To analyze the mechanism of the antitumor effect of an adenoviral vector expressing the p53 tumor suppressor (Ad-p53) in vivo, we quantitatively assessed p53-targeted gene expression and visualized transcriptional activity of p53 in tumors in nude mice treated with Ad-p53. Human lung cancer (H1299) xenografts established in nude mice were treated by intratumoral administration of Ad-p53. The levels of expression of exogenous p53 and p53-targeted genes p21, MDM2, Noxa, and p53AIP1 were quantified by real-time reverse transcription-PCR (RT-PCR) and induction of apoptosis was observed histochemically on days 1-3, 7, and 14 after treatment. Expression of mRNA of exogenous p53 and p53-targeted genes (except p53AIP1) was at its maximum 1 day after Ad-p53 treatment and then decreased rapidly; apoptosis was evident in situ 2-3 days after treatment. We developed a noninvasive and simple method for monitoring the transcriptional activity of exogenous p53 following intratumoral administration of Ad-p53 in nude mice. We established H1299 cells that express the green fluorescent protein (GFP) reporter gene under the control of p53-responsive p21 promoter (i.e., the p53R-GFP reporter system). Xenografts of these cells in nude mice were treated by intratumoral administration of Ad-p53, and the transcriptional activity of exogenous p53 could be visualized as intratumoral GFP expression in real time by 3-CCD camera. Expression of GFP was maximal 3 days after treatment and decreased remarkably by 7 days after treatment. We demonstrated that Ad-p53 treatment rapidly induced p53-targeted genes and apoptosis in tumors and succeeded in visualizing p53 transcriptional activity in vivo. We also found that Ad-p53 infection induced phosphorylation of p53 at Ser46 in p-53 infection H1299 cells in vitro but not in p53-resistant H22Br cells, suggesting that phosphorylation of Ser46 is involved in p53-dependent apoptosis. Our data indicate that quantitative analysis of p53-targeted gene expression by real-time quantitative RT-PCR and visualization of p53 transcriptional activity in fresh xenografts by using the p53R-GFP reporter system may be useful in assessing the mechanisms of the antitumor effects of Ad-p53 and novel therapeutic approaches.
|Number of pages||8|
|Journal||Molecular cancer therapeutics|
|Publication status||Published - Jan 2004|
ASJC Scopus subject areas
- Cancer Research