Halaschek-Wiener J, Wacheck V, Kloog Y, Jansen B. Ras inhibition leads to transcriptional activation of p53 and down-regulation of Mdm2: two mechanisms that cooperatively increase p53 function in colon cancer cells.
Cell Signal 2005;
16:1319-27. [PMID:
15337531 DOI:
10.1016/j.cellsig.2004.04.003]
[Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2003] [Revised: 03/30/2004] [Accepted: 04/04/2004] [Indexed: 02/07/2023]
Abstract
Activated Ras, operating through the Raf/MEK/ERK pathway, is known to regulate transcription of both Mdm2 and its inhibitor p19ARF, resulting in opposing effects on the tumor suppressor protein p53. We show here that a decrease in Ras in SW480 cells induced either by the Ras inhibitor farnesylthiosalicylic acid (FTS) or by K-Ras antisense oligonucleotides, resulted in a similar increase in p53 protein. The increase in p53 was accompanied by an increase in p21(waf1/cip1) mRNA transcripts and protein. Consistent with the Ras/Raf/MEK/ERK-mediated control of Mdm2, treatment of SW480 cells with the Ras inhibitor FTS caused a marked (80%) decrease in Mdm2, which itself would account for the increase in p53. However, FTS also caused a 1.6-fold increase in p53 mRNA, indicative of a Ras-dependent mechanism that regulates p53 transcription. Thus, oncogenic Ras appears to attenuate p53 in SW480 cells by two independent regulatory mechanisms, the one leading to increased Mdm2-dependent p53 degradation and the other leading to a decrease in p53 transcription.
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