Staphylococcus aureus alpha-toxin inhibits CD8(+) T cell-mediated killing of cancer cells in cutaneous T-cell lymphoma

Staphylococcus aureus and its toxins have been linked to disease progression and mortality in advanced stages of cutaneous T-cell lymphoma (CTCL). CD8(+) T cells play a crucial role in anti-cancer responses and high CD8(+) T cell numbers in tumor lesions are associated with a favorable prognosis in CTCL. Here, we show that CD8(+) T cells from both healthy donors and Sézary syndrome patients are highly susceptible to cell death induced by Staphylococcal alpha-toxin, whereas malignant T cells are not. Importantly, alpha-toxin almost completely blocks cytotoxic killing of CTCL tumor cells by peptide-specific CD8(+) T cells, leading to their escape from induced cell death and continued proliferation. These findings suggest that alpha-toxin may favor the persistence of malignant CTCL cells in vivo by inhibiting CD8(+) T cell cytotoxicity. Thus, we propose a novel mechanism by which colonization with Staphylococcus aureus may contribute to cancer immune evasion and disease progression in CTCL.