# Therapeutic manipulation and spatial quantification of the tumor microenvironment in colorectal cancer

## TL;DR

The study identifies two main types of cancer-associated fibroblasts in colorectal cancer and shows how targeting TGFβ signaling can reshape the tumor environment to improve immune response.

## Contribution

A simplified framework for CAF classification and a method to measure therapeutic response through spatial metrics in CRC.

## Key findings

- TGFβ signaling drives transitions between PDGFRA+ and ACTA2+ fibroblast states.
- ALK5 inhibition shifts CAF composition and enhances T-cell presence.
- Multiscale spatial analysis detects stromal drug response without tumor shrinkage.

## Abstract

Colorectal cancer (CRC) is a complex ecosystem shaped by bidirectional interactions between epithelium and the tumor microenvironment, prominently mediated by TGFβ signaling. Cancer-associated fibroblasts (CAFs) are regulators of epithelial plasticity and immune cell recruitment; yet, their diversity has impacted translationally applicable spatial analysis. Here, we distil the fibroblast continuum into two overarching CAF populations that are largely transcriptomically distinct and are marked by PDGFRA+ and ACTA2+ expression, enabling robust spatial identification using single immunohistochemical markers. We show that TGFβ signaling drives dynamic transitions between these states. In a preclinical model, selective ALK5 inhibition remodels CAF composition in vivo, reconfiguring local immune neighborhoods and indirectly altering epithelial stem cell states. Finally, we demonstrate that multiscale spatial analysis provides a quantitative readout of stromal-immune-epithelial remodeling following therapy. These findings establish a simplified, translationally relevant CAF framework and highlight spatially resolved stromal dynamics as measurable indicators of therapeutic response in CRC.

•TGF-β drives transitions between PDGFRA+ and ACTA2+ fibroblast phenotypic states•ALK5 inhibition depletes ACTA2+ CAFs and expands PDGFRA+ fibroblasts•Fibroblast remodeling shifts neutrophil niches to T-cell-enriched niches•Multiscale spatial metrics detect stromal drug response without tumor shrinkage

TGF-β drives transitions between PDGFRA+ and ACTA2+ fibroblast phenotypic states

ALK5 inhibition depletes ACTA2+ CAFs and expands PDGFRA+ fibroblasts

Fibroblast remodeling shifts neutrophil niches to T-cell-enriched niches

Multiscale spatial metrics detect stromal drug response without tumor shrinkage

Health sciences; medicine; oncology; cancer