Cancer-associated fibroblasts in the tumor microenvironment of tongue carcinoma is a heterogeneous cell population

Objectives: To examine different immunophenotypes of cancer-associated fibroblasts (CAFs) in tongue squamous cell carcinoma (TSCC) and to investigate how they related to clinical outcomes. Methods: Serial sections from 54 cases of TSCC were immunohistochemically stained with α-smooth muscle actin (αSMA, CAF marker) to determine CAF density, and double-immunostained with αSMA combined with CD80 and CD86 (myeloid/monocytic-derived cell markers), Nanog (mesenchymal stem cell marker) and CD133 (hematopoietic/endothelial stem cell marker). Density of cells co-expressing these marker combinations was semi-quantitatively assessed in 5 randomly selected high power fields within the tumor area and scored as 1 – one-to-five stained cells in each field, 2 – more than 5 stained cells in each field; any finding less than score 1, was allocated a score of 0. Results: There were 26 CAF-poor, 16 CAF-rich and 12 CAF-intermediated cases. CD86⁺αSMA⁺ cells were the most frequent (80.4%) followed by CD80⁺αSMA⁺ (72%) and Nanog⁺αSMA⁺ cells (56%). The CD133⁺αSMA⁺ phenotype was found only in association with blood vessels. High density of αSMA⁺ CAFs was associated with disease recurrence and poor survival (p < 0.05). Increased density of CD86⁺αSMA⁺ cells was significantly associated with CAF-rich tumors and with poor survival (p < 0.05). Conclusion: In TSCC, CAFs demonstrate heterogeneous and overlapping phenotypes with the myeloid/monocytic type being the most frequent and having an impact on the clinical outcomes. Further studies are needed in order to further characterize CAF phenotypes in carcinomas of various oral sites, as this may open new frontiers for personalized medicine.