Abstract 1819: Reprogramming the tumor microenvironment by targeting endothelial DNA repair

Abstract

The tumor microenvironment (TME) plays a critical role in orchestrating immune infiltration, tumor progression and response to therapeutics. Therefore, strategies to manipulate the TME including cytokine gene therapy, antibodies to reverse macrophage polarization etc are under active investigation. We have identified an alternative approach to target the TME by disrupting DNA repair in the tumor endothelial cells (ECs). We discovered a seven-microRNA (miR) signature induced in ECs in in vitro and in vivo by oxidative stress and DNA damage. The top miR candidate in this signature, miR-103 altered the TME by inducing DNA damage in ECs, eliciting type I interferons, upregulating immune costimulatory receptors and decreasing PD-L1 expressing tumor associated macrophages and granulocytes. Moreover, miR-103 treatment had a paracrine effect on the tumors and upregulated Fas and TRAIL receptors. Mechanistically, these functions of miR-103 were largely due to its downregulation of the three prime exonuclease TREX1. Local, systemic or vascular targeted delivery of miR-103 decreased both angiogenesis and tumor burden in multiple mouse tumor models. Complementary to the role of miR-103, two additional miRs in the miR signature, miRs 494 and 99b each induced senescence in the vasculature by downregulating the Mre11a-Rad50-NBN (MRN) complex. Ectopic expression of miRs 494 or 99b decreased telomerase activity, increase p21 levels with a concomitant decrease in pRb levels. Vascular targeted delivery of miR-494 decreased angiogenesis in vivo whereas systemic delivery decreased tumor growth. Interestingly, both miR mimics and the MRN knockdowns induced the transcription of a number of senescence associated genes including CD44. Taken together these data suggest that miRs 494 and 99b targeting of the MRN complex induces senescence. The MRN complex interacts with the ATM kinase, histone H2AX and TREX1 suggesting that the miRs we identified disrupt critical nodes of a DNA Damage Response (DDR) network. Our findings reveal a complex, miR mediated cross talk between EC DNA damage pathways, the TME and tumor cells. These interactions can be exploited for designing therapies that synergize with tumor cell killing to enhance host anti-tumor responses. Citation Format: Cristina Espinosa-Diez, RaeAnna Wilson, Rebecca Ruhl, Nathan Kanner, Namita Chatterjee, Clay Hudson, Sudarshan Anand, Shushan Rana. Reprogramming the tumor microenvironment by targeting endothelial DNA repair [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1819. doi:10.1158/1538-7445.AM2017-1819