Diminished CD68+ Cancer-Associated Fibroblast Subset Induces Regulatory T-Cell (Treg) Infiltration and Predicts Poor Prognosis of Oral Squamous Cell Carcinoma Patients

Although cancer-associated fibroblasts (CAFs) are crucial stromal cells, characterizing their heterogeneity is far from complete. This study reports 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 the CD68(+) CAF subset of OSCC (n=104) was determined by CD68/actin alpha 2, smooth muscle (ACTA2+; alpha-SMA) immunohistochemistry of serial sections. The CD68(+) alpha-SMA(+) CAF subsetwas elevated fromdysplasia to OSCC. Moreover, although both the tumor center and invasive front harbor an abundant CD68(+) CAF subset, patients with low-CD68(+) CAFs in the tumor center showed more recurrence after operation and shorter survival time, indicating the different function of CD68(+) CAFs in tumor initiation and progression. Functional analysis in the OSCC-CAF co-culture systemfound knockdown of CD68 did not change the phenotype of CAFs, tumor growth, or migration. Unexpectedly, low-CD68(+) CAFs were associated with aberrant immune balance. A high proportion of tumor-supportive Tregs was 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 Treg recruitment. Thus, up-regulated CD68(+) fibroblasts participate in tumor initiation, but the lowCD68(+) CAF subset in OSCC is conducive to regulatory T-cell (Treg) recruitment in the tumormicroenvironment and contribute to poor prognosis of OSCC patients.