1027

CDKN1B

epithelial mesenchymal transition (EMT) has been implicated in neoplastic invasion and metastasis. We have previously generated six cell lines from human gingival mucosal keratinocytes immortalized by E6/E7 of human papillomavirus type 16. Ldk and NuB1 lines represented EMT phenotype and other four lines represented cobblestone non-EMT phenotype. These cell lines were utilized as model cells to determine whether inhibitors of apoptosis proteins and cell-cycle regulators were molecular players during EMT. EMT cells exhibited increased expression of vimentin, vascular endothelial growth factor (VEGF) receptor1 and the ability to form tubules on Matrigel as well as to grow anchorage independently. We found that EMT cells expressed significantly elevated levels of cIAP-1, Bclx and p27(kip) higher than non-EMT cells. These proteins could therefore be used as intrinsic indicators of EMT of human gingival keratinocytes.

The continued turn over of human embryonic stem cells (hESC) while maintaining an undifferentiated state is dependent on the regulation of the cell cycle. Here we asked the question if a single cell cycle gene could regulate the self-renewal or pluripotency properties of hESC. We identified that the protein expression of the p27(Kip)(1) cell cycle inhibitor is low in hESC cells and increased with differentiation. By adopting a gain and loss of function strategy we forced or reduced its expression in undifferentiating conditions to define its functional role in self-renewal and pluripotency. Using undifferentiation conditions, overexpression of p27(Kip)(1) in hESC lead to a G(1)phase arrest with an enlarged and flattened hESC morphology and consequent loss of self-renewal ability. Loss of p27(Kip)(1) caused an elongated/scatter cell-like phenotype involving up-regulation of Brachyury and Twist gene expression. We demonstrate the novel finding that p27(Kip)(1) protein occupies the Twist1 gene promoter and manipulation of p27(Kip)(1) by gain and loss of function is associated with Twist gene expression changes. These results define p27(Kip)(1) expression levels as critical for self-renewal and pluripotency in hESC and suggest a role for p27(Kip)(1) in controlling an epithelial to mesenchymal transition (EMT) in hESC.

Transmembrane 4L six family member 5 (TM4SF5) can regulate cell-cell adhesion and cellular morphology via cytoplasmic p27(Kip1)-mediated changes in RhoA activity. However, how TM4SF5 causes cytosolic p27(Kip1) stabilization remains unknown. In this study we found that TM4SF5-mediated Ser10 phosphorylation of p27(Kip1) required for cytosolic localization was not always correlated with Akt activity. Inhibition or suppression of c-Jun N-terminal kinase (JNK) in TM4SF5-expressing cells decreased Ser10 phosphorylation of p27(Kip1) and rescued expression levels and localization of adherence junction molecules to cell-cell contacts. These observations suggest involvement of JNKs in TM4SF5-mediated p27(Kip1) Ser10 phosphorylation and localization during epithelial-mesenchymal transition.CI - Copyright (c) 2011 Elsevier Ireland Ltd. All rights reserved.

p27 shifts from CDK inhibitor to oncogene when phosphorylated by PI3K effector kinases. Here, we show that p27 is a cJun coregulator, whose assembly and chromatin association is governed by p27 phosphorylation. In breast and bladder cancer cells with high p27pT157pT198 or expressing a CDK-binding defective p27pT157pT198 phosphomimetic (p27CK-DD), cJun is activated and interacts with p27, and p27/cJun complexes localize to the nucleus. p27/cJun up-regulates TGFB2 to drive metastasis in vivo. Global analysis of p27 and cJun chromatin binding and gene expression shows that cJun recruitment to many target genes is p27 dependent, increased by p27 phosphorylation, and activates programs of epithelial-mesenchymal transformation and metastasis. Finally, human breast cancers with high p27pT157 differentially express p27/cJun-regulated genes of prognostic relevance, supporting the biological significance of the work.CI - Copyright (c) 2019 the Author(s). Published by PNAS.