Biomedical subjects

Samir M Hanash

Publications and source records attributed to Samir M Hanash.

At least 37 records · Page 2Linked to original sources

PubMed2003

Protein profiles associated with survival in lung adenocarcinoma.

Morphologic assessment of lung tumors is informative but insufficient to adequately predict patient outcome. We previously identified transcriptional profiles that predict patient survival, and here we identify proteins associated with patient survival in lung adenocarcinoma. A total of 682 individual protein spots were quantified in 90 lung adenocarcinomas by using quantitative two-dimensional polyacrylamide gel electrophoresis analysis. A leave-one-out cross-validation procedure using the top 20 survival-associated proteins identified by Cox modeling indicated that protein profiles as a whole can predict survival in stage I tumor patients (P = 0.01). Thirty-three of 46 survival-associated proteins were identified by using mass spectrometry. Expression of 12 candidate proteins was confirmed as tumor-derived with immunohistochemical analysis and tissue microarrays. Oligonucleotide microarray results from both the same tumors and from an independent study showed mRNAs associated with survival for 11 of 27 encoded genes. Combined analysis of protein and mRNA data revealed 11 components of the glycolysis pathway as associated with poor survival. Among these candidates, phosphoglycerate kinase 1 was associated with survival in the protein study, in both mRNA studies and in an independent validation set of 117 adenocarcinomas and squamous lung tumors using tissue microarrays. Elevated levels of phosphoglycerate kinase 1 in the serum were also significantly correlated with poor outcome in a validation set of 107 patients with lung adenocarcinomas using ELISA analysis. These studies identify new prognostic biomarkers and indicate that protein expression profiles can predict the outcome of patients with early-stage lung cancer.

Adenocarcinoma↗

PubMed2003

Increased C-CRK proto-oncogene expression is associated with an aggressive phenotype in lung adenocarcinomas.

The C-CRK gene, cellular homolog of the avian v-crk oncogene, encodes two alternatively spliced adaptor signaling proteins, CRKI (28 kDa) and CRKII (40 kDa). Both CRKI and CRKII have been shown to activate kinase signaling and anchorage-independent growth in vitro and CRKI transformed cells readily form tumors in nude mice. Affymetrix oligonucleotide arrays were used to analyse 86 lung adenocarcinomas and 10 uninvolved lung tissues. C-CRK mRNA expression was increased in more advanced (stage III versus stage I), larger (T(2-4) versus T(1)), and poorly differentiated tumors and in tumors from patients demonstrating poor survival (P=0.00034). An overlapping series of 93 lung adenocarcinomas (64 stage I and 29 stage III) and 10 uninvolved lung specimens were measured for quantitative differences in CRKI and CRKII protein levels using 2-D PAGE. CRK protein spots were identified using mass spectrometry and 2-D Western blotting. A significant increase in levels of the CRKI oncoprotein and the phosphorylated isoform of CRKII was observed in tumors (P<0.05). No difference in protein level was evident between stages. Concordant with mRNA expression, CRKI and CRKII were increased in poorly differentiated tumors (P<0.05). CRK immunohistochemical analysis of tumor tissue arrays using the same tumor series also demonstrated increased abundance of nuclear and cytoplasmic CRK in more proliferative tumors (P<0.05). This study provides the first quantitative analysis of discrete CRKI and CRKII protein isoforms in human lung tumors and provides evidence that the C-CRK proto-oncogene may foment a more aggressive phenotype in lung cancers.

Adenocarcinoma↗

PubMed2003

Novel candidate targets of beta-catenin/T-cell factor signaling identified by gene expression profiling of ovarian endometrioid adenocarcinomas.

The activity of beta-catenin (beta-cat), a key component of the Wnt signaling pathway, is deregulated in about 40% of ovarian endometrioid adenocarcinomas (OEAs), usually as a result of CTNNB1 gene mutations. The function of beta-cat in neoplastic transformation is dependent on T-cell factor (TCF) transcription factors, but specific genes activated by the interaction of beta-cat with TCFs in OEAs and other cancers with Wnt pathway defects are largely unclear. As a strategy to identify beta-cat/TCF transcriptional targets likely to contribute to OEA pathogenesis, we used oligonucleotide microarrays to compare gene expression in primary OEAs with mutational defects in beta-cat regulation (n = 11) to OEAs with intact regulation of beta-cat activity (n = 17). Both hierarchical clustering and principal component analysis based on global gene expression distinguished beta-cat-defective tumors from those with intact beta-cat regulation. We identified 81 potential beta-cat/TCF targets by selecting genes with at least 2-fold increased expression in beta-cat-defective versus beta-cat regulation-intact tumors and significance in a t test (P < 0.05). Seven of the 81 genes have been previously reported as Wnt/beta-cat pathway targets (i.e., BMP4, CCND1, CD44, FGF9, EPHB3, MMP7, and MSX2). Differential expression of several known and candidate target genes in the OEAs was confirmed. For the candidate target genes CST1 and EDN3, reporter and chromatin immunoprecipitation assays directly implicated beta-cat and TCF in their regulation. Analysis of presumptive regulatory elements in 67 of the 81 candidate genes for which complete genomic sequence data were available revealed an apparent difference in the location and abundance of consensus TCF-binding sites compared with the patterns seen in control genes. Our findings imply that analysis of gene expression profiling data from primary tumor samples annotated with detailed molecular information may be a powerful approach to identify key downstream targets of signaling pathways defective in cancer cells.

Binding Sites↗

PubMed2003

Early changes in gene expression profiles of hepatic GVHD uncovered by oligonucleotide microarrays.

The liver, skin, and gastrointestinal tract are major target organs of acute graft-versus-host disease (GVHD), the major complication of allogeneic bone marrow transplantation (BMT). In order to gain a better understanding of acute GVHD in the liver, we compared the gene expression profiles of livers after experimental allogeneic and syngeneic BMT using oligonucleotide microarray. At 35 days after allogeneic BMT when hepatic GVHD was histologically evident, genes related to cellular effectors and acute-phase proteins were up-regulated, whereas genes largely related to metabolism and endocrine function were down-regulated. At day 7 after BMT before the development of histologic changes in the liver, interferon gamma (IFN-gamma)-inducible genes, major histocompatibility (MHC) class II molecules, and genes related to leukocyte trafficking had been up-regulated. Immunohistochemistry demonstrated that expression of IFN-gamma protein itself was increased in the spleen but not in hepatic tissue. These results suggest that the increased expression of genes associated with the attraction and activation of donor T cells induced by IFN-gamma early after BMT is important in the initiation of hepatic GVHD in this model and provide new potential molecular targets for early detection and intervention of acute GVHD.

Acute-Phase Proteins↗

PubMed2003

Overexpression of oncoprotein 18 correlates with poor differentiation in lung adenocarcinomas.

We examined the expression of oncoprotein 18 (Op18) in 93 lung adenocarcinomas and 10 uninvolved lung samples using quantitative two-dimensional PAGE analysis with confirmation by mass spectrometry and two-dimensional Western blot analysis. mRNA expression was examined using oligonucleotide microarrays, and the cellular localization of the Op18 protein was examined using immunohistochemical analysis of tissue microarrays. Three phosphorylated forms and one unphosphorylated form of the Op18 protein were identified and found to be overexpressed in lung adenocarcinomas as compared with normal lung. The percentage of phosphorylated to total Op18 protein isoforms increased from 3.2% in normal lung to 7.9% in lung tumors. Both the phosphorylated and unphosphorylated Op18 proteins were significantly increased in poorly differentiated tumors as compared with moderately or well differentiated lung adenocarcinomas (p<0.03), suggesting that up-regulated expression of Op18 reflects a poor differentiation status and higher cell proliferation rates. This was further verified in A549 and SKLU1 lung adenocarcinoma cell lines by examining Op18 levels and phosphorylation status following treatment that altered either cell proliferation or differentiation. The increased expression of Op18 protein was significantly correlated with its mRNA level indicating that increased transcription likely underlies elevated expression of Op18. The overexpression of Op18 proteins in poorly differentiated lung adenocarcinomas and the elevated expression of the phosphorylated forms of Op18 may offer a new target for drug- or gene-directed therapy and may have potential utility as a tumor marker.

Adenocarcinoma↗

PubMed2003

Molecular profiling of the immune response in colon cancer using protein microarrays: occurrence of autoantibodies to ubiquitin C-terminal hydrolase L3.

We implemented a protein microarray approach to identify proteins that induce a humoral response in colon cancer. Solubilized proteins from the LoVo colon adenocarcinoma cell line were separated into 1760 fractions, arrayed onto nitrocellulose-coated slides, and hybridized with individual sera from 15 newly diagnosed patients with colon cancer, 15 with lung cancer, and 15 healthy subjects. 39/1760 fractions showed enhanced reactivity with sera from patients with colon cancer (p < 0.01) relative to healthy controls. A distinct pattern of reactivity was observed with sera from colon cancer relative to lung cancer. One fraction that exhibited reactivity with 9/15 colon cancer sera was subjected to mass spectrometry leading to the identification of ubiquitin C-terminal hydrolase isozyme 3 (UCH-L3) as a constituent. To validate the occurrence of autoantibodies to UCH-L3, independent analysis was done by means of Western blots. UCH-L3 antibodies were detected in 19/43 sera from patients with colon cancer, and in 0/54 sera from subjects with lung cancer (24), colon adenoma (15) or otherwise healthy (15). Our findings indicate the occurrence of an immune response to a broad set of antigens in colon cancer and the feasibility of identifying the antigenic targets using a combination of protein microarrays and mass spectrometry.

Autoantibodies↗

PubMed2003

Proteomic analysis of eIF-5A in lung adenocarcinomas.

We examined the eIF-5A protein expression in 93 lung adenocarcinomas and 10 uninvolved lung samples using quantitative two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) analysis with identification by mass spectrometry and 2-D Western blots. The same tissue samples were examined for the eIF-5A mRNA expression using oligonucleotide microarrays, and the cellular localization of the eIF-5A protein was examined using immunohistochemical analysis on tissue arrays. Higher eIF-5A protein expression was present in tumors showing poor differentiation, 12/13(th) codon K-ras mutations, p53 nuclear accumulation, and tumors with positive lymphocytic response. The eIF-5A mRNA was also significantly increased in lung adenocarcinomas compared to normal lung, but the eIF-5A protein expression was not correlated to its mRNA levels indicating that the increase in the eIF-5A protein expression in lung tumors is post-transcriptionally/translationally/post-translationally regulated. Patients having a higher eIF-5A protein expression showed a relatively poorer survival suggesting the use of eIF-5A as prognostic marker in lung adenocarcinoma. Moreover, the investigation on agents that inhibit eIF-5A function is encouraged.

Adenocarcinoma↗

PubMed2003

Characterization of gene expression profiles associated with glioma progression using oligonucleotide-based microarray analysis and real-time reverse transcription-polymerase chain reaction.

Diffuse astrocytoma of World Health Organization (WHO) grade II has an inherent tendency to spontaneously progress to anaplastic astrocytoma (WHO grade III) and/or glioblastoma (WHO grade IV). The molecular basis of astrocytoma progression is still poorly understood, in particular with respect to the progression-associated changes at the mRNA level. Therefore, we compared the transcriptional profile of approximately 6800 genes in primary WHO grade II gliomas and corresponding recurrent high-grade (WHO grade III or IV) gliomas from eight patients using oligonucleotide-based microarray analysis. We identified 66 genes whose mRNA levels differed significantly (P < 0.01, > or =2-fold change) between the primary and recurrent tumors. The microarray data were corroborated by real-time reverse transcription-polymerase chain reaction analysis of 12 selected genes, including 7 genes with increased expression and 5 genes with reduced expression on progression. In addition, the expression of these 12 genes was determined in an independent series of 43 astrocytic gliomas (9 diffuse astrocytomas, 10 anaplastic astrocytomas, 17 primary, and 7 secondary glioblastomas). These analyses confirmed that the transcript levels of nine of the selected genes (COL4A2, FOXM1, MGP, TOP2A, CENPF, IGFBP4, VEGFA, ADD3, and CAMK2G) differed significantly in WHO grade II astrocytomas as compared to anaplastic astrocytomas and/or glioblastomas. Thus, we identified and validated a set of interesting candidate genes whose differential expression likely plays a role in astrocytoma progression.

Adult↗

PubMed2003

Distinct transcriptional profiles of adrenocortical tumors uncovered by DNA microarray analysis.

Comprehensive expression profiling of tumors using DNA microarrays has been used recently for molecular classification and biomarker discovery, as well as a tool to identify and investigate genes involved in tumorigenesis. Application of this approach to a cohort of benign and malignant adrenocortical tissues would be potentially informative in all of these aspects. In this study, we generated transcriptional profiles of 11 adrenocortical carcinomas (ACCs), 4 adrenocortical adenomas (ACAs), 3 normal adrenal cortices (NCs), and 1 macronodular hyperplasia (MNH) using Affymetrix HG_U95Av2 oligonucleotide arrays representing approximately 10,500 unique genes. The expression data set was used for unsupervised hierarchical cluster analysis as well as principal component analysis to visually represent the expression data. An analysis of variance on the three classes (NC, ACA plus MNH, and ACC) revealed 91 genes that displayed at least threefold differential expression between the ACC cohort and both the NC and ACA cohorts at a significance level of P < 0.01. Included in these 91 genes were those known to be up-regulated in adrenocortical tumors, such as insulin-like growth factor (IGF2), as well as novel differentially expressed genes such as osteopontin (SPP) and serine threonine kinase 15 (STK15). Increased expression of IGF2 was identified in 10 of 11 ACCs (90.9%) and was verified by quantitative reverse transcriptase-polymerase chain reaction. Select proliferation-related genes (TOP2A and Ki-67) were validated at the protein level using immunohistochemistry and adrenocortical tissue microarrays. Our results demonstrated significant and consistent gene expression changes in ACCs compared to benign adrenocortical lesions. Moreover, we identified several genes that represent potential diagnostic markers and may play a role in the pathogenesis of ACC.

Adenoma↗

PubMed2002

Global profiling of the cell surface proteome of cancer cells uncovers an abundance of proteins with chaperone function.

There is currently limited data available pertaining to the global characterization of the cell surface proteome. We have implemented a strategy for the comprehensive profiling and identification of surface membrane proteins. This strategy has been applied to cancer cells, including the SH-SY5Y neuroblastoma, the A549 lung adenocarcinoma, the LoVo colon adenocarcinoma, and the Sup-B15 acute lymphoblastic leukemia (B cell) cell lines and ovarian tumor cells. Surface membrane proteins of viable, intact cells were subjected to biotinylation then affinity-captured and purified on monomeric avidin columns. The biotinylated proteins were eluted from the monomeric avidin columns as intact proteins and were subsequently separated by two-dimensional PAGE, transferred to polyvinylidene difluoride membranes, and visualized by hybridization with streptavidin-horseradish peroxidase. Highly reproducible, but distinct, two-dimensional patterns consisting of several hundred biotinylated proteins were obtained for the different cell populations analyzed. Identification of a subset of biotinylated proteins among the different cell populations analyzed using matrix-assisted laser desorption ionization and tandem mass spectrometry uncovered proteins with a restricted expression pattern in some cell line(s), such as CD87 and the activin receptor type IIB. We also identified more widely expressed proteins, such as CD98, and a sushi repeat-containing protein, a member of the selectin family. Remarkably, a set of proteins identified as chaperone proteins were found to be highly abundant on the cell surface, including GRP78, GRP75, HSP70, HSP60, HSP54, HSP27, and protein disulfide isomerase. Comprehensive profiling of the cell surface proteome provides an effective approach for the identification of commonly occurring proteins as well as proteins with restricted expression patterns in this compartment.

Activin Receptors, Type II↗

PubMed2002

The hepatocyte nuclear factor 3 alpha gene, HNF3alpha (FOXA1), on chromosome band 14q13 is amplified and overexpressed in esophageal and lung adenocarcinomas.

Genomic amplification is observed in many, if not all, types of human malignancy and is one of the mechanisms for the activation of dominant-acting oncogenes in tumorigenesis. In the present study, three amplified restriction fragments were identified in an esophageal adenocarcinoma (P16) using the restriction landmark genome scanning two-dimensional gel technique. These fragments were cloned, sequenced, and mapped to chromosome band 14q13. Using the sequence tagged site-amplification mapping approach, we defined the core-amplified domain by screening 75 normal-tumor paired esophageal samples. The frequency of 14q13 amplification is 6.7% in esophageal tumors, and the amplicon spans >6 Mb in 1 tumor but is contained in a region <0.3 Mb in all of the remaining amplified tumors. Quantitative reverse transcription-PCR (RT-PCR) of 8 genes and expressed sequence tags located within the core-amplified domain revealed that the HNF3alpha (FOXA1)(4) gene, a forkhead gene family member, was overexpressed in all of the amplified esophageal tumors. HNF3alpha amplification was confirmed by Southern blot and interphase fluorescence in situ hybridization analyses, and the results of real-time RT-PCR were consistent with that of the regular quantitative RT-PCR. Increased immunohistochemical nuclear staining of the HNF3alpha protein was detected in all of the tumors containing 14q13 amplification. Affymetrix oligonucleotide microarrays of 86 lung adenocarcinomas demonstrated that expression of the HNF3alpha mRNA was elevated (> or =2.5-fold of mean expression in normal lung) in 37% (32 of 86) of the tumors analyzed. Gene amplification of HNF3alpha was detected in 2 of the 5 overexpressed lung tumors examined. This is the first report of HNF3alpha amplification, and overexpression in esophageal and lung adenocarcinomas. Amplification of HNF3alpha in esophageal and lung tumors may suggest a potential oncogenic role for this gene in tumorigenesis.

Adenocarcinoma↗

PubMed2002

Gene expression in ovarian cancer reflects both morphology and biological behavior, distinguishing clear cell from other poor-prognosis ovarian carcinomas.

Biologically and clinically meaningful tumor classification schemes have long been sought. Some malignant epithelial neoplasms, such as those in the thyroid and endometrium, exhibit more than one pattern of differentiation, each associated with distinctive clinical features and treatments. In other tissues, all carcinomas, regardless of morphological type, are treated as though they represent a single disease. To better understand the biological and clinical features seen in the four major histological types of ovarian carcinoma (OvCa), we analyzed gene expression in 113 ovarian epithelial tumors using oligonucleotide microarrays. Global views of the variation in gene expression were obtained using PCA. These analyses show that mucinous and clear cell OvCas can be readily distinguished from serous OvCas based on their gene expression profiles, regardless of tumor stage and grade. In contrast, endometrioid adenocarcinomas show significant overlap with other histological types. Although high-stage/grade tumors are generally separable from low-stage/grade tumors, clear cell OvCa has a molecular signature that distinguishes it from other poor-prognosis OvCas. Indeed, 73 genes, expressed 2- to 29-fold higher in clear cell OvCas compared with each of the other OvCa types, were identified. Collectively, the data indicate that gene expression patterns in ovarian adenocarcinomas reflect both morphological features and biological behavior. Moreover, these studies provide a foundation for the development of new type-specific diagnostic strategies and treatments for ovarian cancer.

Adenocarcinoma, Clear Cell↗

PubMed2002

Food deprivation-induced expression of minoxidil sulfotransferase in the hypothalamus uncovered by microarray analysis.

We used oligonucleotide microarrays to analyze comprehensively hypothalamic gene expression changes that correlate with energy homeostasis. We compared the hypothalamic gene expression profiles of freely fed and 48-h fasted rats using 26,379 oligonucleotide probe sets. Expression of 96 genes was up-regulated and expression of 73 genes was down-regulated in a statistically significant manner with fasting. The gene encoding the enzyme minoxidil sulfotransferase, an enzyme that catalyzes the transfer of sulfonate groups to biogenic amines and other substrates, was foremost among a set of genes whose mRNAs were uniformly detectable and displaying the greatest transcriptional changes with fasting. Northern blot analysis indicated that minoxidil sulfotransferase mRNA is up-regulated in the fasted rat and mouse, ob/ob mouse, and fa/fa rat. Results of reverse transcription quantitative PCR indicated that minoxidil sulfotransferase mRNA is also up-regulated in the microdissected arcuate and paraventricular nuclei of the fasted rat. Several index genes known to be either up-regulated (neuropeptide Y) or down-regulated (amphetamine-regulated transcript and proopiomelanocortin) with fasting were also found to be present among our set of "differentially expressed" genes. This study identifies a novel gene induced by fasting and demonstrates the feasibility of using oligonucleotide microarrays for the study of complex neuronal processes.

Animals↗

PubMed2002

Transforming properties of a Q18-->E mutation of the microtubule regulator Op18.

We have identified a somatic mutation in Op18 in a human esophageal adenocarcinoma. The mutant form of Op18 (M-Op18) was cloned and sequenced, revealing a substitution of a G for C at nucleotide 155, which results in a Q18-->E substitution in the protein. M-Op18 cDNA was expressed in NIH/3T3 cells, which resulted in foci formation and tumor growth in immunodeficient mice. Cell cycle analysis of M-Op18-expressing cells revealed a doubling in the percentage of cells in G2/M relative to cells overexpressing wild-type Op18, a decrease in M-Op18-specific phosphorylation, and alterations in tubulin ultrastructure in M-Op18-expressing cells. These results suggest that the somatic mutation identified in Op18 has profound effects on cell homeostasis that may lead to tumorigenicity.

3T3 Cells↗

PubMed2002

A distinct repertoire of autoantibodies in hepatocellular carcinoma identified by proteomic analysis.

Chronic infections with hepatitis B (HBV) and hepatitis C (HCV) viruses are major risk factors for hepatocellular carcinoma (HCC). We have utilized a proteomic approach to determine whether a distinct repertoire of autoantibodies can be identified in HCC. Sera from 37 patients with HCC and 31 subjects chronically infected with HBV or HCV without HCC were investigated. Sera from 116 patients with other cancers, three patients with systemic lupus erythematosus, and 24 healthy subjects were utilized as controls. We report the identification of eight proteins, for each of which autoantibodies were detected in sera from more than 10% of patients with HCC but not in sera from healthy individuals (p < 0.05). Autoantibodies to four of these proteins were detected at a comparable frequency in sera from patients with chronic hepatitis. The other four proteins, which consisted of calreticulin isoforms, cytokeratin 8, nucleoside diphosphate kinase A, and F(1)-ATP synthase beta-subunit, induced autoantibodies among patients with HCC, independently of their HBV/HCV status. Calreticulin, and a novel truncated form of calreticulin (Crt32) we have identified, most commonly elicited autoantibodies among patients with HCC (27%). We conclude that a distinct repertoire of autoantibodies is associated with HCC that may have utility in early diagnosis of HCC among high risk subjects with chronic hepatitis.

Adult↗

PubMed2002

Discordant protein and mRNA expression in lung adenocarcinomas.

The relationship between gene expression measured at the mRNA level and the corresponding protein level is not well characterized in human cancer. In this study, we compared mRNA and protein expression for a cohort of genes in the same lung adenocarcinomas. The abundance of 165 protein spots representing 98 individual genes was analyzed in 76 lung adenocarcinomas and nine non-neoplastic lung tissues using two-dimensional polyacrylamide gel electrophoresis. Specific polypeptides were identified using matrix-assisted laser desorption/ionization mass spectrometry. For the same 85 samples, mRNA levels were determined using oligonucleotide microarrays, allowing a comparative analysis of mRNA and protein expression among the 165 protein spots. Twenty-eight of the 165 protein spots (17%) or 21 of 98 genes (21.4%) had a statistically significant correlation between protein and mRNA expression (r > 0.2445; p < 0.05); however, among all 165 proteins the correlation coefficient values (r) ranged from -0.467 to 0.442. Correlation coefficient values were not related to protein abundance. Further, no significant correlation between mRNA and protein expression was found (r = -0.025) if the average levels of mRNA or protein among all samples were applied across the 165 protein spots (98 genes). The mRNA/protein correlation coefficient also varied among proteins with multiple isoforms, indicating potentially separate isoform-specific mechanisms for the regulation of protein abundance. Among the 21 genes with a significant correlation between mRNA and protein, five genes differed significantly between stage I and stage III lung adenocarcinomas. Using a quantitative analysis of mRNA and protein expression within the same lung adenocarcinomas, we showed that only a subset of the proteins exhibited a significant correlation with mRNA abundance.

Adenocarcinoma↗

PubMed2002

Operomics: integrated genomic and proteomic profiling of cells and tissues.

In the post-genome era, technologies are becoming available that allow the profiling of tissues and cell populations at multiple levels including genomic (DNA and RNA), proteomic (proteins and peptides) and post-proteomic (eg metabolomic). Operomics refers to the molecular analysis of tissues and cells at the three levels that are connected through the coding process - namely, DNA, RNA and protein. The premise is that no one level or type of analysis fully captures gene expression and that functional changes at the proteome level cannot be simply predicted from analyses at the DNA or RNA levels. An important determinant that weakens a direct link between RNA and protein levels is translational control that differentially regulates mRNA translation. In this paper, the approaches for genomic and proteomic profiling and the contribution of translational control are reviewed.

DNA Methylation↗

PubMed2002

Microarray analyses during adipogenesis: understanding the effects of Wnt signaling on adipogenesis and the roles of liver X receptor alpha in adipocyte metabolism.

Wnt signaling maintains preadipocytes in an undifferentiated state. When Wnt signaling is enforced, 3T3-L1 preadipocytes no longer undergo adipocyte conversion in response to adipogenic medium. Here we used microarray analyses to identify subsets of genes whose expression is aberrant when differentiation is blocked through enforced Wnt signaling. Furthermore, we used the microarray data to identify potentially important adipocyte genes and chose one of these, the liver X receptor alpha (LXR alpha), for further analyses. Our studies indicate that enforced Wnt signaling blunts the changes in gene expression that correspond to mitotic clonal expansion, suggesting that Wnt signaling inhibits adipogenesis in part through dysregulation of the cell cycle. Experiments designed to uncover the potential role of LXR alpha in adipogenesis revealed that this transcription factor, unlike CCAAT/enhancer binding protein alpha and peroxisome proliferator-activated receptor gamma, is not adipogenic but rather inhibits adipogenesis if inappropriately expressed and activated. However, LXR alpha has several important roles in adipocyte function. Our studies show that this nuclear receptor increases basal glucose uptake and glycogen synthesis in 3T3-L1 adipocytes. In addition, LXR alpha increases cholesterol synthesis and release of nonesterified fatty acids. Finally, treatment of mice with an LXR alpha agonist results in increased serum levels of glycerol and nonesterified fatty acids, consistent with increased lipolysis within adipose tissue. These findings demonstrate new metabolic roles for LXR alpha and increase our understanding of adipogenesis.

Adipocytes↗