GJA4 expressed on cancer associated fibroblasts (CAFs)-A 'promoter' of the mesenchymal phenotype

Area of Science:

• Oncology
• Cancer Biology
• Molecular Medicine

Background:

• Colorectal cancer (CRC) is a major global health challenge.
• Connexin 37 (Cx37), encoded by gap junction protein alpha 4 (GJA4), is implicated in CRC progression, epithelial-mesenchymal transition (EMT), and the tumor immune microenvironment.
• The precise mechanisms of GJA4's role in tumor stroma malignancy remain unclear.

Purpose of the Study:

• To elucidate the mechanism by which GJA4 in tumor stroma promotes colorectal cancer.
• To investigate the role of GJA4 in fibroblast activation and EMT.
• To explore the interaction of GJA4 with the tumor immune microenvironment, specifically M2 macrophages.

Main Methods:

• Hematoxylin-eosin (HE) and immunohistochemical (IHC) staining for GJA4 expression and localization.
• Single-cell analysis, spatial transcriptomics, and immunofluorescence (IF) for cellular and spatial profiling.
• Functional assays including wound healing, Transwell, and Cell Counting Kit-8 (CCK8) for cell behavior.
• Western blotting (WB), Sirius red staining, and in vivo experiments to assess molecular mechanisms and tumor progression.

Main Results:

• GJA4 expressed on fibroblasts promotes CRC via fibroblast activation and EMT through a fibroblast-dependent pathway.
• GJA4 collaborates with M2 macrophages to impede T cell infiltration by fostering an immune-excluded desmoplastic barrier.
• GJA4 expression correlates significantly with pathological staging and D-dimer levels in CRC patients.

Conclusions:

• GJA4 on fibroblasts promotes a tumor mesenchymal phenotype in CRC.
• The interplay between GJA4+ fibroblasts and M2 macrophages presents a potential therapeutic target for improving cancer immunotherapy outcomes.