De novo expression of gastrokines in pancreatic precursor lesions impede the development of pancreatic cancer.

Molecular events occurring in stepwise progression from pre-malignant lesions (pancreatic intraepithelial neoplasia; PanIN) to the development of pancreatic ductal adenocarcinoma (PDAC) are poorly understood. Thus, characterization of early PanIN lesions may reveal markers that can help in diagnosing PDAC at an early stage and allow understanding the pathology of the disease. We performed the molecular and histological assessment of patient-derived PanINs, tumor tissues and pancreas from mouse models with PDAC (KC mice that harbor K-RAS mutation in pancreatic tissue), where we noted marked upregulation of gastrokine (GKN) proteins.

Manual microdissection combined with antisense RNA-longSAGE for the analysis of limited cell numbers.

Establishing a gene expression profile of defined subtypes of cells within an organ is still challenging because it frequently requires microdissection and subsequent amplification of the limited amount of messenger RNA (mRNA) isolated from the microdissected tissue in order to be able to proceed with comprehensive gene expression analyses via microarray or serial analysis of gene expression (SAGE) technology. Here we describe a manual microdissection strategy for the isolation of high-quality RNA. Furthermore, a strategy for combining linear amplification of RNA with longSAGE is described that allows the use of antisense RNA (aRNA) generated via the well-established linear amplification of RNA procedure together with the conventional SAGE or longSAGE technology.

aRNA-LongSAGE: SAGE with antisense RNA.

In order to generate serial analysis of gene expression (SAGE) libraries from very small samples such as microdissected cells, the starting material must first be amplified via PCR or linear amplification of RNA. In microarray experiments, it has been shown that linear amplification of RNA can be used to generate reliable gene expression profiles and leads to the detection of expression differences that are not seen with nonamplified starting material. As the product of the amplification is amplified antisense RNA (aRNA), linear amplification of RNA cannot be used in combination with the conventional SAGE protocol.

Discarding duplicate ditags in LongSAGE analysis may introduce significant error.

Background: During gene expression analysis by Serial Analysis of Gene Expression (SAGE), duplicate ditags are routinely removed from the data analysis, because they are suspected to stem from artifacts during SAGE library construction. As a consequence, naturally occurring duplicate ditags are also removed from the analysis leading to an error of measurement.

Results: An algorithm was developed to analyze the differential occurrence of SAGE tags in different ditag combinations.

aRNA-longSAGE: a new approach to generate SAGE libraries from microdissected cells.

Large-scale gene expression analyses of microdissected primary tissue are still difficult because generally only a limited amount of mRNA can be obtained from microdissected cells. The introduction of the T7-based RNA amplification technique was an important step to reduce the amount of RNA needed for such analyses. This amplification technique produces amplified antisense RNA (aRNA), which so far has precluded its direct use for serial analysis of gene expression (SAGE) library production.