Biomedical subjects

Yumei Feng

Publications and source records attributed to Yumei Feng.

6 recordsLinked to original sources

PubMed2006

Differentially expressed genes between primary cancer and paired lymph node metastases predict clinical outcome of node-positive breast cancer patients.

The axillary lymph node status remains the most valuable prognostic factor for breast cancer patients. However, approximately 20-30% of node-positive patients remain free of distant metastases within 15-30 years. It is important to develop molecular markers that are able to predict for the risk of distant metastasis and to develop patient-tailored therapy strategies. We hypothesize that the lymph node metastases may represent the most metastatic fraction of the primary cancers. Therefore, we sought to identify the differentially expressed genes by microarray between the primary tumors and their paired lymph node metastases samples collected from 26 patients. A set of 79 differentially expressed genes between primary cancers and metastasis samples was identified to correctly separate most of primary cancers from lymph node metastases. And decreased expression of matrix metalloproteinase 2, fibronectin, osteoblast specific factor 2, collagen type XI alpha 1 in lymph node metastases were further confirmed by real-time RT-PCR performed on 30 specimen pairs. This set of genes also classified 35 primary cancers into two groups with different prognosis: "high risk group" and "low risk group." Patients in "high risk group" had a 4.65-fold hazard ratio (95% CI 1.02-21.13, P = 0.047) to develop a distant metastasis within 43 months comparing with the "low risk group." This suggested that the gene signature consisting of 79 differentially expressed genes between primary cancers and lymph node metastases could also predict clinical outcome of node-positive patients, and that the molecular classification based on the gene signature could guide patient-tailored therapy.

Breast Neoplasms↗

PubMed2006

Transcriptional activation of the carboxylesterase 2 gene by the p53 pathway.

The p53 tumor suppressor is an important regulator of cellular response to chemotherapeutic agents by virtue of the protein's ability, upon activation by phosphorylation, to transcriptionally activate a number of genes involved in cell proliferation, apoptosis, and metabolism. Transcriptome analysis following introduction of a constitutively active form of p53 (p53T18D/S20D) into colon carcinoma cell lines identified transcriptional activation of the carboxylesterase 2 (CES-2) gene, which is involved in drug metabolism. We examined whether p53 activated by the DNA-damaging drug 5-fluorouracil (5-FU) also induces CES-2 expression. Our experiments showed that 5-FU induced CES-2 expression in two colon carcinoma cell lines that express wild-type p53 (HCT116 p53(+/+) and RKO) but not in five lines that are p53-null (HCT116 p53(-/- )) or express mutated p53 (HT29, KM12C, KM12SM, and KM12L4A). Sequence analysis revealed a putative p53-binding element in the first intron of CES-2 that differed from consensus by one nucleotide. A reporter gene assay showed that the luciferase construct with the p53-binding element responded to 5-FU treatment, whereas the reporter construct without the binding element did not. Chromatin immunoprecipitation assay confirmed that p53 bound the CES-2 fragment containing the p53-binding element after 5-FU treatment, whereas p21 binding to p53 was present with or without chemotherapy. Knockdown of expression of CES-2 and p53 by small interference RNA in RKO and HCT116 p53(+/+) cells attenuated the anti-proliferation effects of CPT11. These results taken together show that activated p53 directly regulates CES-2 expression via a p53-binding site, representing a novel mechanism through which the p53 pathway modulates drug metabolism. In addition, the degree of homology in the p53-binding element may determine the strength of p53 regulation.

Adenocarcinoma↗

PubMed2006

Inactivation of IkappaB contributes to transcriptional activation of spermidine/spermine N(1)-acetyltransferase.

Spermidine/spermine N(1)-acetyltransferase (SSAT) is a key enzyme in polyamine catabolism. We recently reported that the combination of N(1), N(11)-diethylnorspermine (DENSPM) and 5-fluorouracil (5-FU) synergistically induces SSAT expression, depletes polyamine levels and causes apoptosis in colon cancer cells. To determine whether new RNA and protein synthesis is required for SSAT induction, we examined the effect of actinomycin D (ActD) and cycloheximide (CHX). ActD alone blocked the induction of SSAT expression; however, the combination of CHX and DENSPM markedly induced SSAT expression and caused mitochondrial damage, suggesting that an inhibitory labile protein is involved in SSAT transactivation. SSAT promoter analysis identified two putative Rel/Nuclear Factor kappaB (NFkappaB) binding sites. Thus, we hypothesized that IkappaB is the labile inhibitory protein and that its removal contributes to the activation of NFkappaB. CHX quickly eliminated the IkappaB protein in the cells and increased the levels of the two subunits of NFkappaB, p65 and p50, in the nucleus. Luciferase reporter gene assay showed that SSAT promoter constructs containing the two putative NFkappaB binding elements responded to CHX as well as TNFalpha, whereas the promoter without the two sites did not. Chromatin immunoprecipitation (ChIP) assay showed that NFkappaB was indeed bound to the SSAT promoter after CHX treatment. Further, dominant negative IkappaB attenuated the CHX and DENSPM-induced SSAT expression and mitochondria damage. These results taken together suggest that the inhibition of IkappaB and activation of NFkappaB activate SSAT.

Acetyltransferases↗

PubMed2005

Characterization of a monoclonal antibody that antagonizes the function of human endostatin.

Endostatin, a 20-kDa proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. The anti-angiogenic effects of endostatin include inhibition of endothelial cell migration and proliferation, and inhibition of the activity of MMP2. Structure-function analysis of endostatin that implies this contravention function buried in separate fragments of endostatin introduces new issues into the understanding of the structure-function relationship of endostatin. We developed and characterized a novel murine MAb, 4E7, to human endostatin, which antagonizes the function of endostatin. As we show here, MAb 4E7 blocks the anti-migration/adhesion effects of endostatin in vitro and the anti-angiogenesis effect of endostatin in vivo, but the inhibition effect of endostatin on endothelial cell proliferation is not affected by MAb4E7. These results suggest that the anti-migration and anti-proliferation functions of endostatin may have distinct structural foundations.

Animals↗

PubMed2004

Alkali burn causes aldehyde dehydrogenase 3A1 (ALDH3A1) decrease in mouse cornea.

PURPOSE: Aldehyde dehydrogenase 3A1 (ALDH3A1) is the most abundant soluble protein component in the mouse cornea, produced mainly by corneal epithelial cells. High levels of ALDH3A1 in cornea contribute to maintenance of a stable an d transparent corneal structure. Alkali burn is a common damage to the corneal surface, which produces an alkaline hydrolysis of matrix proteins and induces an inflammatory reaction. Our study was intended to detect changes in ALDH3A1 expression after corneal alkaline burn. METHODS: To address this issue we employed RTQ-PCR to monitor the transcriptional change of ALDH3A1 after alkali burn. We used zymography to test enzyme activity changes of ALDH3A1 in the alkali burn cornea; And SDS-PAGE and mass spectrometry technology were used to verify protein content changes and to identify ALDH3A1 protein. RESULTS: Using zymography, ALDH3A1 enzymic activity was observed to decrease immediately after corneal alkali burn and the levels recovered following healing. Proteins extracted from alkali burned corneas, when run on SDS-PAGE, showed the same sized band (about 54 kDa, which is the molecular weight of ALDH3A1) but in much smaller quantity, compared to normal corneas. This result was further verified by mass spectrometry fingerprinting of the in-gel lysis product. An immediate decrease of ALDH3A1 transcription after alkali burning of the cornea was also found using RTQ-PCR. This level of transcription was gradually restored during healing. CONCLUSIONS: Alkali burn of the corneal surface caused a rapid decrease of ALDH3A1 in the corneal at both the RNA and protein levels, which leads to the loses of the protective component of the corneal surface and makes it vulnerable to further damage. The ALDH3A1 level in the cornea gradually recovered during the healing process. Use of an anti-oxidation reagent as a treatment ingredient for alkali burn of the corneal surface could compensate for the decrease of anti-oxidation protection potential caused by ALDH3A1 loss.

Aldehyde Dehydrogenase↗

PubMed2004

Differential gene and protein expression in primary breast malignancies and their lymph node metastases as revealed by combined cDNA microarray and tissue microarray analysis.

BACKGROUND: Metastatic disease is a major adverse prognostic factor in breast carcinoma. Lymph node metastases often represent the first step in the metastatic process. METHODS: To gain insight into the molecular events that underlie breast carcinoma metastasis, the authors compared gene expression profiles, obtained by cDNA microarray analysis, of nine matched primary tumors and metastases after screening for enrichment of tumor cells. Statistical analysis identified genes that are expressed at elevated or decreased levels in metastases relative to the corresponding primary tumors. Multidimensional scaling analysis indicated that in terms of expression levels, primary tumors were tightly clustered, whereas metastases exhibited a greater spread; this finding points to the more heterogeneous nature of metastases. Among the differentially expressed entities were the invasion- and tissue modeling-related genes IGFBP5, fibronectin, and MMP2; the cell cycle regulatory gene cyclin D1; other genes, such as enolase 2; and an expressed sequence tag similar to angiopoietin 1. To validate and extend these initial findings, the authors constructed a tissue microarray consisting of 100 primary malignancies paired with their lymph node metastases. Antibodies for the IGFBP-5, fibronectin, MMP-2, cyclin D1, and MDM-2 proteins were used to stain tissue array sections. RESULTS: Consistent with microarray data, statistically significant overexpression of IGFBP-5, down-regulation of cyclin D1, and unchanged MDM-2 levels were observed in metastatic tumor cells. Nonetheless, although fibronectin and MMP2 mRNA expression levels were decreased in many metastasis specimens, expression levels of the corresponding proteins in the extracellular matrix were elevated in most metastases. Decreased expression of fibronectin and MMP2 in lymph node metastases was further confirmed by real-time polymerase chain reaction assays performed on five additional specimen pairs. CONCLUSIONS: The results of the current study suggest that extracellular matrix protein expression and nuclear gene expression are associated via a negative-feedback regulatory mechanism. Therefore, gene expression profiling and tissue array validation should be combined to elucidate molecular events associated with the metastatic process.

Breast Neoplasms↗