Spatial transcriptome mapping of the desmoplastic growth pattern of colorectal liver metastases by in situ sequencing reveals a biologically relevant zonation of the desmoplastic rim

Abstract Purpose: We describe the fibrotic rim formed in the desmoplastic growth pattern (DHGP) of colorectal cancer liver metastasis (CLM) using in situ sequencing (ISS). The origin of the desmoplastic rim is still a matter of debate, and the detailed cellular organization has not yet been fully elucidated. Understanding the biology of the DHGP in CLM can explore targeted treatment to improve survival. Experimental design: We used ISS, targeting 150 genes, to characterize the desmoplastic rim by unsupervised clustering of gene co-expression patterns. The cohort comprised 10 chemo-naïve liver metastasis resection samples with a DHGP. Results: Unsupervised clustering of spatially mapped genes revealed molecular and cellular diversity within the desmoplastic rim. We confirmed the presence of the ductular reaction and cancer-associated fibroblasts. Importantly, we discovered angiogenesis and outer and inner zonation in the rim, characterized by NGFR and POSTN expression. Conclusions: ISS enabled the analysis of the cellular organization of the fibrous rim surrounding CLM with a DHGP and suggests a transition from the outer part of the rim, with nonspecific liver injury response, into the inner part, with gene expression indicating collagen synthesis and extracellular matrix remodeling influenced by the interaction with cancer cells, creating a cancer cell supportive environment. Moreover, we found angiogenic processes in the rim. Our results provide a potential explanation of the origin of the rim in DHGP and lead to exploring novel targeted treatments for patients with CLM to improve survival.