Spatially Distinct Reprogramming of the Tumor Microenvironment Based On Tumor Invasion in Diffuse-Type Gastric Cancers.

Abstract

Histologic features of diffuse-type gastric cancer indicate that the tumor microenvironment (TME) may substantially impact tumor invasiveness. However, cellular components and molecular features associated with cancer invasiveness in the TME of diffuse-type gastric cancers are poorly understood. We performed single-cell RNA-sequencing (scRNA-seq) using tissue samples from superficial and deep invasive layers of cancerous and paired normal tissues freshly harvested from five patients with diffuse-type gastric cancer. The scRNA-seq results were validated by immunohistochemistry (IHC) and duplex <i>in situ</i> hybridization (ISH) in formalin-fixed paraffin-embedded tissues. Seven major cell types were identified. Fibroblasts, endothelial cells, and myeloid cells were categorized as being enriched in the deep layers. Cell type-specific clustering further revealed that the superficial-to-deep layer transition is associated with enrichment in inflammatory endothelial cells and fibroblasts with upregulated <i>CCL2</i> transcripts. IHC and duplex ISH revealed the distribution of the major cell types and CCL2-expressing endothelial cells and fibroblasts, indicating tumor invasion. Elevation of CCL2 levels along the superficial-to-deep layer axis revealed the immunosuppressive immune cell subtypes that may contribute to tumor cell aggressiveness in the deep invasive layers of diffuse-type gastric cancer. The analyses of public datasets revealed the high-level coexpression of stromal cell-specific genes and that <i>CCL2</i> correlated with poor survival outcomes in patients with gastric cancer. This study reveals the spatial reprogramming of the TME that may underlie invasive tumor potential in diffuse-type gastric cancer. This TME profiling across tumor layers suggests new targets, such as CCL2, that can modify the TME to inhibit tumor progression in diffuse-type gastric cancer.<i>See related commentary by Huang and Brekken, p. 6284</i>.