Biomedical subjects

Samir M Hanash

Publications and source records attributed to Samir M Hanash.

41 records · Page 3Linked to original sources

PubMed2002

Identification of tumor-associated antigens using proteomics.

In the post-genomic era, the identification of tumor-associated antigens that elicit a humoral response is allowed at the protein level using proteomics. Indeed, the screening of autoantibodies using 2-D Western blot experiments with sera from cancer patients, followed by the subsequent identification of the target protein by mass spectrometry and database search has permitted the exploitation of the B-cell repertoire of patients with cancer. Applied to several types of cancer, a proteomic-based approach has revealed a high frequency of autoantibodies in sera from patients. Several of the antigenic proteins identified may constitute novel cancer markers and may have clinical utility in diagnosis or in establishing prognosis. Furthermore, the approach has allowed to distinguish isoforms that may help to define epitopes. On the other hand, the analysis of the expression levels of some of the antigenic proteins has revealed differential expression in tumors as compared with healthy tissues that might explain antigenicity.

Antigens, Neoplasm↗

PubMed2002

Integrating cancer genomics and proteomics in the post-genome era.

The dawn of the post-genome era is leading to extraordinary opportunities in biomedicine. Our group has embarked on a major effort to integrate genomics, transcriptomics and proteomics for the profiling of tumor tissues, an approach we refer to as operomics. Our major goals are the molecular classification of tumors and the identification of markers for the early detection of cancer. Molecular analyses of tumors rely on microdissected tissues, which are simultaneously investigated for genomic, transcriptomic and proteomic changes. Genomic alterations in tumor cells being investigated include deletions, amplifications and methylation changes across the entire genome as well as point mutations in specific genes. Expression analysis at the RNA level is being undertaken using oligonucleotide and cDNA based microarrays. An important aspect of our approach is the large-scale identification and quantitative analysis of tumor proteins in whole cell lysates as well as in protein compartments. Protein separation strategies include two-dimensional polyacrylamide gel electrophoresis and liquid chromatography. Specific protein subsets, of interest include membrane proteins, secreted proteins and antigenic proteins as sources of biomarkers for early detection of cancer. Our current approach is illustrated with findings stemming from our studies of human gliomas.

Brain Neoplasms↗

PubMed2002

Proteomic analysis of lung adenocarcinoma: identification of a highly expressed set of proteins in tumors.

PURPOSE: The goal of this study was to identify potential protein markers in lung adenocarcinomas. EXPERIMENTAL DESIGN: A series of 93 lung adenocarcinomas (64 stage I and 29 stage III) and 10 uninvolved lung samples were examined for quantitative differences in protein expression using two-dimensional PAGE. Candidate proteins were identified using matrix-assisted laser desorption/ionization mass spectrometry or peptide sequencing. The levels of the individual isoforms of nine proteins found to be overexpressed in the lung tumors were examined. Potential mechanisms for overexpression were examined by comparing mRNA expression levels, assessed using oligonucleotide arrays, to the protein values in the same samples. RESULTS: Antioxidant enzyme AOE372, ATP synthase subunit d (ATP5D), beta1,4-galactosyltransferase, cytosolic inorganic pyrophosphatase, glucose-regulated M(r) 58,000 protein, glutathione-S-transferase M4, prolyl 4-hydroxylase beta subunit, triosephosphate isomerase, and ubiquitin thiolesterase (UCHL1) were identified as being significantly overexpressed in lung adenocarcinomas. The expression of these proteins was increased from 1.4- to 10.6-fold as compared with uninvolved lung tissue. The expression of the individual protein isoforms was correlated with 10 clinicopathological variables as well as with each gene's mRNA level in the same sample. Both isoforms of glucose-regulated M(r) 58,000 protein were found to be significantly correlated with their mRNA expression profiles (P < 0.05), indicating that increased transcription likely underlies the increased expression of these proteins. CONCLUSIONS: Two-dimensional PAGE and mass spectrometry can identify proteins showing increased expression in lung adenocarcinoma. The association of specific isoforms of these proteins with clinical variables and understanding the regulation of their expression will aid in determination of their potential use as biomarkers in this cancer.

Adenocarcinoma↗

PubMedDate not supplied

N-myc modulates expression of p73 in neuroblastoma.

The human p73 gene is a homolog of p53, which has been localized to chromosome 1p36 in a region that is frequently deleted in neuroblastoma. Transfection of the p73 gene into neuroblastoma cells that lack detectable p73 protein has been shown to result in growth suppression and to induce neuronal differentiation. In this study, we have identified by means of restriction landmark genome scanning (RLGS) a genomic fragment that was frequently reduced in intensity in neuroblastomas. The cloned fragment contained exon 1 of p73 as well as intronic and promoter sequences. We investigated the genomic and expression status of p73 and N-myc in 34 neuroblastoma tumors and 12 neuroblastoma cell lines. Approximately a third of neuroblastomas in our series exhibited deletion of p73. Most tumors analyzed exhibited reduced expression of p73, as determined by quantitative RT-PCR, in the absence of detectable p73 gene deletion. The reduced expression of p73 correlated with overexpression of N-myc in a statistically significant manner. The N-myc gene was transfected into two neuroblastoma cell lines that lacked N-myc amplification to determine its effect on p73 RNA levels. p73 was detectable at low level by RT-PCR in untransfected SK-N-AS cells and became undetectable following N-myc transfection, whereas in SH-EP1 cells, p73 levels were substantially reduced following transfection but remained detectable. Our data suggest that the N-myc gene modulates expression of p73, allowing neuroblastoma cells to escape the growth suppressing properties of p73.

Blotting, Southern↗

PubMedDate not supplied

Mxi1-0, an alternatively transcribed Mxi1 isoform, is overexpressed in glioblastomas.

The c-Myc transcription factor regulates expression of genes related to cell growth, division, and apoptosis. Mxi1, a member of the Mad family, represses transcription of c-Myc-regulated genes by mediating chromatin condensation via histone deacetylase and the Sin3 corepressor. Mxi1 is a c-Myc antagonist and suppresses cell proliferation in vitro. Here, we describe the identification of Mxi1-0, a novel Mxi1 isoform that is alternatively transcribed from an upstream exon. Mxi1-0 and Mxi1 have different amino-terminal sequences, but share identical Max- and DNA-binding domains. Both isoforms are able to bind Max, to recognize E-box binding sites, and to interact with Sin3. Despite these similarities and in contrast to Mxi1, Mxi1-0 is predominantly localized to the cytoplasm and fails to repress c-Myc-dependent transcription. Although Mxi1-0 and Mxi1 are coexpressed in both human and mouse cells, the relative levels of Mxi1-0 are higher in primary glioblastoma tumors than in normal brain tissue. This variation in the levels of Mxi1-0 and Mxi1 suggests that Mxi1-0 may modulate the Myc-inhibitory activity of Mxi1. The identification of Mxi1-0 as an alternatively transcribed Mxi1 isoform has significant implications for the interpretation of previous Mxi1 studies, particularly those related to the phenotype of the mxi1 knockout mouse.

Amino Acid Sequence↗