Immunosuppressive Environment in Basal Cell Carcinoma: The Role of Regulatory T Cells

Abstract

Interaction between tumour survival tactics and anti-tumour immune response is a major determinant for cancer growth. Regulatory T cells (T-regs) contribute to tumour immune escape, but their role in basal cell carcinoma (BCC) is not understood. The fraction of T-regs among T cells was analysed by immunohistochemistry followed by automated image analysis in facial BCC, peritumoural skin and normal, buttock skin. Quantitative real-time PCR (qRT-PCR) was performed for Foxp3 and cytokines involved in T-reg attraction and T-cell activation. T-regs comprised 45% of CD4-cells surrounding BCC. Foxp3 was highly expressed in BCC, but absent in buttock skin. Unexpectedly, expression of Foxp3 was increased in peritumoural skin, with the FoxP3/CD3 fractions exceeding those of BCC (p = 0.0065). Transforming growth factor (TGF)-β and T-reg chemokine expression was increased in BCC and peritumoural skin, but not in buttock skin, with expression levels correlating with Foxp3. T-regs are abundantly present both in BCC and in peritumoural skin, mediating an immunosuppressed microenvironment permissive for skin cancer