Antisense MDM2 enhances E2F1-induced apoptosis and the combination sensitizes androgen-dependent and androgen-independent prostate cancer cells to radiation

Thirupandiyur S. Udayakumar, Paul Hachem, Mansoor M. Ahmed, Sudhir Agrawal, Alan Pollack

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We have previously shown in separate studies that MDM2 knockdown via antisense MDM2 (AS-MDM2) and E2F1 overexpression via adenoviral-mediated E2F1 (Ad-E2F1) sensitized prostate cancer cells to radiation. Because E2F1 and MDM2 affect apoptosis through both common and independent pathways, we hypothesized that coupling these two treatments would result in increased killing of prostate cancer cells. In this study, the effect of Ad-E2F1 and AS-MDM2 in combination with radiation was investigated in three prostate cancer cell lines: LNCaP cells, LNCaP-Res cells [androgen insensitive with functional p53 and androgen receptor (AR)], and PC3 cells (androgen insensitive, p53null, and ARnull). A supra-additive radiosensitizing effect was observed in terms of clonogenic inhibition and induction of apoptosis (caspase-3 + caspase-7 activity) in response to Ad-E2F1 plus AS-MDM2 treatments in all three cell lines. In LNCaP and LNCaP-Res, these combination treatments elevated the levels of phospho-Ser15 p53 with significant induction of p21 waf1/cip1, phospho-γH2AX, PUMA, and Bax levels and reduction of AR and bcl-2 expression. Similarly, ARnull and p53null PC-3 cells showed elevated levels of Bax and phospho-γH2AX expression. These findings show that the combination of Ad-E2F1 and AS-MDM2 significantly increases cell death in prostate cancer cells exposed to radiation and that this effect occurs in the presence or absence of AR and p53.

Original languageEnglish (US)
Pages (from-to)1742-1754
Number of pages13
JournalMolecular Cancer Research
Issue number11
StatePublished - Nov 1 2008


ASJC Scopus subject areas

  • Molecular Biology
  • Oncology
  • Cancer Research

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