Differential secretome analysis reveals CST6 as a suppressor of breast cancer bone metastasis

Immune mediated support of metastasis: Implication for bone invasion

Bone is a common organ affected by metastasis in various advanced cancers, including lung, breast, prostate, colorectal, and melanoma. Once a patient is diagnosed with bone metastasis, the patient's quality of life and overall survival are significantly reduced owing to a wide range of morbidities and the increasing difficulty of treatment. Many studies have shown that bone metastasis is closely related to bone microenvironment, especially bone immune microenvironment. However, the effects of various immune cells in the bone microenvironment on bone metastasis remain unclear. Here, we described the changes in various immune cells during bone metastasis and discussed their related mechanisms. Osteoblasts, adipocytes, and other non-immune cells closely related to bone metastasis were also included. This review also summarized the existing treatment methods and potential therapeutic targets, and provided insights for future studies of cancer bone metastasis.

Type 2 Cystatins and Their Roles in the Regulation of Human Immune Response and Cancer Progression

Cystatins are a family of intracellular and extracellular protease inhibitors that inhibit cysteine cathepsins-a group of lysosomal cysteine proteases that participate in multiple biological processes, including protein degradation and post-translational cleavage. Cysteine cathepsins are associated with the development of autoimmune diseases, tumor progression, and metastasis. Cystatins are categorized into three subfamilies: type 1, type 2, and type 3. The type 2 cystatin subfamily is the largest, containing 10 members, and consists entirely of small secreted proteins. Although type 2 cystatins have many shared biological roles, each member differs in structure, post-translational modifications (e.g., glycosylation), and expression in different cell types. These distinctions allow the type 2 cystatins to have unique biological functions and properties. This review provides an overview of type 2 cystatins, including their biological similarities and differences, their regulatory effect on human immune responses, and their roles in tumor progression, immune evasion, and metastasis.

Mechanism of regulating macrophages/osteoclasts in attenuating wear particle-induced aseptic osteolysis

Joint replacement surgery is the most effective treatment for end-stage arthritis. Aseptic loosening caused by periprosthetic osteolysis is a common complication after joint replacement. Inflammation induced by wear particles derived from prosthetic biomaterials is a major cause of osteolysis. We emphasize that bone marrow-derived macrophages and their fusion-derived osteoclasts play a key role in this pathological process. Researchers have developed multiple intervention approaches to regulate macrophage/osteoclast activation. Aiming at wear particle-induced periprosthetic aseptic osteolysis, this review separately discusses the molecular mechanism of regulation of ROS formation and inflammatory response through intervention of macrophage/osteoclast RANKL-MAPKs-NF-κB pathway. These molecular mechanisms regulate osteoclast activation in different ways, but they are not isolated from each other. There is also a lot of crosstalk among the different mechanisms. In addition, other bone and joint diseases related to osteoclast activation are also briefly introduced. Therefore, we discuss these new findings in the context of existing work with a view to developing new strategies for wear particle-associated osteolysis based on the regulation of macrophages/osteoclasts.

Taxifolin Inhibits Breast Cancer Growth by Facilitating CD8+ T Cell Infiltration and Inducing a Novel Set of Genes including Potential Tumor Suppressor Genes in 1q21.3

Taxifolin inhibits breast cancer (BC) via novel mechanisms. In a syngeneic mouse BC model, taxifolin suppressed 4T-1 cell-derived allografts. RNA-seq of 4T-1 tumors identified 36 differentially expressed genes (DEGs) upregulated by taxifolin. Among their human homologues, 19, 7, and 2 genes were downregulated in BCs, high-proliferative BCs, and BCs with high-fatality risks, respectively. Three genes were established as tumor suppressors and eight were novel to BC, including HNRN, KPRP, CRCT1, and FLG2. These four genes exhibit tumor suppressive actions and reside in 1q21.3, a locus amplified in 70% recurrent BCs, revealing a unique vulnerability of primary and recurrent BCs with 1q21.3 amplification with respect to taxifolin. Furthermore, the 36 DEGs formed a multiple gene panel (DEG36) that effectively stratified the fatality risk in luminal, HER2+, and triple-negative (TN) equivalent BCs in two large cohorts: the METABRIC and TCGA datasets. 4T-1 cells model human TNBC cells. The DEG36 most robustly predicted the poor prognosis of TNBCs and associated it with the infiltration of CD8+ T, NK, macrophages, and Th2 cells. Of note, taxifolin increased the CD8+ T cell content in 4T-1 tumors. The DEG36 is a novel and effective prognostic biomarker of BCs, particularly TNBCs, and can be used to assess the BC-associated immunosuppressive microenvironment.

Multimodal AI for prediction of distant metastasis in carcinoma patients

Metastasis of cancer is directly related to death in almost all cases, however a lot is yet to be understood about this process. Despite advancements in the available radiological investigation techniques, not all cases of Distant Metastasis (DM) are diagnosed at initial clinical presentation. Also, there are currently no standard biomarkers of metastasis. Early, accurate diagnosis of DM is however crucial for clinical decision making, and planning of appropriate management strategies. Previous works have achieved little success in attempts to predict DM from either clinical, genomic, radiology, or histopathology data. In this work we attempt a multimodal approach to predict the presence of DM in cancer patients by combining gene expression data, clinical data and histopathology images. We tested a novel combination of Random Forest (RF) algorithm with an optimization technique for gene selection, and investigated if gene expression pattern in the primary tissues of three cancer types (Bladder Carcinoma, Pancreatic Adenocarcinoma, and Head and Neck Squamous Carcinoma) with DM are similar or different. Gene expression biomarkers of DM identified by our proposed method outperformed Differentially Expressed Genes (DEGs) identified by the DESeq2 software package in the task of predicting presence or absence of DM. Genes involved in DM tend to be more cancer type specific rather than general across all cancers. Our results also indicate that multimodal data is more predictive of metastasis than either of the three unimodal data tested, and genomic data provides the highest contribution by a wide margin. The results re-emphasize the importance for availability of sufficient image data when a weakly supervised training technique is used. Code is made available at: https://github.com/rit-cui-lab/Multimodal-AI-for-Prediction-of-Distant-Metastasis-in-Carcinoma-Patients.

Microneedle Patch for Painless Intradermal Collection of Interstitial Fluid Enabling Multianalyte Measurement of Small Molecules, SARS-CoV-2 Antibodies, and Protein Profiling

Blood sampling is a common practice to monitor health, but it entails a series of drawbacks for patients including pain and discomfort. Thus, there is a demand for more convenient ways to obtain samples. Modern analytical techniques enable monitoring of multiple bioanalytes in smaller samples, opening possibilities for new matrices, and microsampling technologies to be adopted. Interstitial fluid (ISF) is an attractive alternative matrix that shows good correlation with plasma concentration dynamics for several analytes and can be sampled in a minimally invasive and painless manner from the skin at the point-of-care. However, there is currently a lack of sampling devices compatible with clinical translation. Here, to tackle state-of-the-art limitations, a cost-effective and compact single-microneedle-based device designed to painlessly collect precisely 1.1 µL of dermal ISF within minutes is presented. The fluid is volume-metered, dried, and stably stored into analytical-grade paper within the microfluidic device. The obtained sample can be mailed to a laboratory, quantitatively analyzed, and provide molecular insights comparable to blood testing. In a human study, the possibility to monitor various classes of molecular analytes is demonstrated in ISF microsamples, including caffeine, hundreds of proteins, and SARS-CoV-2 antibodies, some being detected in ISF for the first time.

The Secretome of Parental and Bone Metastatic Breast Cancer Elicits Distinct Effects in Human Osteoclast Activity after Activation of β2 Adrenergic Signaling

The sympathetic nervous system (SNS), particularly through the β2 adrenergic receptor (β2-AR), has been linked with breast cancer (BC) and the development of metastatic BC, specifically in the bone. Nevertheless, the potential clinical benefits of exploiting β2-AR antagonists as a treatment for BC and bone loss-associated symptoms remain controversial. In this work, we show that, when compared to control individuals, the epinephrine levels in a cohort of BC patients are augmented in both earlier and late stages of the disease. Furthermore, through a combination of proteomic profiling and functional in vitro studies with human osteoclasts and osteoblasts, we demonstrate that paracrine signaling from parental BC under β2-AR activation causes a robust decrease in human osteoclast differentiation and resorption activity, which is rescued in the presence of human osteoblasts. Conversely, metastatic bone tropic BC does not display this anti-osteoclastogenic effect. In conclusion, the observed changes in the proteomic profile of BC cells under β-AR activation that take place after metastatic dissemination, together with clinical data on epinephrine levels in BC patients, provided new insights on the sympathetic control of breast cancer and its implications on osteoclastic bone resorption.

Integrative, In Silico and Comparative Analysis of Breast Cancer Secretome Highlights Invasive-Ductal-Carcinoma-Grade Progression Biomarkers

Globally, BC is the most frequently diagnosed cancer in women. The aim of this study was to identify novel secreted biomarkers that may indicate progression to high-grade BC malignancies and therefore predict metastatic potential. A total of 33 studies of breast cancer and 78 of other malignancies were screened via a systematic review for eligibility, yielding 26 datasets, 8 breast cancer secretome datasets, and 18 of other cancers that were included in the comparative secretome analysis. Sequential bioinformatic analysis using online resources enabled the identification of enriched GO_terms, overlapping clusters, and pathway reconstruction. This study identified putative predictors of IDC grade progression and their association with breast cancer patient mortality outcomes, namely, HSPG2, ACTG1, and LAMA5 as biomarkers of in silico pathway prediction, offering a putative approach by which the abovementioned proteins may mediate their effects, enabling disease progression. This study also identified ITGB1, FBN1, and THBS1 as putative pan-cancer detection biomarkers. The present study highlights novel, putative secretome biomarkers that may provide insight into the tumor biology and could inform clinical decision making in the context of IDC management in a non-invasive manner.

CST6 suppresses osteolytic bone disease in multiple myeloma by blocking osteoclast differentiation

Osteolytic bone disease is a hallmark of multiple myeloma (MM). A significant fraction (~20%) of MM patients do not develop osteolytic lesions (OL). The molecular basis for the absence of bone disease in MM is not understood. We combined PET-CT and gene expression profiling (GEP) of purified bone marrow (BM) CD138+ MM cells from 512 newly diagnosed MM patients to reveal that elevated expression of cystatin M/E (CST6) was significantly associated with the absence of OL in MM. An enzyme-linked immunosorbent assay revealed a strong correlation between CST6 levels in BM serum/plasma and CST6 mRNA expression. Both recombinant CST6 protein and BM serum from patients with high CST6 significantly inhibited the activity of the osteoclast-specific protease cathepsin K, and blocked osteoclast differentiation and function. Recombinant CST6 inhibited bone destruction in ex vivo and in vivo myeloma models. Single cell RNA-sequencing identified that CST6 attenuates polarization of monocytes to osteoclast precursors. Furthermore, CST6 protein blocks osteoclast differentiation by suppressing cathepsin-mediated cleavage of NF-κB/p100 and TRAF3 following RANKL stimulation. Secretion by MM cells of CST6, an inhibitor of osteoclast differentiation and function, suppresses osteolytic bone disease in MM and probably other diseases associated with osteoclast-mediated bone loss.

Cystatin SN promotes epithelial-mesenchymal transition and serves as a prognostic biomarker in lung adenocarcinoma

Background

Cystatins are a class of proteins that can inhibit cysteine protease and are widely distributed in human bodily fluids and secretions. Cystatin SN (CST1), a member of the CST superfamily, is abnormally expressed in a variety of tumors. However, its effect on the occurrence and development of lung adenocarcinoma (LUAD) remains unclear.

Methods

We obtained transcriptome analysis data of CST1 from The Cancer Genome Atlas (TCGA) and GSE31210 databases. The association of CST1 expression with prognosis, gene mutations and tumor immune microenvironment was analyzed using public databases. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were performed to investigate the potential mechanisms of CST1.

Results

In this study, we found that CST1 was highly expressed in lung adenocarcinoma and was associated with prognosis and tumor immune microenvironment. Genetic mutations of CST1 were shown to be related to disease-free survival (DFS) by using the c-BioPortal tool. Potential proteins binding to CST1 were identified by constructing a protein-protein interaction (PPI) network. Gene set enrichment analysis (GSEA) of CST1 revealed that CST1 was notably enriched in epithelial-mesenchymal transition (EMT). Cell experiments confirmed that overexpression of CST1 promoted lung adenocarcinoma cells migration and invasion, while knockdown of CST1 significantly inhibited lung adenocarcinoma cells migration and invasion.

Conclusions

Our comprehensive bioinformatics analyses revealed that CST1 may be a novel prognostic biomarker in LUAD. Experiments confirmed that CST1 promotes epithelial-mesenchymal transition in LUAD cells. These findings will help to better understand the distinct role of CST1 in LUAD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09685-z.

Identification and Validation of Invasion-Related Molecular Subtypes and Prognostic Features for Cervical Cancer

Background

As one of the main causes leading to female cancer deaths, cervical cancer shows malignant features of local infiltration and invasion into adjacent organs and tissues. This study was designed to categorize novel molecular subtypes according to cervical cancer invasion and screen reliable prognostic markers.

Methods

Invasion-related gene sets and expression profiles of invasion-related genes were collected from the CancerSEA database and The Cancer Genome Atlas (TCGA), respectively. Samples were clustered by nonnegative matrix factorization (NMF) to obtain different molecular subgroups, immune microenvironment characteristics of which were further systematically compared. Limma was employed to screen differentially expressed gene sets in different subtypes, followed by Lasso analysis for dimension reduction. Multivariate and univariate Cox regression analysis was performed to determine prognostic characteristics. The Kaplan-Meier test showed the prognostic differences of patients with different risks. Additionally, receiver operating characteristic (ROC) curves were applied to validate the prognostic model performance. A nomogram model was developed using clinical and prognostic characteristics of cervical cancer, and its prediction accuracy was reflected by calibration curve.

Results

This study filtered 19 invasion-related genes with prognosis significance in cervical cancer and 2 molecular subtypes (C1, C2). Specifically, the C1 subtype had an unfavorable prognosis, which was associated with the activation of the TGF-beta signaling pathway, focal adhesion, and PI3K-Akt signaling pathway. 875 differentially expressed genes were screened, and 8 key genes were finally retained by the dimension reduction analysis. An 8-gene signature was established as an independent factor predictive of the prognosis of cervical cancer. The signature performance was even stronger when combined with N stage.

Conclusion

Based on invasion-related genes, the present study categorized two cervical cancer subtypes with distinct TME characteristics and established an 8-gene marker that can accurately and independently predict the prognosis of cervical cancer.

Active demethylation upregulates CD147 expression promoting non-small cell lung cancer invasion and metastasis

Non-small cell lung cancer (NSCLC) is a fatal disease, and its metastatic process is poorly understood. Although aberrant methylation is involved in tumor progression, the mechanisms underlying dynamic DNA methylation remain to be elucidated. It is significant to study the molecular mechanism of NSCLC metastasis and identify new biomarkers for NSCLC early diagnosis. Here, we performed MeDIP-seq and hMeDIP-seq analyses to detect the genes regulated by dynamic DNA methylation. Comparison of the 5mC and 5hmC sites revealed that the CD147 gene underwent active demethylation in NSCLC tissues compared with normal tissues, and this demethylation upregulated CD147 expression. Significantly high levels of CD147 expression and low levels of promoter methylation were observed in NSCLC tissues. Then, we identified the CD147 promoter as a target of KLF6, MeCP2, and DNMT3A. Treatment of cells with TGF-β triggered active demethylation involving loss of KLF6/MeCP2/DNMT3A and recruitment of Sp1, Tet1, TDG, and SMAD2/3 transcription complexes. A dCas9-SunTag-DNMAT3A-sgCD147-targeted methylation system was constructed to reverse CD147 expression. The targeted methylation system downregulated CD147 expression and inhibited NSCLC proliferation and metastasis in vitro and in vivo. Accordingly, we used cfDNA to detect the levels of CD147 methylation in NSCLC tissues and found that the CD147 methylation levels exhibited an inverse relationship with tumor size, lymphatic metastasis, and TNM stage. In conclusion, this study clarified the mechanism of active demethylation of CD147 and suggested that the targeted methylation of CD147 could inhibit NSCLC invasion and metastasis, providing a highly promising therapeutic target for NSCLC.

CST6 protein and peptides inhibit breast cancer bone metastasis by suppressing CTSB activity and osteoclastogenesis

Background: Bone metastasis is a frequent symptom of breast cancer and current targeted therapy has limited efficacy. Osteoclasts play critical roles to drive osteolysis and metastatic outgrowth of tumor cells in bone. Previously we identified CST6 as a secretory protein significantly downregulated in bone-metastatic breast cancer cells. Functional analysis showed that CST6 suppresses breast-to-bone metastasis in animal models. However, the functional mechanism and therapeutic potential of CST6 in bone metastasis is unknown.

Methods: Using in vitro osteoclastogenesis and in vivo metastasis assays, we studied the effect and mechanism of extracellular CST6 protein in suppressing osteoclastic niches and bone metastasis of breast cancer. A number of peptides containing the functional domain of CST6 were screened to inhibit bone metastasis. The efficacy, stability and toxicity of CST6 recombinant protein and peptides were evaluated in preclinical metastasis models.

Results: We show here that CST6 inhibits osteolytic bone metastasis by inhibiting osteoclastogenesis. Cancer cell-derived CST6 enters osteoclasts by endocytosis and suppresses the cysteine protease CTSB, leading to up-regulation of the CTSB hydrolytic substrate SPHK1. SPHK1 suppresses osteoclast maturation by inhibiting the RANKL-induced p38 activation. Importantly, recombinant CST6 protein effectively suppresses bone metastasis in vitro and in vivo. We further identified several peptides mimicking the function of CST6 to suppress cancer cell-induced osteoclastogenesis and bone metastasis. Pre-clinical analyses of CTS6 recombinant protein and peptides demonstrated their potentials in treatment of breast cancer bone metastasis.

Conclusion: These findings reveal the CST6-CTSB-SPHK1 signaling axis in osteoclast differentiation and provide a promising approach to treat bone diseases with CST6-based peptides.

A Pan-Cancer Analysis of Cystatin E/M Reveals Its Dual Functional Effects and Positive Regulation of Epithelial Cell in Human Tumors

Cystatin E/M (CST6), a representative cysteine protease inhibitor, plays both tumor-promoting and tumor-suppressing functions and is pursued as an epigenetically therapeutic target in special cancer types. However, a comprehensive and systematic analysis for CST6 in pan-cancer level is still lacking. In the present study, we explored the expression pattern of CST6 in multiple cancer types across ∼10,000 samples from TCGA (The Cancer Genome Atlas) and ∼8,000 samples from MMDs (Merged Microarray-acquired Datasets). We found that the dynamic expression alteration of CST6 was consistent with dual function in different types of cancer. In addition, we observed that the expression of CST6 was globally regulated by the DNA methylation in its promoter region. CST6 expression was positively correlated with the epithelial cell infiltration involved in epithelial-to-mesenchymal transition (EMT) and proliferation. The relationship between CST6 and tumor microenvironment was also explored. In particular, we found that CST6 serves a protective function in the process of melanoma metastasis. Finally, the clinical association analysis further revealed the dual function of CST6 in cancer, and a combination of the epithelial cell infiltration and CST6 expression could predict the prognosis for SKCM patients. In summary, this first CST6 pan-cancer study improves the understanding of the dual functional effects on CST6 in different types of human cancer.

Proteomic profiling of extracellular vesicles and particles reveals the cellular response to cisplatin in NSCLC

BACKGROUND

Cisplatin-based chemotherapy is a therapeutic strategy against non-small cell lung cancer (NSCLC). However, cancers relapse after chemotherapy due to a dormant state of residual cancer cells. Extracellular vesicles and particles (EVPs) are active carriers of proteins and nucleic acid. Here, we aimed to study the molecular alterations and proteomic characteristics of EPV in dormant and reactivated cancer cells induced by cisplatin.

METHODS

We used a short-term single dose of cisplatin to induce the dormant and reactivated cell status. We examined the gene expressional profiling and proteomic profiling of EVPs from dormant and reactivated cancer cells by RNA-sequencing and LC-MS/MS.

RESULTS

We found substantial changes in gene expression and protein level in EVP. The genes with higher expression in dormant cancer cells were lipid transporter- and lipid metabolic-related genes. A total of 111 EVP proteins were upregulated in dormant cancer cells compared to those in control cells. Fifty differential expressed proteins (DEPs) were identified in EVPs from reactivated cancer cells compared to those in dormant cancer cells. Among the DEPs, we found that apolipoproteins such as APOA1 and APOE were significantly increased in dormant cancer cell-derived EVPs. Integration of EVP proteomes with transcriptional profiles of cancer cells revealed that the proteomic profiling of EVP derived from cancer cells can reflect the cellular status of cancer cells, which showed an activated lipid metabolism in dormant state.

CONCLUSION

Lipoproteins enriched in EVPs reflect the activated lipid metabolism in dormant cancer cells and may provide potential biomarkers or therapeutic targets for cisplatin-based therapy.

Metastatic Breast Cancer, Organotropism and Therapeutics: A Review

The final stage of breast cancer involves spreading breast cancer cells to the vital organs like the brain, liver lungs and bones in the process called metastasis. Once the target organ is overtaken by the metastatic breast cancer cells, its usual function is compromised causing organ dysfunction and death. Despite the significant research on breast cancer metastasis, it's still the main culprit of breast cancer-related deaths. Exploring the complex molecular pathways associated with the initiation and progression of breast cancer metastasis could lead to the discovery of more effective ways of treating the devastating phenomenon. The present review article highlights the recent advances to understand the complexity associated with breast cancer metastases, organotropism and therapeutic advances.

miRNA-6715-5p Inhibits Cellular Proliferation and Invasion in Colorectal Cancer by Directly Targeting CST4

Background

Data on the correlation between CST4 and colorectal cancer (CRC) metastasis are scarce. The aim of this study was to analyze CST4 expression and investigate its biological roles and related microRNA- (miRNA-) mediated regulation in CRC.

Methods

The expression of CST4 was examined in cancer tissues and their corresponding adjacent normal tissues from 40 gastric adenocarcinoma patients. The expression level of CST4 in specimens (cancer and normal tissues) was assessed through immunohistochemistry and/or quantitative polymerase chain reaction. miRNAs targeting CST4 in CRC were predicted by bioinformatics software. CST4 was knocked down in HCT116 cells and candidate miRNAs were transfected into HCT116 cells, and the effects of CST4 knockdown and miRNA transfection on cell proliferation and invasion were examined using CCK8, cell colony formation, and Transwell migration assays. Luciferase double-reporter assays were performed to verify the relationship between miRNA and CST4.

Results

The expression of CST4 in CRC tissues was significantly higher than that in normal paracancerous tissues, but the results for miRNA-6715-5p were opposite. Regardless of CST4 knockdown or miRNA-6715-5p overexpression, the proliferation and invasion ability of HCT116 cells decreased significantly. Luciferase double-reporter assays showed that the upregulation of miR-6715-5p significantly reduced the luciferase activities of the CST4 3'-UTR plasmid in HCT116 cells.

Conclusion

CST4 may be involved in CRC proliferation and metastasis. miRNA-6715-5p directly targets CST4 and negatively regulates its expression.

Cystatin M/E (Cystatin 6): A Janus-Faced Cysteine Protease Inhibitor with Both Tumor-Suppressing and Tumor-Promoting Functions

Alongside its contribution in maintaining skin homeostasis and its probable involvement in fetal and placental development, cystatin M/E (also known as cystatin 6) was first described as a tumor suppressor of breast cancer. This review aims to provide an update on cystatin M/E with particular attention paid to its role during tumorigenesis. Cystatin M/E, which is related to type 2 cystatins, displays the unique property of being a dual tight-binding inhibitor of both legumain (also known as asparagine endopeptidase) and cysteine cathepsins L, V and B, while its expression level is epigenetically regulated via the methylation of the CST6 promoter region. The tumor-suppressing role of cystatin M/E was further reported in melanoma, cervical, brain, prostate, gastric and renal cancers, and cystatin M/E was proposed as a biomarker of prognostic significance. Contrariwise, cystatin M/E could have an antagonistic function, acting as a tumor promoter (e.g., oral, pancreatic cancer, thyroid and hepatocellular carcinoma). Taking into account these apparently divergent functions, there is an urgent need to decipher the molecular and cellular regulatory mechanisms of the expression and activity of cystatin M/E associated with the safeguarding homeostasis of the proteolytic balance as well as its imbalance in cancer.

Investigating proteome changes between primary and metastatic cutaneous squamous cell carcinoma using SWATH mass spectrometry

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common malignancy worldwide and the first as the cause of death from keratinocytic carcinomas. Around 5% of primary cSCCs metastasize, leading to a 5-year survival rate of only 11 %.

OBJECTIVE

This paper aims to investigate the proteome profile of primary and metastatic cSCC lesions for the identification of potential diagnostic biomarkers and molecular alterations.

METHODS

Liquid chromatography coupled with SWATH-MS workflow was used to analyse the proteome profile of formalin-fixed and paraffin-embedded samples of primary (n = 20) and metastatic cSCC (n = 25) lesions. Statistical and bioinformatics analysis was performed to identify differentially abundant proteins and molecular alterations between the lesions.

RESULTS

A total of 5037 proteins were identified across the samples of which 19 proteins including ISG15, APOA1 and MARCKS with roles in metastasis were increased and 11 proteins including DMKN, APCS and CST6 decreased in metastatic cSCC lesions relative to the primary phenotypes (adj. p-value <0.05). The proteomic data separated the lesions based on their histopathological diagnosis. Bioinformatics analysis revealed that cell migration, cell survival and immune response are likely activated, and apoptosis is inhibited in metastatic cSCC lesions, indicating increased lesion complexity as the disease progresses from primary to the metastatic phenotype. Two samples were reclassified after PCA analysis.

CONCLUSION

SWATH-MS analysis identified important molecular changes between primary and metastatic cSCC samples. Exploring these findings further will allow their translation into the clinic for improved tumour diagnosis, staging and therapeutic intervention.

Placental transcriptome profile of women with sickle cell disease reveals differentially expressed genes involved in migration, trophoblast differentiation and inflammation

Sickle cell disease (SCD) is a group of disorders whose common characteristic is the presence of hemoglobin (Hb) S in erythrocytes. The main consequence of this abnormality is vaso-occlusion, which can affect almost all organs including the placenta. This study aimed to evaluate the gene expression profile in placentas of women with SCD by means of total RNA sequencing. For this, we proposed a case-control study, with three groups of pregnant women: HbSS (n = 10), HbSC (n = 14) and HbAA (n = 21). The results showed differences in expression in a number of genes such as NOS2 (fold change, FC = 4.52), HLAG (FC = 5.56), ASCL2 (FC = 3.61), CXCL10 (FC = -3.66) and IL1R2 (FC = 3.92) for the HbSC group and S100A8 (FC = -3.82), CPXM2 (FC = 4.57), CXCL10 (FC = -4.59), CXCL11 (FC = -3.72) and CAMP (FC = -4.55) for the HbSS group. Differentially expressed genes are mainly associated with migration, trophoblast differentiation and inflammation. The causes leading to altered gene expression in placentas of sickle cell patients are not fully understood, but the presence of intravascular hemolysis and vaso-occlusion, with cycles of ischemia and reperfusion, may contribute to the emergence of an environment which can be very harmful for placental physiology, altering the nutrient supply and metabolic exchange for fetal growth.

Epigenetics of Circulating Tumor Cells in Breast Cancer

Liquid biopsy based on the analysis of circulating tumor cells (CTCs) has emerged as an important field of research. Molecular characterization of CTCs can provide insights into cancer biology and biomarkers for the clinic, representing a non-invasive powerful tool for monitoring breast cancer metastasis and predict the therapeutic response. Epigenetic mechanisms play a key role in the control of gene expression and their alteration contributes to cancer development and progression. These epigenetic modifications in CTCs have been described mainly related to modifications of the DNA methylation pattern and changes in the expression profile of noncoding RNAs. Here we summarize the recent findings on the epigenetic characterization of CTCs in breast cancer and their clinical value as tumor biomarkers, and discuss challenges and opportunities in this field.

Secreted Pyruvate Kinase M2 Promotes Lung Cancer Metastasis through Activating the Integrin Beta1/FAK Signaling Pathway

Cancer cell-derived secretomes have been documented to play critical roles in cancer progression. Intriguingly, alternative extracellular roles of intracellular proteins are involved in various steps of tumor progression, which can offer strategies to fight cancer. Herein, we identify lung cancer progression-associated secretome signatures using mass spectrometry analysis. Among them, PKM2 is verified to be highly expressed and secreted in lung cancer cells and clinical samples. Functional analyses demonstrates that secreted PKM2 facilitates tumor metastasis. Furthermore, mass spectrometry analysis and functional validation identify integrin β1 as a receptor of secreted PKM2. Mechanistically, secreted PKM2 directly bound to integrin β1 and subsequently activated the FAK/SRC/ERK axis to promote tumor metastasis. Collectively, our findings suggest that PKM2 is a potential serum biomarker for diagnosing lung cancer and that targeting the secreted PKM2-integrin β1 axis can inhibit lung cancer development, which provides evidence of a potential therapeutic strategy in lung cancer.

An anticancer effect of umbilical cord-derived mesenchymal stem cell secretome on the breast cancer cell line

Nowadays, Mesenchymal stem cells (MSCs) have become one of the most attractive tools for treating tumors, due to their specific characteristics, the most prominent of which are tropism toward tumor. These cells will exert their effects through their secretion. In this study, our aim was to evaluate the anti-cancer effect of umbilical cord-derived mesenchymal cells (UCMSC) secretome, on MCF-7 tumor cells. MSCs were extracted from the umbilical cord of mothers, having normal delivery or cesarean section. After culture, the supernatants of these cells were collected and freeze-dried. The cytotoxic effect of freeze-dried secretome was examined at different concentrations on MCF-7 and the optimum concentrations (IC50) were calculated, using MTT assay. These results were confirmed by BrdU assay. The effect of induction of apoptosis of the MSC secretome on MCF-7 was determined, using annexin V/PI method by flow cytometry. The results of our study indicate that the isolation and growth time of UCMSCs of mothers who were naturally delivered was lower than those who received cesarean section. Co-culture studies showed that MSCs had cytotoxic effects on MCF-7 cells. The MSC secretome also showed cytotoxic effects on the MCF-7 cell line, this effect was mediated by induction of apoptosis, which was dose-dependent with an IC50 of 10 mg/mL.

Cystatins in cancer progression: More than just cathepsin inhibitors

Cystatins are endogenous and reversible inhibitors of cysteine peptidases that are important players in cancer progression. Besides their primary role as regulators of cysteine peptidase activity, cystatins are involved in cancer development and progression through proteolysis-independent mechanisms. Mechanistic studies of cystatin function revealed that they affect all stages of cancer progression including tumor growth, apoptosis, invasion, metastasis and angiogenesis. Recently, the involvement of cystatins in the antitumor immune responses was reported. In this review, we discuss molecular mechanisms and clinical aspects of cystatins in cancer. Altered expression of cystatins in cancer resulting in harmful excessive cysteine peptidase activity has been a subject of several studies in order to find correlations with clinical outcome and therapy response. However, involvement in anti-tumor immune response and signaling cascades leading to cancer progression designates cystatins as possible targets for development of new anti-tumor drugs.

A secretome profile indicative of oleate-induced proliferation of HepG2 hepatocellular carcinoma cells

Increased fatty acid (FA) is often observed in highly proliferative tumors. FAs have been shown to modulate the secretion of proteins from tumor cells, contributing to tumor survival. However, the secreted factors affected by FA have not been systematically explored. Here, we found that treatment of oleate, a monounsaturated omega-9 FA, promoted the proliferation of HepG2 cells. To examine the secreted factors associated with oleate-induced cell proliferation, we performed a comprehensive secretome profiling of oleate-treated and untreated HepG2 cells. A comparison of the secretomes identified 349 differentially secreted proteins (DSPs; 145 upregulated and 192 downregulated) in oleate-treated samples, compared to untreated samples. The functional enrichment and network analyses of the DSPs revealed that the 145 upregulated secreted proteins by oleate treatment were mainly associated with cell proliferation-related processes, such as lipid metabolism, inflammatory response, and ER stress. Based on the network models of the DSPs, we selected six DSPs (MIF, THBS1, PDIA3, APOA1, FASN, and EEF2) that can represent such processes related to cell proliferation. Thus, our results provided a secretome profile indicative of an oleate-induced proliferation of HepG2 cells.

By exposing liver cancer cells to oleate, an unsaturated fatty acid, researchers have discovered a group of secreted proteins that may help explain why fatty acids increase proliferative capacity in tumors. Soyeon Park from Pohang University of Science and Technology in South Korea and coworkers treated liver cancer cells with oleate and then measured all the proteins released from the cells. Comparison with untreated cells revealed 145 proteins secreted at elevated levels—most of which were involved in metabolism, stress responses and other proliferation-related processes—and another 192 proteins secreted at reduced levels. The researchers ran additional biochemical analyses on six secreted proteins to validate the changes following exposure to oleate. The authors suggest that these validated proteins could now serve as biomarkers of tumor aggressiveness or as future drug targets.

Metastases of malignant neoplasms: Historical, biological, & clinical considerations

The metastasis of neoplastic cells from their site of origin to distant anatomic locations continues to be the principal cause of death from malignant tumors, and that fact has been recognized by physicians for over a century. After the work done by Halsted in the treatment of breast cancer in the 1880s, accepted surgical canon held that metastasis occurred in a linear fashion, with centrifugal "growth in continuity" from the primary neoplasm that first involved regional lymph nodes. Those structures were considered to then be the sources of more distant, visceral metastases. With that premise in mind, radical and "ultra-radical" surgical procedures were devised to remove as many lymph nodes as possible in the treatment of carcinomas and melanomas. However, such interventions were ineffective in altering tumor-related mortality. This review considers the details of the historical material just mentioned. It also reviews currently-held concepts on biological mechanisms of metastasis, the "sentinel" lymph node biopsy technique, and the important topic of metastatic tumor "dormancy" as the cause of surgical treatment failure. Finally, predictive models of tumor behavior are discussed, which are based on gene signatures. These will likely be the key to identifying malignant lesions of low surgical stage that ultimately prove fatal through later manifestation of metastasis.

Overexpression of CST4 promotes gastric cancer aggressiveness by activating the ELFN2 signaling pathway

Gastric cancer is one of the most lethal malignancies of gastrointestinal cancer and its prognosis remains dismal because of the paucity of effective therapeutic targets. Here, we show that cystatin 4 (CST4) is markedly upregulated in gastric cancer cell lines and clinical tissues. Ectopic expression of CST4 in gastric cancer cells promoted proliferation, migration, and invasion of gastric cancer cells in vitro. Furthermore, CST4 overexpression significantly promoted the tumorigenicity of gastric cancer cells in vivo, whereas silencing endogenous CST4 caused an opposite outcome. In addition, extracellular leucine rich repeat and fibronectin type III domain containing 2 (ELFN2) was identified as a downstream target of CST4 in gastric cancer cells and was positively correlated with ELFN2 expression in gastric cancer tissues. Finally, we demonstrated that CST4 enhanced gastric cancer aggressiveness by regulating ELFN2 signaling. Together, our results provide new evidence that CST4 overexpression promotes the progression of gastric cancer and might represent a novel therapeutic target for its treatment.

Differential effects on lung and bone metastasis of breast cancer by Wnt signalling inhibitor DKK1

Metastatic cancer is a systemic disease, and metastasis determinants might elicit completely different effects in various target organs. Here we show that tumour-secreted DKK1 is a serological marker of breast cancer metastasis organotropism and inhibits lung metastasis. DKK1 suppresses PTGS2-induced macrophage and neutrophil recruitment in lung metastases by antagonizing cancer cell non-canonical WNT/PCP-RAC1-JNK signalling. In the lungs, DKK1 also inhibits WNT/Ca²⁺-CaMKII-NF-κB signalling and suppresses LTBP1-mediated TGF-β secretion of cancer cells. In contrast, DKK1 promotes breast-to-bone metastasis by regulating canonical WNT signalling of osteoblasts. Importantly, targeting canonical WNT may not be beneficial to treatment of metastatic cancer, while combinatory therapy against JNK and TGF-β signalling effectively prevents metastasis to both the lungs and bone. Thus, DKK1 represents a class of Janus-faced molecules with dichotomous roles in organotropic metastasis, and our data provide a rationale for new anti-metastasis approaches.

Identification of Nucleobindin-2 as a Potential Biomarker for Breast Cancer Metastasis Using iTRAQ-based Quantitative Proteomic Analysis

Metastasis is a lethal step in the progression of breast cancer. None of the metastasis-associated biomarkers identified up to now has a definite prognostic value in breast cancer patients. This study was designed to identify biomarkers for breast cancer metastasis and predictors of the prognosis of breast cancer patients. The differentially expressed proteins between 23 paired primary breast tumor and metastatic lymph nodes were identified by quantitative iTRAQ proteomic analysis. Immunohistochemistry was applied to locate and assess the expression of NUCB2 in paired primary breast tumor and metastatic lymph node tissues (n = 106). The relationship between NUCB2 expression and the clinicopathological characteristics of breast cancer patients (n = 189) were analyzed by χ² test. Kaplan-Meier analysis and Cox hazard regression analysis were utilized to investigate the relationship between its expression and prognosis of breast cancer patients. The iTRAQ proteomic results showed that 4,837 confidential proteins were identified, 643 of which were differentially expressed in the primary breast cancer tissues and the paired metastatic lymph nodes. NUCB2 protein was found decreased in paired metastatic lymph nodes (P = 0.000), with the positive expression rate being 82% in primary breast cancer tissues and 47% in paired metastatic lymph nodes, respectively. According to Kaplan-Meier analysis, the overall survival time of patients with positive expression of NUCB2 protein were shorter than those with negative NUCB2 expression (P = 0.004). Cox regression model suggested that NUCB2 was a risk factor of breast cancer patients (P = 0.045, RR = 1.854). We conclude that NUCB2 can be used as a potential biomarker for breast cancer metastasis and a prognostic predictor of breast cancer patients.

Identification of Nidogen 1 as a lung metastasis protein through secretome analysis

Secreted proteins play crucial roles in mediating tumor-stroma interactions during metastasis of cancer to different target organs. To comprehensively profile secreted proteins involved in lung metastasis, we applied quantitative mass spectrometry-based proteomics and identified 392 breast cancer-derived and 302 melanoma-derived proteins secreted from highly lung metastatic cells. The cancer-specific lung metastasis secretome signatures (LMSSs) displayed significant prognostic value in multiple cancer clinical data sets. Moreover, we observed a significant overlap of enriched pathways between the LMSSs of breast cancer and melanoma despite an overall small overlap of specific proteins, suggesting that common biological processes are executed by different proteins to enable the two cancer types to metastasize to the lung. Among the novel candidate lung metastasis proteins, Nidogen 1 (NID1) was confirmed to promote lung metastasis of breast cancer and melanoma, and its expression is correlated with poor clinical outcomes. In vitro functional analysis further revealed multiple prometastatic functions of NID1, including enhancing cancer cell migration and invasion, promoting adhesion to the endothelium and disrupting its integrity, and improving vascular tube formation capacity. As a secreted prometastatic protein, NID1 may be developed as a new biomarker for disease progression and therapeutic target in breast cancer and melanoma.

Proteomic approaches to decipher cancer cell secretome

In this review, we give an overview of the actual proteomic approaches used in the study of cancer cells secretome. In particular, we describe the proteomic strategies to decipher cancer cell secretome initially focusing on the different aspects of sample preparation. We examine the issues related to the presence of low abundant proteins, the analysis of secreted proteins in the conditioned media with or without the removal of fetal bovine serum and strategies developed to reduce intracellular protein contamination. As regards the identification and quantification of secreted proteins, we described the different proteomic approaches used, i.e. gel-based, MS-based (label-based and label-free), and the antibody and array-based methods, together with some of the most recent applications in the field of cancer research. Moreover, we describe the bioinformatics tools developed for the in silico validation and characterization of cancer cells secretome. We also discuss the most important available tools for protein annotation and for prediction of classical and non-classical secreted proteins. In summary in this review advances, concerns and challenges in the field of cancer secretome analysis are discussed.

The Identification of Macrophage-enriched Glycoproteins Using Glycoproteomics

Prostate cancer is a leading cause of cancer-related deaths of men in the United States. Whereas the localized disease is highly treatable by surgical resection and radiation, cancer that has metastasized remains incurable. Immune cells that primarily scavenge debris and promote prostate cancer angiogenesis and wound repair are M2 macrophages. They are phenotypically similar to M2 tumor-associated macrophages (M2-TAMs) and have been reported to associate with solid tumors and aide in proliferation, metastasis, and resistance to therapy. As an invasive species within the tumor microenvironment, this makes M2-TAMs an ideal therapeutic target in prostate cancer. To identify novel surface glycoproteins expressed on M2 macrophages, we developed a novel method of creating homogeneous populations of human macrophages from human CD14⁺ monocytes in vitro These homogeneous M1 macrophages secrete pro-inflammatory cytokines, and our M2 macrophages secrete anti-inflammatory cytokines as well as vascular endothelial growth factor (VEGF). To identify enriched surface glycoproteins, we then performed solid-phase extraction of N-linked glycopeptides followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) on our homogeneous macrophage populations. We discovered five novel peptides that are enriched exclusively on human M2 macrophages relative to human M1 macrophages and human CD14⁺ monocytes. Finally, we determined whether these surface glycoproteins, found enriched on M2 macrophages, were also expressed in human metastatic castrate-resistant prostate cancer (mCRPC) tissues. Using mCRPC tissues from rapid autopsies, we were able to determine M2 macrophage infiltration by using immunohistochemistry and flow cytometry. These findings highlight the presence of macrophage infiltration in human mCRPC but also surface glycoproteins that could be used for prognosis of localized disease and for targeting strategies.

Characterization of long noncoding RNA and messenger RNA signatures in melanoma tumorigenesis and metastasis

The incidence of melanoma, the most aggressive and life-threatening form of skin cancer, has significantly risen over recent decades. Therefore, it is essential to identify the mechanisms that underlie melanoma tumorigenesis and metastasis and to explore novel and effective melanoma treatment strategies. Accumulating evidence s uggests that aberrantly expressed long noncoding RNAs (lncRNAs) have vital functions in multiple cancers. However, lncRNA functions in melanoma tumorigenesis and metastasis remain unclear. In this study, we investigated lncRNA and messenger RNA (mRNA) expression profiles in primary melanomas, metastatic melanomas and normal skin samples from the Gene Expression Omnibus database. We used GSE15605 as the training set (n = 74) and GSE7553 as the validation set (n = 58). In three comparisons (primary melanoma versus normal skin, metastatic melanoma versus normal skin, and metastatic melanoma versus primary melanoma), 178, 295 and 48 lncRNAs and 847, 1758, and 295 mRNAs were aberrantly expressed, respectively. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses to examine the differentially expressed mRNAs, and potential core lncRNAs were predicted by lncRNA-mRNA co-expression networks. Based on our results, 15 lncRNAs and 144 mRNAs were significantly associated with melanoma tumorigenesis and metastasis. A subsequent analysis suggested a critical role for a five-lncRNA signature during melanoma tumorigenesis and metastasis. Low expression of U47924.27 was significantly associated with decreased survival of patients with melanoma. To the best of our knowledge, this study is the first to explore the expression patterns of lncRNAs and mRNAs during melanoma tumorigenesis and metastasis by re-annotating microarray data from the Gene Expression Omnibus (GEO) microarray dataset. These findings reveal potential roles for lncRNAs during melanoma tumorigenesis and metastasis and provide a rich candidate reservoir for future studies.

Proteomic Analysis of Secreted Proteins from Cell Microenvironment

Cell microenvironment consists of various types of cells which communicate with each other by vast number of secreted proteins. An unbiased profiling of these secreted proteins on a global scale is often critical for understanding the intercellular signaling in an autocrine or paracrine manner. Mass spectrometry-based proteomics has become one of the most popular technology for characterization of the secreted proteins. In this chapter, we discuss the standard workflow for secreted proteins characterization, including harvesting secreted proteins from conditioned media, digesting the obtained proteins, liquid chromatography-mass spectrometry analysis, and downstream data analysis.

Predicting and Overcoming Chemotherapeutic Resistance in Breast Cancer

Our understanding of breast cancer and its therapeutic approach has improved greatly due to the advancement of molecular biology in recent years. Clinically, breast cancers are characterized into three basic types based on their immunohistochemical properties. They are triple-negative breast cancer, estrogen receptor (ER) and progesterone receptor (PR)-positive-HR positive breast cancer, and human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Even though these subtypes have been characterized, assessment of a breast cancer's receptor status is still widely used to determine whether or not a targeted therapy could be applied. Moreover, drug resistance is common in all breast cancer types despite the different treatment modalities applied. The development of resistance to different therapeutics is not mutually exclusive. It seems that tumor could be resistant to multiple treatment strategies, such as being both chemoresistant and monoclonal antibody resistant. However, the underlying mechanisms are complicated and need further investigation. In this chapter, we aim to provide a brief review of the different types of breast cancer and their respective treatment strategies. We also review the possible mechanisms of potential drug resistance associated with each treatment type. We believe that a better understanding of the drug resistance mechanisms can lead to a more effective and efficient therapeutic success.

Cystatin E/M Suppresses Tumor Cell Growth through Cytoplasmic Retention of NF-κB

We and others have shown that the cystatin E/M gene is inactivated in primary human tumors, pointing to its role as a tumor suppressor gene. However, the molecular mechanism of tumor suppression is not yet understood. Using plasmid-directed cystatin E/M gene overexpression, a lentivirus-mediated tetracycline-inducible vector system, and human papillomavirus 16 (HPV 16) E6 and E7 gene-immortalized normal human epidermal keratinocytes, we demonstrated intracellular and non-cell-autonomous apoptotic growth inhibition of tumor cell lines and that growth inhibition is associated with cytoplasmic retention of NF-κB. We further demonstrated decreased phosphorylation of IκB kinase (IKKβ) and IκBα in the presence of tumor necrosis factor alpha (TNF-α), confirming the role of cystatin E/M in the regulation of the NF-κB signaling pathway. Growth suppression of nude mouse xenograft tumors carrying a tetracycline-inducible vector system was observed with the addition of doxycycline in drinking water, confirming that the cystatin E/M gene is a tumor suppressor gene. Finally, immunohistochemical analyses of cervical carcinoma in situ and primary tumors have shown a statistically significant inverse relationship between the expression of cystatin E/M and cathepsin L and a direct relationship between the loss of cystatin E/M expression and nuclear expression of NF-κB. We therefore propose that the cystatin E/M suppressor gene plays an important role in the regulation of NF-κB.

Interleukin-6 Induced "Acute" Phenotypic Microenvironment Promotes Th1 Anti-Tumor Immunity in Cryo-Thermal Therapy Revealed By Shotgun and Parallel Reaction Monitoring Proteomics

Cryo-thermal therapy has been emerged as a promising novel therapeutic strategy for advanced breast cancer, triggering higher incidence of tumor regression and enhanced remission of metastasis than routine treatments. To better understand its anti-tumor mechanism, we utilized a spontaneous metastatic mouse model and quantitative proteomics to compare N-glycoproteome changes in 94 serum samples with and without treatment. We quantified 231 highly confident N-glycosylated proteins using iTRAQ shotgun proteomics. Among them, 53 showed significantly discriminated regulatory patterns over the time course, in which the acute phase response emerged as the most enhanced pathway. The anti-tumor feature of the acute response was further investigated using parallel reaction monitoring target proteomics and flow cytometry on 23 of the 53 significant proteins. We found that cryo-thermal therapy reset the tumor chronic inflammation to an “acute” phenotype, with up-regulation of acute phase proteins including IL-6 as a key regulator. The IL-6 mediated “acute” phenotype transformed IL-4 and Treg-promoting ICOSL expression to Th1-promoting IFN-γ and IL-12 production, augmented complement system activation and CD86⁺MHCII⁺ dendritic cells maturation and enhanced the proliferation of Th1 memory cells. In addition, we found an increased production of tumor progression and metastatic inhibitory proteins under such “acute” environment, favoring the anti-metastatic effect. Moreover, cryo-thermal on tumors induced the strongest “acute” response compared to cryo/hyperthermia alone or cryo-thermal on healthy tissues, accompanying by the most pronounced anti-tumor immunological effect. In summary, we demonstrated that cryo-thermal therapy induced, IL-6 mediated “acute” microenvironment shifted the tumor chronic microenvironment from Th2 immunosuppressive and pro-tumorigenic to Th1 immunostimulatory and tumoricidal state. Moreover, the magnitude of “acute” and “danger” signals play a key role in determining the efficacy of anti-tumor activity.

Biological roles of human bone morphogenetic protein 9 in the bone microenvironment of human breast cancer MDA-MB-231 cells

Bone marrow stroma plays a critical role in the bone metastasis of breast cancer. Bone marrow-derived mesenchymal stem cells (BMSC) are critical to facilitate cancer progression. Human bone morphogenetic protein 9 (BMP9) is the most potent osteogenic factor and one of bone-stored growth factors involved in both promotion and inhibition of different cancers. However, it is unclear whether BMP9 correlates with the bone metastasis of breast cancer. This study was to evaluate the role of BMP9 in the interaction between BMSC and breast cancer cells (BCC). To determine whether BMP9 is able to block the tumor promoting effect of BMSC, an in vitro model was developed using breast cancer MDA-MB-231 cells co-cultured with bone marrow-derived mesenchymal stem cells HS-5 with-BMP9 overexpression. The expressions of metastasis-related genes were detected to identify important factors mediating the role of BMP9 in breast cancer cells. Results showed BMP9 could inhibit invasion and promote apoptosis of MDA-MB-231 cells. The expressions of interleukin-6 (IL-6), matrix metalloproteinase-2 (MMP-2) and monocyte chemoattratctant protein-1 (MCP-1) decreased in the MDA-MB-231 cells of BMP9 over-expression group, and the expressions of epithelial-mesenchymal transition (EMT)-related molecules was also reduced. On the other hand, the expression of stromal cell derived factor-1 (SDF-1) decreased in HS-5 cells of BMP9 over-expression group. Taken together, BMP9 is able to inhibit the migration and promote the apoptosis of breast cancer by regulating the interaction between MDA-MB-231 cells and HS-5 cells in which SDF-1/CXCR4-PI3K pathway and EMT are involved.

Clinical and molecular complexity of breast cancer metastases

Clinical oncology is advancing toward a more personalized treatment orientation, making the need to understand the biology of metastasis increasingly acute. Dissecting the complex molecular, genetic and clinical phenotypes underlying the processes involved in the development of metastatic disease, which remains the principal cause of cancer-related deaths, could lead to the identification of more effective prognostication and targeted approaches to prevent and treat metastases. The past decade has witnessed significant progress in the field of cancer metastasis research. Clinical and technological milestones have been reached which have tremendously enriched our understanding of the complex pathways undertaken by primary tumors to progress into lethal metastases and how some of these processes might be amenable to therapy. The aim of this review article is to highlight the recent advances toward unraveling the clinical and molecular complexity of breast cancer metastases. We focus on genes mediating breast cancer metastases and organ-specific tropism, and discuss gene signatures for prediction of metastatic disease. The challenges of translating this information into clinically applicable tools for improving the prognostication of the metastatic potential of a primary breast tumor, as well as for therapeutic interventions against latent and active metastatic disease are addressed.

The hypoxic cancer secretome induces pre-metastatic bone lesions through lysyl oxidase

Tumour metastasis is a complex process involving reciprocal interplay between cancer cells and host stroma at both primary and secondary sites, and is strongly influenced by microenvironmental factors such as hypoxia. Tumour-secreted proteins play a crucial role in these interactions and present strategic therapeutic potential. Metastasis of breast cancer to the bone affects approximately 85% of patients with advanced disease and renders them largely untreatable. Specifically, osteolytic bone lesions, where bone is destroyed, lead to debilitating skeletal complications and increased patient morbidity and mortality. The molecular interactions governing the early events of osteolytic lesion formation are currently unclear. Here we show hypoxia to be specifically associated with bone relapse in patients with oestrogen-receptor negative breast cancer. Global quantitative analysis of the hypoxic secretome identified lysyl oxidase (LOX) as significantly associated with bone-tropism and relapse. High expression of LOX in primary breast tumours or systemic delivery of LOX leads to osteolytic lesion formation whereas silencing or inhibition of LOX activity abrogates tumour-driven osteolytic lesion formation. We identify LOX as a novel regulator of NFATc1-driven osteoclastogenesis, independent of RANK ligand, which disrupts normal bone homeostasis leading to the formation of focal pre-metastatic lesions. We show that these lesions subsequently provide a platform for circulating tumour cells to colonize and form bone metastases. Our study identifies a novel mechanism of regulation of bone homeostasis and metastasis, opening up opportunities for novel therapeutic intervention with important clinical implications.

Development of a prognostic genetic signature to predict the metastatic risk associated with cutaneous melanoma

PURPOSE

The development of a genetic signature for the identification of high-risk cutaneous melanoma tumors would provide a valuable prognostic tool with value for stage I and II patients who represent a remarkably heterogeneous group with a 3% to 55% chance of disease progression and death 5 years from diagnosis.

EXPERIMENTAL DESIGN

A prognostic 28-gene signature was identified by analysis of microarray expression data. Primary cutaneous melanoma tumor tissue was evaluated by RT-PCR for expression of the signature, and radial basis machine (RBM) modeling was performed to predict risk of metastasis.

RESULTS

RBM analysis of cutaneous melanoma tumor gene expression reports low risk (class 1) or high risk (class 2) of metastasis. Metastatic risk was predicted with high accuracy in development (ROC = 0.93) and validation (ROC = 0.91) cohorts of primary cutaneous melanoma tumor tissue. Kaplan-Meier analysis indicated that the 5-year disease-free survival (DFS) rates in the development set were 100% and 38% for predicted classes 1 and 2 cases, respectively (P < 0.0001). DFS rates for the validation set were 97% and 31% for predicted classes 1 and 2 cases, respectively (P < 0.0001). Gene expression profile (GEP), American Joint Committee on Cancer stage, Breslow thickness, ulceration, and age were independent predictors of metastatic risk according to Cox regression analysis.

CONCLUSIONS

The GEP signature accurately predicts metastasis risk in a multicenter cohort of primary cutaneous melanoma tumors. Preliminary Cox regression analysis indicates that the signature is an independent predictor of metastasis risk in the cohort presented.

Proteomic profiling of the tumor microenvironment: recent insights and the search for biomarkers

Although gain of oncogene functions and loss of tumor suppressor functions are driving forces in tumor development, the tumor microenvironment, comprising the extracellular matrix, surrounding stroma, signaling molecules and infiltrating immune and other cell populations, is now also recognized as crucial to tumor development and metastasis. Many interactions at the tumor cell-environment interface occur at the protein level. Proteomic approaches are contributing to the definition of the protein constituents of the microenvironment and their sources, modifications, interactions and turnover, as well as providing information on how these features relate to tumor development and progression. Recently, proteomic studies have revealed how cancer cells modulate the microenvironment through their secreted proteins and how they can alter their protein constituents to adapt to the microenvironment. Moreover, the release of proteins from the microenvironment into the circulatory system has relevance for the development of blood-based cancer diagnostics. Here, we review how proteomic approaches are being applied to studies of the tumor microenvironment to decipher tumor-stroma interactions and to elucidate the role of host cells in the tumor microenvironment.

Cancer secretomes and their place in supplementing other hallmarks of cancer

The secretome includes all macromolecules secreted by cells, in particular conditions at defined times, allowing cell-cell communication. Cancer cell secretomes that are altered compared to normal cells have shown significant potential for elucidating cancer biology. Proteins of secretomes are secreted by various secretory pathways and can be studied using different methods. Cancer secretomes seem to play an important role in known hallmarks of cancers such as excessive proliferation, reduced apoptosis, immune invasion, angioneogenesis, alteration in energy metabolism, and development of resistance against anti-cancer therapy [1, 2]. If a significant role of an altered secretome can be identified in cancer cells, using advanced mass spectrometry-based techniques, this may allow researchers to screen and characterize the secretome proteins involved in cancer progression and open up new opportunities to develop new therapies. We aim to elaborate upon recent advances in cancer cell secretome analysis using different proteomics techniques. In this review, we highlight the role of the altered secretome in contributing to already recognized and emerging hallmarks of cancer and we discuss new challenges in the field of secretome analysis.

Omic-profiling in breast cancer metastasis to bone: implications for mechanisms, biomarkers and treatment

Despite well-recognised advances in breast cancer treatment, there remain substantial numbers of patients who develop metastatic disease, of which up to 70% involves spread to bone, resulting in skeletal complications which have a major negative impact on mortality and quality of life. Bisphosphonates and newer bone-targeted agents have reduced the prevalence of skeletal complications, yet there remains significant unmet clinical need, particularly for the development of more specific therapies for the prevention and treatment of metastatic bone disease, for the prediction of risk of its development in individual patients and for the prediction of response to treatments. Modern 'omic' strategies can potentially make a major contribution to meeting this need. Technological advances in the field of nucleic acid sequencing, mass spectrometry and metabolic profiling have driven progress in genomics, transcriptomics (functional genomics), proteomics and metabolomics. This review appraises the recent application of these approaches to studies of breast cancer metastasis (particularly to bone), with a focus on understanding how omic approaches may lead to new therapeutic options and to novel biomarker molecules or molecular signatures with potential value in clinical practise. The increasingly recognised need for rigorous sample quality control and both pre-clinical and clinical validation to meet the ultimate goals of clinical utility and patient benefit is discussed. Future directions of omic driven research in breast cancer metastasis are considered, in particular micro-RNAs and their role in the post-transcriptional regulation of gene function and the possible role of cancer-stem cells and epigenetic modifications in the development of distant metastases.

Using a systems biology approach to understand and study the mechanisms of metastasis

Metastasis remains the main cause for cancer-related deaths due to the lack of effective therapy. The clonal selection model has long been thought to be the primary mechanism of metastatic progression but many different mechanisms have been hypothesized for the progression from tumorigenesis to the successful dissemination and expansion of tumor cells at the secondary site. MicroRNAs, germline polymorphisms in combination with the tumor microenvironment are few of the different pathways to explain the metastatic cascade. Technological advances for high-throughput screening of cells such as expression profiling, next generation sequencing, as well as global network analyses have advanced the studies of these mechanisms. Combined with new insights into the various mechanisms of metastasis a systems biology approach has also been shown to be useful in identifying metastasis-specific gene signatures as well as predicting disease outcome. Furthermore, the results of these studies have been relevant for identifying biomarkers for metastatic disease.

Metallopanstimulin-1 regulates invasion and migration of gastric cancer cells partially through integrin β4

MPS-1 (metallopanstimulin-1), also known as ribosomal protein S27, was overexpressed in gastric cancer cells. However, how MPS-1 contributes to gastric carcinogenesis has not been well characterized. Here, we show that high expression of MPS-1 was observed in gastric cancer tissues and associated with gastric cancer cell metastasis. Alteration of MPS-1 expression regulates invasion and migration of gastric cancer cells both in vitro and in vivo. Furthermore, by using Signal-Net and cluster analyses of microarray data we identified integrin β4 (ITGB4) as a downstream target of MPS-1 that mediates its effects on cell metastasis. Knockdown of MPS-1 expression in gastric cancer cells led to significant reduction of ITGB4 expression at both the RNA and protein levels. Mechanically, we found that overexpression of ITGB4 in MPS-1 knockdown cells largely recovers the ability of invasion and migration. Conversely, knockdown of ITGB4 partially reduced cell invading/migrating ability induced by MPS-1 overexpression. Moreover, MPS-1 and ITGB4 expressions are positively correlated in gastric cancer cell lines and tissues. Finally, the survival analyses show that the expression of MPS-1 and ITGB4 is associated with poor outcomes in gastric cancer patients. Collectively, our findings suggest that MPS-1 regulates cell invasiveness and migration partially through ITGB4 and that MPS-1/ITGB4 signaling axis may serve as therapeutic targets in the treatment of gastric cancer.

Sieving through the cancer secretome

Cancer is among the most prevalent and serious health problems worldwide. Therefore, there is an urgent need for novel cancer biomarkers with high sensitivity and specificity for early detection and management of the disease. The cancer secretome, encompassing all the proteins that are secreted by cancer cells, is a promising source of biomarkers as the secreted proteins are most likely to enter the blood circulation. Moreover, since secreted proteins are responsible for signaling and communication with the tumor microenvironment, studying the cancer secretome would further the understanding of cancer biology. Latest developments in proteomics technologies have significantly advanced the study of the cancer secretome. In this review, we will present an overview of the secretome sample preparation process and summarize the data from recent secretome studies of six common cancers with high mortality (breast, colorectal, gastric, liver, lung and prostate cancers). In particular, we will focus on the various platforms that were employed and discuss the clinical applicability of the key findings in these studies. This article is part of a Special Issue entitled: An Updated Secretome.

Comparative secretome analyses using a hollow fiber culture system with label-free quantitative proteomics indicates the influence of PARK7 on cell proliferation and migration/invasion in lung adenocarcinoma

As the leading cause of cancer death worldwide, lung cancer lacks effective diagnosis tools and treatments to prevent its metastasis. Fortunately, secretome has clinical usages as biomarkers and protein drugs. To discover the secretome that influences lung adenocarcinoma metastasis, the hollow fiber culture (HFC) system was used along with label-free proteomics approach to analyze cell secretomes between CL1-0 and CL1-5 cell lines, which exhibit low and high metastatic potentials. Among the 703 proteins quantified, 50 possessed different levels between CL1-0 and CL1-5. PARK7 was a primary focus because of the lack of research involving lung adenocarcinoma. The cell proliferation, migration, and invasion properties of CL1-0, CL1-5, and A549 cells were significantly diminished when the expression of their PARK7 proteins was reduced. Conversely, these functions were promoted when PARK7 was overexpressed in CL1-0. In clinical expression, PARK7 levels within tissue specimens and plasma samples were significantly higher in the cancer group. This represents the first time the HFC system has been used with label-free quantification to discern the elements of metastasis in lung adenocarcinoma cell secretomes. Likewise, PARK7 has never been researched for its role in promoting lung adenocarcinoma progression.