Background V-domain Ig suppressor of T cell activation (VISTA) is a B7 family member that regulates a spectrum of immune responses.¹ VISTA functions as an inhibitory checkpoint for T-cell activation, making it a promising target for combination cancer immunotherapy.² VISTA is widely expressed on immune and tumor cells but predominantly resides on tumor-infiltrating myeloid cells in multiple murine cancer models.³ The interaction of VISTA with its ligand P-selectin glycoprotein ligand 1 (PSGL-1) is regulated by pH, and the acidic pH (~6.0) in the tumor microenvironment (TME) facilitates VISTA binding to PSGL-1.⁴ Thus, inhibiting this VISTA:PSGL-1 interaction could reduce the immune-inhibitory activity of VISTA and enhance antitumor immune responses.^{5 6}

Patient selection and tumor histology are key factors in determining successful outcomes of immunotherapy. Understanding the expression and interactions of VISTA in the TME is critical for the development of VISTA-targeting drugs. We report here exploratory multiplex IHC and computational analysis of tumor tissue microarrays to profile VISTA and PSGL-1 expression on immune cells, as well as their spatial interactions across ten cancer types.

Methods Multi-tumor tissue microarrays containing 24 cores from each of 10 tumor types (TriStar Technologies, Inc) were imaged by CODEX using a customized 53-plex panel of oligonucleotide-conjugated antibodies covering a variety of immune, epithelial, stromal, and functional markers. High-dimensional data were analyzed with a suite of novel computational tools developed by Enable Medicine that facilitate fast, accurate analysis at scale and in an automated fashion.

Results We profiled VISTA and PSGL-1 expression on immune cell populations across cancer indications. VISTA expression was found predominantly on T-cells, granulocytes, and macrophages. Colon, skin, and kidney cancers showed enrichment of VISTA+ myeloid cells relative to other indications. We also characterized VISTA-PSGL-1 cell-cell interactions within both tumor and stromal regions of tissue cores. These cell-type interactions were more abundant in tumor regions, and were relatively enriched in stomach and colon cancers. Finally, we explored whether these features correlate with known tumor classifications (e.g. hot/cold status and tumor mutational burden).

Conclusions This spatial proteomics analysis reveals several tumor types that may have high engagement of the VISTA-PSGL-1 immune checkpoint, suggesting that these indications may be particularly responsive to anti-VISTA therapies currently in development. In addition, the findings contribute to our ongoing investigation of the molecular mechanisms by which VISTA mediates immune suppression in the TME.

References

1. Yuan L, Tatineni J, Mahoney KM, Freeman GJ. VISTA: a mediator of quiescence and a promising target in cancer immunotherapy. Trends Immunol 2021 Mar;42(3):209-227.

2. Gao J, et al. VISTA is an inhibitory immune checkpoint that is increased after ipilimumab therapy in patients with prostate cancer. Nat. Med 2017 May;23(5):551-555.

3. Le Mercier I, Chen W, Lines JL, et al. VISTA regulates the development of protective anti-tumor immunity. Cancer Res 2014;74:1933-44.

4. Johnston RJ, Su LJ, Pinckney J, Critton D, et al. VISTA is an acidic pH-selective ligand for PSGL-1. Nature 2019 Oct;574(7779):565-570.

5. Mehta N, Maddineni S, Kelly RL, Lee RB, Hunter SA, Silberstein JL, Parra Sperberg RA, Miller CL, Rabe A, Labanieh L, Cochran JR. An engineered antibody binds a distinct epitope and is a potent inhibitor of murine and human VISTA. Sci Rep 2020 Sep 16;10(1):15171.

6. Thisted T, Smith FD, Mukherjee A, Kleschenko Y, Feng F, et al. VISTA checkpoint inhibition by pH-selective antibody SNS-101 with optimized safety and pharmacokinetic profiles enhances PD-1 response. Nat Commun 2024;15(1):2917.