Diminished CD68 cancer-associated fibroblasts subset induces Tregs infiltration and predicts poor prognosis of oral squamous cell carcinoma patients.

Although cancer-associated fibroblasts (CAFs) are the most crucial stromal cells, characterizing their heterogeneity is far from complete. Based on our previously identified transcriptional profile of CAFs, we here reported a novel subset of CAFs in oral squamous cell carcinoma (OSCC), which positively expressed CD68, the classic marker of macrophages. The spatial and temporal distribution of CD68 CAFs subset of OSCC (n=104) was determined by CD68/α-SMA immunohistochemistry of serial sections. We found that CD68 α-SMA CAFs subset was elevated from dysplasia to OSCC. Moreover, although both tumor center and invasive front harbor abundant CD68CAFs subset, patients with low CD68 CAFs in tumor center showed more postoperative recurrence and shorter survival time, indicating the different function of CD68 CAFs in tumor initiation and progression. Functional analysis in OSCC-CAFs co-culture system found that knockdown of CD68 did not change the phenotype of CAFs, tumor growth or migration. Unexpectedly, low CD68 CAFs was associated with aberrant immune balance. High proportion of tumor-supportive Tregs were found in patients with low CD68 CAFs. Mechanistically, knockdown of CD68 in CAFs contributed to the up-regulation of chemokine CCL17 and CCL22 of tumor cells to enhance Tregs recruitment. Thus, up-regulated CD68 fibroblasts participate in tumor initiation but low CD68 CAFs subset in OSCC is conducive to Tregs recruitment in tumor microenvironment, and contribute to poor prognosis of OSCC patients.