Comparison of immunosuppressive and immunomodulatory cells in keratoacanthoma and cutaneous squamous cell carcinoma

An imbalance of immunosuppressive and immunomodulatory cells plays an important role in inhibiting the anti-tumour immune response in a tumour-bearing host. Among such cells, regulatory T cells (Tregs), together with immunosuppressive macrophages, such as CD163⁺ M2 macrophages, play roles in maintaining the tumour microenvironment. In contrast, interleukin-27 (IL-27) induces STAT1 and STAT3 activation, thus resulting in the enhancement of naive CD4 T-cell proliferation, the promotion of early Th1 differentiation, and the induction of the anti-tumour immune response. The purpose of this study was to investigate the involvement of immunosuppressive cells, such as Tregs and CD163⁺ macrophages, as well as immunomodulatory cells (i.e. IL-27-producing cells) in keratoacanthoma (KA) and invasive squamous cell carcinoma (SCC). We also examined the presence of CD3⁺ Foxp3⁺ Tregs cells in lesional skin from 10 patients with KA and 18 patients with SCC. Increased numbers of CD3⁺ Foxp3⁺ Tregs were observed in SCC compared with KA. In parallel with Tregs, higher numbers of CD163⁺ macrophages and MMP-9⁺ cells were detected only in SCC. In contrast, IL-27-producing cells were increased only in KA. In addition, the expression of pSTAT1 on tumour cells was observed only in KA. These findings suggest that the induction of immunosuppressive and immunomodulatory cells differs between KA and SCC.