Combined serum and tissue proteomic study applied to a c-Myc transgenic mouse model of hepatocellular carcinoma identified novel disease regulated proteins suitable for diagnosis and therapeutic intervention strategies

Differential Proteomic Analysis of Hepatocellular Carcinomas from Ppp2r5d Knockout Mice and Normal (Knockout) Livers

BACKGROUND

Hepatocellular carcinoma (HCC) is the major type of primary liver cancer. Mice lacking the tumor-suppressive protein phosphatase 2A subunit B56δ (Ppp2r5d) spontaneously develop HCC, correlating with increased c-MYC oncogenicity.

MATERIALS AND METHODS

We used two-dimensional difference gel electrophoresis-coupled matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to identify differential proteomes of livers from wild-type, non-cancerous and HCC-affected B56δ knockout mice.

RESULTS

A total of 23 proteins were differentially expressed/regulated in liver between wild-type and non-cancerous knockout mice, and 119 between non-cancerous and HCC knockout mice ('cancer proteins'). Overlap with our reported differential transcriptome data was poor. Overall, 56% of cancer proteins were reported before in HCC proteomics studies; 44% were novel. Gene Ontology analysis revealed cancer proteins mainly associated with liver metabolism (18%) and mitochondria (15%). Ingenuity Pathway Analysis identified 'cancer' and 'gastrointestinal disease' as top hits.

CONCLUSION

We identified several proteins for further exploration as novel potential HCC biomarkers, and independently underscored the relevance of Ppp2r5d knockout mice as a valuable hepatocarcinogenesis model.

Serum proteome mapping of EGF transgenic mice reveal mechanistic biomarkers of lung cancer precursor lesions with clinical significance for human adenocarcinomas

Atypical adenomatous hyperplasia (AAH) of the lung is a pre-invasive lesion (PL) with high risk of progression to lung cancer (LC). However, the pathways involved are uncertain. We searched for novel mechanistic biomarkers of AAH in an EGF transgenic disease model of lung cancer. Disease regulated proteins were validated by Western immunoblotting and immunohistochemistry (IHC) of control and morphologically altered respiratory epithelium. Translational work involved clinical resection material. Collectively, 68 unique serum proteins were identified by 2DE-MALDI-TOF mass spectrometry and 13 reached statistical significance (p < 0.05). EGF, amphiregulin and the EGFR endosomal sorting protein VPS28 were induced up to 5-fold while IHC confirmed strong induction of these proteins. Furthermore, ApoA1, α-2-macroglobulin, and vitamin-D binding protein were nearly 6- and 2-fold upregulated in AAH; however, ApoA1 was oppositely regulated in LC to evidence disease stage dependent regulation of this tumour suppressor. Conversely, plasminogen and transthyretin were highly significantly repressed by 3- and 20-fold. IHC confirmed induced ApoA1, Fetuin-B and transthyretin expression to influence calcification, inflammation and tumour-infiltrating macrophages. Moreover, serum ApoA4, ApoH and ApoM were 2-, 2- and 6-fold repressed; however tissue ApoM and sphingosine-1-phosphate receptor expression was markedly induced to suggest a critical role of sphingosine-1-phosphate signalling in PL and malignant transformation. Finally, a comparison of three different LC models revealed common and unique serum biomarkers mechanistically linked to EGFR, cMyc and cRaf signalling. Their validation by IHC on clinical resection material established relevance for distinct human lung pathologies. In conclusion, we identified mechanistic biomarker candidates recommended for in-depth clinical evaluation.

Regulation of glycosylphosphatidylinositol-anchored proteins and GPI-phospholipase D in a c-Myc transgenic mouse model of hepatocellular carcinoma and human HCC

Recent research implicated glycosylphosphatidylinositol-anchored proteins (GPI-AP) and GPI-specific phospholipase D (GPI-PLD) in the pathogenesis of fatty liver disease and hepatocellular carcinoma (HCC). Given that c-Myc is frequently amplified in HCC, we investigated their regulation in a c-Myc transgenic disease model of liver cancer and HCC patient samples. Whole genome scans defined 54 significantly regulated genes coding for GPI-AP of which 29 and 14 were repressed in expression in transgenic tumors and steatotic human hepatocyte cultures, respectively, to influence lipid-mediated signal transduction, extracellular matrix and immunity pathways. Analysis of gene specific promoter revealed >95% to carry c-Myc binding sites thus establishing a link between c-Myc activity and transcriptional response. Alike, serum GPI-PLD activity was increased 4-fold in transgenic mice; however its tissue activity was reduced by 70%. The associated repression of the serine/threonine phosphatase 2A (PP2A), i.e. a key player of c-Myc proteolysis, indicates co-ordinate responses aimed at impairing tissue GPI-PLD anti-proliferative activities. Translational research identified >4-fold increased GPI-PLD serum protein expression though enzyme activities were repressed by 60% in NASH and HCC patients. Taken collectively, c-Myc influences GPI-AP signaling transcriptionally and posttranslational and represses GPI-AP anti-proliferative signaling in tumors. The findings broaden the perspective of molecular targeted therapies and disease monitoring.

Combined Plasma and Tissue Proteomic Study of Atherogenic Model Mouse: Approach To Elucidate Molecular Determinants in Atherosclerosis Development

Atherogenic cardiovascular diseases are the major cause of mortality. Prevention and prediction of incidents is important; however, biomarkers that directly reflect the disease progression remain poorly investigated. To elucidate molecular determinants of atherogenesis, proteomic approaches are advantageous by using model animals for comparing changes occurring systematically (bloodstream) and locally (lesion) in accordance with the disease progression stages. We conducted differential mass spectrometric analysis between apolipoprotein E deficient (apoED) and wild-type (wt) mice using the plasma and arterial tissue of both types of mice obtained at four pathognomonic time points of the disease. A total of 100 proteins in the plasma and 390 in the arterial tissues were continuously detected throughout the four time points; 29 were identified in common. Of those, 13 proteins in the plasma and 36 in the arterial tissues showed significant difference in abundance between the apoED and wt mice at certain time points. Importantly, we found that quantitative variation patterns regarding the pathognomonic time points did not always correspond between the plasma and arterial tissues, resulting in gaining insight into atherosclerotic plaque progression. These characteristic proteins were found to be components of inflammation, thrombus formation, and vascular remodeling, suggesting drastic and integrative alteration in accordance with atherosclerosis development.

Carbonic anhydrase 1 is a promising biomarker for early detection of non-small cell lung cancer

This study aimed to identify candidate biomarkers associated with stage I non-small cell lung cancer (NSCLC). Sera from three groups, a lung cancer group (n = 11), benign control group (n = 12), and normal control group (n = 10), were collected and pooled. Protein expression profiles were analyzed by a combination of two-dimensional electrophoresis (2DE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). These methods were used to separate, screen, and identify proteins that were differentially expressed between stage I NSCLC and controls. Differentially expressed proteins were validated by both Western blot and ELISA in an expanded sample size (22, 18, and 18 in three groups, respectively). MALDI-MS identified 12 differentially expressed proteins in the lung cancer group compared to the two control groups. Expression of carbonic anhydrase 1 (CA1) was validated by Western blot. CA1 was significantly elevated in the lung cancer group compared to controls. ELISA results confirmed that CA1 in the lung cancer group (3.18 ± 1.27 ng/mL, n = 22) was highly expressed in stage I NSCLC patients compared to those in the benign control group (2.21 ± 0.71 ng/mL, n = 18) and the normal control group (2.04 ± 0.63 ng/mL, n = 18) (P = 0.001). In conclusion, we provide evidence that CA1 is highly expressed in the sera of stage I NSCLC patients. Additionally, CA1 might serve as a novel biomarker for early detection of NSCLC.

Mouse models for liver cancer

Hepatocellular carcinoma (HCC), the most common form of primary liver cancer is the third leading cause of cancer-related cell death in human and the fifth in women worldwide. The incidence of HCC is increasing despite progress in identifying risk factors, understanding disease etiology and developing anti-viral strategies. Therapeutic options are limited and survival after diagnosis is poor. Therefore, better preventive, diagnostic and therapeutic tools are urgently needed, in particular given the increased contribution from systemic metabolic disease to HCC incidence worldwide. In the last three decades, technological advances have facilitated the generation of genetically engineered mouse models (GEMMs) to mimic the alterations frequently observed in human cancers or to conduct intervention studies and assess the relevance of candidate gene networks in tumor establishment, progression and maintenance. Because these studies allow molecular and cellular manipulations impossible to perform in patients, GEMMs have improved our understanding of this complex disease and represent a source of great potential for mechanism-based therapy development. In this review, we provide an overview of the current state of HCC modeling in the mouse, highlighting successes, current challenges and future opportunities.

Proteomics analysis of tumor microenvironment: Implications of metabolic and oxidative stresses in tumorigenesis

Tumorigenesis is always concomitant with microenvironmental alterations. The tumor microenvironment is a heterogeneous and complex milieu, which exerts a variety of stresses on tumor cells for proliferation, survival, or death. Recently, accumulated evidence revealed that metabolic and oxidative stresses both play significant roles in tumor development and progression that converge on a common autophagic pathway. Tumor cells display increased metabolic autonomy, and the hallmark is the exploitation of aerobic glycolysis (termed Warburg effect), which increased glucose consumption and decreased oxidative phosphorylation to support growth and proliferation. This characteristic renders cancer cells more aggressive; they devour tremendous amounts of nutrients from microenvironment to result in an ever-growing appetite for new tumor vessel formation and the release of more "waste," including key determinants of cell fate like lactate and reactive oxygen species (ROS). The intracellular ROS level of cancer cells can also be modulated by a variety of stimuli in the tumor microenvironment, such as pro-growth and pro-inflammatory factors. The intracellular redox state serves as a double-edged sword in tumor development and progression: ROS overproduction results in cytotoxic effects and might lead to apoptotic cell death, whereas certain level of ROS can act as a second-messenger for regulation of such cellular processes as cell survival, proliferation, and metastasis. The molecular mechanisms for cancer cell responses to metabolic and oxidative stresses are complex and are likely to involve multiple molecules or signaling pathways. In addition, the expression and modification of these proteins after metabolic or oxidative stress challenge are diverse in different cancer cells and endow them with different functions. Therefore, MS-based high-throughput platforms, such as proteomics, are indispensable in the global analysis of cancer cell responses to metabolic and oxidative stress. Herein, we highlight recent advances in the understanding of the metabolic and oxidative stresses associated with tumor progression with proteomics-based systems biology approaches.

Association between apolipoprotein E genotype, chronic liver disease, and hepatitis B virus

BACKGROUND/AIMS

Apolipoprotein E (ApoE) plays an important role in regulating lipid and lipoprotein metabolism, and ApoE genotypes are known to affect plasma lipoprotein concentrations. We investigated whether ApoE genotype determines the disease outcome in hepatitis B virus (HBV)-infected individuals, and verified the association between ApoE genotype and the occurrence of hepatocellular carcinoma (HCC) in patients with chronic liver diseases of various etiologies.

METHODS

This hospital-based, case-controlled study enrolled 156 subjects (47 healthy controls, 50 HBV-related liver cirrhosis patients, and 59 HCC patients). ApoE genotypes were determined using PCR-based ApoE genotyping kits. The biological significance of ApoE genotype was verified by measuring serum ApoE levels using an ELISA kits.

RESULTS

The ε3 allele was the most common allele, with allele frequencies among the entire cohort of 5.8%, 84.3%, and 9.9% for the ε2, ε3, and ε4 alleles, respectively. Significantly more of those patients carrying the ε3/3 genotype had developed liver cirrhosis compared to the control subjects. Being an ApoE4 carrier was associated with a lower probability of developing liver cirrhosis. The allele frequencies and genotype distribution of ApoE did not differ significantly between the liver cirrhosis and HCC patients. The serum level of ApoE was significantly higher in patients with liver cirrhosis than in the healthy controls, but did not differ significantly with the ApoE genotype.

CONCLUSIONS

The ApoE ε3/3 genotype frequency was higher in patients with HBV-associated liver cirrhosis than in the controls.

2D-DIGE analysis of sera from transgenic mouse models reveals novel candidate protein biomarkers for human gastric cancer

The gp130(F/F) genetically engineered mouse (GEM) model reproducibly and predictably develops a gastric adenoma phenotype resembling the primary lesions of human intestinal-type gastric cancer (GC). Accordingly, changes to the serum proteome of gp130(F/F) mice may uncover early-stage GC biomarkers. Here, we have employed several double and compound mutant GEM strains that display distinct phenotypes with respect to gastric tumour load and inflammatory response, thereby mimicking different states of inflammation-associated early-stage GC in humans. This allowed us to distinguish between proteomic changes associated with tumourigenesis rather than confounding systemic inflammation. The comparative proteomic workflow involved depletion of high abundance proteins, 2D-DIGE analysis and protein identification by LC-MS/MS. The differential expression of 112 2D-DIGE spots specifically correlated with the tumour-bearing phenotype, corresponding to 31 murine proteins and their 28 human orthologues. Eight proteins were selected for validation in GC patient sera versus healthy controls. Significant increases in serum apolipoprotein E and haptoglobin, and decreases in afamin and clusterin, were confirmed by ELISA. Receiver operating characteristic analysis revealed that these proteins may be more sensitive and specific discriminators of GC than the existing clinical marker CA72-4.

Identification of transaldolase as a novel serum biomarker for hepatocellular carcinoma metastasis using xenografted mouse model and clinic samples

Hepatocellular carcinoma (HCC) is one of serious disorders with the highest morbidities and mortalities worldwide. Metastasis is the major concern that causes death in HCC. The goal of this study was to screen and identify potential serum proteins indicating HCC metastasis. Serum samples collected from control and HCCLM3-R metastatic HCC tumor model at specific stages of metastasis (1 wk, 3 wks and 6 wks) were subjected to iTRAQ labeling followed by 2DLC-ESI-MS/MS analysis. A total of 554 proteins were identified and 80 proteins were differential expressed at least between one adjacent time points. Among them, expression level of transaldolase (TALDO) was validated in mouse and human serum. The level of TALDO protein was found to be higher in metastatic mice serum compared to that of non-metastatic mice. Human specific TALDO was then identified in mouse serum through human specific peptides. Immunohistochemical and western blot analysis showed that the expression of TALDO in human HCC tissues and HCC cell lines was associated with its metastatic behavior. Subsequent screening of TALDO expression in 72 clinical serum samples (comprising 36 non-metastatic HCC and 36 metastatic HCC samples) revealed higher TALDO level in the serum of metastatic HCC patients. A receiver operating characteristic (ROC) curve estimated a maximal sensitivity of 77.8% and 86.1% specificity for TALDO in detection of HCC metastasis. The present results demonstrated that the nude mouse xenograft model is an efficient system for performing metastasis-related biomarker discovery. TALDO may be useful biomarkers for the detection of HCC metastasis.