25 Different subsets of carcinoma-associated fibroblasts promote oral carcinoma cell invasion by distinct mechanisms

Abstract

Bidirectional tumor–stroma interactions have tumor-promoting effects, and heterogeneity of carcinoma-associated fibroblasts (CAFs) has been showed, but its functional relevance for tumor development and invasion is still poorly understood. This study identified two CAF subtypes in oral squamous cell carcinoma (OSCC) based on transcriptome analysis. Approximately 40% of significantly up-regulated genes when CAFs were compared to normal fibroblasts (NFs) were transforming growth factor-β (TGF-β) targets, highlighting the crucial role of this factor in CAF activation. One subgroup had a transcriptome closer to NFs and thus was termed CAF-N; the other showed a more divergent gene expression pattern and was termed CAF-D. Both CAF subgroups supported significantly higher tumor take in NOD/SCID Ilγ2 deficient mice and deeper invasion of malignant keratinocytes than NFs or dysplasia-associated fibroblasts (DAF), but CAF-Ns supported a significantly deeper invasion and increased tumor formation than CAF-Ds. CAF-N were characterized by a secretome closer to NFs, included a significantly higher proportion of motile fibroblasts, and showed enhanced migration in response to TGF-β1. Migratory enhanced NFs (by TGF-β1-pretreated) induced invasive properties in transformed oral keratinocytes, while inhibition of CAF-N migration impaired invasion of malignant oral keratinocytes, showing the essential role for fibroblast motility in oral carcinoma invasion supported by CAF-Ns. In contrast, CAF-Ds synthesized significantly higher levels of TGF-β1, but contained only a low percentage of motile fibroblasts and did not respond to TGF-β1. CAF-Ds and TGF-β1 induced enhanced migration of malignant keratinocytes and increased expression of EMT markers. Taken together, these data shows that different subsets of CAFs promote tumor formation and carcinoma cell invasion by different mechanisms.