Identification of biomarkers for hepatocellular carcinoma using network-based bioinformatics methods
© Zhang et al.; licensee BioMed Central Ltd. 2013
Received: 10 May 2013
Accepted: 30 August 2013
Published: 1 October 2013
Hepatocellular carcinoma (HCC) is one of the most common types of cancer worldwide. Despite several efforts to elucidate molecular mechanisms involved in this cancer, they are still not fully understood.
To acquire further insights into the molecular mechanisms of HCC, and to identify biomarkers for early diagnosis of HCC, we downloaded the gene expression profile on HCC with non-cancerous liver controls from the Gene Expression Omnibus (GEO) and analyzed these data using a combined bioinformatics approach.
The dysregulated pathways and protein-protein interaction (PPI) network, including hub nodes that distinguished HCCs from non-cancerous liver controls, were identified. In total, 29 phenotype-related differentially expressed genes were included in the PPI network. Hierarchical clustering showed that the gene expression profile of these 29 genes was able to differentiate HCC samples from non-cancerous liver samples. Among these genes, CDC2 (Cell division control protein 2 homolo g), MMP 2 (matrix metalloproteinase-2) and DCN (Decorin were the hub nodes in the PPI network.
This study provides a portfolio of targets useful for future investigation. However, experimental studies should be conducted to verify our findings.
KeywordsHepatocellular carcinoma Biomarker Protein-protein interaction
Hepatocellular carcinoma (HCC), a primary liver cancer, is the fifth most common cancer worldwide and the third most common cause of cancer mortality. An estimated 748,300 new liver cancer cases and 695,900 cancer deaths occurred worldwide in 2008. This disease is most prevalent in eastern and southeastern Asia, and in middle Africa, with more than half of patients with HCC being reported from China. In addition, evidence has been accumulating in various countries that the incidence of HCC is rising[4–7]. To improve treatment and prognosis of HCC, information about the phenotypic and molecular changes associated with the development of this disease should be determined.
Much is known about the causes and development of HCC. The main causative agents, hepatitis B virus (HBV), hepatitis C virus (HCV), and aflatoxin B1, together account for about 80% of all HCCs in humans[1, 8–11]. Hepatocarcinogenesis is a complex process associated with the accumulation of genetic and epigenetic changes that occur during initiation and progression of the cancer. In recent years, a number of genomic studies have identified genes that are uniquely upregulated or downregulated in HCC tissues. For example, Lee et al. suggested that cystatin B (CSTB) or the combination of CSTB and α-fetoprotein may be useful markers for diagnosis with high sensitivity of patients with HCC. In addition, potential biomarkers for detection of early HCC, such as glypican 3 (GPC3), ADAM metallopeptidase domain 12 (ADAM12), serine/threonine kinase 15 (STK15), phospholipase A2 (PLA2), and heat-shock protein 70 (HSP70) have also been suggested by previous studies. However, despite several previous efforts, the current understanding or early diagnosis of HCC is still rather limited.
The advancement of microarray technology now enables elucidation of the molecular mechanism of HCC development and identification of novel diagnostic biomarkers. In this study, to acquire further insights into the molecular mechanisms of HCC, we downloaded gene expression profiles of 10 HCCs and 10 noncancerous liver controls from the Gene Expression Omnibus (GEO) database, and analyzed those data using bioinformatics tools. We identified a set of interactive genes that were significantly downregulated or upregulated in HCC. These data may help to improve the diagnostic accuracy of HCC.
The gene expression profiles of HCC with non-cancerous liver controls, which were deposited by Deng and colleagues (accession number: GSE19665,) (approved by ethics committee of Mianyang Central Hospital) were downloaded from GEO. The mRNA expression in ten HCCs (five HBV-related and five HCV-related HCCs) and the 10 matched non-cancerous liver samples (five HBV-related and five HCV-related chronic hepatitis or cirrhosis) was analyzed byoligonucleotide arrays (GeneChip Human Genome U133 plus 2.0; Affymetrix Inc., Santa Clara, CA, USA). For global normalization, the average signal in an array was made equal to 100. We downloaded the raw CEL data and the annotation file for the platform.
Protein-protein interaction data
A total of 36,289 pairs of protein-protein interactions (PPIs) were downloaded from the Human Protein Reference Database (HRPD; http://www.hprd.org/) in March, 2011. Of these, 34,704 pairs of PPIs have relationships with expression profiles. Data preprocessing and identification of differentially expressed genes.
The Affy package in R[20, 21] was used to preprocess the raw expression data. We first converted the probe-level data in the CEL files into expression measures. For each sample, the expression values of all probes for a given gene were reduced to a single value by taking the average expression value; this yielded a set of 19,803 genes. The Significance Analysis of Microarrays (SAM) software was used to identify differentially expressed genes (DEGs). We considered a false discovery rate (FDR, corrected by the Benjamini and Hochberg method) of less than 0.01 to be significant.
Functional enrichment tests
The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database records networks of molecular interactions in the cells, and variants of these interactions specific to particular organisms. To explore the dysfunctional pathways in HCC, we inputted the candidate genes into the Database for Annotation, Visualization, and Integrated Discovery (DAVID; http://david.abcc.ncifcrf.gov/) for pathway enrichment analysis. DAVID is a web-based software suite designed to categorize complex, high content, genomic and proteomic datasets. FDR <0.05 was selected as the cut-off criterion.
Construction of the PPI network
First, we identified phenotype-related genes by calculating the Pearson correlation coefficient (r). The genes that showed significant correlation with HCC (r >0.8 or r < −0.8) were selected as phenotype-related genes. The phenotype-related genes and DEGs were then intersected to obtain the phenotype-related DEGs. Meanwhile, we filtered the significant PPIs in the HPRD database with a cut-off criterion of r >0.8 or r < −0.8. Finally, we mapped the phenotype-related genes for HCC to the significant PPIs, and constructed a PPI network using Cytoscape software.
Identification of DEGs
The gene expression profile of GSE19665 was downloaded from the GEO database and theSAM method was used to identify DEGs in HCC compared with non-cancerous controls. At FDR <0.01, 2,767 genes were identified as DEGs. Of these, 1,359 genes (49.11%) were upregulated and the remaining 1,408 genes (50.89%) were downregulated.
Functional enrichment tests
The enriched pathways for differentially expressed genes (FDR < 0.05)
Complement and coagulation cascades
The enriched pathways for up-regulated genes (FDR< 0.05)
Base excision repair
Nucleotide excision repair
Ubiquitin mediated proteolysis
Progesterone-mediated oocyte maturation
The enriched pathways for down-regulated genes (FDR < 0.05)
Complement and coagulation cascades
Chemokine signaling pathway
Cytokine-cytokine receptor interaction
Hematopoietic cell lineage
Arachidonic acid metabolism
Intestinal immune network for IgA production
Construction of PPI network
In total, 314 phenotype-related genes were identified with r > 0.8 or r < −0.8. Most of these genes were DEGs between HCCs and noncancerous liver samples, except for ISCA2 (iron-sulfur cluster assembly 2 homolog).
Although previous studies have generated a large number of biomarkers for early diagnosis of HCC, the efficiency of current therapy of patients with this disease is still low. In addition, the molecular mechanism of HCC is still not fully understood. In this study, we analyzed the gene expression profile of HCC and non-cancerous liver samples using a combined bioinformatics approach. The dysregulated pathways and PPI network, including hub nodes that distinguished HCCs from noncancerous liver controls, were identified.
Our approach identified an HCC molecular signature of 29 genes. Hierarchical clustering showed that the gene expression profile of these 29 genes was able to differentiate HCC samples from noncancerous livers. Of these genes, CDC2, MMP2, and DCN were hub nodes in the PPI network. Studies suggest that more centralized genes in the network are more likely than peripheral genes to be key drivers of proper cellular function.
CDC2, also known as CDK1, is a member of the serine/threonine protein kinase family. This protein is a catalytic subunit of the highly conserved protein kinase complex known as M-phase promoting factor, which is essential for G1/S and G2/M phase transitions of the eukaryotic cell cycle. In our study, CDC2 was differentially expressed in HCC compared with noncancerous lives. A previous study suggested that CDC2 plays the most crucial role of the G2/M modulators in cell cycle progression and cell proliferation of HCC, and significantly predicts the recurrence of this carcinoma. Another study showed that CDC2 and CDK2 are activated in HCC, and this may be due to a complex interplay between the level of cyclin, CDK, CDK inhibitors, and inhibitory phosphorylation. In accordance with this study, our PPI network showed that CDC2 directly interacted with CCNB1, CCNB2, and CDKN3. In addition, FOXM1 (Forkhead box protein M1), TOP2A, RRM2, and ECT2 were also identified as having interactions with CDC2. FOXM1 is a human cell cycle transcription factor that is known to play a key role in regulating timely mitotic progression and chromosomal segregation during cell division. Xia et al. reported that activation of FOXM1 through the ERK/CREB pathway is involved in HBV-related hepatocarcinogenesis. Overexpression of TOP2A was reported to be correlated with earlier onset, shorter survival time, and resistance to chemotherapy in HCC. RRM2 is located in a region of frequent cytogenetic aberration in HCC. Chua et al. suggested that gallium maltolate might be a promising chemotherapeutic agent for treatment of HCC by targeting RRM2.
MMP2 is a key member of the matrix metalloproteinase (MMP) family, which is involved in many pathological conditions, particularly cancer metastasis and angiogenesis[35, 36]. Our result suggested that MMP2 is upregulated in HCC, and this result is in line with previous studies[37–41]. The PPI network in our study showed that MMP2 directly interacted with six DEGs: TIMP2, CXCL12, DCN, FGFR1, THBS1, and IGFBP3. TIMP2 is the tissue inhibitor of MMP2. An imbalance between the proteolytic activity of MMP2 and TIMP2 is responsible for degradation of extracellular matrix (ECM) components, and plays a crucial role in tumor invasion and in metastasis formation. Theret et al. also found a correlation between MMP mRNA levels and MMP2 and TIMP2 mRNA levels, as well as with MMP2 activation in HCCs. THBS1 is a matricellular protein capable of modulating angiogenesis, and high expression of THBS1was shown to be associated with tumor invasiveness and progression in HCC. IGBP-3 is a mediator of growth suppression signals and a putative tumor suppressor. It was reported that IGFBP-3 mediates growth suppression signals via the transforming growth factor-β and/or Rb pathways in HCC.
DCN is a small cellular or pericellular matrix proteoglycan that is closely related in structure to biglycan protein. Our result suggested that DCN is differentially expressed in HCC and interacts with DPT, THBS1, MMP2 and COL14A1. Few studies have reported DCN expression in HCC, therefore its potential role in hepatocarcinogenesis remains to be investigated. In addition, increased expression levels of S100A8 and S100A9 have been detected in various human cancers in recent years. Nemeth et al. suggest that S100A8 and S100A9 are novel nuclear factor-κB target genes in HCC cells, and increased expression of these proteins supports malignant progression by activation of reactive oxygen species-dependent signaling pathways.
There are some limitations to our study. First, we did not generate the microarray data ourselves but took them from the GEO database. Second, as differences exist between HBV-related and HCV-related cancers, elaboration of HBV-specific or HCV-specific genes may be more important. Third, validation of the results in other datasets or samples is lacking in this study, therefore, further experimental studies based on a larger sample size are needed to confirm our results. This would be the next step in our research.
In conclusion, we have identified an HCC molecular signature of 29 genes. Of these genes, CDC2, MMP2, and DCN were hub nodes in the PPI network. However, further experimental studies are necessary to confirm our results and to elucidate the role of these genes in HCC pathogenesis and to determine their potential as molecular targets for the development of new therapeutic approaches for HCC.
Lingyan Zhang and Ying Guo should be regarded as co-first authors.
This work was supported by Grant 81171365 from the National Natural Science Foundation of China. We have no conflict of interest to state. We have obtained permission for inclusion of previously published material in this article.
- El-Serag HB, Rudolph KL: Hepatocellular carcinoma: epidemiology and molecular carcinogenesis. Gastroenterology 2007, 132: 2557–2576. 10.1053/j.gastro.2007.04.061View ArticlePubMedGoogle Scholar
- Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D: Global cancer statistics. CA Cancer J Clin 2011, 61: 69–90. 10.3322/caac.20107View ArticlePubMedGoogle Scholar
- Avila MA, Berasain C, Sangro B, Prieto J: New therapies for hepatocellular carcinoma. Oncogene 2006, 25: 3866–3884. 10.1038/sj.onc.1209550View ArticlePubMedGoogle Scholar
- Bosch FX, Ribes J, Diaz M, Cleries R: Primary liver cancer: worldwide incidence and trends. Gastroenterology 2004, 127: S5-S16. 10.1053/j.gastro.2004.09.011View ArticlePubMedGoogle Scholar
- El-Serag HB, Mason AC: Rising incidence of hepatocellular carcinoma in the United States. N Engl J Med 1999, 340: 745–750. 10.1056/NEJM199903113401001View ArticlePubMedGoogle Scholar
- Harnois DM: Hepatitis C virus infection and the rising incidence of hepatocellular carcinoma. Mayo Clin Proc 2012, 87: 7–8. 10.1016/j.mayocp.2011.11.004PubMed CentralView ArticlePubMedGoogle Scholar
- Hassan MM, Frome A, Patt YZ, El-Serag HB: Rising prevalence of hepatitis C virus infection among patients recently diagnosed with hepatocellular carcinoma in the United States. J Clin Gastroenterol 2002, 35: 266–269. 10.1097/00004836-200209000-00013View ArticlePubMedGoogle Scholar
- Soini Y, Chia SC, Bennett WP, Groopman JD, Wang JS, DeBenedetti VM, Cawley H, Welsh JA, Hansen C, Bergasa NV, et al.: An aflatoxin-associated mutational hotspot at codon 249 in the p53 tumor suppressor gene occurs in hepatocellular carcinomas from Mexico. Carcinogenesis 1996, 17: 1007–1012. 10.1093/carcin/17.5.1007View ArticlePubMedGoogle Scholar
- Cramp ME: Hbv + Hcv = Hcc? Gut 1999, 45: 168–169. 10.1136/gut.45.2.168PubMed CentralView ArticlePubMedGoogle Scholar
- Blum HE: Hepatocellular carcinoma: therapy and prevention. World J Gastroenterol 2005, 11: 7391–7400.PubMedGoogle Scholar
- Bosch FX, Ribes J, Borras J: Epidemiology of primary liver cancer. Semin Liver Dis 1999, 19: 271–285. 10.1055/s-2007-1007117View ArticlePubMedGoogle Scholar
- Lee MJ, Yu GR, Park SH, Cho BH, Ahn JS, Park HJ, Song EY, Kim DG: Identification of cystatin B as a potential serum marker in hepatocellular carcinoma. Clin Cancer Res 2008, 14: 1080–1089. 10.1158/1078-0432.CCR-07-1615View ArticlePubMedGoogle Scholar
- Marrero JA, Lok AS: Newer markers for hepatocellular carcinoma. Gastroenterology 2004, 127: S113-S119. 10.1053/j.gastro.2004.09.024View ArticlePubMedGoogle Scholar
- Capurro M, Wanless IR, Sherman M, Deboer G, Shi W, Miyoshi E, Filmus J: Glypican-3: a novel serum and histochemical marker for hepatocellular carcinoma. Gastroenterology 2003, 125: 89–97. 10.1016/S0016-5085(03)00689-9View ArticlePubMedGoogle Scholar
- Daduang J, Limpaiboon T, Daduang S: Biomarker to distinguish hepatocellular carcinoma from cholangiocarcinoma by serum a disintegrin and metalloprotease 12. Arch Med Sci 2011, 7: 1013–1016.PubMed CentralView ArticlePubMedGoogle Scholar
- Smith MW, Yue ZN, Geiss GK, Sadovnikova NY, Carter VS, Boix L, Lazaro CA, Rosenberg GB, Bumgarner RE, Fausto N, et al.: Identification of novel tumor markers in hepatitis C virus-associated hepatocellular carcinoma. Cancer Res 2003, 63: 859–864.PubMedGoogle Scholar
- Chuma M, Sakamoto M, Yamazaki K, Ohta T, Ohki M, Asaka M, Hirohashi S: Expression profiling in multistage hepatocarcinogenesis: identification of HSP70 as a molecular marker of early hepatocellular carcinoma. Hepatology 2003, 37: 198–207. 10.1053/jhep.2003.50022View ArticlePubMedGoogle Scholar
- Deng YB, Nagae G, Midorikawa Y, Yagi K, Tsutsumi S, Yamamoto S, Hasegawa K, Kokudo N, Aburatani H, Kaneda A: Identification of genes preferentially methylated in hepatitis C virus-related hepatocellular carcinoma. Cancer Sci 2010, 101: 1501–1510. 10.1111/j.1349-7006.2010.01549.xView ArticlePubMedGoogle Scholar
- Mathivanan S, Periaswamy B, Gandhi TK, Kandasamy K, Suresh S, Mohmood R, Ramachandra YL, Pandey A: An evaluation of human protein-protein interaction data in the public domain. BMC Bioinforma 2006, 7(5):S19.View ArticleGoogle Scholar
- Team RDC: R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing; 2011.Google Scholar
- Gautier L, Cope L, Bolstad BM, Irizarry RA: affy–analysis of Affymetrix GeneChip data at the probe level. Bioinformatics 2004, 20: 307–315. 10.1093/bioinformatics/btg405View ArticlePubMedGoogle Scholar
- Tusher VG, Tibshirani R, Chu G: Significance analysis of microarrays applied to the ionizing radiation response. Proc Natl Acad Sci USA 2001, 98: 5116–5121. 10.1073/pnas.091062498PubMed CentralView ArticlePubMedGoogle Scholar
- Benjamini Y, Drai D, Elmer G, Kafkafi N, Golani I: Controlling the false discovery rate in behavior genetics research. Behav Brain Res 2001, 125: 279–284. 10.1016/S0166-4328(01)00297-2View ArticlePubMedGoogle Scholar
- Kanehisa M: The KEGG database. Novartis Found Symp 2002, 247: 91–101. discussion 101–103, 119–128, 244–152View ArticlePubMedGoogle Scholar
- da Huang W, Sherman BT, Lempicki RA: Systematic and integrative analysis of large gene lists using DAVID bioinformatics resources. Nat Protoc 2009, 4: 44–57.View ArticlePubMedGoogle Scholar
- Shannon P, Markiel A, Ozier O, Baliga NS, Wang JT, Ramage D, Amin N, Schwikowski B, Ideker T: Cytoscape: a software environment for integrated models of biomolecular interaction networks. Genome Res 2003, 13: 2498–2504. 10.1101/gr.1239303PubMed CentralView ArticlePubMedGoogle Scholar
- Horvath S, Zhang B, Carlson M, Lu KV, Zhu S, Felciano RM, Laurance MF, Zhao W, Qi S, Chen Z, et al.: Analysis of oncogenic signaling networks in glioblastoma identifies ASPM as a molecular target. Proc Natl Acad Sci USA 2006, 103: 17402–17407. 10.1073/pnas.0608396103PubMed CentralView ArticlePubMedGoogle Scholar
- Ito Y, Takeda T, Sakon M, Monden M, Tsujimoto M, Matsuura N: Expression and prognostic role of cyclin-dependent kinase 1 (cdc2) in hepatocellular carcinoma. Oncology 2000, 59: 68–74. 10.1159/000012140View ArticlePubMedGoogle Scholar
- Li KK, Ng IO, Fan ST, Albrecht JH, Yamashita K, Poon RY: Activation of cyclin-dependent kinases CDC2 and CDK2 in hepatocellular carcinoma. Liver 2002, 22: 259–268. 10.1046/j.0106-9543.2002.01629.xView ArticlePubMedGoogle Scholar
- Myatt SS, Lam EW: The emerging roles of forkhead box (Fox) proteins in cancer. Nat Rev Cancer 2007, 7: 847–859. 10.1038/nrc2223View ArticlePubMedGoogle Scholar
- Xia L, Huang W, Tian D, Zhu H, Zhang Y, Hu H, Fan D, Nie Y, Wu K: Upregulated FoxM1 expression induced by hepatitis B virus X protein promotes tumor metastasis and indicates poor prognosis in hepatitis B virus-related hepatocellular carcinoma. J Hepatol 2012, 57: 600–612. 10.1016/j.jhep.2012.04.020View ArticlePubMedGoogle Scholar
- Wong N, Yeo W, Wong WL, Wong NL, Chan KY, Mo FK, Koh J, Chan SL, Chan AT, Lai PB, et al.: TOP2A overexpression in hepatocellular carcinoma correlates with early age onset, shorter patients survival and chemoresistance. Int J Cancer 2009, 124: 644–652. 10.1002/ijc.23968View ArticlePubMedGoogle Scholar
- Crawley JJ, Furge K: Identification of frequent cytogenetic aberrations in hepatocellular carcinoma using gene-expression microarray data. Genome Biol 2002, 3: RESEARCH0075.PubMed CentralView ArticlePubMedGoogle Scholar
- Chua MS, Bernstein LR, Li R, So SK: Gallium maltolate is a promising chemotherapeutic agent for the treatment of hepatocellular carcinoma. Anticancer Res 2006, 26: 1739–1743.PubMedGoogle Scholar
- Ellerbroek SM, Stack MS: Membrane associated matrix metalloproteinases in metastasis. Bioessays 1999, 21: 940–949. 10.1002/(SICI)1521-1878(199911)21:11<940::AID-BIES6>3.0.CO;2-JView ArticlePubMedGoogle Scholar
- Seiki M: The cell surface: the stage for matrix metalloproteinase regulation of migration. Curr Opin Cell Biol 2002, 14: 624–632. 10.1016/S0955-0674(02)00363-0View ArticlePubMedGoogle Scholar
- Maatta M, Soini Y, Liakka A, Autio-Harmainen H: Differential expression of matrix metalloproteinase (MMP)-2, MMP-9, and membrane type 1-MMP in hepatocellular and pancreatic adenocarcinoma: implications for tumor progression and clinical prognosis. Clin Cancer Res 2000, 6: 2726–2734.PubMedGoogle Scholar
- Ogasawara S, Yano H, Momosaki S, Nishida N, Takemoto Y, Kojiro S, Kojiro M: Expression of matrix metalloproteinases (MMPs) in cultured hepatocellular carcinoma (HCC) cells and surgically resected HCC tissues. Oncol Rep 2005, 13: 1043–1048.PubMedGoogle Scholar
- Musso O, Theret N, Campion JP, Turlin B, Milani S, Grappone C, Clement B: In situ detection of matrix metalloproteinase-2 (MMP2) and the metalloproteinase inhibitor TIMP2 transcripts in human primary hepatocellular carcinoma and in liver metastasis. J Hepatol 1997, 26: 593–605. 10.1016/S0168-8278(97)80425-4View ArticlePubMedGoogle Scholar
- Chen RX, Xia YH, Xue TC, Ye SL: Osteopontin promotes hepatocellular carcinoma invasion by up-regulating MMP-2 and uPA expression. Mol Biol Rep 2011, 38: 3671–3677. 10.1007/s11033-010-0481-8View ArticlePubMedGoogle Scholar
- Xiang ZL, Zeng ZC, Tang ZY, Fan J, Sun HC, Tan YS: Expression of cytokeratin 19 and matrix metalloproteinase 2 predicts lymph node metastasis in hepatocellular carcinoma. Mol Biol Rep 2011, 38: 3531–3539. 10.1007/s11033-010-0463-xView ArticlePubMedGoogle Scholar
- Giannelli G, Bergamini C, Marinosci F, Fransvea E, Quaranta M, Lupo L, Schiraldi O, Antonaci S: Clinical role of MMP-2/TIMP-2 imbalance in hepatocellular carcinoma. Int J Cancer 2002, 97: 425–431. 10.1002/ijc.1635View ArticlePubMedGoogle Scholar
- Theret N, Musso O, L'Helgoualc'h A, Campion JP, Clement B: Differential expression and origin of membrane-type 1 and 2 matrix metalloproteinases (MT-MMPs) in association with MMP2 activation in injured human livers. Am J Pathol 1998, 153: 945–954. 10.1016/S0002-9440(10)65636-2PubMed CentralView ArticlePubMedGoogle Scholar
- Poon RT, Chung KK, Cheung ST, Lau CP, Tong SW, Leung KL, Yu WC, Tuszynski GP, Fan ST: Clinical significance of thrombospondin 1 expression in hepatocellular carcinoma. Clin Cancer Res 2004, 10: 4150–4157. 10.1158/1078-0432.CCR-03-0435View ArticlePubMedGoogle Scholar
- Yumoto E, Nakatsukasa H, Hanafusa T, Yumoto Y, Nouso K, Matsumoto E, Onishi T, Takuma Y, Tanaka H, Fujikawa T, et al.: IGFBP-3 expression in hepatocellular carcinoma involves abnormalities in TGF-beta and/or Rb signaling pathways. Int J Oncol 2005, 27: 1223–1230.PubMedGoogle Scholar
- Gebhardt C, Nemeth J, Angel P, Hess J: S100A8 and S100A9 in inflammation and cancer. Biochem Pharmacol 2006, 72: 1622–1631. 10.1016/j.bcp.2006.05.017View ArticlePubMedGoogle Scholar
- Nemeth J, Stein I, Haag D, Riehl A, Longerich T, Horwitz E, Breuhahn K, Gebhardt C, Schirmacher P, Hahn M, et al.: S100A8 and S100A9 are novel nuclear factor kappa B target genes during malignant progression of murine and human liver carcinogenesis. Hepatology 2009, 50: 1251–1262. 10.1002/hep.23099View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.