| Research Abstract |
In process of searching for genes that could respond to mechanical detachment in bronchial epithelial cells, we found two molecules, ARF-GEP100 and thymidine phosphorylase (TP) as candidates.
A human cDNA encoding an 841-aa guanine nucleotide-exchange protein(GEP) for ADP-ribosylation factors(ARFs), named ARF-GEP100, which contains a Sec7 domain, a pleckstrin homology(PH)-like domain, and an incomplete IQ-motif, was identified. On Northern blot analysis of human tissues, 〜8-kb mRNA that hybridized with an ARF-GEP100 cDNA was abundant in leukocytes, brain, and spleen. Lesser amounts were detected in lung, placenta, small intestine, liver, and kidney. ARF-GEP100 accelerated [35S]GTPgS binding to ARF1 amd ARF5 2-to 3-fold, and to ARF6 ca. 12-fold. We also found that ARF-GEP100 was expressed at higher levels in non-small cell lung cancers, suggesting that ARF-GEPIOO might affect tumor invasion as ARF6 activation is required for various processes that involved actin rearrangements such as ce
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ll spreading and Rac-mediated membrane ruffling.
TP is expressed at higher levels in a variety of human cancers than in adjacent normal tissue. We investigated the role of TP in human non-small cell lung cancers (NSCLC). The concentrations of TP in the tumors and the adjacent normal tissue from surgically respected specimens of 54 cases of primary NSCLC were measured by using an enzyme-linked immunosorbent assay. TP concentrations in the tumors were 169 ± 18 Unit/mg protein (mean ± SD, with a range of 19 to 702), whereas those in adjacent normal tissue were 43 ± 4 Unit/mg protein (mean ± SD, with a range of 6 to 163). Among clinicopathological factors examined, we found that the concentrations of TP correlated with tumor differentiation. Although 5-chloro-6- {1- (2-iminopyrrolidinyl)methyl} uracil hydrochloride, a specific TP inhibitor, did not affect the growth of A549 human lung cancer cells, Matrigel invasion assay showed that A549 transfected with TP (A549/TP) had higher invasive potential than mock transfectant, A549/CV cells. These results demonstrate that TP may play an important role in tumor differentiation and invasiveness in NSCLC and suggest that TP could be a novel target for NSCLC treatment. Less
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