Kristina Paul

VISTA is a key immune checkpoint receptor under investigation as a target for cancer immunotherapy. However, a better understanding of the signaling mechanisms of VISTA is needed to optimize the therapeutic potential. Here, we identified a conserved four amino acid (NPGF) intracellular motif in VISTA that suppresses cell proliferation by constraining cell-intrinsic growth receptor signaling. A class of triple-negative breast cancers (TNBC) with high VISTA expression and low proliferative index was identified and characterized. The NPGF motif bound to the adapter protein NUMB and recruited Rab11 endosomal recycling machinery. The NPGF motif sequestered NUMB at endosomes, which interfered with EGFR trafficking and signaling to suppress tumor growth. These tumor suppressive effects did not require canonical VISTA ligands or a functioning immune system. Mutation of the VISTA NPGF domain reverted VISTA-induced growth suppression in multiple breast cancer mouse models. The NPGF motif was also required for response of VISTA+ TNBCs to VISTA-blocking antibodies. These results define a mechanism by which VISTA recruits adapter proteins to control malignant epithelial cell growth and signaling. They also define distinct intracellular residues that are critical for response to therapeutic antibodies that could be exploited to improve immunotherapy.

Although three-dimensional (3D) genome architecture is crucial for gene regulation, its role in disease remains elusive. We traced the evolution and malignant transformation of colorectal cancer (CRC) by generating high-resolution chromatin conformation maps of 33 colon samples spanning different stages of early neoplastic growth in persons with familial adenomatous polyposis (FAP). Our analysis revealed a substantial progressive loss of genome-wide cis-regulatory connectivity at early malignancy stages, correlating with nonlinear gene regulation effects. Genes with high promoter–enhancer (P–E) connectivity in unaffected mucosa were not linked to elevated baseline expression but tended to be upregulated in advanced stages. Inhibiting highly connected promoters preferentially represses gene expression in CRC cells compared to normal colonic epithelial cells. Our results suggest a two-phase model whereby neoplastic transformation reduces P–E connectivity from a redundant state to a rate-limiting one for transcriptional levels, highlighting the intricate interplay between 3D genome architecture and gene regulation during early CRC progression.