[Study of gene expression difference in lung carcinogenesis by cDNA microarray]

Lung cancer is a kind of disease with high incidence and mortality, however its molecular mechanism is not clear yet. This study was designed to investigate gene expression differences among lung cancer tissues, lung paracancerous tissues,matched peripheral normal lung tissues and the metastases of lymph nodes, and to seek the relatively high expressed genes in lung carcinoma tissues, providing possible theoretical basis for early diagnosis and treatment of pulmonary carcinoma.

Fresh lung cancer tissue, lung paracancerous tissue, matched normal lung tissue and metastases of lymph nodes were deep-frozen in liquid nitrogen; their total RNA were extracted for reversed transcription cDNA probes, which were labeled and subsequently used to hybridize with cDNA microarray with 588 genes. Different gene expression profiles were obtained by analyzing the integrated density (ID) of spot images on the X-ray.

In lung cancer tissues, 40 genes were detected to be differentially expressed, 36 of which such as early growth response protein 1 (EGR1), secreted apoptosis related protein 1 (SARP1) were upregulated while the others such as myeloid cell leukemia protein 1 (MCL1) were downregulated. The upregulated genes were mainly oncogene/suppressor gene, cell cycle regulatory gene, growth factors and apoptosis-related genes. In lung paracancerous tissues, 33 genes had different expression, 20 of which such as matrix metalloproteinase-9 (MMP-9) were upregulated, and the other 13 such as MCL1,endothelin 2 (ET2) were downregulated. In metastases of lymph nodes, there were 21 genes found to be differently expressed, 15 of which such as CD40 receptor-associated factor 1 (CRAF1) were downregulated while the rest were upregulated, and the upregulated genes (6 in 15) were mainly the genes associated with adhesion molecules, matrix metalloproteinases and collagen.

EGR1, SARP1, NDKA, etc. may be the key genes in pulmonary carcinogenesis course. At the same time, MMP9, thrombospondin 2 (TSP2), etc.may play an important role in pulmonary cancer metastasis and infiltration.