Abstract 792: DRAGO (KIAA0247), a new p53-regulated antioncogene.
Authors: Rusconi Paolo , Polato Federica , Musi Alberto , Broggini Massimo 
Published: August 2014

INTRODUCTION: The present work aims at functionally characterize DRAGO (DRug Activated Gene Overexpressed)/KIAA0247, an unknown, highly evolutionary-conserved gene. Data obtained in the lab showed that DRAGO is up-regulated by p53 in response to chemotherapeutic compound treatment in vitro and that its ectopic overexpression in cells growing in culture leads to cell death. DRAGO knockout mice are normal, fertile and do not develop tumors. At clinical level, lower DRAGO mRNA levels correlate to worse prognosis in colorectal and ovarian cancer patients. Preliminary evidences suggest a potential involvement of DRAGO in the control of immune response.

EXPERIMENTAL PROCEDURES: to verify if DRAGO may cooperate with p53 in counteracting tumor onset we crossed DRAGO and p53 knockout mice and evaluated the distribution of spontaneous tumors and the survival of double transgenic mice. DRAGO KO mice were generated by Cre recombinase-mediated-cassette-exchange approach. p53 KO mice were purchased from Jackson Lab. Mice were bred and PCR genotyped. Survival analysis were performed with GraphPad Prism 5 ®. Formalin fixed and paraffin embedded histological samples were hematoxylin/eosin stained and assessed by pathologists for diagnosis.

As regards macrophages isolation, PECs (Peritoneal Exudate Cells) were collected from DRAGO +/+ or -/- mice and M1 and M2 response were induced in vitro by LPS and IL4 treatment respectively. Gene expression was assessed with The TaqMan® Mouse Immune Array. Results were validated by FACS analysis.

RESULTS: DRAGO knockout negatively influenced survival: on a p53-/- background, deletion of either one or both DRAGO alleles progressively reduced survival (median survival: 166 and 139 days respectively) compared with DRAGO+/+ mice (190days). On a p53+/- background, DRAGO-/- and DRAGO+/- mice showed similar survival decrease (446 and 431 days respectively) compared with DRAGO+/+ mice (570 days). DRAGO genotype did not influence tumor incidence both in the p53-/- subpopulations (lymphomas 70%, sarcomas 30%), and in the p53+/- subpopulations (sarcomas 60%, lymphomas and carcinomas 20%).

PEC gene expression assessment displayed significant overexpression of CCR4 receptor on DRAGO-/- PECs, both in physiological conditions and upon M1 and M2 phenotype induction. FACS analysis confirmed that CCR4 expression is higher on DRAGO-/- PECs compared to DRAGO+/+ counterpart (43% vs 25% of positive cells).

CONCLUSIONS: crossing p53 and DRAGO knockout mice allowed us to demonstrate the oncosuppressive role of DRAGO in vivo and its cooperation with p53. Deletion of one or both DRAGO alleles determined a detrimental effect over survival both in p53-/- and in p53+/- mice. Also, DRAGO genotype did not affect tumor incidence on both p53 backgrounds. Preliminary data suggest that DRAGO might have a role in the macrophage functionality.

Citation Format: Paolo Rusconi, Federica Polato, Alberto Musi, Massimo Broggini. DRAGO (KIAA0247), a new p53-regulated antioncogene. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 792. doi:10.1158/1538-7445.AM2013-792