Fibroblast dynamics in colorectal cancer: stability, plasticity, and novel markers.

Colorectal cancer (CRC) is one of the most commonly diagnosed and globally spread malignant diseases. Cancer-associated fibroblasts (CAFs) are key architects of the tumor microenvironment, yet their origin, stability, and interconvertibility remain poorly understood. Using transcriptomic profiling of fibroblasts from colorectal cancer (CRC) patients, we identify highly expressed (HEX) markers that define fibroblast subpopulations and uncover mechanisms governing their plasticity. We find that ADH1B marks normal colon-associated fibroblasts (NAFs), which consist of PI16-NAFs and ADAMDEC1-NAFs. ITGA3 delineates the total CAF population, which comprises myofibroblastic CAFs (myCAFs), whose characterizing markers were associated with poor prognosis and proteolytic inflammatory CAFs (piCAFs), characterized by markers not associated with prognosis. An AGT/TGM2-expressing fibroblast subset is present in both healthy and tumor tissues, suggesting alternative trajectories to the classical NAF-to-CAF transition model. While PI16-NAFs, AGT/TGM2-fibroblasts, and myCAFs maintain stable identities in long-term culture, the ADAMDEC1-NAF and piCAF phenotypes are lost in vitro. ITGA3-CAFs demonstrate dynamic plasticity, with TGF-β stably inducing myCAF formation and TNF-α or inhibition of DNA methylation promoting transient piCAF emergence. These findings redefine fibroblast heterogeneity in CRC and reveal a coexisting stable and plastic fibroblast network that may be amenable to modulation and provides a framework for future functional and translational studies. We identified highly expressed markers (HEX markers) to distinguish CAFs, NAFs and corresponding subpopulations in CRC. ADH1B characterized NAFs, which consisted of stable (solid outline) PI16-NAFs and unstable (dashed outline) ADAMDEC1-NAFs. ITGA3 identified CAFs consisting of stable myCAFs associated with poor prognosis and unstable piCAFs not associated with prognosis. AGT/TGM2 fibroblasts did not express ADH1B or ITGA3, were stable in culture and could be detected in both healthy colon and CRC. Treatment of PI16-NAFs with LPS or IFN-γ induced ADAMDEC1-NAFs, TGF-β the formation of myCAFs, while treatment with TNF-α led to the formation of piCAFs. Reduced DNA methylation converted myCAFs and PI16-NAFs into piCAFs.