KLRK1 and Burkitt lymphoma: However, one study indicated that, while various flavonoids were tested, pre-treatment of Burkitt’s lymphoma cells with luteolin did not change levels of NKG2D ligands on tumor cells or the subsequent NK cell lytic activity against these cells, unlike naringenin, which enhanced NK cell cytolytic activity by increasing the expression of NKG2D ligands (56).