Proinflammation represents a pathophysiological state on the early stage of a number of diseases, especially the infectious and immunological ones. In recent years, proinflammation has attracted much attention, and the term "proinflammation factors" appears frequently in the literature. While investigating leukemia and leukemic cells from the angle of "proinflammation state", we got some intriguing findings, e.g. we detected the significantly elevated expression of proinflammation factor IL-18 in patients with acute myeloid leukemia (AML), which could up-regulate matrix metalloproteinases (MMP) and specific tissue inhibitors (TIMPs). The increased MMP may play a role in the aggressiveness of myeloid leukemic cells, and be associated with a poor prognosis. This phenomenon reflects an ignored aspect of leukemia. Investigations from the angle of "proinflammation state" have broaden the fields of tumor and leukemia study.