Targeting the vasculature to enhance anti-tumor immunity

Tumor-associated endothelial cells (ECs) line the blood vessels that promote the growth and support the
dissemination and survival of cancer cells. The tumor vasculature is also a gatekeeper that controls the
passage of immune cells both into and out of the tumor microenvironment. We recently used single cell RNA
sequencing (sc-RNAseq) to characterize EC heterogeneity in a mammary tumor model; from these studies, we
turned our attention to DNA methyltransferase1 (DNMT1) which has well-defined roles in stem/progenitor cell
self-renewal via it's ability to re-establish patterns of methylation in dividing cells, but no known role in
regulating EC function in tumors. Using mice with conditional deletion of DNMT1 in ECs (DNMT1iECKO mice),
we show inhibition of tumor growth and metastatic seeding and reduced vessel complexity/branching. We
propose these effects are due to a loss of methylation-dependent EC specification required for
neovascularization and are due to de-repression of Th1 chemokines (e.g. Cxcl9/Cxcl10, and Cxcl11) and cell
adhesion molecules (e.g. Vcam1, Icam1/2, and E-selectin) in ECs that recruit and retain cytotoxic T-
lymphocytes to impair tumor growth. In aim 1 we will use DNMT1iECKO mice and vascular-tropic nanoparticles
to determine how targeting DNMT1 regulates EC morphogenesis, perfusion, and permeability during cancer
cell survival. In aim 2 we will use metastasis models to assess how vascular DNMT1 shapes the tumor
immune microenvironment via its ability to regulate cell adhesion molecules (CAMs) and CTL-mobilizing
chemokines in ECs. In aim 3 we will examine mechanisms of immune suppression by a FGF2/DNMT1 axis
that triggers methylation-induced silencing of CAMs and chemokines in tumor-associated ECs. To complete
our goals, we have assembled a team of investigators with expertise in DNA methylation (S. Bhatnager), tumor
immune micro environments (V. Engelhard), and the development of microfluidics devices to study EC-to-T-cell
interactions (R. Kamm). Together, our study characterizes a completely unexplored area; namely, identifying
how methylation-dependent pathways regulate the complex functional diversity, specification, and
immunosuppressive features of tumor-associated ECs.