Data from A Novel E1B-55kD-Deleted Oncolytic Adenovirus Carrying Mutant KRAS-Regulated <i>hdm2</i> Transgene Exerts Specific Antitumor Efficacy on Colorectal Cancer Cells

Abstract

&lt;div&gt;Abstract&lt;p&gt;E1B-55kD-deleted adenoviruses have been used as conditionally replicative adenoviruses (CRAds) for therapeutic purposes in tumors with loss-of-function p53 mutation. To target cancer cells that harbor activating mutant KRAS (KRAS&lt;sup&gt;aMut&lt;/sup&gt;) but spare p53&lt;sup&gt;wild&lt;/sup&gt; normal cells, we constructed and examined by reporter assays a KRAS&lt;sup&gt;aMut&lt;/sup&gt; but not p53-responsive promoter, the Δ&lt;i&gt;p53RE&lt;/i&gt;P2 promoter. The Δ&lt;i&gt;p53RE&lt;/i&gt;P2 promoter, derived from human double minute 2 (&lt;i&gt;hdm2&lt;/i&gt;) P2 promoter with its p53 response elements being deleted, was used to regulate the expression of the &lt;i&gt;hdm2 &lt;/i&gt;transgene in a novel E1B-55kD-deleted CRAd, the Ad-KRhdm2. The Ad-KRhdm2 selectively replicated in and exerted cytopathic effects on KRAS&lt;sup&gt;aMut&lt;/sup&gt; colorectal cancer cell lines (HCT116, LoVo, LS174T, LS123, and SW620), regardless of their &lt;i&gt;p53&lt;/i&gt; gene statuses, by forming plaques and exhibiting cytopathic effect in cultured cells. Ad-KRhdm2, like other E1B-55kD-deleted adenoviruses, also exerted selective cytopathic effects on tumor cells with loss-of-function p53 mutant. The multiplicities of infection of Ad-KRhdm2 required to decrease 50% viability of KRAS&lt;sup&gt;aMut&lt;/sup&gt; tumor cells cultured for 7 days were 440 to 3,400 times less than those of MRC5 normal fibroblasts and KRAS&lt;sup&gt;wild&lt;/sup&gt;/p53&lt;sup&gt;wild&lt;/sup&gt; RKO tumor cells. Intratumoral injection of Ad-KRhdm2 vectors exhibited specific lytic activities in nude mouse xenografts of KRAS&lt;sup&gt;aMut&lt;/sup&gt; cell lines (LoVo, SW620, and LS174T) but not in xenografts of RKO cells. Transduction of KRAS&lt;sup&gt;aMut&lt;/sup&gt;/p53&lt;sup&gt;wild&lt;/sup&gt; HCT116, LoVo, and LS174T cells by Ad-KRhdm2 significantly increased Hdm2 expression, decreased p53 level, and abolished the p53-transactivating &lt;i&gt;p21&lt;sup&gt;Cip1&lt;/sup&gt;&lt;/i&gt; promoter activity. Ad-KRhdm2 has shown its therapeutic potential in KRAS&lt;sup&gt;aMut&lt;/sup&gt; cancer cells and warrants further clinical trials. Mol Cancer Ther; 9(2); 450–60&lt;/p&gt;&lt;/div&gt;