Successful intratumoral human treg targeting in vivo using treg-dependent tumor model in novel humanized SGM3-IL15 mice 4422

Description Rationale Test the effects of AUMsilence FOXP3 anti-sense oligonucleotides (ASO) targeting of intratumoral human CD4+ FOXP3+ regulatory T cells (Tregs) in vivo. We aimed to design a tumor model in mice, fully supporting development and function of human Treg (to access their pro-tumoral effects) and T cells (to access their ability to attack tumors). Moreover, that model should support natural trafficking of human cells to tumors, development of suppressive tumor microenvironment, and, ideally, the development of T cell exhaustion. To do so, we evaluated two novel Jax strains of humanized mice, NSG-SGM3 and NSG-SGM3-IL15. Both strains of mice had high % of reconstitution by human CD45+ cells (>80%), and 23-35% of fully functional Tregs in livers, spleens and blood. A549 lung tumors had similar but slow growth in both strains, and tumors were highly enriched by Tregs (15-35%) and by exhausted T cells. Treatment of mice with FOXP3 ASO resulted in a decrease in tumor growth, while scramble treated mice developed larger tumors and multiple lung metastases. FOXP3 expression decreased 2.7 times in tumors (p = 0.02), but not in the spleens and livers of ASO treated mice. Moreover, targeting of Tregs led to decreased expression of 7 out of 8 tested T cell exhaustion markers in tumors, confirming our previous observation that intratumoral Treg may promote T cell exhaustion. Conclusion AUMsilence FOXP3 ASO therapy has powerful anti-tumoral effects in vivo in humanized NSG-SGM3 mice. Funding Sources NIH/NCI SBIR grant R43CA275470 Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)