Investigation of archived formalin-fixed paraffin-embedded (FFPE) pancreatic tissue with whole-genome gene expression microarray.

ABSTRACT: In recent years, the use of FFPE tissue in gene expression microarray (GEM) studies has become a topic of increased interest, because pathology departments worldwide contain an invaluable source of biological disease-specific FFPE- tissue material. Thus far, some published studies on FFPE tissue consider the processed tissue amenable, whereas other studies assert that the tissue is not useful in GEM. In general, pancreatic tissue is known to contain large amounts of nucleases, leading to high turnover rates and degradation of RNA in the tissue. This characteristic, in combination with FFPE processing time and its effect on the tissue, does not make FFPE pancreatic tissue the obvious choice for GEM. The basis for using FFPE pancreatic tissue in RNA-based assays seems suboptimal. Previous GEM studies have used different FFPE tissue types, but GEM studies on FFPE pancreatic tissue have not been published. In most studies, the tissue was specially processed for use with GEMs. Here we demonstrate the usefulness of randomly archived FFPE pancreatic tissues for GEMs. For this purpose we included FFPE pancreatic tissue from patients with congenital hyperinsulinism or insulinoma; In these patients, pancreas resection is performed when medical treatment is not adequate to prevent hyperinsulinemic hypoglycemia or when patients do not respond to medical treatment. Although ribonuclease-rich, we obtained biologically relevant and disease-specific, significant genes; cancer-related genes and genes involved in a) the regulation of insulin secretion and synthesis, b) amino acid metabolism, and c) calcium ion homeostasis. This application may extend the possibilities of gene expression studies to many tissue types, especially in rare diseases, for which fresh frozen tissue is not readily available. A total of 15 samples were included in this study using a 58K chip. 29,134 human 60mer oligonucleotide targets were arrayed on the chips in duplicates. Each chip is hybridized with sample material (labelled with Cy5) from one patient and reference material (labelled with Cy3). Reference material contains pooled RNA from four different cancer cell lines; HeLa (cervical epithelium), SK-BR-3 (mammary gland), HT29 (colon) and A431 (skin) cells. Seven patients with congenital hyperinsulinism (five FFPE and two frozen samples), one patient with insulinoma and five controls were included in the study. Inclusion criteria for controls was that their cause of death was not pancreas-related. Samples were obtained from archived FFPE pancreatic material. The insulinoma sample was included in the study, because the biopsy was originally divided with one part being frozen and the other part being routinely formalin-fixed and paraffin-embedded. In the study we therefore include a frozen insulinoma sample and a FFPE insulinoma sample that was processed in duplicate.

ORGANISM(S): Homo sapiens

SUBMITTER: Nete Michelsen 

PROVIDER: E-GEOD-32610 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress