Identification and analysis of differentially expressed genes in human pulmonary adenocarcinoma

Increasing evidence indicates a shift is occurring in the distribution of lung cancer subtypes, with relative and absolute increases in the number of adenocarcinomas. The exact reason for this remains unclear. Molecular and cytogenetic studies have identified several genetic changes occurring in the development of pulmonary adenocarcinoma but many more remain unknown. Until recently, identification of unknown genes relied heavily on the use of linkage-based studies, which are both laborious and time-consuming. Recently, a new technique has been developed to investigate gene expression with greater accuracy and experimental ease: differential display reverse transcription polymerase chain reaction (DDRT-PCR).;In this study DDRT-PCR has been applied to search for novel, differentially expressed genes in human pulmonary adenocarcinoma, using both human normal and adenocarcinoma cell lines and matched surgical tissues. Human cell lines were used in preliminary experiments to adapt and establish the experimental techniques. Results from these studies produced three differentially expressed bands, one of which was a true positive. This cDNA tag was found to show 100% sequence homology to human fibronectin mRNA. Fibronectin is known to show different patterns of expression in various tumours. Similar studies were set up using human surgical specimens collected from two major thoracic units. Results from one matched human tissue sample identified eight differentially expressed bands. Again only one of these demonstrated true differential expression with a northern blot.;Expression of the tissue-positive band, called H8, was diminished in pulmonary adenocarcinoma RNA samples and may represent a novel tumour suppressor gene. The sequence data that has been obtained from the H8 cDNA tag appears to correspond to the 3' untranslated region. Northern blotting studies revealed high levels of H8 in normal lung tissue matched to other types of lung tumour, normal liver, stomach and colon, with lower expression in the corresponding tumour samples.