Spatial heterogeneity, stromal phenotypes, and therapeutic vulnerabilities in colorectal cancer peritoneal metastasis

Purpose: Peritoneal metastases (PM) in colorectal cancer (CRC) portend a poor prognosis. We sought to elucidate molecular features differentiating primary tumors (PTs) from PMs and actionable targets facilitating transcoelomic dissemination and progression. Experimental Design: We performed multi-omic profiling of 227 samples from 136 patients, including 56 primary tumor (PT) and 120 synchronous PMs comprising 34 matched PT-PM pairs. Whole exome, and bulk RNA-seq analysis was conducted to identify underlying genomic aberrations and transcriptomic differences between primary and peritoneal lesions. We spatially characterized the microenvironment of tumor-stroma compartments and studied the roles of stromal phenotypes in promulgating tumorigenesis. Results: Whole exome sequencing found genomic alterations and clonality patterns between PTs and PMs remain broadly similar. Transcriptomic profiles however, suggest a transition as tumors reach the peritoneum towards a more mesenchymal tumor profile and fibrotic tumor microenvironment. Applying spatial profiling, we identify a fibro-collagenous and immune-infiltrated stromal phenotype (stromal cluster [SC] 2) characterized by increased cancer-associated fibroblasts, memory B cells, M2 macrophages and T-cell exhaustion. These findings were orthogonally validated by multiplex immunohistochemistry. Patients with SC2 stroma had poorer survival and were characterized by high SERPINE-1 (PAI-1) expression. PM in patients with SC2 stroma were associated with enriched oncogenic pathways such as TGF-β. PAI-1 inhibition of CRC PM cell-lines with a novel biologic demonstrated reduced IL2-STAT5 and TGF-β pathways and cell death. Conclusions: Our findings unveil distinctive and actionable molecular signatures, offering deeper insights into the intricate crosstalk between tumor cells and stromal microenvironments enabling PM in CRC.