Colorectal cancer (CRC) shows strong heterogeneity in tumor microenvironment (TME) dynamics, but the mechanisms that shape epithelial–stromal crosstalk are still unclear. Here we focus on A-kinase anchor protein 12 (AKAP12) and Leiomodin 1 (LMOD1) and test a compartment-dependent model in which this program aligns with tight-junction features in epithelium but with a fibrotic, immune-suppressive program in stroma. Single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) were employed to profile gene expression patterns in CRC tissues. Immunohistochemistry (IHC) and multiplex immunofluorescence (mIF) validated protein expression and localization. Cell–cell communication analysis and trajectory inference were used to dissect spatial interaction networks. Functional experiments were employed to validate the role of the AKAP12-LMOD1 axis in CAFs in regulating ECM remodeling and antitumor immunity. AKAP12-LMOD1 exhibited a compartment-dependent pattern in CRC. In ACTA2⁻ epithelial regions, the epithelial AKAP12-LMOD1 signal was lower in tumors than in matched normal epithelium and showed a positive association with the tight-junction marker CLDN1. In ACTA2⁺ stromal regions, AKAP12-LMOD1 was enriched, positively associated with the gap-junction marker GJA4, and higher in tumor stroma than matched normal stroma. In a CAF–macrophage non-contact co-culture model, AKAP12 overexpression supported CAF activation and collagen deposition, and shifted macrophages toward an M2-like phenotype; LMOD1 knockdown or SB-431542 partially reversed these effects. Stromal AKAP12-LMOD1-enriched regions also aligned with fibrosis- and M2-related features, and these stromal patterns were prominent in mucinous carcinoma. This study defines AKAP12-LMOD1 as a compartment-dependent stromal program in CRC that links ACTA2⁺ stroma to gap-junction features, fibrosis, and M2-like macrophage polarization, while showing a distinct epithelial association with tight-junction features. These findings support a stroma-centered working model for AKAP12–LMOD1 in CRC microenvironmental heterogeneity and suggest that stromal modulation of this program, together with targeting fibrosis and M2-like immune features, may be explored as hypothesis-level, subtype-oriented therapeutic directions in stroma-rich CRC.
Ye et al. (Mon,) studied this question.