CD147+ Cancer-Associated Fibroblasts Promote PD-L1 Expression in Hepatocellular Carcinoma via TIMP2/MMP2/IL-6 Signaling.
TL;DR
This study delineates a novel CAF-driven immunosuppressive pathway in HCC, where CD147+ CAFs enhance tumor cell PD-L1 expression and susceptibility to immune checkpoint blockade via a TIMP2/MMP2/IL-6 axis.
Abstract
Background
Targeting CD147 on hepatocellular carcinoma (HCC) cells has demonstrated therapeutic efficacy. Cancer-associated fibroblasts (CAFs) have been identified as critical components of the tumor microenvironment. The role of CD147 in CAFs is still unclear, and this study aims to explore its function.
Methods
We analyzed single-cell RNA-seq data to identify CD147 expression in CAFs. Flow cytometry and multiplex immunohistochemistry (mIHC) were used to validate protein levels. CD147 function was assessed via shRNA/overexpression. Protein interactions were examined by molecular docking and co-immunoprecipitation (Co-IP). Organoid co-culture system was established to study tumor-immune interactions.
Results
Single-cell sequencing and mIHC analyses have confirmed the presence of CD147+CAFs within tumor and adjacent tissues, with tumor-derived CAFs exhibiting elevated CD147 transcript levels. The proportion of CD147+ CAFs varied among patients and demonstrated no significant correlation with CD147 expression in HCC cells. Functionally, CD147+ CAFs secreted higher levels of IL-6 compared to CD147- counterparts. We elucidated a mechanism wherein CD147 on CAFs competitively binds to the tissue inhibitor of metalloproteinase 2 (TIMP2), thereby diminishing TIMP2-mediated inhibition of matrix metalloproteinase 2 (MMP2). Free MMP2 enhances IL-6 secretion via the integrin α5β1 signaling pathway. IL-6 subsequently upregulates PD-L1 expression on HCC cells. This phenomenon was validated both in vitro and organoid co-culture model, where a higher burden of CD147+ CAFs correlated with increased levels of IL-6 and PD-L1.
Conclusions
Our study delineates a novel CAF-driven immunosuppressive pathway in HCC, where CD147+ CAFs enhance tumor cell PD-L1 expression and susceptibility to immune checkpoint blockade via a TIMP2/MMP2/IL-6 axis. CLINICAL
Significance
CD147 has been primarily viewed as a therapeutic marker on HCC cells and has supported the development of CD147-targeted treatment strategies. This study shows that CD147 is also expressed in CAFs and functions as an independent regulator of the immune microenvironment by promoting IL 6 secretion and tumor PD-L1 upregulation. Importantly, CD147 expression in CAFs is not correlated with its expression in tumor cells. These findings suggest that evaluation of CD147 in both tumor and stromal compartments may improve patient stratification and may identify additional patients who could potentially benefit from CD147-targeted or combination immunotherapy approaches.