Purpose:

VSIR is a novel immune checkpoint protein whose expression on tumor cells across cancers remains largely uncharacterized. Here we purposed to decode the pan-cancer biologic and clinical significance of VSIR overexpression in the tumor compartment.

Experimental Design:

We performed multi-omics integrative analyses of 9,735 tumor samples to identify cancers with non-leukocytic expression of VSIR (VSIR High), followed by association with overall survival and immune cell infiltration levels. Orthogonal assessments of VSIR protein expression and lymphocytic infiltration were performed using quantitative immunofluorescence (QIF).

Results:

Integrative modeling identified a subset of cancer types as being enriched for VSIR High tumors. VSIR High tumors were associated with significantly poorer overall survival in immunogenic ovarian serous adenocarcinoma (SA) and oral cavity squamous cell carcinoma (SCC). QIF assessments in an independent validation cohort confirmed overexpression of VSIR as being associated with poorer overall survival within immunogenic oral cavity SCC. VSIR overexpression was associated with lower CD4 helper T-cell infiltration in both ovarian SA and oral cavity SCC, but did not impact CD8 T-cell infiltration. VSIR overexpressing tumors in both cancer types exhibited significantly higher STAT3 signaling activity. Pharmacologic inhibition of STAT3 signaling resulted in dose-dependent reduction of VSIR expression in ovarian SA and oral cavity SCC cells.

Conclusions:

The STAT3-VSIR axis is a potentially significant immunomodulatory mechanism in oral cavity and ovarian cancers, whose activation is associated with poorer survival and an immune microenvironment marked by decreased CD4 helper T-cell activity. The role of VSIR as a tumor-intrinsic modulator of resistance to immunotherapy warrants further exploration.

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