Protein pattern difference in the colon cancer cell lines examined by two-dimensional differential in-gel electrophoresis and mass spectrometry

Human Triosephosphate Isomerase Is a Potential Target in Cancer Due to Commonly Occurring Post-Translational Modifications

Cancer involves a series of diseases where cellular growth is not controlled. Cancer is a leading cause of death worldwide, and the burden of cancer incidence and mortality is rapidly growing, mainly in developing countries. Many drugs are currently used, from chemotherapeutic agents to immunotherapy, among others, along with organ transplantation. Treatments can cause severe side effects, including remission and progression of the disease with serious consequences. Increased glycolytic activity is characteristic of cancer cells. Triosephosphate isomerase is essential for net ATP production in the glycolytic pathway. Notably, some post-translational events have been described that occur in human triosephosphate isomerase in which functional and structural alterations are provoked. This is considered a window of opportunity, given the differences that may exist between cancer cells and their counterpart in normal cells concerning the glycolytic enzymes. Here, we provide elements that bring out the potential of triosephosphate isomerase, under post-translational modifications, to be considered an efficacious target for treating cancer.

PAD4-dependent citrullination of nuclear translocation of GSK3β promotes colorectal cancer progression via the degradation of nuclear CDKN1A

Peptidylarginine deiminase 4 (PAD4), a Ca²⁺-dependent enzyme, catalyzes the conversion of arginine to citrulline and has been strongly associated with many malignant tumors. However, the molecular mechanisms of PAD4 in the development and progression of colorectal cancer (CRC) remain unclearly defined. In our study, PAD4 expression was increased in CRC tissues and cells, and was closely related to tumor size, lymph node metastasis. Moreover, the transcription factor KLF9 directly bound to PADI4 gene promoter, leading to overexpression of PAD4 in CRC cells, which augmented cell growth and migration. We revealed that PAD4 interacted with and citrullinated glycogen synthase kinase-3β (GSK3β) in CRC cells, and GSK3β Arg-344 was the dominating PAD4-citrullination site. Furthermore, IgL2 and catalytic domains of PAD4 directly bound to the kinase domain of GSK3β in CRC cells. Mechanistically, PAD4 promoted the transport of GSK3β from the cytoplasm to the nucleus, thereby increasing the ubiquitin-dependent proteasome degradation of nuclear cyclin-dependent kinase inhibitor 1 (CDKN1A). Our study is the first to reveal the details of a critical PAD4/GSK3β/CDKN1A signaling axis for CRC progression, and provides evidence that PAD4 is a potential diagnosis biomarker and therapeutic target in CRC.

Protein modifications throughout the lung cancer proteome unravel the cancer-specific regulation of glycolysis

Glycolytic reprogramming is a typical feature of cancer. However, the cancer-specific modulation of glycolytic enzymes requires systematic elucidation. Here, we report a range of dysregulated modifications in association with a family of enzymes specifically related to the glycolysis pathway by systematic identification of delta masses at the proteomic scale in human non-small-cell lung cancer. The most significant modification is the delta mass of 79.967 Da at serine 58 (Ser58) of triosephosphate isomerase (TPI), which is confirmed to be phosphorylation. Blocking TPI Ser58 phosphorylation dramatically inhibits glycolysis, cancer growth, and metastasis. The protein kinase PRKACA directly phosphorylates TPI Ser58, thereby enhancing TPI enzymatic activity and glycolysis. The upregulation of TPI Ser58 phosphorylation is detected in various human tumor specimens and correlates with poor survival. Therefore, our study identifies a number of cancer-specific protein modifications spanned on glycolytic enzymes and unravels the significance of TPI Ser58 phosphorylation in glycolysis and lung cancer development.

Impact of Tissue Enolase 1 Protein Overexpression in Esophageal Cancer Progression

Enolase (ENO) 1 is a key glycolytic enzyme and important player in tumorigenesis. ENO1 overexpression has been correlated with tumor progression and/or worse prognosis in several solid malignancies. However, data concerning the impact of ENO1 in cancer conflict. The study correlated local and circulating ENO1 protein levels in esophageal cancer (EC) with clinicopathological data, to assess its potential clinical value. ENO1 expression was analyzed by immunohistochemistry in paired tumor and non-tumor tissue samples from 40 EC cases and mucosal biopsies from 45 Barrett's esophagus (BE) cases, plus in plasma from these patients and 25 matched healthy controls. ENO1 was abnormally elevated in cancer-cell cytoplasm in both EC types, in esophageal squamous cell carcinoma and in adenocarcinoma (EAC), increasing significantly with tumor stage progression and the transition from BE to EAC. EAC patients exhibited significantly lower ENO1 plasma concentrations than normal subjects. Neither local nor systemic ENO1 expression levels were significantly associated with overall survival. These results indicate ENO1 as potential biomarker, delineating a population of patients with Barrett's esophagus at high risk of cancer, and as new therapeutic opportunity in EC patient management. However, further confirmation might be necessary.

Therapeutic Targeting of Cancer Metabolism with Triosephosphate Isomerase

The increase in glycolytic flux in cancer, known as aerobic glycolysis, is one of the most important hallmarks of cancer. Therefore, glycolytic enzymes have importance in understanding the molecular mechanism of cancer progression. Triosephosphate isomerase (TPI) is one of the key glycolytic enzymes. Furthermore, it takes a part in gluconeogenesis, pentose phosphate pathway and fatty acid biosynthesis. To date, it has been shown altered levels of TPI in various cancer types, especially in metastatic phenotype. According to other studies, TPI might be considered as a potential therapeutic target and a cancer-related biomarker in different types of cancer. However, its function in tumor formation and development has not been fully understood. Here, we reviewed the relationship between TPI and cancer for the first time.

Proteomic Analysis of Primary Colon Cancer and Synchronous Solitary Liver Metastasis

BACKGROUND/AIM

Colon cancer is prone to distant metastases to other sites and the risk of recurrence is relatively high. Therefore, the identification of liver metastasis-related factors is important for the diagnosis or treatment of colon cancer. The aim of this study was to identify the metastasis-related factors that are differentially expressed in synchronous solitary liver metastasis compared to primary colon cancer.

MATERIALS AND METHODS

Tissues of primary colon cancer and associated with liver metastases of five patients were used for mass spectrometry. Identified proteins were validated by western blotting. The in silico analysis was performed using the STRING database and GeneMANIA.

RESULTS

We identified 58 differentially expressed proteins (DEPs), including 51 under-expressed and 7 over-expressed proteins among a total of 164 identified proteins. Major hubs of protein-protein networks were ACTC1, PRDX6, TPI1, and ALDH1A1. DEPs were located in the extracellular region and cytoplasm and were involved in the regulation of enzymatic activity. The metabolic process was significantly enriched in biological processes and an involvement in the KEGG pathway.

CONCLUSION

These DEPs can potentially be used as biomarkers for the diagnosis of liver metastasis and they may provide a new strategy for developing anti-metastatic liver drugs in colon cancer patients.

Physical Biomarkers of Disease Progression: On-Chip Monitoring of Changes in Mechanobiology of Colorectal Cancer Cells

Disease can induce changes to subcellular components, altering cell phenotype and leading to measurable bulk-material mechanical properties. The mechanical phenotyping of single cells therefore offers many potential diagnostic applications. Cells are viscoelastic and their response to an applied stress is highly dependent on the magnitude and timescale of the actuation. Microfluidics can be used to measure cell deformability over a wide range of flow conditions, operating two distinct flow regimes (shear and inertial) which can expose subtle mechanical properties arising from subcellular components. Here, we investigate the deformability of three colorectal cancer (CRC) cell lines using a range of flow conditions. These cell lines offer a model for CRC metastatic progression; SW480 derived from primary adenocarcinoma, HT29 from a more advanced primary tumor and SW620 from lymph-node metastasis. HL60 (leukemia cells) were also studied as a model circulatory cell, offering a non-epithelial comparison. We demonstrate that microfluidic induced flow deformation can be used to robustly detect mechanical changes associated with CRC progression. We also show that single-cell multivariate analysis, utilising deformation and relaxation dynamics, offers potential to distinguish these different cell types. These results point to the benefit of multiparameter determination for improving detection and accuracy of disease stage diagnosis.

R. R, Thomas S, Nisha P. Short chain fatty acids enriched fermentation metabolites of soluble dietary fibre from Musa paradisiaca drives HT29 colon cancer cells to apoptosis

In this study, the prebiotic potential of soluble dietary fibre extracted from plantain inflorescence (PIF) was investigated. PIF demonstrated prebiotic potential by enhancing the growth of the probiotics under study and thereby hindered colon cancer development. The soluble dietary fibre from Musa paradisiaca inflorescence (PIF) was fermented using Lactobacillus casei and Bifidobacterium bifidum. The fermentation supernatants (LS and BS) were enriched with short chain fatty acids (SCFA) and were able to initiate apoptotic signalling in HT29 colon cancer cells leading to cell death. Both BS and LS exhibited cytotoxic effect; induced DNA damage and enhanced generation of reactive oxygen species in HT29 cells leading to apoptosis. The induction of apoptosis was facilitated by the reduction of membrane potential of mitochondria and ATP synthesis; enhanced delivery of cytochrome c and interference with the expression of pro/antiapoptotic proteins. BS, which exhibited better activity, was further analysed for the identification of differentially regulated proteins by performing two dimensional electrophoresis and MALDI-TOF mass spectrometry. Results emphasized on the fact that, the exposure to BSalteredthe HT29 proteins expression, particularly the upregulation of apoptosis- inducing factor-AIFM1 leading to apoptosis of HT29 cells.

New strategies for targeting glucose metabolism-mediated acidosis for colorectal cancer therapy

Colorectal cancer (CRC) is a heterogeneous group of diseases that are the result of abnormal glucose metabolism alterations with high lactate production by pyruvate to lactate conversion, which remodels acidosis and offers an evolutional advantage for tumor cells, even enhancing their aggressive phenotype. This review summarizes recent findings that involve multiple genes, molecules, and downstream signaling in the dysregulated glycolytic pathway, which can allow a tumor to initiate acid byproducts and to progress, thereby resulting in acidosis commonly found in the tumor microenvironment of CRC. Moreover, the relationship between CRC cells and the tumor acidic microenvironment, especially for regulating lactate production and lactate dehydrogenase A levels, is also discussed, as well as comprehensively defining different aspects of glycolytic pathways that affect cancer cell proliferation, invasion, and migration. Furthermore, this review concentrates on glucose metabolism-mediated transduction factors in CRC, which include acid-sensing ion channels, triosephosphate isomerase and key glycolysis-related enzymes that regulate glycolytic metabolites, coupled with the effect on tumor cell glycolysis as well as signaling pathways. In conclusion, glucose metabolism mediated by glycolytic pathways that are integral to tumor acidosis in CRC is demonstrated. Therefore, selective metabolic inhibitors or agents against these targets in glucose metabolism through glycolytic pathways may be clinically useful to regulate the tumor's acidic microenvironment for CRC treatment and to identify specific targets that regulate tumor acidosis through a cancer patient-personalized approach. Furthermore, strategies for modifying the metabolic processes that effectively inhibit cancer cell growth and tumor progression and activate potent anticancer effects may provide more effective antitumor prospects for CRC therapy.

Triose-phosphate isomerase is a novel target of miR-22 and miR-28, with implications in tumorigenesis

Aerobic glycolysis is the hallmark of many cancer cells that results in a high rate of adenosine triphosphate (ATP) production and, more importantly, biosynthetic intermediates, which are required by the fast-growing tumor cells. The molecular mechanism responsible for the increased glycolytic influx of tumor cells is still not fully understood. In the present study, we have attempted to address the above question by exploring the role of the glycolytic enzyme, triose-phosphate isomerase (TPI), in the cancer cells. The western blot analysis of the 30 human colorectal cancer samples depicted higher post-transcriptional expression of TPI in the tumor tissue relative to the normal tissue. In addition, we identified two novel microRNAs, miR-22 and miR-28, that target the TPI messenger RNA (mRNA) and regulate its expression. miR-22 and the miR-28 showed significant inverse expression status viz-a-viz the expression of the TPI. The specificity of the miR-22/28 regulation of the TPI mRNA was confirmed by various biochemical and mutagenic assays. Moreover, the hypoxia conditions resulted in an increased expression of the TPI protein, with a concomitant decrease in miR-22/28. The physiological significance of the TPI and miR-22/28 interaction for the glycolytic influx was confirmed by the l-lactate production in the HCT-116^+/+ cells. Overall, our data demonstrate the novel microRNA mediated post-transcriptional regulation of the TPI glycolytic enzyme, which may be one of the possible reasons for the increased glycolytic capacity of the tumor cells.

Next Generation Immunotherapy for Pancreatic Cancer: DNA Vaccination is Seeking New Combo Partners

Pancreatic Ductal Adenocarcinoma (PDA) is an almost incurable radio- and chemo-resistant tumor, and its microenvironment is characterized by a strong desmoplastic reaction associated with a significant infiltration of T regulatory lymphocytes and myeloid-derived suppressor cells (Tregs, MDSC). Investigating immunological targets has identified a number of metabolic and cytoskeletal related molecules, which are typically recognized by circulating antibodies. Among these molecules we have investigated alpha-enolase (ENO1), a glycolytic enzyme that also acts a plasminogen receptor. ENO1 is also recognized by T cells in PDA patients, so we developed a DNA vaccine that targets ENO1. This efficiently induces many immunological processes (antibody formation and complement-dependent cytotoxicity (CDC)-mediated tumor killing, infiltration of effector T cells, reduction of infiltration of myeloid and Treg suppressor cells), which significantly increase the survival of genetically engineered mice that spontaneously develop pancreatic cancer. Although promising, the ENO1 DNA vaccine does not completely eradicate the tumor, which, after an initial growth inhibition, returns to proliferate again, especially when Tregs and MDSC ensue in the tumor mass. This led us to develop possible strategies for combinatorial treatments aimed to broaden and sustain the antitumor immune response elicited by DNA vaccination. Based on the data we have obtained in recent years, this review will discuss the biological bases of possible combinatorial treatments (chemotherapy, PI3K inhibitors, tumor-associated macrophages, ENO1 inhibitors) that could be effective in amplifying the response induced by the immune vaccination in PDA.

Proteins are potent biomarkers to detect colon cancer progression

Colon cancer is the most common type of cancer and major cause of death worldwide. The detection of colon cancer is difficult in early stages. However, the secretory proteins have been used as ideal biomarker for the detection of colon cancer progress in cancer patients. Serum/tissue protein expression could help general practitioners to identify colon cancer at earlier stages. By this way, we use the biomarkers to evaluate the anticancer drugs and their response to therapy in cancer models. Recently, the biomarker discovery is important in cancer biology and disease management. Also, many measurable specific molecular components have been studied in colon cancer therapeutics. The biomolecules are mainly DNA, RNA, metabolites, enzymes, mRNA, aptamers and proteins. Thus, in this review we demonstrate the important protein biomarker in colon cancer development and molecular identification of protein biomarker discovery.

Role of triosephosphate isomerase and downstream functional genes on gastric cancer

Triosephosphate isomerase (TPI) is highly expressed in many types of human tumors and is involved in migration and invasion of cancer cells. However, TPI clinicopathological significance and malignant function in gastric cancer (GC) have not been well defined. The present study aimed to examine TPI expression in GC tissue and its biological functions. Furthermore, we investigated its downstream genes by gene chip technology. Our results showed that TPI expression was higher in gastric cancer tissues than adjacent tissues, although no statistical differences were found between TPI expression and clinicopathological factors. TPI overexpression in human gastric carcinoma cell line BGC-823 enhanced cell proliferation, invasion and migration, but did not change cell cycle distribution, while TPI knockdown suppressed proliferation, invasion and migration, induced apoptosis and increased G2/M arrest of human gastric carcinoma cell line MGC-803. Since the cell division cycle associated 5 (CDCA5) was identified as the one with the most decreased expression after TPI knockdown, we investigated its role in MGC-803 cells. The results showed that CDCA5 knockdown also inhibited proliferation, migration, induced apoptosis and increased G2/M arrest similarly to TPI knockdown. CDCA5 overexpression promoted MGC-803 cell proliferation, clone formation and migration abilities. These results indicated that TPI expression level might affect GC cell behavior, suggesting that both TPI and CDCA5 might be considered as potential tumor markers related with GC development and might be potential new targets in GC treatment.

Clinical significance and prognostic value of Triosephosphate isomerase expression in gastric cancer

Triosephosphate isomerase (TPI) is highly expressed in many human cancers and is involved in migration and invasion of cancer cells. However, TPI clinicopathological significance and prognostic value in gastric cancer (GC) are not yet well defined. The aim of the present work was to evaluate TPI expression in GC tissue and its prognostic value in GC patients.TPI expression was analyzed in 92 primary GC tissues and 80 adjacent normal mucosa tissues from GC patients undergoing gastrectomy by immunohistochemical analysis of tissue microarrays (TMAs). Univariate and multivariate analyses were performed to investigate TPI prognostic significance in GC patients.Immunohistochemical staining score showed that TPI expression in cancer tissues was significantly higher than in adjacent normal mucosa (P < .001). Univariate analysis revealed that TPI expression, depth of invasion, lympho node metastasis, tumor node metastasis (TNM) stage, and tumor diameter were associated with negative prognostic predictors for overall survival in GC patients (P < .05). High TPI expression represented a significant predictor of shorter survival in GC patients with positive lymphatic metastasis (P = .022) and tumor diameter >5 cm (P = .018). Cox multivariate analysis identified TPI expression, TNM stage, and tumor diameter as independent prognostic factors in GC patients.TPI expression might be considered as a novel prognostic factor to evaluate GC patients' survival.

Measurement of enolase activity in cell lysates

Enolase (EC 4.2.1.11) is a cytosolic metalloenzyme responsible for the conversion of 2-phosphoglycerate into phosphoenolpyruvate, the second to last step in glycolysis. In mammals, enolase is encoded by three homologous genes. These gene products not only possess distinct biochemical and immunological properties but also show different tissue distribution. Besides its glycolytic function, α-enolase plays a variety of roles in pathophysiological settings including oncogenesis, tumor progression, ischemia, and bacterial infection. The expression levels of α-enolase have been attributed diagnostic and prognostic value in a number of tumors. Furthermore, neuron-specific α-enolase is released into the cerebrospinal fluid as well as in the systemic circulation upon traumatic brain injury and ischemic episodes. Thus, the measurement of the enzymatic activity of enolase is relevant for diverse fields of investigation, including oncometabolism. Here, we described simple and rapid protocols to measure the activity of enolase in lysates from mammalian cells and tissues.

Alpha-enolase is upregulated on the cell surface and responds to plasminogen activation in mice expressing a ∆133p53α mimic

The p53 protein is a master regulator of the stress response. It acts as a tumor suppressor by inducing transcriptional activation of p53 target genes, with roles in apoptosis, cell cycle arrest and metabolism. The discovery of at least 12 isoforms of p53, some of which have tumor-promoting properties, has opened new avenues of research. Our previous work studied tumor phenotypes in four mouse models with different p53 backgrounds: wild-type p53, p53 null, mutant p53 lacking the proline domain (mΔpro), and a mimic for the human Δ133p53α p53 isoform (Δ122p53). To identify the major proteins affected by p53 function early in the response to DNA damage, the current study investigated the entire proteome of bone marrow, thymus, and lung in the four p53 models. Protein extracts from untreated controls and those treated with amsacrine were analyzed using two-dimensional fluorescence difference gel electrophoresis. In the bone marrow, reactive proteins were universally decreased by wild-type p53, including α-enolase. Further analysis of α-enolase in the p53 models revealed that it was instead increased in Δ122p53 hematopoietic and tumor cell cytosol and on the cell surface. Alpha-enolase on the surface of Δ122p53 cells acted as a plasminogen receptor, with tumor necrosis factor alpha induced upon plasminogen stimulation. Taken together, these data identified new proteins associated with p53 function. One of these proteins, α-enolase, is regulated differently by wild-type p53 and Δ122p53 cells, with reduced abundance as part of a wild-type p53 response and increased abundance with Δ122p53 function. Increased cell surface α-enolase on Δ122p53 cells provides a possible explanation for the model’s pro-inflammatory features and suggests that p53 isoforms may direct an inflammatory response by increasing the amount of α-enolase on the cell surface.

Elevated levels of 14-3-3 proteins, serotonin, gamma enolase and pyruvate kinase identified in clinical samples from patients diagnosed with colorectal cancer

BACKGROUND

Colorectal cancer (CRC), a heterogeneous disease that is common in both men and women, continues to be one of the predominant cancers worldwide. Lifestyle, diet, environmental factors and gene defects all contribute towards CRC development risk. Therefore, the identification of novel biomarkers to aid in the management of CRC is crucial. The aim of the present study was to identify candidate biomarkers for CRC, and to develop a better understanding of their role in tumourogenesis.

METHODS

In this study, both plasma and tissue samples from patients diagnosed with CRC, together with non-malignant and normal controls were examined using mass spectrometry based proteomics and metabolomics approaches.

RESULTS

It was established that the level of several biomolecules, including serotonin, gamma enolase, pyruvate kinase and members of the 14-3-3 family of proteins, showed statistically significant changes when comparing malignant versus non-malignant patient samples, with a distinct pattern emerging mirroring cancer cell energy production.

CONCLUSION

The diagnosis and management of CRC could be enhanced by the discovery and validation of new candidate biomarkers, as found in this study, aimed at facilitating early detection and/or patient stratification together with providing information on the complex behaviour of cancer cells.

Serum annexin A2 levels in patients with colon cancer in comparison to healthy controls and in relation to tumor pathology

BACKGROUND

The deregulation and localization of the Annexins is consistently reported to have close relation to tumor cell malignancy, invasion, and metastasis as well as clinical progression of tumors. This study aimed to evaluate serum Annexin A2 (Anx A2) levels in patients with colon cancer in comparison to healthy controls and in relation to demographics and tumor pathology.

MATERIAL AND METHODS

A total of 100 patients (mean (SD) age: 58 (5.8) years, 55.0% females) with colon cancer and 70 controls (mean (SD) age: 59 (5.4) years, 50.0% females) were included. Serum levels for Anx A2 were evaluated in relation to study group, demographics, and tumor pathology.

RESULTS

Serum levels for Anx A2 were significantly lower in patients with colon cancer than in controls (13.1 (4.5) vs. 22.8 (2.1) ng/mL, p<0.001) and significantly decreased with increase in tumor size (p=0.003), and at higher stages of TNM (p=0.004), tumor invasion (p=0.005), lymph node metastasis (p=0.003), and distant metastasis (p=0.005).

CONCLUSIONS

Our findings indicate a significant decrease in Anx A2 expression in colon cancer patients compared to healthy controls and in parallel with tumor progression.

Intratumoral decorin gene delivery by AAV vector inhibits brain glioblastomas and prolongs survival of animals by inducing cell differentiation

Glioblastoma multiforme (GBM) is the most malignant cancer in the central nervous system with poor clinical prognosis. In this study, we investigated the therapeutic effect of an anti-cancer protein, decorin, by delivering it into a xenograft U87MG glioma tumor in the brain of nude mice through an adeno-associated viral (AAV2) gene delivery system. Decorin expression from the AAV vector in vitro inhibited cultured U87MG cell growth by induction of cell differentiation. Intracranial injection of AAV-decorin vector to the glioma-bearing nude mice in vivo significantly suppressed brain tumor growth and prolonged survival when compared to control non-treated mice bearing the same U87MG tumors. Proteomics analysis on protein expression profiles in the U87MG glioma cells after AAV-mediated decorin gene transfer revealed up- and down-regulation of important proteins. Differentially expressed proteins between control and AAV-decorin-transduced cells were identified through MALDI-TOF MS and database mining. We found that a number of important proteins that are involved in apoptosis, transcription, chemotherapy resistance, mitosis, and fatty acid metabolism have been altered as a result of decorin overexpression. These findings offer valuable insight into the mechanisms of the anti-glioblastoma effects of decorin. In addition, AAV-mediated decorin gene delivery warrants further investigation as a potential therapeutic approach for brain tumors.

Comparative proteomics analysis of oral cancer cell lines: identification of cancer associated proteins

Background

A limiting factor in performing proteomics analysis on cancerous cells is the difficulty in obtaining sufficient amounts of starting material. Cell lines can be used as a simplified model system for studying changes that accompany tumorigenesis. This study used two-dimensional gel electrophoresis (2DE) to compare the whole cell proteome of oral cancer cell lines vs normal cells in an attempt to identify cancer associated proteins.

Results

Three primary cell cultures of normal cells with a limited lifespan without hTERT immortalization have been successfully established. 2DE was used to compare the whole cell proteome of these cells with that of three oral cancer cell lines. Twenty four protein spots were found to have changed in abundance. MALDI TOF/TOF was then used to determine the identity of these proteins. Identified proteins were classified into seven functional categories – structural proteins, enzymes, regulatory proteins, chaperones and others. IPA core analysis predicted that 18 proteins were related to cancer with involvements in hyperplasia, metastasis, invasion, growth and tumorigenesis. The mRNA expressions of two proteins – 14-3-3 protein sigma and Stress-induced-phosphoprotein 1 – were found to correlate with the corresponding proteins’ abundance.

Conclusions

The outcome of this analysis demonstrated that a comparative study of whole cell proteome of cancer versus normal cell lines can be used to identify cancer associated proteins.

Gelsolin and ceruloplasmin as potential predictive biomarkers for cervical cancer by 2D-DIGE proteomics analysis

This study aimed to identify candidate proteins which may serve as potential biological markers for cervical cancer using 2D-DIGE. Serum samples of controls, patients with cervical intraepithelial neoplasia grade 3 (CIN 3), squamous cell carcinoma of early (SCC I and II) and late (SCC III and IV) stage were subjected to 2D-DIGE. Differentially expressed spots were identified by tandem mass spectrometry. Validation of candidate proteins in serum and tissue samples were then performed by ELISA and immunohistochemistry (IHC) analysis respectively. A total of 20 differentially expressed proteins were identified. These proteins were found to play key roles in the apoptosis pathway, complement system, various types of transportation such as hormones, fatty acids, lipid, vitamin E and drug transportation, coagulation cascade, regulation of iron and immunologic response. Based on their functional relevancy to the progression of various cancers, 4 proteins namely the complement factor H, CD5-like antigen, gelsolin and ceruloplasmin were chosen for further validation using ELISA. Biological network analysis showed that ceruloplasmin and gelsolin are closely interacted with the oncogene NF-κb. These two proteins were further validated using the IHC. Gelsolin and ceruloplasmin may serve as potential predictive biomarkers for the progression of high grade lesions.

Evaluation of ¹⁸F-FDG and ¹⁸F-FLT for monitoring therapeutic responses of colorectal cancer cells to radiotherapy

In order to compare the efficacy of (18)F-fluorothymidine (FLT) and (18)F-fluorodeoxyglucose (FDG) for monitoring early responses to irradiation, two human colorectal cancer (CRC) cell lines SW480 and SW620, which were derived from the primary lesions and the metastatic lymph node, underwent X-ray irradiation of 0, 10, or 20 Gy and were examined at 0, 24 and 72 h After irradiation, reduced proliferation of both SW480 and SW620 cells was observed in a dose-dependent manner (P<0.001), G0-G1 arrest was also noted in both cell types after 72 h in the 20 Gy group (P<0.001). Although increased apoptosis was observed in both cell lines after irradiation (P<0.001), a greater percentage of SW480 cells underwent apoptosis in response to irradiation than SW620 cells. Increased Hsp27 and decreased integrin β3, Ki67 and VEGFR2 expression was observed over time via immunocytochemistry and Western blot analysis (P<0.001), however, no significant changes were noted in response to irradiation. Finally, reduced uptake of (18)F-FLT by SW480 or SW620 cells was observed at 24-h post-irradiation, however, reduced (18)F-FDG uptake was only observed after 72 h. Therefore, we conclude that (18)F-FLT is a more suitable positron emission tomography (PET) tracer for monitoring early responses to irradiation in primary and metastatic lymph node CRC cells.

Three are better than one: plasminogen receptors as cancer theranostic targets

Activation of plasminogen on the cell surface initiates a cascade of protease activity with important implications for several physiological and pathological events. In particular, components of the plasminogen system participate in tumor growth, invasion and metastasis. Plasminogen receptors are in fact expressed on the cell surface of most tumors, and their expression frequently correlates with cancer diagnosis, survival and prognosis. Notably, they can trigger multiple specific immune responses in cancer patients, highlighting their role as tumor-associated antigens. In this review, three of the most characterized plasminogen receptors involved in tumorigenesis, namely Annexin 2 (ANX2), Cytokeratin 8 (CK8) and alpha-Enolase (ENOA), are analyzed to ascertain an overall view of their role in the most common cancers. This analysis emphasizes the possibility of delineating new personalized therapeutic strategies to counteract tumor growth and metastasis by targeting plasminogen receptors, as well as their potential application as cancer predictors.

Comparative label-free LC-MS/MS analysis of colorectal adenocarcinoma and metastatic cells treated with 5-fluorouracil

A label-free mass spectrometric strategy was used to examine the effect of 5-fluorouracil (5-FU) on the primary and metastatic colon carcinoma cell lines, SW480 and SW620, with and without treatment. 5-FU is the most common chemotherapeutic treatment for colon cancer. Pooled biological replicates were analyzed by nanoLC-MS/MS and protein quantification was determined via spectral counting. Phenotypic and proteomic changes were evident and often similar in both cell lines. The SW620 cells were more resistant to 5-FU treatment, with an IC(50) 2.7-fold higher than that for SW480. In addition, both cell lines showed pronounced abundance changes in pathways relating to antioxidative stress response and cell adhesion remodeling due to 5-FU treatment. For example, the detoxification enzyme NQO1 was increased with treatment in both cell lines, while disparate members of the peroxiredoxin family, PRDX2 or PRDX5 and PRDX6, were elevated with 5-FU exposure in either SW480 or SW620, respectively. Cell adhesion-associated proteins CTNNB1 and RhoA showed decreased expression with 5-FU treatment in both cell lines. The differential quantitative response in the proteomes of these patient-matched cell lines to drug treatment underscores the subtle molecular differences separating primary and metastatic cancer cells.

α-Enolase, a multifunctional protein: its role on pathophysiological situations

α-Enolase is a key glycolytic enzyme in the cytoplasm of prokaryotic and eukaryotic cells and is considered a multifunctional protein. α-enolase is expressed on the surface of several cell types, where it acts as a plasminogen receptor, concentrating proteolytic plasmin activity on the cell surface. In addition to glycolytic enzyme and plasminogen receptor functions, α-Enolase appears to have other cellular functions and subcellular localizations that are distinct from its well-established function in glycolysis. Furthermore, differential expression of α-enolase has been related to several pathologies, such as cancer, Alzheimer's disease, and rheumatoid arthritis, among others. We have identified α-enolase as a plasminogen receptor in several cell types. In particular, we have analyzed its role in myogenesis, as an example of extracellular remodelling process. We have shown that α-enolase is expressed on the cell surface of differentiating myocytes, and that inhibitors of α-enolase/plasminogen binding block myogenic fusion in vitro and skeletal muscle regeneration in mice. α-Enolase could be considered as a marker of pathological stress in a high number of diseases, performing several of its multiple functions, mainly as plasminogen receptor. This paper is focused on the multiple roles of the α-enolase/plasminogen axis, related to several pathologies.

Improving colorectal cancer management: the potential of proteomics

Colorectal cancer (CRC) is the third most common cancer worldwide. Successful treatment is heavily dependent on tumor stage at the time of detection, but unfortunately CRC is often only detected in advanced stages. New biomarkers in the form of genes or proteins that can be used for diagnosis, prognostication, follow-up, and treatment selection and monitoring could be of great benefit for the management of CRC. Furthermore, proteins could prove valuable new targets for therapy. Therefore, clinical proteomics has gained a lot of scientific interest in this regard. To get an overall insight into the extent to which this research has contributed to a better management of CRC, we give a comprehensive overview of the results of proteomics research on CRC, focusing on expression proteomics, in other words, protein profiling studies. Furthermore, we evaluate the potential of the discriminating proteins identified in this research for clinical use as biomarkers for (early) diagnosis, prognosis and follow-up of CRC or as targets for new therapeutic regimens.

Proteomic signatures of the desmoplastic invasion front reveal collagen type XII as a marker of myofibroblastic differentiation during colorectal cancer metastasis

Cancer-associated fibroblasts (CAFs), represent a pivotal compartment of solid cancers (desmoplasia), and are causatively implicated in cancer development and progression. CAFs are recruited by growth factors secreted by cancer cells and they present a myofibroblastic phenotype, similar to the one obtained by resident fibroblasts during wound healing. Paracrine signaling between cancer cells and CAFs results in a unique protein expression profile in areas of desmoplastic reaction, which is speculated to drive metastasis. In an attempt to decipher large-scale proteomic profiles of the cancer invasive margins, we developed an in vitro coculture model system, based on tumor-host cell interactions between colon cancer cells and CAFs. Proteomic analysis of conditioned media derived from these cocultures coupled to mass spectrometry and bioinformatic analysis was performed to uncover myofibroblastic signatures of the cancer invasion front. Our analysis resulted in the identification and generation of a desmoplastic protein dataset (DPD), consisting of 152 candidate proteins of desmoplasia. By using monoculture exclusion datasets, a secretome algorithm and gene-expression meta-analysis in DPD, we specified a 22-protein “myofibroblastic signature” with putative importance in the regulation of colorectal cancer metastasis. Of these proteins, we investigated collagen type XII by immunohistochemistry, a fibril-associated collagen with interrupted triple helices (FACIT), whose expression has not been reported in desmoplastic lesions in any type of cancer. Collagen type XII was highly expressed in desmoplastic stroma by and around alpha-smooth muscle actin (α-SMA) positive CAFs, as well as in cancer cells lining the invasion front, in a small cohort of colon cancer patients. Other stromal markers, such as collagen type III, were also expressed in stromal collagen, but not in cancer cells. In a complementary fashion, gene expression meta-analysis revealed that COL12A1 is also an upregulated gene in colorectal cancer. Our proteomic analysis identified previously documented markers of tumor invasion fronts and our DPD could serve as a pool for future investigation of the tumor microenvironment. Collagen type XII is a novel candidate marker of myofibroblasts, and/or cancer cells undergoing dedifferentiation.

The association of annexin A2 and cancers

Annexins are a group of calcium- and phospholipid-dependent proteins. As a member of the annexin, annexin A2 (Anxa2) is widely distributed in nucleus, cytoplasm and extracellular surface and mainly expressed in human endothelial cells, mononuclear cells, macrophages, marrow cells and some tumor cells. Accumulated evidences indicated that Anxa2 deregulation was associated with the occurrence, invasion and metastasis of cancers. Anxa2 up-regulation was related to the development, invasion, metastasis and drug resistance of hepatocellular carcinoma, colorectal cancer, breast cancer, pancreatic cancer, acute promyelocytic leukemia and renal cell carcinoma; while Anxa2 down-regulation was associated with prostate cancer, esophageal squamous carcinoma and nasopharyngeal carcinoma and sinonasal adenocarcinoma. The association between Anxa2 and malignant tumors as well as the potential action mechanisms were summarized in current work. Anxa2 might be used as a potential biomarker for the diagnosis, treatment and prognosis of certain tumors.

O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) in primary and metastatic colorectal cancer clones and effect of N-acetyl-β-D-glucosaminidase silencing on cell phenotype and transcriptome

O-linked β-N-acetylglucosamine (O-GlcNAc) glycosylation is a regulatory post-translational modification occurring on the serine or threonine residues of nucleocytoplasmic proteins. O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase and O-GlcNAcase (OGA), which are responsible for O-GlcNAc addition and removal, respectively. Although O-GlcNAcylation was found to play a significant role in several pathologies such as type II diabetes and neurodegenerative diseases, the role of O-GlcNAcylation in the etiology and progression of cancer remains vague. Here, we followed O-GlcNAcylation and its catalytic machinery in metastatic clones of human colorectal cancer and the effect of OGA knockdown on cellular phenotype and on the transcriptome. The colorectal cancer SW620 metastatic clone exhibited increased O-GlcNAcylation and decreased OGA expression compared with its primary clone, SW480. O-GlcNAcylation elevation in SW620 cells, through RNA interference of OGA, resulted in phenotypic alterations that included acquisition of a fibroblast-like morphology, which coincides with epithelial metastatic progression and growth retardation. Microarray analysis revealed that OGA silencing altered the expression of about 1300 genes, mostly involved in cell movement and growth, and specifically affected metabolic pathways of lipids and carbohydrates. These findings support the involvement of O-GlcNAcylation in various aspects of tumor cell physiology and suggest that this modification may serve as a link between metabolic changes and cancer.

Secreted clusterin in colon tumor cell models and its potential as diagnostic marker for colorectal cancer

We studied the specific changes of the secreted protein clusterin and its cytoplasmic precursor regarding colorectal tumorigenesis, using in vitro differentiation of Caco-2 cells. In tumor-like stage, we observed an overexpression of both precursor and secreted clusterin, corroborated in the cell line SW-480. Noticeably, SW-620 cells (from a tumoral node, thus with metastatic capacity) did not show overexpression of either precursor or secreted clusterin, suggesting a downregulation related to local metastasis. We further investigated clusterin in serum, finding a significant increase in colorectal cancer patients, with 81% sensitivity, 79% specificity, and an area under the ROC curve of 0.85.

Proteomic analysis of colorectal cancer metastasis: stathmin-1 revealed as a player in cancer cell migration and prognostic marker

Metastasis accounts largely for the high mortality rate of colorectal cancer (CRC) patients. In this study, we performed comparative proteome analysis of primary CRC cell lines HCT-116 and its metastatic derivative E1 using 2-D DIGE. We identified 74 differentially expressed proteins, many of which function in transcription, translation, angiogenesis signal transduction, or cytoskeletal remodeling pathways, which are indispensable cellular processes involved in the metastatic cascade. Among these proteins, stathmin-1 (STMN1) was found to be highly up-regulated in E1 as compared to HCT-116 and was thus selected for further functional studies. Our results showed that perturbations in STMN1 levels resulted in significant changes in cell migration, invasion, adhesion, and colony formation. We further showed that the differential expression of STMN1 correlated with the cells' metastatic potential in other paradigms of CRC models. Using immunohistochemistry, we also showed that STMN1 was highly expressed in colorectal primary tumors and metastatic tissues as compared to the adjacent normal colorectal tissues. Furthermore, we also showed via tissue microarray analyses of 324 CRC tissues and Kaplan-Meier survival plot that CRC patients with higher expression of STMN1 have poorer prognosis.

Proteomics identification of ITGB3 as a key regulator in reactive oxygen species-induced migration and invasion of colorectal cancer cells

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and second in females worldwide. Unfortunately 40-50% of patients already have metastatic disease at presentation when prognosis is poor with a 5-year survival of <10%. Reactive oxygen species (ROS) have been proposed to play a crucial role in tumor metastasis. We now show that higher levels of ROS accumulation are found in a colorectal cancer-derived metastatic cell line (SW620) compared with a cell line (SW480) derived from the primary lesion from the same patient. In addition, ROS accumulation can affect both the migratory and invasive capacity of SW480 and SW620 cells. To explore the molecular mechanism underlying ROS-induced migration and invasion in CRC, we have compared protein expression patterns between SW480 and SW620 cells using a two-dimensional electrophoresis-based proteomics strategy. A total of 63 altered proteins were identified from tandem MS analysis. Cluster analysis revealed dysregulated expression of multiple redox regulative or ROS responsive proteins, implicating their functional roles in colorectal cancer metastasis. Molecular and pathological validation demonstrated that altered expression of PGAM1, GRB2, DJ-1, ITGB3, SOD-1, and STMN1 was closely correlated with the metastatic potential of CRC. Functional studies showed that ROS markedly up-regulated expression of ITGB3, which in turn promoted an aggressive phenotype in SW480 cells, with concomitant up-regulated expression of STMN1. In contrast, knockdown of ITGB3 expression could mitigate the migratory and invasive potential of SW620 or H(2)O(2)-treated SW480 cells, accompanied by down-regulated expression of STMN1. The function of ITGB3 was dependent on the surface expression of integrin αvβ3 heterodimer. Furthermore, STMN1 expression and the PI3K-Akt-mTOR pathway were found to be involved in ROS-induced and ITGB3-mediated migration and invasion of colorectal cancer cells. Taken together, these studies suggest that ITGB3 plays an important role in ROS-induced migration and invasion in CRC.

Identification of key players for colorectal cancer metastasis by iTRAQ quantitative proteomics profiling of isogenic SW480 and SW620 cell lines

This study compared the whole cell proteome profiles of two isogenic colorectal cancer (CRC) cell lines (primary SW480 cell line and its lymph node metastatic variant SW620), as an in vitro metastatic model, to gain an insight into the molecular events of CRC metastasis. Using iTRAQ (isobaric tags for relative and absolute quantitation) based shotgun proteomics approach, we identified 1140 unique proteins, out of which 147 were found to be significantly altered in the metastatic cell. Ingenuity pathway analysis with those significantly altered proteins, revealed cellular organization and assembly as the top-ranked altered biological function. Differential expression pattern of 6 candidate proteins were validated by Western blot. Among these, the low expression level of β-catenin combined with the up-regulation of CacyBP (Calcyclin binding Protein), a β-catenin degrading protein, in the metastatic cell provided a rational guide for the downstream functional assays. The relative expression pattern of these two proteins was further validated in three other CRC cells by Western blot and quantitative immunofluorescence studies. Overexpression of CacyBP in three different primary CRC cell lines showed significant reduction in adhesion characteristics as well as cellular β-catenin level as confirmed by our experiments, indicating the possible involvement of CacyBP in CRC metastasis. In short, this study demonstrates successful application of a quantitative proteomics approach to identify novel key players for CRC metastasis, which may serve as biomarkers and/or drug targets to improve CRC therapy.

Proliferation-inhibiting and apoptosis-inducing effects of ursolic acid and oleanolic acid on multi-drug resistance cancer cells in vitro

OBJECTIVE

To investigate the proliferation-inhibiting and apoptosis-inducing effects of ursolic acid (UA) and oleanolic acid (OA) on multi-drug resistance (MDR) cancer cells in vitro.

METHODS

UA and OA in different concentrations (0-100 μmol/L) were added separately to cultures of different cancer cell lines, including the human colon cancer cell lines SW480 and SW620, human acute myelocytic leukemia cancer cell lines HL60 and HL60/ADR, human chronic myelogenous leukemia cell lines K562 and K562/ADR, and the human breast cancer cell lines MCF-7 and MCF-7/ADR. Effects of UA and OA on cell proliferation were detected by 3-(4,5-dimethyl-2-thiazole)-2-5-biphenly-tetrazole bromide (MTT) method and effects on cell apoptosis were tested by flow cytometry (FCM) and Western blot at 24, 48, and 72 h after treatment.

RESULTS

Both UA and OA showed significant inhibition on parent and MDR cell lines in a time- and concentration-dependent manner; the drug-resistant multiple of them on K562 and K562/ADR as well as on HL60 and HL60/ADR was 1; the effects of UA were better than those of OA in inhibiting cell growth of solid colonic cancer and breast cancer. After SW480 cells were treated by UA at the concentrations of 0-40 μmol/L for 48 h, FCM showed that annexin V (AV) positive cells and hypodiploid peak ratio increased along with the increase in the drug's concentrations; and Western blot found that expressions of Bcl-2, Bcl-xL and survivin decreased in a concentration-dependent manner.

CONCLUSIONS

Both UA and OA have antitumor effects on cancer cells with MDR, and the optimal effect is shown by UA on colonic cancer cells. Also, UA shows cell apoptosis-inducing effect on SW480, possibly by way of down-regulating the expressions of apoptosis antagonistic proteins, Bcl-2, Bcl-xL, and survivin.

Chemometrics of differentially expressed proteins from colorectal cancer patients

AIM: To evaluate the usefulness of differentially expressed proteins from colorectal cancer (CRC) tissues for differentiating cancer and normal tissues.

METHODS: A Proteomic approach was used to identify the differentially expressed proteins between CRC and normal tissues. The proteins were extracted using Tris buffer and thiourea lysis buffer (TLB) for extraction of aqueous soluble and membrane-associated proteins, respectively. Chemometrics, namely principal component analysis (PCA) and linear discriminant analysis (LDA), were used to assess the usefulness of these proteins for identifying the cancerous state of tissues.

RESULTS: Differentially expressed proteins identified were 37 aqueous soluble proteins in Tris extracts and 24 membrane-associated proteins in TLB extracts. Based on the protein spots intensity on 2D-gel images, PCA by applying an eigenvalue > 1 was successfully used to reduce the number of principal components (PCs) into 12 and seven PCs for Tris and TLB extracts, respectively, and subsequently six PCs, respectively from both the extracts were used for LDA. The LDA classification for Tris extract showed 82.7% of original samples were correctly classified, whereas 82.7% were correctly classified for the cross-validated samples. The LDA for TLB extract showed that 78.8% of original samples and 71.2% of the cross-validated samples were correctly classified.

CONCLUSION: The classification of CRC tissues by PCA and LDA provided a promising distinction between normal and cancer types. These methods can possibly be used for identification of potential biomarkers among the differentially expressed proteins identified.

Proteomic analysis of pancreatic intraepithelial neoplasia and pancreatic carcinoma in rat models

AIM

To detect the proteomic variabilities of pancreatic intraepithelial neoplasia (PanIN) and pancreatic carcinoma (PC) induced by 7,12-dimethylbenzanthracene (DMBA) in rat models and to identify potential biomarkers.

METHODS

Sixty adult male Sprague Dawley rats were randomized into three groups. The rats had DMBA implanted into their pancreas for one (n = 20) or two months (n = 20) or assigned to the normal group (n = 20). The rats were killed after one or two months, and were evaluated histopathologically. Three tissue samples from each group of rats with either normal pancreas, PanIN (PanIN-2) or PC were examined by 2D-DIGE. The different expression spot features were analyzed by matrix-assisted laser desorption/ionization-time of flight/time of flight (MALDI-TOF/TOF) tandem mass spectrometry. The expression of enolase 1, a differentially expressed protein, was identified by immunohistochemistry.

RESULTS

There was significant difference in the proportions of neoplastic changes between the 1- and 2-mogroups (P = 0.0488). There was an increase in the frequency of adenocarcinomas in the 2-mo group compared with the 1-mo group (P = 0.0309). No neoplastic changes were observed in any of the animals in the normal group. Enolase 1, pancreatic ELA3B, necdin, Hbp23, CHD3, hnRNP A2/B1, Rap80, and Gnb2l1 were up-regulated in the PanIN and PC tissues, and CEL, TPT1, NME2, PCK2, an unnamed protein product, and glycine C-acetyltransferase were down-regulated in the PanIN and PC tissues. The immunohistochemical results showed that enolase 1 expression was up-regulated in the pancreatic cancer tissues of rats and humans.

CONCLUSION

The pancreatic protein expression changes induced by DMBA suggest potential molecular targets for the early diagnosis and treatment of PC.

α-Enolase: a promising therapeutic and diagnostic tumor target

α-enolase (ENOA) is a metabolic enzyme involved in the synthesis of pyruvate. It also acts as a plasminogen receptor and thus mediates activation of plasmin and extracellular matrix degradation. In tumor cells, ΕΝΟΑ is upregulated and supports anaerobic proliferation (Warburg effect), it is expressed at the cell surface, where it promotes cancer invasion, and is subjected to a specific array of post-translational modifications, namely acetylation, methylation and phosphorylation. Both ENOA overexpression and its post-translational modifications could be of diagnostic and prognostic value in cancer. This review will discuss recent information on the biochemical, proteomics and immunological characterization of ENOA, particularly its ability to trigger a specific humoral and cellular immune response. In our opinion, this information can pave the way for effective new therapeutic and diagnostic strategies to counteract the growth of the most aggressive human disease.

Identification of serum biomarkers for colorectal cancer metastasis using a differential secretome approach

Lymph node metastasis is the major concern that causes death in colorectal cancers. However, biomarkers for cancer metastasis are still lacking. In this study, we applied an LC-MS/MS-based label-free quantitative proteomics approach to compare the differential secretome of a primary cell line SW480 and its lymph node metastatic cell line SW620 from the same colorectal cancer patient. We identified a total of 910 proteins from the conditioned media and 145 differential proteins between SW480 and SW620 (>1.5-fold change). The differential expression pattern of 6 candidate proteins was validated by Western blot analysis. Among them, trefoil factor 3 and growth/differentiation factor 15, two up-regulated proteins in SW620, were further analyzed in a large cohort of clinical tissue and serum samples. Sandwich ELISA assay showed that the serum levels of both proteins were significantly higher in lymph node metastatic colorectal cancers. Receiver operating characteristic curve analysis confirmed that serum trefoil factor 3 and growth/differentiation factor 15 could provide a discriminatory diagnostic test for predicting colorectal cancer metastasis. Immunohistochemical analysis also showed that the overexpression of trefoil factor 3 or growth/differentiation factor 15 in colorectal cancer was associated with lymph node metastatic behavior. This study showed an accurate, sensitive, and robust label-free quantitation approach for differential analysis of cancer secretome. The comparison of the cancer secretome in vitro is a feasible strategy to obtain valuable biomarkers for potential clinical application. Both trefoil factor 3 and growth/differentiation factor 15 could serve as potential biomarkers for the prediction of colorectal cancer metastasis.

Urinary proteome profiling using 2D-DIGE and LC-MS/MS

Proteomic methodologies have been at the forefront of cancer research for several years. The use of proteomic strategies to study all expressed genes aims to discover biomarkers indicative of the physiological state of cancer cells at specific time points, enabling early diagnosis, following cancer development/progression, screening and monitoring the efficacy of new therapeutic agents. Onco-proteomics has the potential to impact on oncology practice by delivering individualised highly selective clinical care. 2D-DIGE (2D difference in gel electrophoresis) enables simultaneous examination and comparison of multiple samples using cyanine dyes to label amino acid residues that are then separated based on charge and mass. These advantages combined with universal availability have until recently made 2D-DIGE a first method of choice in cancer proteome analysis of diverse specimens, including tissues, cell lines, blood and other body fluids.

Triosephosphate isomerase and peroxiredoxin 6, two novel serum markers for human lung squamous cell carcinoma

There is currently substantial interest in the identification of human tumor antigens for the diagnosis and immunotherapy of cancer. In our previous study, secretion character and up-regulation of triosephosphate isomerase were observed in lung squamous cell carcinoma, and autoantibodies against triosephosphate isomerase and peroxiredoxin 6 were detected in the sera from over 25% of patients, but in none of the healthy controls. In this study, peroxiredoxin 6 was also found at higher levels in the sera of the patients. Up-regulated triosephosphate isomerase and peroxiredoxin 6 were further validated by enzyme-linked immunosorbent assay in an additional 61 lung squamous cell carcinoma patients, 23 lung adenocarcinoma patients, 56 other types of carcinoma patients, 12 benign lung disease patients, and 59 healthy controls. We found that both triosephosphate isomerase and peroxiredoxin 6 were specifically elevated in lung squamous cell carcinoma sera compared with other groups, with the exception of peroxiredoxin 6 in lung adenocarcinoma patients. Positive correlation between triosephosphate isomerase and distant metastasis was found. At the cut-off point 0.221 (optical density value) on the receiver operating characteristic curve, triosephosphate isomerase could comparatively discriminate lung squamous cell carcinoma from healthy controls with a sensitivity of 65.6%, specificity 84.7%, and total accuracy 75%. For peroxiredoxin 6, at the cut-off point 0.151, it could discriminate the two groups with a sensitivity of 70.5%, specificity 62.7%, and total accuracy 65.8%. With both triosephosphate isomerase and peroxiredoxin 6, discriminant analysis results showed that 68.9% of the lung squamous cell carcinoma and 83.1% of healthy controls were correctly classified. We concluded that triosephosphate isomerase and peroxiredoxin 6 could be markers for lung squamous cell carcinoma.

Application of proteomics in colorectal cancer research

Colorectal cancer is one of the most common malignant tumors in China. Its morbidity and mortality are increasing year by year. The emergence of proteomics has pushed colorectal cancer research forward. In this article, we will review the application of proteomics in the study of the diagnosis, pathogenesis and treatment of colorectal cancer.

Evaluation of metastatic and angiogenic potentials of human colon carcinoma cells in chick embryo model systems

Increased metastatic and angiogenic potentials of aggressive human colon carcinoma cells were verified in independent chick embryo models by comparing in vivo highly metastatic SW620 colon carcinoma cell line with its isogenic, non-metastatic SW480 cell variant. In the experimental metastasis model, both cell types rapidly arrested in the chorioallantoic membrane (CAM) vasculature as demonstrated by quantitative PCR and immunohistochemistry. Live cell imaging also indicated that both SW620 and SW480 cells efficiently extravasated from the CAM capillary system. However, only few SW480 cells were present in the CAM tissue after 24-48 h. In contrast, the numbers of SW620 cells increased exponentially, indicating proliferative and survival advantages of metastatic colon carcinoma cells in vivo. Multicellular SW620 foci were identified in close proximity to CAM blood vessels. A positive correlation between increased metastatic ability and VEGF-expression of colon carcinoma SW620 cells was demonstrated by the substantial inhibitory effects of anti-VEGF treatment on the levels of metastatic colonization and density of blood vessels adjacent to tumor cell foci. Furthermore, the chick embryo angiogenesis model confirmed high levels of VEGF-dependent angiogenesis induced by SW620 cells, but not SW480 cells. Thus, chick embryo experimental metastasis and CAM angiogenesis models appear to coordinately reflect critical features of advanced colon carcinomas, i.e., the acquisition of enhanced survival and increased angiogenic potentials, both constituting critical determinants of colon cancer progression. The use of rapid and quantitative chick embryo models might provide alternative approaches to conventional mammalian model systems for screening anti-cancer agents.

Murine fecal proteomics: a model system for the detection of potential biomarkers for colorectal cancer

Tumor related products shed into the feces offer a potential source of biomarkers for the detection of colorectal cancer (CRC). Using SDS-PAGE followed by nanoflow reversed-phased LC-MS/MS to analyse fecal samples from Apc(Min/+) mice (that develop spontaneous multiple intestinal neoplasia with age) we have identified 336 proteins (115 proteins of murine origin, 201 from fecal bacteria, 18 associated with food intake and 2 of apparent parasitic origin). 75% of the murine proteins identified in this study are predicted to be extracellular or associated with the cell plasma membrane. Of these proteins, a number of the murine homologues of colorectal cancer associated proteins (CCAP) such as hemoglobin, haptoglobin, hemopexin, alpha-2-macroglobulin and cadherin-17 have been identified, demonstrating the potential of fecal proteomics for detecting potential biomarkers and paving the way for subsequent MS/MS based biomarker studies on similar human samples.

Proteomic analysis of low dose arsenic and ionizing radiation exposure on keratinocytes

Human exposure to arsenic and ionizing radiation (IR) occur environmentally at low levels. While the human health effects of arsenic and IR have been examined separately, there is little information regarding their combined effects at doses approaching environmental levels. Arsenic toxicity may be affected by concurrent IR especially given their known individual carcinogenic actions at higher doses. We found that keratinocytes responded to either low dose arsenic and/or low dose IR exposure, resulting in differential proteomic expression based on 2-DE, immunoblotting and statistical analysis. Seven proteins were identified that passed a rigorous statistical screen for differential expression in 2-DE and also passed a strict statistical screen for follow-up immunoblotting. These included: alpha-enolase, epidermal-fatty acid binding protein, heat shock protein 27, histidine triad nucleotide-binding protein 1, lactate dehydrogenase A, protein disulfide isomerase precursor, and S100A9. Four proteins had combined effects that were different than would be expected based on the response to either individual toxicant. These data demonstrate a possible reaction to the combined insult that is substantially different from that of either separate treatment. Several proteins had different responses than what has been seen from high dose exposures, adding to the growing literature suggesting that the cellular responses to low dose exposures are distinct.