Expression and Characterization of Genes by Expressed Sequence Tag Analysis in the Rat Thymus during Regeneration following Acute Thymic Involution Induced by Cyclophosphamide / 체질인류학회지

The thymus is the central lymphoid organ for the development of bone marrow-derived precursor cells into mature T-cells. Understanding the molecular mechanism of thymic involution and regeneration is critical to develop methods to normalize or improve host immunity from the decreased immune function caused by thymic involution. In this study, the regenerating thymus cDNA library was constructed in the rat from a model of thymic involution and regeneration induced by cyclophosphamide. Expressed sequence tags (ESTs) were obtained by partial sequencing of 700 randomly selected insert-containing clones. A total of 630 ESTs were analyzed, of which 486 ESTs (78%) matched to known genes and 125 ESTs (19%) matched to other ESTs (unknown genes). The 19 ESTs (3%) did not match with any known sequences. The ESTs were grouped into six main functional categories: metabolism (44%), signaling components (20%), membrane transport (7%), cytoskeleton (2%), cell division (2%) and defense (2%). As a result of RT-PCR analysis, expression of putative gene 01, putative E2IG2 gene, musculin and osteoactivin significantly increased in rat thymus during regeneration. The putative gene 01 showed complete homology with mitochondrial ribosomal protein S4 by homology search and multiple alignment of amino acid. These results provide the extensive molecular information on thymus regeneration and will be useful source to identify various genes which may play an important role in the thymus regeneration as well as to clone novel genes. Furthermore, the availability of these data will serve as a basis for further research to understand the molecular mechanism of thymus regeneration.

PAUF promotes adhesiveness of pancreatic cancer cells by modulating focal adhesion kinase

Pancreatic cancer is a notorious disease with a poor prognosis and low survival rates, which is due to limited advances in understanding of the molecular mechanism and inadequate development of effective treatment options over the decades. In previous studies, we demonstrated that a novel soluble protein named pancreatic adenocarcinoma up-regulated factor (PAUF) acts on tumor and immune cells and plays an important role in metastasis and progression of pancreatic cancer. Here we show that PAUF promotes adhesiveness of pancreatic cancer cells to various extracellular matrix (ECM). Our results further support a positive correlation of activation and expression of focal adhesion kinase (FAK), a key player in tumor cell metastasis and survival, with PAUF expression. PAUF-mediated adhesiveness was significantly attenuated upon blockade of the FAK pathway. Moreover, PAUF appeared to enhance resistance of pancreatic cancer cells to anoikis via modulation of FAK. Our results suggest that PAUF-mediated FAK activation plays an important role in pancreatic cancer progression.

Pancreatic adenocarcinoma up-regulated factor (PAUF) enhances the expression of beta-catenin, leading to a rapid proliferation of pancreatic cells

It is not yet understood how the enhanced expression of pancreatic adenocarcinoma up-regulated factor (PAUF; a novel oncogene identified in our recent studies), contributes to the oncogenesis of pancreatic cells. We herein report that PAUF up-regulates the expression and transcriptional activity of beta-catenin while the suppression of PAUF by shRNA down-regulates beta-catenin. The induction of beta-catenin by PAUF is mediated by the activities of Akt and GSK-3beta, but inhibition of downstream ERK does not reduce beta-catenin expression. To test whether PAUF emulates either the Wnt3a-mediated or the protein kinase A-mediated signaling pathway for the stabilization of beta-catenin, we examined the phosphorylation status of beta-catenin in the presence of PAUF compared with that of beta-catenin during treatment with Wnt3a or dibutyryl cAMP, a cell permeable cyclic AMP analogue. PAUF expression induces phosphorylation at Ser-33/37/Thr-41 and Ser-675 of beta-catenin but no phosphorylation at Ser-45, indicating that a unique phosphorylation pattern of beta-catenin is caused by PAUF. Finally, the expression of PAUF up-regulates both cyclin-D1 and c-Jun, target genes of beta-catenin, leading to a rapid proliferation of pancreatic cells; conversely decreased PAUF expression (by shRNA) results in the reduced proliferation of pancreatic cells. Treatment with hexachlorophene (an inhibitor of beta-catenin) reduces the proliferation of pancreatic cells despite the presence of PAUF. Taken together, we propose that PAUF can up-regulate and stabilize beta-catenin via a novel pattern of phosphorylation, thereby contributing to the rapid proliferation of pancreatic cancer cells.