Maria O. Hernandez

Kaposi sarcoma (KS) is defined by aberrant angiogenesis driven by Kaposi sarcoma herpesvirus (KSHV)–infected spindle cells with endothelial characteristics. KS research is hindered by rapid loss of KSHV infection upon explant culture of tumor cells. Here, we established KS patient-derived xenografts (PDXs) through orthotopic implantation of cutaneous KS biopsies into immunodeficient mice. KS tumors were maintained in 27 of 28 PDXs until the experimental end point. KSHV latency-associated nuclear antigen–positive (LANA ⁺ ) endothelial cells exhibited higher Ki-67 staining and increased density compared with their respective input biopsies. Spatial analysis of the PDXs revealed increased expression of viral transcripts from latent and lytic gene classes and enrichment in pathways of angiogenesis and endothelium development, similar to KS tumor biopsies. C-X-C chemokine receptor type 4 (CXCR4), a receptor for the inflammatory C-X-C motif chemokine ligand 12 (CXCL12), was more highly expressed in infected tumor cells than uninfected cells, suggesting a direct response to virus infection. Cells with fibroblast characteristics derived from PDXs were permissive for de novo KSHV infection, and one lineage produced CXCL12, which was also elevated in the sera of patients with KSHV-associated diseases compared with those of patients who had KS alone. Together, the reproducible expansion of KSHV-infected endothelial cells in PDXs from multiple donors and the similar recapitulation of molecular and pathologic features of KS support KS PDXs as a preclinical model for the discovery of pathogenic mechanisms and candidate therapeutics.

Marker genes used for annotating major cell types in single cell RNA sequencing analysis.

Antibody panel used in co-detection by indexing (CODEX) multiplexed immunofluorescence tissue imaging.

Patient demographics, genetic, and histopathology characteristics.

Additional SRC-enriched markers from single cell RNA sequencing analysis.

Leading edge analysis following GSEA demonstrating enriched pathways associated with ECM remodeling between SRC and EP.

Germline CDH1 loss-of-function mutations are causally linked to an increased lifetime risk of diffuse gastric cancer (DGC). Early, multifocal signet ring cell (SRC) lesions are ubiquitous among CDH1 variant carriers, yet only a subset of patients will develop advanced DGC. A multiomic analysis was performed to establish the molecular phenotype of early SRC lesions and how they differ from advanced DGC using 20 samples from human total gastrectomy specimens of germline CDH1 variant carriers. Spatial transcriptomic analysis demonstrated reduced CDH1 gene expression and increased expression of extracellular matrix remodeling in SRC lesions compared with unaffected adjacent gastric epithelium. Single-cell RNA sequencing revealed an SRC-enriched signature with markers REG1A, VIM, AQP5, PRR4, MUC6, and AGR2. Importantly, SRC lesions lacked alterations in known drivers of gastric cancer (TP53, ARID1A, and KRAS) and activation of associated signal transduction pathways. Advanced DGC demonstrated E-cadherin reexpression, somatic TP53 and ERBB3 mutations, and upregulated CTNNA1, MYC, and MET expression when compared with SRC lesions. Implications: The marked differences in the genomic and transcriptomic profiles of SRC lesions and advanced DGC support the consideration of SRC lesions as precancers in patients with germline CDH1 mutations.