Although a growing body of data have been gathered on the expression of MIF in several tumors, the exact mechanism of its function is unknown. MIF has begun to be recognized recently as a protumorigenic factor ( 13) in addition to its effects on proinflammatory and immune responses. Spontaneous regressions and differentiation are common in infants and in early-stage tumors, whereas neuroblastoma is extremely aggressive in older children with late-stage tumors ( 12). Neuroblastoma is the most frequent solid extracranial neoplasia in children and is responsible for ≈15% of all pediatric cancer deaths ( 11). Neuroblastoma is a malignant tumor of neural crest origin that may arise anywhere along the sympathetic ganglia or within the adrenal medulla. A comprehensive review and comparisons of various expression measures are given in refs. These techniques include the detection signals that are prominently featured in Affymetrix Micorarray Suite 5.0 ( mas 5.0) software, the model-based expression index ( 3), and the robust multichip average ( 4, 5). Several techniques have been proposed for extracting expression profiles from the information at probe level. The expression profile of an mRNA molecule of a gene is obtained by the combined intensity information from probes in a probe set, which consists of 11-20 probe pairs of oligonucleotides of 25 bp in length, interrogating a different part of the sequence of a gene. The high-density oligonucleotide array technology allows researchers to monitor tens of thousands of genes in a single hybridization experiment as they are expressed differently in tissues and cells. Our data not only demonstrate that targeting MIF expression is a promising therapeutic strategy in human neuroblastoma therapy but also indicate the MIF target genes for additional study.Īffymetrix GeneChip arrays ( 1, 2) have been widely used for monitoring mRNA expression in many areas of biomedical research. In addition, we demonstrated that down-regulation of MIF expression could result in a reduction in cell proliferation and tumor growth in vitro and in vivo. On the other hand, some tumor-suppressor genes such as EPHB6, visinin-like protein 1 ( VSNL-1), and BLU were up-regulated in MIF-reduced cells. MIF-regulated genes associated with tumor development including IL-8 and C- met, which are overexpressed in many tumors, were down-regulated in MIF-reduced cells. Among those genes, 44 were altered >2-fold. With semilinear in-slide model analysis, expression of 166 genes was altered with a P value no greater than 0.001. The improved specificity and sensitivity are demonstrated by using a study on the impact of macrophage migration inhibitory factor (MIF) reduction in neuroblastoma cells. The normalized expression ratios are analyzed further by a modified two-sample t test along with a sieved permutation scheme for computing P values. This normalization step is vital for Affymetrix arrays to reveal relevant biological results when comparing gene expression in multiple arrays. It is demonstrated that the intensity effect can be estimated accurately and removed effectively. A semilinear in-slide model is introduced to remove the intensity effect in the scanning process.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |