Lipids can affect the relevant anti-tumor functions of NK cells through the lipid antigen repertoire and the regulation of CD1d expression [213], PPAR-γ can up-regulate CD1d to promote the lipid metabolism of NK cells, however, recently some researchers found that lipid accumulation may inhibit this expression process, leading to suppression of the normal anti-tumor function of NK cells [223]. The gene discussed is CD1D; the disease is neoplasm.