POTENTIAL OF THE UTILIZATION OF NK CELLS EXTRACTED FROM PERFUSATES OF DONOR GRAFT LIVERS OR HOST CIRRHOTIC LIVERS AS AN ADJUVANT ANTICANCER THERAPY AFTER LIVER TRANSPLANTATION FOR PATIENTS WITH HEPATOCELLULAR CARCINOMA.:

P1041 Many studies have demonstrated that liver NK cells have higher levels of NK activity against infected or transformed targets than do spleen or peripheral blood (PB) NK cells. The highly activity levels are thought to be due to the elevated expression levels of TNF family members, including Fas ligand, and the increased production of perforin, granzymes and cytokines by these cells. Among the TNF family members, TNF-related apoptosis-inducing ligand (TRAIL) has recently been shown to be critical for NK cell-mediated anti-tumor function. Since TRAIL is constitutively expressed by NK cells in the liver unlike in other tissues in mice, this molecule might be involved in liver NK cell-mediated malignant cell killing. We investigated the potential role of PB and liver NK cells in the protection against recurrence after liver transplantation in patients with hepatocellular carcinoma. PB mononuclear cell (PBMCs) and liver mononuclear cells (LMNCs) were obtained from both donors and recipients in the living-related donor liver transplantation (LDLTs) (1-haprotype identical combination). LMNCs were extracted from liver perfusates. The proportion of NK cells in LMNCs was significantly larger than that in PBMCs (46.9±6.0, 25.7±6.8%, respectively, n =8). The total number of NK cells in LMNCs from the donor graft was significantly larger than that in LMNCs from the host cirrhosis liver (129±32x106, 70±25x106 cells, respectively). Inconsistent with the results of mouse studies, freshly isolated human liver NK cells did not express TRAIL on their surfaces. By stimulation with either IL-2 or IL-12 in vitro, however, the expression of TRAIL was significantly induced on liver NK cells but not on PB NK cells (IL-2 induced TRAIL more efficiently than did IL-12). Such TRAIL expression was more remarkable on normal graft liver NK cells than that on host cirrhotic liver NK cells. We have previously shown that the majority of TRAIL+ liver NK cells lack expression of Ly-49 inhibitory receptors recognizing self-major histocompatibility complex class I in mice, indicating a propensity to targeting self-hepatocytes. Inconsistent with this fact, expression of Killing Inhibitory Receptors (KIR) (CD94, CD158a and CD158b) increased on liver NK cells by IL-2 stimulation in parallel with TRAIL expression. This might be a compensatory mechanism to protect self-class I-expressing cells from activated NK cell-mediated killing. The NK cytotoxicity against HEPG2, a hepatoma cell line, in both LMNCs from the normal graft livers and host cirrhotic livers was markedly increased by IL-2 stimulation (58.3±28.6, 55.2±22.7%, respectively), but the cytotoxicity against host-PB lymphocytes was not increased. The NK cytotoxicity against HEPG2 in PBMCs was significantly lower even after IL-2 stimulation than that in LMNCs. These findings indicate the possibility of adjuvant anticancer therapy by administration of IL-2-stimulated NK cells extracted from perfusates of either donor graft livers or host cirrhotic livers into patients with hepatocellular carcinoma after LDLT.