Consistent with the result with Pld2−/− mice (Fig. 1a,b), growth of the tumor produced by B16 melanoma cells in Pld2−/− mice grafted with Pld2−/− bone marrow cells (rKOdKO) was significantly enhanced compared with that in WT mice grafted with control bone marrow cells (rWTdWT) (Fig. 3b). The gene discussed is PLD2; the disease is melanoma.