An integrated data analysis approach to characterize genes highly expressed in hepatocellular carcinoma
ONCOGENE
Authors: Patil, MA; Chua, MS; Pan, KH; Lin, R; Lih, CJ; Cheung, ST; Ho, C; Li, R; Fan, ST; Cohen, SN; Chen, X; So, S
Abstract
Hepatocellular carcinoma (HCC) is one of the major causes of cancer deaths worldwide. New diagnostic and therapeutic options are needed for more effective and early detection and treatment of this malignancy. We identified 703 genes that are highly expressed in HCC using DNA microarrays, and further characterized them in order to uncover novel tumor markers, oncogenes, and therapeutic targets for HCC. Using Gene Ontology annotations, genes with functions related to cell proliferation and cell cycle, chromatin, repair, and transcription were found to be significantly enriched in this list of highly expressed genes. We also identified a set of genes that encode secreted ( e. g. GPC3, LCN2, and DKK1) or membrane-bound proteins ( e. g. GPC3, IGSF1, and PSK-1), which may be attractive candidates for the diagnosis of HCC. A significant enrichment of genes highly expressed in HCC was found on chromosomes 1q, 6p, 8q, and 20q, and we also identified chromosomal clusters of genes highly expressed in HCC. The microarray analyses were validated by RT-PCR and PCR. This approach of integrating other biological information with gene expression in the analysis helps select aberrantly expressed genes in HCC that may be further studied for their diagnostic or therapeutic utility.
The plasma peptides of ovarian cancer
CLINICAL PROTEOMICS
Authors: Dufresne, Jaimie; Bowden, Pete; Thavarajah, Thanusi; Florentinus-Mefailoski, Angelique; Chen, Zhuo Zhen; Tucholska, Monika; Norzin, Tenzin; Ho, Margaret Truc; Phan, Morla; Mohamed, Nargiz; Ravandi, Amir; Stanton, Eric; Slutsky, Arthur S.; dos Santos, Claudia C.; Romaschin, Alexander; Marshall, John C.; Addison, Christina; Malone, Shawn; Heyland, Daren; Scheltens, Philip; Killestein, Joep; Teunissen, Charlotte E.; Diamandis, Eleftherios P.; Siu, K. W. Michael; Marshall, John G.
Abstract
BackgroundIt may be possible to discover new diagnostic or therapeutic peptides or proteins from blood plasma by using liquid chromatography andtandem mass spectrometryto identify, quantify and compare the peptides cleaved ex vivo from different clinical populations. The endogenous tryptic peptides of ovarian cancer plasma were compared to breast cancer and female cancer normal controls, other diseases with their matched or normal controls, plus ice cold plasma to control for pre-analytical variation.MethodsThe endogenous tryptic peptides or tryptic phospho peptides (i.e. without exogenous digestion) were analyzed from 200l of EDTA plasma. The plasma peptides were extracted by a step gradient of organic/water withdifferential centrifugation, dried, and collected over C18 for analytical HPLC nano electrospray ionization and tandem mass spectrometry (LC-ESI-MS/MS)with a linear quadrupole ion trap. The endogenous peptides of ovarian cancer were compared to multiple disease and normal samples from different institutions alongside ice cold controls. Peptides were randomly and independently sampled by LC-ESI-MS/MS. Precursor ions from peptides >E4 counts were identified by theSEQUEST and X!TANDEMalgorithms, filtered in SQL Server, before testing of frequency counts by Chi Square ((2)), foranalysiswith the STRING algorithm,and comparison of precursor intensity by ANOVA in the R statistical systemwith theTukey-Kramer Honestly Significant Difference (HSD) test.ResultsPeptides and/or phosphopeptides of common plasma proteins such as HPR, HP, HPX, and SERPINA1 showed increased observation frequency and/or precursor intensity in ovarian cancer. Many cellular proteins showed large changes in frequency by Chi Square ((2)>60, p<0.0001) in the ovarian cancer samples such as ZNF91, ZNF254, F13A1, LOC102723511, ZNF253, QSER1, P4HA1, GPC6, LMNB2, PYGB, NBR1, CCNI2, LOC101930455, TRPM5, IGSF1, ITGB1, CHD6, SIRT1, NEFM, SKOR2, SUPT20HL1, PLCE1, CCDC148, CPSF3, MORN3, NMI, XTP11, LOC101927572, SMC5, SEMA6B, LOXL3, SEZ6L2, and DHCR24. The protein gene symbols with large Chi Square values were significantly enriched in proteins that showed a complex set of previously established functional and structural relationships by STRING analysis. Analysis of the frequently observed proteins by ANOVA confirmed increases in mean precursor intensity in ZFN91, TRPM5, SIRT1, CHD6, RIMS1, LOC101930455 (XP_005275896), CCDC37 and GIMAP4 between ovarian cancer versus normal female and other diseases or controls by the Tukey-Kramer HSD test.ConclusionHere we show that separation of endogenous peptides with a step gradient of organic/water and differential centrifugation followed by random and independent sampling by LC-ESI-MS/MS with analysis of peptide frequency and intensity by SQL Server and R revealed significant difference in the ex vivo cleavage of peptides between ovarian cancer and other clinical treatments. There was striking agreement between the proteins discovered from cancer plasmaversus previous biomarkers discovered in tumors by genetic or biochemical methods. The results indicate that variation in plasma proteins from ovarian cancer may be directly discovered by LC-ESI-MS/MS that will be a powerful tool for clinical research.