To investigate whether the cytolytic activity of NK cells is affected by the thyroid cancer microenvironment, the cells were cultured in the presence or absence of supernatants from papillary (TPC-1) and anaplastic (FRO and 850-5C) thyroid cancer cell cultures along with human IL-2 for 48 h; the cytotoxicity of NK cells was measured against K562 cells. This evidence concerns the gene IL2 and thyroid gland carcinoma.