Molecular characterization of lung dysplasia induced by c-raf-1. Mus musculus

Background: Lung cancer is a multistage process with poor prognosis and high morbidity. Importantly, the genetics of dysplasia, a facultative cancer, at the edge of malignant transformation is unknown. Results: We employed laser microdissection to harvest dysplastic as opposed to transgenic but otherwise morphologically unaltered epithelium and compared findings to non-transgenic lung. We then employed microarrays to search genome wide for gene regulatory networks. A total of 120 and 287 genes were significantly regulated, respectively. Dysplasia was exclusive associated with up-regulation of genes coding for cell growth and proliferation, cell-to-cell signalling and interaction, lipid metabolism, development, and cancer. Likewise, when dysplasia was compared with non-transgenic cells up-regulation of cancer associated genes, tight junction proteins, xenobiotic defence and developmental regulators was observed. We additionally confirmed regulation of some genes by immunohistochemistry and therefore demonstrate good concordance between gene regulation and coded protein. Conclusion: Our study identified transcriptional networks at successive stages of tumor-development, i.e. from histological unaltered but transgenic lungs to nuclear atypia. Our animal model revealed interesting and novel candidate genes and pathways that provide clues on the mechanism forcing respiratory epithelium into dysplasia and subsequently cancer, some of which might also be useful in the molecular imaging and flagging of early stages of disease. Overall design: In our study, we used predominately 5 month old mice to gain information at an early stage of tumor development where isolated foci of transformed cells in distinct areas of the lung are visible. By use of laser microdissection pressure catapulting (LMPC) dysplastic cells in well defined lesions [18] could be isolated. Dysplastic lesions were than compared with transgenic but otherwise normal cells or tumor cells. We applied whole genome microarrays to determine differentially expressed genes as to identify the gene regulatory networks associated with dysplasia and, as will be reported in a second part of our study, the subsequent malignant transformation. Overall, our study revealed interesting and novel genes and pathways that may contribute to the early stages of lung cancer development many of which are worthy for their exploration as candidate biomarkers and for molecular imaging of early stages of disease.