The Fibroblast Problem: Why Liver Cancer Drugs So Often Fail

Hepatocellular carcinoma, the most common form of liver cancer, has an uncomfortable secret. The drugs designed to defeat it—tyrosine kinase inhibitors such as sorafenib and lenvatinib, and immune checkpoint inhibitors that unleash the immune system—work for some patients and fail for many others, and oncologists have struggled to explain why. A new review published in Medical Oncology argues that a long-underappreciated cast member of the tumor may hold much of the answer: the cancer-associated fibroblast, a cell that is not itself malignant but that can be co-opted by the tumor into acting as its bodyguard, pharmacist, and shield all at once.

The review, led by Tao Huang and Qiaoying Li of Southwest Medical University in Sichuan, China, together with colleagues, takes an unusually rigorous approach to a field notorious for loose claims. Rather than accepting every published association between fibroblasts and drug failure, the authors graded the evidence according to strict criteria: whether a defined drug was actually being administered, whether treatment-related outcomes were measured, and—critically—whether blocking the fibroblast pathway functionally restored drug sensitivity in experiments. Only mechanisms passing these tests earn the label of true resistance mechanisms. The distinction matters, because fibroblasts drive tumor progression in many ways, and progression is not the same thing as resistance to therapy.

Cancer-associated fibroblasts arise largely from hepatic stellate cells, the liver’s resident vitamin A-storing cells that normally lie dormant until injury wakes them. In chronic liver disease they become the workhorses of fibrosis, laying down scar tissue. When a tumor takes root in this scarred landscape, the activated fibroblasts multiply and diversify into subtypes with very different personalities: inflammatory fibroblasts that pump out signaling molecules, myofibroblastic fibroblasts that build dense extracellular matrix, and even antigen-presenting fibroblasts that can interact directly with immune cells. Single-cell and spatial transcriptomic studies have mapped these populations in hepatocellular carcinoma in increasing detail, and the picture that emerges is of a tumor wrapped in a living, communicating stroma.

The most convincing resistance story in the review concerns a fibroblast-secreted protein called SPP1, also known as osteopontin. When patients receive sorafenib or lenvatinib, fibroblasts respond by secreting SPP1, which binds integrins on the surface of tumor cells and activates a bypass signaling route through protein kinase C alpha. In effect, the drug blocks the main growth pathway while the fibroblasts quietly open a side door. Experiments in which SPP1 was knocked down genetically or blocked pharmacologically restored the tumor cells’ sensitivity to the kinase inhibitors, satisfying the review’s strictest evidentiary standard. This is no longer a correlation; it is a mechanism with a demonstrated rescue experiment behind it.

A second well-supported pathway involves the chemokine CXCL12. Fibroblast-derived CXCL12 signals through its receptor CXCR4 on hepatocellular carcinoma cells, triggering upregulation of a molecule called FOLR1, the folate receptor 1. The result is a reduction in the apoptosis—the programmed cell death—that sorafenib is supposed to induce. Independent work using quantitative proteomics had already implicated FOLR1 in sorafenib resistance through activation of autophagy, the cellular recycling program that helps stressed cancer cells survive. When researchers interfered with the CXCL12–CXCR4 axis, including with the CXCR4 antagonist plerixafor, sorafenib’s killing power returned.

The third mechanistically resolved pathway is perhaps the most elegant. Fibroblasts deposit fibronectin bearing an extra domain A, an embryonic splice variant of the matrix protein that is largely absent from healthy adult liver but abundant in tumors and fibrotic tissue. This oncofetal form of fibronectin, long recognized as a molecular marker of hepatocellular carcinoma, appears to signal through the innate immune receptor Toll-like receptor 4 on tumor cells, activating the transcription factor NF-κB and the metabolic enzyme SHMT1. The consequence is a shift in redox metabolism: the cancer cells adapt to the oxidative stress that sorafenib generates and simply keep going. Blocking this axis restores drug sensitivity, completing the causal chain from fibroblast product to receptor to transcription factor to metabolic enzyme to survival.

When the review turns to immunotherapy, the evidence becomes more circumstantial, and the authors are careful to say so. Periostin-positive fibroblasts, a stromal subset identified in patient tumors, are associated with recruitment of macrophages through the interleukin-6 signaling pathway, elevated SPP1 expression within those macrophages, physical exclusion of immune cells from the tumor, and reduced responsiveness to immune checkpoint inhibitors. The proposed chain of events is coherent: fibroblasts build a stromal-immune barrier that keeps cytotoxic T cells at arm’s length, so the checkpoint drug has no targets to reactivate. But unlike the tyrosine kinase inhibitor stories, no experiment has yet shown that selectively reversing this specific periostin-positive fibroblast program restores immunotherapy responses in hepatocellular carcinoma. The association is strong; the causal proof is pending.

That gap reflects a broader and sobering lesson from the fibroblast field. In pancreatic cancer, the classic cautionary tale, researchers depleted carcinoma-associated fibroblasts in mouse models and expected tumors to shrink. Instead, the tumors became more aggressive and the animals died faster, revealing that some fibroblasts restrain cancer rather than feed it. The review emphasizes that fibroblast heterogeneity makes blanket depletion strategies dangerous: eliminating the wrong subtype could dismantle the stromal barriers that contain the tumor while sparing the very cells that drive resistance. The field’s central question has accordingly shifted from whether to target fibroblasts to which ones, when, and how.

Translational efforts are already adapting to this nuance. Nanoparticle systems have been engineered to deliver small interfering RNA directly to fibroblasts, silencing stromal targets such as microfibril-associated protein 5 in antistromal therapy for hepatocellular carcinoma. Other platforms exploit fibroblast biology for drug delivery: lipid nanoparticles that transform in size in response to fibroblast activation protein activity, releasing their payload deep within fibrotic tumor tissue, and dual-targeting nanoparticles that simultaneously remodel the stroma and reprogram immune cells. CXCR4 antagonist-loaded nanoparticles have been shown to reprogram the tumor microenvironment and enhance immunotherapy in preclinical models. Even diagnostic imaging is joining in, with fibroblast activation protein-targeted PET tracers now being tested to monitor liver fibrosis and tumor burden, potentially allowing clinicians to stratify patients by the stromal character of their tumors before choosing a therapy.

The review’s authors, funded by the National Natural Science Foundation of China, frame their conclusions as a call for discipline in a rapidly growing literature. The fibroblast field has generated an abundance of associations—extracellular vesicles carrying resistance-promoting microRNAs, exosomal signals that decrease sorafenib sensitivity, fibroblast-derived growth factors that sustain tumor cells through metabolic crosstalk—but only a handful of mechanisms in hepatocellular carcinoma have been validated with the combination of defined drug exposure, treatment outcomes, and functional rescue. SPP1, CXCL12–FOLR1, and fibronectin extra domain A now stand on the firmest ground, each with a plausible route to clinical intervention. For patients whose liver cancers stop responding to the current arsenal, the hope is that the next generation of treatments will not merely attack the tumor harder, but will disarm the cellular accomplices that have been quietly protecting it all along.

Subject of Research: Cancer-associated fibroblast mechanisms of therapeutic resistance in hepatocellular carcinoma

Article Title: Cancer-associated fibroblasts in therapeutic resistance of hepatocellular carcinoma: evidence, mechanisms, and translational implications

Article References: Huang, T., Li, Q., Yu, Z., Wu, Z., Cheng, H., Zhang, X., Yang, L., & Wang, S. (2026). Cancer-associated fibroblasts in therapeutic resistance of hepatocellular carcinoma: evidence, mechanisms, and translational implications. Medical Oncology, 43(11), Article 314. https://doi.org/10.1007/s12032-026-03435-y

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03435-y

Keywords: hepatocellular carcinoma, cancer-associated fibroblasts, therapeutic resistance, tyrosine kinase inhibitors, immune checkpoint inhibitors, sorafenib, lenvatinib, SPP1, CXCL12, fibronectin extra domain A, tumor microenvironment, spatial transcriptomics