line, utilizing a fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) approach. Two sets of intracellular biomarker candidates were identified: one for colorectal cancer, and the other for metastatic colorectal cancer. Our results suggest that cooperative expression of FABP5 and cyclophilin A might be linked to Her2 signaling. Upregulation of LDHB and downregulation of GAPDH suggest the existence of a specific nonglycolytic energy production pathway in metastatic colorectal cancer cells. Downregulation of 14-3-3ζ/δ, cystatin-B, Ran and thioredoxin could be a result of their secretion, which then stimulates metastasis via activity in the sera and ascitic fluids. We propose a possible flow scheme to describe the dynamics of protein expression in colorectal cancer cells leading to tumor progression and metastasis via cell proliferation, angiogenesis, disorganization of actin filaments and epithelial-mesenchymal transition. Our results suggest that colorectal tumor progression may be regulated by signaling mediated by Her2, hypoxia, and TGFβ.

Cytoskeletal stiffness, friction, and fluidity of cancer cell lines with different metastatic potential

We quantified mechanical properties of cancer cells differing in metastatic potential. These cells included normal and H-ras-transformed NIH3T3 fibroblast cells, normal and oncoprotein-overexpressing MCF10A breast cancer cells, and weakly and strongly metastatic cancer cell line pairs originating from human cancers of the skin (A375P and A375SM cells), kidney (SN12C and SN12PM6 cells), prostate (PC3M and PC3MLN4 cells), and bladder (253J and 253JB5 cells). Using magnetic twisting cytometry, cytoskeletal stiffness (g') and internal friction (g″) were measured over a wide frequency range. The dependencies of g' and g″ upon frequency were used to determine the power law exponent x which is a direct measure of cytoskeletal fluidity and quantifies where the cytoskeleton resides along the spectrum of solid-like (x = 1) to fluid-like (x = 2) states. Cytoskeletal fluidity x increased following transformation by H-ras oncogene expression in NIH3T3 cells, overexpression of ErbB2 and 14-3-3-ζ in MCF10A cells, and implantation and growth of PC3M and 253J cells in the prostate and bladder, respectively. Each of these perturbations that had previously been shown to enhance cancer cell motility and invasion are shown here to shift the cytoskeleton towards a more fluid-like state. In contrast, strongly metastatic A375SM and SN12PM6 cells that disseminate by lodging in the microcirculation of peripheral organs had smaller x than did their weakly metastatic cell line pairs A375P and SN12C, respectively. Thus, enhanced hematological dissemination was associated with decreased x and a shift towards a more solid-like cytoskeleton. Taken together, these results are consistent with the notion that adaptations known to enhance metastatic ability in cancer cell lines define a spectrum of fluid-like versus solid-like states, and the position of the cancer cell within this spectrum may be a determinant of cancer progression.

A novel function of YWHAZ/β-catenin axis in promoting epithelial-mesenchymal transition and lung cancer metastasis

YWHAZ, also known as 14-3-3zeta, has been reportedly elevated in many human tumors, including non-small cell lung carcinoma (NSCLC) but little is known about its specific contribution to lung cancer malignancy. Through a combined array-based comparative genomic hybridization and expression microarray analysis, we identified YWHAZ as a potential metastasis enhancer in lung cancer. Ectopic expression of YWHAZ on low invasive cancer cells showed enhanced cell invasion, migration in vitro, and both the tumorigenic and metastatic potentials in vivo. Gene array analysis has indicated these changes associated with an elevation of pathways relevant to epithelial-mesenchymal transition (EMT), with an increase of cell protrusions and branchings. Conversely, knockdown of YWHAZ levels with siRNA or short hairpin RNA (shRNA) in invasive cancer cells led to a reversal of EMT. We observed that high levels of YWHAZ protein are capable of activating β-catenin-mediated transcription by facilitating the accumulation of β-catenin in cytosol and nucleus. Coimmunoprecipitation assays showed a decrease of ubiquitinated β-catenin in presence of the interaction between YWHAZ and β-catenin. This interaction resulted in disassociating β-catenin from the binding of β-TrCP leading to increase β-catenin stability. Using enforced expression of dominant-negative and -positive β-catenin mutants, we confirmed that S552 phosphorylation of β-catenin increases the β-catenin/YWHAZ complex formation, which is important in promoting cell invasiveness and the suppression of ubiquitnated β-catenin. This is the first demonstration showing YWHAZ through its complex with β-catenin in mediating lung cancer malignancy and β-catenin protein stability.

Modeling invasive breast cancer: growth factors propel progression of HER2-positive premalignant lesions

The HER2/neu oncogene encodes a receptor-like tyrosine kinase whose overexpression in breast cancer predicts poor prognosis and resistance to conventional therapies. However, the mechanisms underlying aggressiveness of HER2 (human epidermal growth factor receptor 2)-overexpressing tumors remain incompletely understood. Because it assists epidermal growth factor (EGF) and neuregulin receptors, we overexpressed HER2 in MCF10A mammary cells and applied growth factors. HER2-overexpressing cells grown in extracellular matrix formed filled spheroids, which protruded outgrowths upon growth factor stimulation. Our transcriptome analyses imply a two-hit model for invasive growth: HER2-induced proliferation and evasion from anoikis generate filled structures, which are morphologically and transcriptionally analogous to preinvasive patients' lesions. In the second hit, EGF escalates signaling and transcriptional responses leading to invasive growth. Consistent with clinical relevance, a gene expression signature based on the HER2/EGF-activated transcriptional program can predict poorer prognosis of a subgroup of HER2-overexpressing patients. In conclusion, the integration of a three-dimensional cellular model and clinical data attributes progression of HER2-overexpressing lesions to EGF-like growth factors acting in the context of the tumor's microenvironment.

Heat shock factor Hsf1 cooperates with ErbB2 (Her2/Neu) protein to promote mammary tumorigenesis and metastasis

ErbB2/Neu oncogene is overexpressed in 25% of invasive/metastatic breast cancers. We have found that deletion of heat shock factor Hsf1 in mice overexpressing ErbB2/Neu significantly reduces mammary tumorigenesis and metastasis. Hsf1(+/-)ErbB2/Neu(+) tumors exhibit reduced cellular proliferative and invasive properties associated with reduced activated ERK1/2 and reduced epithelial-mesenchymal transition (EMT). Hsf1(+/+)Neu(+) mammary epithelial cells exposed to TGFβ show high levels of ERK1/2 activity and EMT; this is associated with reduced expression of E-cadherin and increased expression of Slug and vimentin, a mesenchymal marker. In contrast, Hsf1(-/-)Neu(+) or Hsf1(+/+)Neu(+) cells do not exhibit activated ERK1/2 and show reduced EMT in the presence of TGFβ. The ineffective activation of the RAS/RAF/MEK/ERK1/2 signaling pathway in cells with reduced levels of HSF1 is due to the low levels of HSP90 in complex with RAF1 that are required for RAF1 stability and maturation. These results indicate a powerful inhibitory effect conferred by HSF1 downstream target genes in the inhibition of ErbB2-induced breast cancers in the absence of the Hsf1 gene.

ZEB/miR-200 feedback loop: at the crossroads of signal transduction in cancer

Embryonic differentiation programs of epithelial-mesenchymal and mesenchymal-epithelial transition (EMT and MET) represent a mechanistic basis for epithelial cell plasticity implicated in cancer. Transcription factors of the ZEB protein family (ZEB1 and ZEB2) and several microRNA species (predominantly miR-200 family members) form a double negative feedback loop, which controls EMT and MET programs in both development and tumorigenesis. In this article, we review crosstalk between the ZEB/miR-200 axis and several signal transduction pathways activated at different stages of tumor development. The close association of ZEB proteins with these pathways is indirect evidence for the involvement of a ZEB/miR-200 loop in tumor initiation, progression and spread. Additionally, the configuration of signaling pathways involving ZEB/miR-200 loop suggests that ZEB1 and ZEB2 may have different, possibly even opposing, roles in some forms of human cancer.

The ERBB network: at last, cancer therapy meets systems biology

Although it is broadly agreed that the improved treatment of patients with cancer will depend on a deeper molecular understanding of the underlying pathogenesis, only a few examples are already available. This Timeline article focuses on the ERBB (also known as HER) network of receptor tyrosine kinases (RTKs), which exemplifies how a constant dialogue between basic research and medical oncology can translate into both a sustained pipeline of novel drugs and ways to overcome acquired treatment resistance in patients. We track the key early discoveries that linked this RTK family to oncogenesis, the course of pioneering clinical research and their merger into a systems-biology framework that is likely to inspire further generations of effective therapeutic strategies.

14-3-3ζ positive expression is associated with a poor prognosis in patients with glioblastoma

BACKGROUND

When identifying clinical markers predicting clinical outcome, disease recurrence and resistance to therapies often determine the diagnosis and therapy of some cancer types.

OBJECTIVE

To investigate whether 14-3-3zeta positive expression is an indicator of prognosis in patients with glioblastoma.

METHODS

Forty-seven patients treated with surgery, radiotherapy, and adjuvant chemotherapy between 2005 and 2007 were divided into 2 groups according to 14-3-3zeta expression in an immunohistochemical study: the 14-3-3zeta negative group (n = 12 patients) and the 14-3-3zeta positive group (n = 35 patients). The clinicopathologic features and survival data for patients in the 14-3-3zeta positive group were compared with data from the patients in the 14-3-3zeta negative group. Kaplan-Meier survival analysis and univariate and multivariate analyses were performed to determine the prognostic factors that influenced patient survival.

RESULTS

14-3-3zeta positive expression was observed in approximately 74.5% of patients with glioblastoma. Patients in the 14-3-3zeta positive group had lower overall survival rates and median survival time than those in the 14-3-3zeta negative group (overall 2-year actuarial survival rates, 8.6% for the 14-3-3zeta positive group vs 16.7% for the 14-3-3zeta negative group; overall 2-year median survival time, 12.9 months for the 14-3-3zeta positive group vs 17.9 months for the 14-3-3zeta negative group, P = .019). 14-3-3zeta positive expression in tumor cells also was correlated with a shorter interval to tumor recurrence (median interval to recurrence, 5.9 months in the 14-3-3zeta positive group vs 8.3 months in the 14-3-3zeta negative group, P = .002). Univariate and multivariate analyses showed that 14-3-3zeta positive expression was an independent prognostic factor.

CONCLUSION

14-3-3zeta positive expression can be used as a potential molecular risk factor in patients with glioblastoma.

14-3-3 regulates the LNK/JAK2 pathway in mouse hematopoietic stem and progenitor cells

Hematopoietic stem and progenitor cell (HSPC) functions are governed by intricate signaling networks. The tyrosine kinase JAK2 plays an essential role in cytokine signaling during hematopoiesis. The adaptor protein LNK is a critical determinant of this process through its inhibitory interaction with JAK2, thereby limiting HSPC self-renewal. LNK deficiency promotes myeloproliferative neoplasm (MPN) development in mice, and LNK loss-of-function mutations are found in human MPNs, emphasizing its pivotal role in normal and malignant HSPCs. Here, we report the identification of 14-3-3 proteins as LNK binding partners. 14-3-3 interfered with the LNK-JAK2 interaction, thereby alleviating LNK inhibition of JAK2 signaling and cell proliferation. Binding of 14-3-3 required 2 previously unappreciated serine phosphorylation sites in LNK, and we found that their phosphorylation is mediated by glycogen synthase kinase 3 and PKA kinases. Mutations of these residues abrogated the interaction and augmented the growth inhibitory function of LNK. Conversely, forced 14-3-3 binding constrained LNK function. Furthermore, interaction with 14-3-3 sequestered LNK in the cytoplasm away from the plasma membrane-proximal JAK2. Importantly, bone marrow transplantation studies revealed an essential role for 14-3-3 in HSPC reconstitution that can be partially mitigated by LNK deficiency. We believe that, together, this work implicates 14-3-3 proteins as novel and positive HSPC regulators by impinging on the LNK/JAK2 pathway.

Dysregulation of cell polarity proteins synergize with oncogenes or the microenvironment to induce invasive behavior in epithelial cells

Changes in expression and localization of proteins that regulate cell and tissue polarity are frequently observed in carcinoma. However, the mechanisms by which changes in cell polarity proteins regulate carcinoma progression are not well understood. Here, we report that loss of polarity protein expression in epithelial cells primes them for cooperation with oncogenes or changes in tissue microenvironment to promote invasive behavior. Activation of ErbB2 in cells lacking the polarity regulators Scribble, Dlg1 or AF-6, induced invasive properties. This cooperation required the ability of ErbB2 to regulate the Par6/aPKC polarity complex. Inhibition of the ErbB2-Par6 pathway was sufficient to block ErbB2-induced invasion suggesting that two polarity hits may be needed for ErbB2 to promote invasion. Interestingly, in the absence of ErbB2 activation, either a combined loss of two polarity proteins, or exposure of cells lacking one polarity protein to cytokines IL-6 or TNFα induced invasive behavior in epithelial cells. We observed the invasive behavior only when cells were plated on a stiff matrix (Matrigel/Collagen-1) and not when plated on a soft matrix (Matrigel alone). Cells lacking two polarity proteins upregulated expression of EGFR and activated Akt. Inhibition of Akt activity blocked the invasive behavior identifying a mechanism by which loss of polarity promotes invasion of epithelial cells. Thus, we demonstrate that loss of polarity proteins confers phenotypic plasticity to epithelial cells such that they display normal behavior under normal culture conditions but display aggressive behavior in response to activation of oncogenes or exposure to cytokines.

Breast cancer signatures for invasiveness and prognosis defined by deep sequencing of microRNA

The transition from ductal carcinoma in situ to invasive ductal carcinoma is a key event in breast cancer progression that is still not well understood. To discover the microRNAs regulating this critical transition, we used 80 biopsies from invasive ductal carcinoma, 8 from ductal carcinoma in situ, and 6 from normal breast. We selected them from a recently published deep-sequencing dataset [Farazi TA, et al. (2011) Cancer Res 71:4443-4453]. The microRNA profile established for the normal breast to ductal carcinoma in situ transition was largely maintained in the in situ to invasive ductal carcinoma transition. Nevertheless, a nine-microRNA signature was identified that differentiated invasive from in situ carcinoma. Specifically, let-7d, miR-210, and -221 were down-regulated in the in situ and up-regulated in the invasive transition, thus featuring an expression reversal along the cancer progression path. Additionally, we identified microRNAs for overall survival and time to metastasis. Five noncoding genes were associated with both prognostic signatures--miR-210, -21, -106b*, -197, and let-7i, with miR-210 the only one also involved in the invasive transition. To pinpoint critical cellular functions affected in the invasive transition, we identified the protein coding genes with inversely related profiles to miR-210: BRCA1, FANCD, FANCF, PARP1, E-cadherin, and Rb1 were all activated in the in situ and down-regulated in the invasive carcinoma. Additionally, we detected differential splicing isoforms with special features, including a truncated EGFR lacking the kinase domain and overexpressed only in ductal carcinoma in situ.

14-3-3 fusion oncogenes in high-grade endometrial stromal sarcoma

14-3-3 proteins are ubiquitously expressed regulators of various cellular functions, including proliferation, metabolism, and differentiation, and altered 14-3-3 expression is associated with development and progression of cancer. We report a transforming 14-3-3 oncoprotein, which we identified through conventional cytogenetics and whole-transcriptome sequencing analysis as a highly recurrent genetic mechanism in a clinically aggressive form of uterine sarcoma: high-grade endometrial stromal sarcoma (ESS). The 14-3-3 oncoprotein results from a t(10;17) genomic rearrangement, leading to fusion between 14-3-3ε (YWHAE) and either of two nearly identical FAM22 family members (FAM22A or FAM22B). Expression of YWHAE-FAM22 fusion oncoproteins was demonstrated by immunoblot in t(10;17)-bearing frozen tumor and cell line samples. YWHAE-FAM22 fusion gene knockdowns were performed with shRNAs and siRNAs targeting various FAM22A exons in an t(10;17)-bearing ESS cell line (ESS1): Fusion protein expression was inhibited, with corresponding reduction in cell growth and migration. YWHAE-FAM22 maintains a structurally and functionally intact 14-3-3ε (YWHAE) protein-binding domain, which is directed to the nucleus by a FAM22 nuclear localization sequence. In contrast to classic ESS, harboring JAZF1 genetic fusions, YWHAE-FAM22 ESS display high-grade histologic features, a distinct gene-expression profile, and a more aggressive clinical course. Fluorescence in situ hybridization analysis demonstrated absolute specificity of YWHAE-FAM22A/B genetic rearrangement for high-grade ESS, with no fusions detected in other uterine and nonuterine mesenchymal tumors (55 tumor types, n = 827). These discoveries reveal diagnostically and therapeutically relevant models for characterizing aberrant 14-3-3 oncogenic functions.

Differential Expression of Key Signaling Proteins in MCF10 Cell Lines, a Human Breast Cancer Progression Model

Breast cancer is a heterogeneous disease that develops through a multistep process whose molecular basis remains poorly understood. The molecular mechanisms of breast cancer progression have been extensively studied using the MCF10 model. We summarized recent results on differential expression of proteins in the MCF10 cell series - MCF10A, MCF10AT1, MCF10DCIS.com and MCF10CA1a - and compared the ability of the latter 3 lines to form tumors in immunodeficient mice. In addition, we also investigated expression of several key signaling proteins in the MCF10 cell series corresponding to different stages of breast cancer progression. MCF10DCIS.com and MCF10CA1a cells were highly tumorigenic; MCF10CA1a cells showed more aggressive tumor growth than MCF10DCIS.com cells. HRAS-driven cancer initiation stage was accompanied by the increased expression of c-Myc, cyclin D1 and IGF-IR. Tumorigenic cell lines expressed higher levels of pErk, pAkt, Stat3 and Pak4 compared to nontumorigenic cells. The expression of CD44v, CD44v3, CD44v6, ERBB2, Cox2 and Smad4 correlated with the increased tumorigenicity of the MCF10 cell lines. The differences in expression of signaling proteins involved in breast cancer progression may provide new insight into the mechanisms of tumorigenesis and useful information for development of targeted therapeutics.

Ductal carcinoma in situ: challenges, opportunities, and uncharted waters

Ductal carcinoma in situ (DCIS) is a heterogeneous group of diseases that differ in biology and clinical behavior. Until 1980, DCIS represented less than 1% of all breast cancer cases. With the increased utilization of mammography, DCIS now accounts for 15% to 25% of newly diagnosed breast cancer cases in the United States. Although our ability to detect DCIS has radically improved, our understanding of the pathophysiology and factors involved in its progression to invasive carcinoma is still poorly defined. In many patients, DCIS will never progress to invasive breast cancer and these women are overtreated. In contrast, some DCIS cases are clinically aggressive and the women may be undertreated. We are able to define some of the predictors of aggressive DCIS compared with DCIS of low malignant potential. However, our ability to risk-stratify DCIS is still in its infancy. Clinical risk factors that predict aggressive disease and increased risk of local recurrence include young age at diagnosis, large lesion size, high nuclear grade, comedo necrosis, and involved margins. Treatment factors such as wider surgical margins and radiation therapy reduce the risk of local recurrence. DCIS represents a key intermediate in the stepwise progression to malignancy, but not all aggressive breast cancers appear to have a DCIS intermediate, notably within triple-negative breast cancer. Ongoing studies of the genetic and epigenetic alterations in precancerous breast lesions (atypia and DCIS) as well as the breast microenvironment are important for developing effective early detection and individualized targeted prevention.

The effect of miR-7 on behavior and global protein expression in glioma cell lines

Malignant glioma is a common cancer of the nervous system. Despite recent research efforts in cancer therapy, the prognosis of patients with malignant glioma has remained dismal. MicroRNAs are noncoding RNAs that inhibit the expression of their targets in a sequence-specific manner, and a few have been shown to act as oncogenes or tumor suppressors. Here, we aimed at exploring the precise biological role of microRNA-7 (miR-7) and the global protein changes in glioma cell lines transiently transfected with miR-7. Transfection of miR-7 into glioma cell lines causes inhibition of cell migration and invasion and suppression of tumorigenesis. Moreover, ectopic expression of miR-7 inhibits lung metastases of glioma in vivo. Among 65 protein spots with differential expression separated by 2-DE, 37 proteins were successfully identified by MS/MS analysis. Of those, the 25 downregulated proteins, which include 14-3-3ζ, eukaryotic translation initiation factor 5A (EIF5A), and annexin A4, may be downstream targets of miR-7, a finding that could elucidate some aspects of the behavior of glioma cells at the protein level. In conclusion, the absence of miR-7 function could cause downstream molecules to switch on or off, resulting in glioma development, invasion, and metastases. MiR-7-based gene treatment may be a novel anti-invasion therapeutic strategy for malignant glioma.

Loss of the 14-3-3σ tumor suppressor is a critical event in ErbB2-mediated tumor progression

14-3-3σ is a putative tumor suppressor involved in cell-cycle progression and epithelial polarity. We demonstrate that loss of one or both copies of the conditional 14-3-3σ allele results in accelerated mammary and salivary tumorigenesis in mice expressing an activated erbB2 oncogene under the endogenous erbB2 promoter. Significantly, the majority of tumors bearing a single conditional 14-3-3σ allele lose expression of the remaining 14-3-3σ allele, which is associated with epigenetic methylation of the 14-3-3σ locus. In addition to accelerated tumor onset, in a mouse mammary tumor virus-driven ErbB2 tumor model, loss of 14-3-3σ results in enhanced metastatic phenotype that is correlated with loss of cellular junctions. Taken together, these results provide compelling evidence that 14-3-3σ is a potent tumor suppressor involved in ErbB2-driven breast cancer initiation and metastasis.

SIGNIFICANCE

14-3-3σ has been identified as a normal mammary epithelial cell marker frequently downregulated during neoplastic development. Consistent with its potential role as a tumor suppressor, we demonstrate that targeted disruption of 14-3-3σ in a number of epithelial tissues can profoundly impact both the initiation and metastatic phases of ErbB2-mediated tumor progression through modulation of a number of distinct signaling networks.

The role of polymeric immunoglobulin receptor in inflammation-induced tumor metastasis of human hepatocellular carcinoma

Background

Expression of the polymeric immunoglobulin receptor (pIgR), a transporter of polymeric IgA and IgM, is commonly increased in response to viral or bacterial infections, linking innate and adaptive immunity. Abnormal expression of pIgR in cancer was also observed, but its clinical relevance remains uncertain.

Methods

A human hepatocellular carcinoma (HCC) tissue microarray (n = 254) was used to investigate the association between pIgR expression and early recurrence. An experimental lung metastasis model using severe combined immune-deficient mice was applied to determine the metastatic potential of Madin–Darby canine kidney (n = 5 mice per group) and SMMC-7721 (n = 12 mice per group) cells overexpressing pIgR vs control cells. RNA interference, immunoprecipitation, and immunoblotting were performed to investigate the potential role for pIgR in the induction of epithelial–mesenchymal transition (EMT). In vitro studies (co-immunoprecipitation, immunoblotting, and migration, invasion, and adhesion assays) were used to determine the mechanisms behind pIgR-mediated metastasis. All statistical tests were two-sided.

Results

High expression of pIgR was statistically significantly associated with early recurrence in early-stage HCC and in hepatitis B surface antigen–positive HCC patients (log-rank P = .02). Mice injected with pIgR-overexpressing cells had a statistically significantly higher number of lung metastases compared with respective control cells (Madin–Darby canine kidney cells: pIgR mean = 29.4 metastatic nodules per lung vs control mean = 0.0 metastatic nodules per lung, difference = 29.4 metastatic nodules per lung, 95% confidence interval = 13.0 to 45.8, P = .001; SMMC-7721 cells: pIgR mean = 10.4 metastatic nodules per lung vs control mean = 2.2 metastatic nodules per lung, difference = 8.2 metastatic nodules per lung, 95% confidence interval = 1.0 to 15.5, P = .03). Furthermore, high expression of pIgR was sufficient to induce EMT through activation of Smad signaling.

Conclusions

pIgR plays a role in the induction of EMT. Our results identify pIgR as a potential link between hepatitis B virus–derived hepatitis and HCC metastasis and provide evidence in support of pIgR as a prognostic biomarker for HCC and a potential therapeutic target.

14-3-3 proteins as potential therapeutic targets

The 14-3-3 family of phosphoserine/phosphothreonine-binding proteins dynamically regulates the activity of client proteins in various signaling pathways that control diverse physiological and pathological processes. In response to environmental cues, 14-3-3 proteins orchestrate the highly regulated flow of signals through complex networks of molecular interactions to achieve well-controlled physiological outputs, such as cell proliferation or differentiation. Accumulating evidence now supports the concept that either an abnormal state of 14-3-3 protein expression, or dysregulation of 14-3-3/client protein interactions, contributes to the development of a large number of human diseases. In particular, clinical investigations in the field of oncology have demonstrated a correlation between upregulated 14-3-3 levels and poor survival of cancer patients. These studies highlight the rapid emergence of 14-3-3 proteins as a novel class of molecular target for potential therapeutic intervention. The current status of 14-3-3 modulator discovery is discussed.

14-3-3 Proteins: diverse functions in cell proliferation and cancer progression

The 14-3-3 proteins were the first phosphoserine/phosphothreonine-binding proteins to be discovered, a finding that provided the foundation for their prominent role in cell signaling. 14-3-3 family members interact with a wide spectrum of proteins including transcription factors, biosynthetic enzymes, cytoskeletal proteins, signaling molecules, apoptosis factors, and tumor suppressors. The interaction with 14-3-3 can have a profound effect on a target protein, altering its localization, stability, conformation, phosphorylation state, activity, and/or molecular interactions. Thus, by modulating the function of a diverse array of binding partners, 14-3-3 proteins have become key regulatory components in many vital cellular processes - processes that are crucial for normal growth and development and that often become dysregulated in human cancer. This review will examine the recent advances that further elucidate the role of 14-3-3 proteins in normal growth and cancer signaling with a particular emphasis on the signaling pathways that impact cell proliferation, cell migration, and epithelial-to-mesenchymal transition.

Overexpression of 14-3-3ζ in cancer cells activates PI3K via binding the p85 regulatory subunit

The ubiquitously expressed 14-3-3 proteins regulate many pathways involved in transformation. Previously, we found that 14-3-3ζ overexpression increased Akt phosphorylation in human mammary epithelial cells. Here, we investigated the clinical relevance and molecular mechanism of 14-3-3ζ overexpression-mediated Akt phosphorylation and the potential impact on breast cancer progression. We found that 14-3-3ζ overexpression was significantly (P = 0.005) associated with increased Akt phosphorylation in human breast tumors. Additionally, 14-3-3ζ overexpression combined with strong Akt phosphorylation was significantly (P=0.01) associated with increased cancer recurrence in patients. In contrast, knockdown of 14-3-3ζ expression by siRNA in cancer cell lines and tumor xenografts reduced Akt phosphorylation. Furthermore, 14-3-3ζ enhanced Akt phosphorylation through activation of PI3K. Mechanistically, 14-3-3ζ bound to the p85 regulatory subunit of PI3K and increased PI3K translocation to the cell membrane. A single 14-3-3 binding motif encompassing serine 83 on p85 is largely responsible for 14-3-3ζ-mediated p85 binding and PI3K/Akt activation. Mutation of serine 83 to alanine on p85 inhibited 14-3-3ζ binding to the p85 subunit of PI3K, reduced PI3K membrane localization and activation, impeded anchorage independent growth and enhanced stress induced apoptosis. These findings revealed a novel mechanism by which 14-3-3ζ overexpression activates PI3K, a key node in the mitogenic signaling network known to promote malignancies in many cell types.

Reversal of endocrine resistance in breast cancer: interrelationships among 14-3-3ζ, FOXM1, and a gene signature associated with mitosis

INTRODUCTION

Despite the benefits of estrogen receptor (ER)-targeted endocrine therapies in breast cancer, many tumors develop resistance. 14-3-3 ζ/YWHAZ, a member of the 14-3-3 family of conserved proteins, is over-expressed in several types of cancer, and our previous work showed that high expression of 14-3-3ζ in ER-positive breast cancers was associated with a poor clinical outcome for women on tamoxifen. Therefore, we now probe the role of 14-3-3ζ in endocrine resistance, and we examine the functional dimensions and molecular basis that underlie 14-3-3ζ activities.

METHODS

From analyses of four independent breast cancer microarray datasets from nearly 400 women, we characterized a gene signature that correlated strongly with high expression of 14-3-3ζ in breast tumors and examined its association with breast cancer molecular subtypes and clinical-pathological features. We investigated the effects of altering 14-3-3ζ levels in ER-positive, endocrine sensitive and resistant breast cancer cells on the regulation of 14-3-3ζ signature genes, and on cellular signaling pathways and cell phenotypic properties.

RESULTS

The gene signature associated with high 14-3-3ζ levels in breast tumors encompassed many with functions in mitosis and cytokinesis, including aurora kinase-B, polo-like kinase-1, CDC25B, and BIRC5/survivin. The gene signature correlated with early recurrence and risk of metastasis, and was found predominantly in luminal B breast cancers, the more aggressive ER-positive molecular subtype. The expression of the signature genes was significantly decreased or increased upon reduction or overexpression of 14-3-3ζ in ER-positive breast cancer cells, indicating their coregulation. 14-3-3ζ also played a critical role in the regulation of FOXM1, with 14-3-3ζ acting upstream of FOXM1 to regulate cell division-signature genes. Depletion of 14-3-3ζ markedly increased apoptosis, reduced proliferation and receptor tyrosine kinase (HER2 and EGFR) signaling, and, importantly, reversed endocrine resistance.

CONCLUSIONS

This study reveals that 14-3-3ζ is a key predictive marker for risk of failure on endocrine therapy and serves a pivotal role impacting growth factor signaling, and promoting cell survival and resistance to endocrine therapies. Targeting 14-3-3ζ and its coregulated proteins, such as FOXM1, should prove valuable in restoring endocrine sensitivity and reducing risk of breast cancer recurrence.

Proteomic patterns of cervical cancer cell lines, a network perspective

Background

Cervical cancer is a major mortality factor in the female population. This neoplastic is an excellent model for studying the mechanisms involved in cancer maintenance, because the Human Papilloma Virus (HPV) is the etiology factor in most cases. With the purpose of characterizing the effects of malignant transformation in cellular activity, proteomic studies constitute a reliable way to monitor the biological alterations induced by this disease. In this contextual scheme, a systemic description that enables the identification of the common events between cell lines of different origins, is required to distinguish the essence of carcinogenesis.

Results

With this study, we sought to achieve a systemic perspective of the common proteomic profile of six cervical cancer cell lines, both positive and negative for HPV, and which differ from the profile corresponding to the non-tumourgenic cell line, HaCaT. Our objectives were to identify common cellular events participating in cancer maintenance, as well as the establishment of a pipeline to work with proteomic-derived results. We analyzed by means of 2D SDS-PAGE and MALDI-TOF mass spectrometry the protein extracts of six cervical cancer cell lines, from which we identified a consensus of 66 proteins. We call this group of proteins, the "central core of cervical cancer". Starting from this core set of proteins, we acquired a PPI network that pointed, through topological analysis, to some proteins that may well be playing a central role in the neoplastic process, such as 14-3-3ζ. In silico overrepresentation analysis of transcription factors pointed to the overexpression of c-Myc, Max and E2F1 as key transcription factors involved in orchestrating the neoplastic phenotype.

Conclusions

Our findings show that there is a "central core of cervical cancer" protein expression pattern, and suggest that 14-3-3ζ is key to determine if the cell proliferates or dies. In addition, our bioinformatics analysis suggests that the neoplastic phenotype is governed by a non-canonical regulatory pathway.

Cancer cell migration: integrated roles of matrix mechanics and transforming potential

Significant progress has been achieved toward elucidating the molecular mechanisms that underlie breast cancer progression; yet, much less is known about the associated cellular biophysical traits. To this end, we use time-lapsed confocal microscopy to investigate the interplay among cell motility, three-dimensional (3D) matrix stiffness, matrix architecture, and transforming potential in a mammary epithelial cell (MEC) cancer progression series. We use a well characterized breast cancer progression model where human-derived MCF10A MECs overexpress either ErbB2, 14-3-3ζ, or both ErbB2 and 14-3-3ζ, with empty vector as a control. Cell motility assays showed that MECs overexpressing ErbB2 alone exhibited notably high migration speeds when cultured atop two-dimensional (2D) matrices, while overexpression of 14-3-3ζ alone most suppressed migration atop 2D matrices (as compared to non-transformed MECs). Our results also suggest that co-overexpression of the 14-3-3ζ and ErbB2 proteins facilitates cell migratory capacity in 3D matrices, as reflected in cell migration speed. Additionally, 3D matrices of sufficient stiffness can significantly hinder the migratory ability of partially transformed cells, but increased 3D matrix stiffness has a lesser effect on the aggressive migratory behavior exhibited by fully transformed cells that co-overexpress both ErbB2 and 14-3-3ζ. Finally, this study shows that for MECs possessing partial or full transforming potential, those overexpressing ErbB2 alone show the greatest sensitivity of cell migration speed to matrix architecture, while those overexpressing 14-3-3ζ alone exhibit the least sensitivity to matrix architecture. Given the current knowledge of breast cancer mechanobiology, these findings overall suggest that cell motility is governed by a complex interplay between matrix mechanics and transforming potential.

Repositioning chloroquine and metformin to eliminate cancer stem cell traits in pre-malignant lesions

Ideal oncology drugs would be curative after a short treatment course if they could eliminate epithelium-originated carcinomas at their non-invasive, pre-malignant stages. Such ideal molecules, which are expected to molecularly abrogate all the instrumental mechanisms acquired by migrating cancer stem cells (CSCs) to by-pass tumour suppressor barriers, might already exist. We here illustrate how system biology strategies for repositioning existing FDA-approved drugs may accelerate our therapeutic capacity to eliminate CSC traits in pre-invasive intraepithelial neoplasias. First, we describe a signalling network signature that overrides bioenergetics stress- and oncogene-induced senescence (OIS) phenomena in CSCs residing at pre-invasive lesions. Second, we functionally map the anti-malarial chloroquine and the anti-diabetic metformin ("old drugs") to their recently recognized CSC targets ("new uses") within the network. By discussing the preclinical efficacy of chloroquine and metformin to inhibiting the genesis and self-renewal of CSCs we finally underscore the expected translational impact of the "old drugs-new uses" repurposing strategy to open a new CSC-targeted chemoprevention era.

Targeting miR-375 in gastric cancer

INTRODUCTION

Gastric cancer remains a major cancer burden in the world, with a poor 5-year survival rate. It is necessary to develop new effective therapeutic strategies to improve the long-term clinical outcome. MicroRNA (miRNA), a class of small non-coding RNA, has been identified as a key regulator of gene expression, and is implicated in the pathogenesis of gastric cancer.

AREAS COVERED

This review summarizes the role of miRNAs in gastric carcinogenesis, with an emphasis on the expression and function of miR-375 in gastric cancer and beyond. It also discusses the opportunities and challenges of miR-375 as a potential therapeutic target for gastric cancer. The genes targeted by miR-375, including JAK2 and 3'-phosphoinositide dependent protein kinase-1 (PDK1), are also candidates for gastric cancer therapy.

EXPERT OPINION

Although radical surgery and rational chemotherapy are still the main treatment for gastric cancer, targeting miRNAs, in combination with other conventional therapies, may serve as a promising therapy strategy to improve the clinical outcome.

14-3-3ζ as a prognostic marker and therapeutic target for cancer

IMPORTANCE OF THE FIELD

The ubiquitously expressed 14-3-3ζ protein is involved in numerous important cellular pathways involved in cancer. Recent research suggests 14-3-3ζ may play a central role regulating multiple pathways responsible for cancer initiation and progression. This review will provide an overview of 14-3-3 proteins and address the role of 14-3-3ζ overexpression in cancer.

AREAS COVERED IN THIS REVIEW

The review covers the basic role of 14-3-3 in regulation of multiple pathways with a focus on 14-3-3ζ as a clinically relevant biomarker for cancer recurrence.

WHAT THE READER WILL GAIN

14-3-3ζ overexpression has been found in multiple cancers; however, the clinical implications were unclear. Recently, 14-3-3ζ has been identified as a biomarker for poor prognosis and chemoresistance in multiple tumor types, indicating a potential clinical application for using 14-3-3ζ in selecting treatment options and predicting cancer patients' outcome.

TAKE HOME MESSAGE

14-3-3ζ is a potential prognostic marker of cancer recurrence and predictive marker for therapeutic resistance. The overexpression of 14-3-3ζ in multiple cancers suggests that it may be a common target to intervene tumor progression; therefore, more efforts are needed for the development of 14-3-3 inhibitors.