Human Intratumoral NKp46+ Natural Killer Cells are Spatially Distanced from T and MHC-I+ Cells with Prognostic Implications in Soft Tissue Sarcoma
Abstract
Soft tissue sarcomas (STS) are heterogenous malignancies with an unmet need for novel immunotherapies. Tumor infiltrating lymphocytes (TILs) have previously been linked with favorable outcomes in STS patients, though the contribution of natural killer (NK) cell subsets, including NKp46 and CD56bright/dim, has yet to be investigated in detail. Despite the known role of MHC-I on immunoregulation of NK and T cells, limited data exist characterizing the spatial relationship of NK cells to MHC-I+/- cells and T cells in the STS tumor microenvironment (TME). Using STS specimens from 130 patients, we evaluated intratumoral NK cell subsets by immunohistochemistry (IHC), flow cytometry, and immunofluorescence (IF) to assess their impact on overall survival (OS) and metastasis-free survival (MFS). We also assessed the spatial localization of NK and T cells by multiplex IF in the TME, specifically analyzing the effects of MHC-I expression status on NK and T cell clustering. High intratumoral NKp46 expression was associated with improved OS by IHC (P=0.04) and IF (P=0.02). CD56dim NK cells were associated with a survival benefit (P=0.05), while higher infiltrates of CD56bright NK cells predicted worse prognosis (P=0.05). CD3-CD56+ NK cells demonstrated a significant inverse relationship with CD3+ T cells by both flow cytometry and IF. Spatial analyses showed NK cells preferentially clustering close to other NK cells with sparse CD3+ T and CD8+ T cells in range (P<0.0001). Additionally, CD3+ T and CD8+ T cells showed significantly greater co-localization with MHC-I+ cells, compared to NKp46+ NK cells (P<0.0001). Intratumoral NK cell subsets, including NKp46+ and CD56bright/dim NK cells, are prognostic in STS and localize closer to MHC-I- cells than they do to T cells or MHC-I+ cells. Although both NK and T cells are associated with improved survival in STS, their differential distribution in the TME based on MHC-I expression status reinforces inherent opposite but interconnected roles for these cells in anti-tumor surveillance.