Differential expression of RAB5A in human lung adenocarcinoma cells with different metastasis potential

For the sake of better understanding the molecular mechanism of neoplasia, we have used the mRNA differential display technique to analyze two human l ung adenocarcinoma cell lines, AGZY83-a and Anip973. Anip973 was isolated f rom AGZY83-a, but manifested much higher metastatic potential than the pare nt line. We found that a significant differential cDNA fragment in Anip973 was over-expressed, then over-expressed cDNA fragment was cloned and sequen ced. It showed that the over-expressed cDNA in Anip973 was RAB5A cDNA. And the RAB5A cDNA sequence was corresponding between the two cells. To determi ne whether RAB5A may be differentially expressed in the two human lung aden ocarcinoma cells at protein level, we further detected RAB5A protein in the two cells by using immunofluorescent method. RAB5A protein was upregulated in highly metastatic Anip973. We also detected the difference in RAB5A gen e expression at RNA level in human non-small cell lung carcinoma by RT-PCR. Using immunohistochemical staining, we also examined RAB5A change at prote in level in 45 cases human non-small cell lung carcinoma paraffin sections. The results proved the evidence of upregulation of RAB5A in malignant tumo r, indicated over-expression of RAB5A gene was correlated with the malignan t degree and metastatic potential of lung cancer(chi(2) test, p < 0.01). Th e RAB5A gene is a member of RAS superfamily, which can transcribe GTP-bindi ng protein that plays an important role in signal transduction of protein t rafficking at the cell surface and GDP/GTP cycle in the regulation of endoc ytotic membrane traffic. Thus our results indicated that over-expression of the RAB5A gene was involved in the process of transformation from AGZY83-a to the higher metastatic cell line Anip973. The result may be a powerful e xperimental evidence that over-expression of RAB5A gene associated with neo plasia metastasis.