Trapasso F, Iuliano R, Boccia A, Stella A, Visconti R, Bruni P, Baldassarre G, Santoro M, Viglietto G, Fusco A. Rat protein tyrosine phosphatase eta suppresses the neoplastic phenotype of retrovirally transformed thyroid cells through the stabilization of p27(Kip1).
Mol Cell Biol 2000;
20:9236-46. [PMID:
11094075 PMCID:
PMC102181 DOI:
10.1128/mcb.20.24.9236-9246.2000]
[Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2000] [Accepted: 09/27/2000] [Indexed: 01/25/2023] Open
Abstract
The r-PTPeta gene encodes a rat receptor-type protein tyrosine phosphatase whose expression is negatively regulated by neoplastic cell transformation. Here we first demonstrate a dramatic reduction in DEP-1/HPTPeta (the human homolog of r-PTPeta) expression in a panel of human thyroid carcinomas. Subsequently, we show that the reexpression of the r-PTPeta gene in highly malignant rat thyroid cells transformed by retroviruses carrying the v-mos and v-ras-Ki oncogenes suppresses their malignant phenotype. Cell cycle analysis demonstrated that r-PTPeta caused G(1) growth arrest and increased the cyclin-dependent kinase inhibitor p27(Kip1) protein level by reducing the proteasome-dependent degradation rate. We propose that the r-PTPeta tumor suppressor activity is mediated by p27(Kip1) protein stabilization, because suppression of p27(Kip1) protein synthesis using p27-specific antisense oligonucleotides blocked the growth-inhibitory effect induced by r-PTPeta. Furthermore, we provide evidence that in v-mos- or v-ras-Ki-transformed thyroid cells, the p27(Kip1) protein level was regulated by the mitogen-activated protein (MAP) kinase pathway and that r-PTPeta regulated p27(Kip1) stability by preventing v-mos- or v-ras-Ki-induced MAP kinase activation.
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