The oncolytic adenovirus Adp53-sensor for selective replication in p53-altered tumors and potential target spectrum is not limited by the p73 status

Oncolytic virotherapy provides a promising mean for the treatment of solid tumors. Central goals of virotherapy are tight restriction of viral replication to tumor cells and a broad range of potential target tumors. Aim of our study was the establishment of a conditionally replicating adenovirus able to recognize the transcriptional p53-status of target cells and to consequently respond by the selective onset of viral replication in cells lacking functional p53. Therefore, we constructed Adp53-sensor expressed E1A under control of a GAL4-binding CMV-promoter and GAL4KRAB-repressor expression was controlled by the p53-sensitive promoter prMinRGC. The artificial promoter prMinRGC showed enormous induction by endogenous or overexpressed p53. Though the promoter was sensitive to overexpressed p73-b, but not to further members of the p53 family, prMinRGC was silent in all p53-altered cells including p73-positive cells. As endogenous p73 seems to be insufficient to activate prMinRGC, the p73-status should not limit the potential tumor spectrum of therapeutic Adp53sensor application. We could further show selectivity and oncolytic efficacy of Adp53sensor by comparing a large panel of cell lines with different p53/p73 status. Furthermore, p53-selectivity was confirmed in human hepatocytes where Adp53-sensor replication was significantly inhibited. Western Blots demonstrated correct function of the p53-dependent, GAL4-KRAB regulated E1A expression in cells with different p53-status. Doxorubicin pretreatment significantly enhanced selectivity of Adp53-sensor. In oncolysis assays Adp53-sensor showed slightly reduced oncolytic properties compared to Ad-wt but was both more p53-selective and efficient compared to ONYX-015. The vector was also more efficient in the treatment of s.c. grown Hep3B-xenografts resulting in partial remissions. Finally, Adp53-sensor virotherapy lead to reduced viral DNA load of mice livers compared to controls. In conclusion, our data suggest that Adp53-sensor represents an effective tool for p53-selective virotherapy of cancer. p53-selectivity and oncolytic properties of Adp53-sensor are improved to ONYX-015. The vector can be applied to a broad tumor spectrum as the selective function is not limited by the p73 status of the target tumors.