RESUMEN
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.
RESUMEN
Branching and processing of N-glycans in the medial-Golgi rely both on the transport of the donor UDP-N-acetylglucosamine (UDP-GlcNAc) to the Golgi lumen by the SLC35A3 nucleotide sugar transporter (NST) as well as on the addition of the GlcNAc residue to terminal mannoses in nascent N-glycans by several linkage-specific N-acetyl-glucosaminyltransferases (MGAT1-MGAT5). Previous data indicate that the MGATs and NSTs both form higher order assemblies in the Golgi membranes. Here, we investigate their specific and mutual interactions using high-throughput FRET- and BiFC-based interaction screens. We show that MGAT1, MGAT2, MGAT3, MGAT4B (but not MGAT5) and Golgi alpha-mannosidase IIX (MAN2A2) form several distinct molecular assemblies with each other and that the MAN2A2 acts as a central hub for the interactions. Similar assemblies were also detected between the NSTs SLC35A2, SLC35A3, and SLC35A4. Using in vivo BiFC-based FRET interaction screens, we also identified novel ternary complexes between the MGATs themselves or between the MGATs and the NSTs. These findings suggest that the MGATs and the NSTs self-assemble into multi-enzyme/multi-transporter complexes in the Golgi membranes in vivo to facilitate efficient synthesis of complex N-glycans.
