Influence of hypoxia on the Cytokine profile of head and neck tumor cell lines and on the proliferation behavior of CD8+T cells

Hypoxic tumor cells in head and neck squamous cell carcinoma (HNSCC) are able to evade immune surveillance by suppressing the function of cytotoxic (CD8+) T cells or activating immunosuppressive cell populations. The mechanisms are poorly understood. The aim of the work was to investigate the influence of hypoxia on the cytokine profile of four HNSCC cell lines as well as the influence of hypoxic preconditioned medium on the proliferation behavior of CD8+T cells. The cytokine profile was evaluated qualitatively (dot blot) and quantitatively (ELISA, multiplex FACS) in the media supernatants of the four HNSCC cell lines FaDu, Cal33, HNO210 and SCC-4 in hypoxia and normoxia. CD8+T cells from donor blood were cultured in the FaDu media supernatants and their proliferation behavior was compared using flow cytometry (CFSE). Proliferation and cytokine changes showed differences between the cell lines and examination methods examined. Interleukin-6 was significantly higher in the FaDu supernatants under hypoxia after 24 and 48 h than in the normoxia control. CD8+T cells cultured with hypoxia-FaDu supernatants showed no differences in their proliferation compared to the negative control (p=0.96). Differences in cytokine secretion could be due to the individual behavior of the tumor cell lines at the biological level. Induction of immunomodulators such as IL-6, as described here in FaDu cells, is known to occur in the hypoxic tumor microenvironment. It is possible that distinct tumor cell lines are differently competent to induce such immune modulation depending on their origin. Whether this corresponds to the situation in vivo is an important question for further studies.