Together, these findings indicate that V␣14͞V␤8.2 is a unique antigen receptor for NKT cells but not for conventional T cells. Because V␣14 NKT cell development was inhibited largely in mice that lack the MHC class I-like molecule CD1d, positive selection of V␣14-expressing immature NKT cells requires CD1d expression (14,15). Recently, it has been shown that glycolipid, ␣-galactosylceramide (␣-GalCer), and glycosylphosphatidylinositol-anchored proteins can be presented by murine CD1d (13, 16). Subsequently, it was demonstrated that NKT cells can recognize cellular lipids or purified phospholipids distinct from ␣-GalCer (17).Although physiological functions of NKT cells remain obscure, some studies have suggested that NKT cells can control autoimmune diseases (18-21) and Th1͞Th2 cell development Here, we have evaluated the role of V␣14 NKT cells in allograft rejection and tolerance by using a murine model of transplantation. We found that V␣14 NKT cells play a critical role in the induction of vascularized cardiac allograft tolerance by blockade of lymphocyte function-associated antigen-1 (LFA-1)͞intercellular adhesion molecule-1 (ICAM-1) or CD28͞B7 interactions. Possible mechanisms for the tolerogenic function of V␣14 NKT cells are examined. Materials and Methods mAbs and Reagents.Hybridomas producing anti-LFA-1 and anti-ICAM-1 mAbs (KBA and KAT-1, respectively) were described previously (32, 33). Hybridomas producing anti-B7-1 and anti-B7-2 mAbs (1G10 and GL1, respectively) were purchased from American Type Culture Collection (ATCC). Hybridoma producing anti-IL-4 mAb (11B11) also was purchased from ATCC. These mAbs were purified from ascites by using protein G column. mAbs against CD1d (1B1) and H-2K b (AF6-88.5, FITC-labeled) were purchased from PharMingen. An annexin V PE staining kit was purchased from PharMingen.

Human invariant Vα24+ NKT cells are a relatively new subpopulation of lymphocytes. It has been reported that Vα24 NKT cells are significantly involved in some human diseases. We have evaluated the number and function of Vα24 NKT cells in both healthy volunteers and cancer patients. In this study we found that Vα24 NKT cells in unfractionated PBMCs obtained from cancer patients did not respond efficiently to α-galactosylceramide (α-GalCer) in vitro. Thus, their proportion after stimulation with α-GalCer was smaller than that found in healthy volunteers. However, the cancer patients’ Vα24 NKT cells retained cytotoxic activity against malignant target cells, and they could efficiently proliferate to α-GalCer when fractionated by sorting. Furthermore, we found that addition of G-CSF to the culture could restore the low proliferative response of Vα24 NKT cells from cancer patients. These results suggest that some functions of NKT cells in cancer patients are impaired, and this observation carries significant implications for immunotherapy-based cancer treatments.

Fatty acid synthase (FAS) is highly expressed in many kinds of human cancers, including colorectal cancer (CRC), and we have investigated the potential use of FAS inhibitors for chemoprevention of liver metastasis of CRC in mice. Expression of FAS was evaluated in murine CRC cell lines Colon 26 and CMT 93. Cerulenin, a natural inhibitor of FAS, induced apoptosis in these cell lines. The ability of cerulenin to prevent development of liver metastatic lesions in Colon 26 was evaluated. The numbers and sizes of liver metastatic CRC tumors were significantly reduced by treating mice with cerulenin. Cerulenin treatment was associated with reduced levels of phosphorylated Akt in Colon 26 cells, suggesting that inhibition of this signal transduction pathway might be involved in the chemopreventive activity of this compound. Based on studies in mouse models, inhibiting FAS would be an effective strategy to prevent and retard growth of liver metastatic tumors of CRC that have high expression of this enzyme. (Cancer Sci 2010; 101: 1861-1865 C olorectal cancer (CRC) is one of the most common cancers in the world with more than 1 million new cases.(1) The liver is the commonest site of distant metastasis in CRC, and approximately 50% of patients ultimately develop liver metastasis in the course of CRC.(1,2) Despite recent advances, systemic chemotherapy for metastatic disease is considered palliative, and we rarely see long-term survivors treated only by chemotherapy.(1) Hepatic resection, the only curative treatment for liver metastasis of CRC, has become the standard treatment, but most cases of liver metastases are inoperable and approximately 50% of the patients treated with hepatectomy have a tumor recurrence in the liver. Fatty acid synthase (FAS) is highly expressed in many human cancers including CRC, (4)(5)(6)(7) and previous studies have shown that cancer cell growth can be suppressed by inhibiting the activity of this enzyme with a natural antibiotic cerulenin, (8) orlistat, which is a pancreatic lipase inhibitor developed for obesity treatment, (9) and C75, which is a stable synthetic small molecule developed specifically for inhibiting FAS.(10) But there are no previous studies in which FAS inhibitors suppressed liver metastasis of CRC.The aim of this study extends the investigation of the potential use of an FAS inhibitor for the chemoprevention of liver metastasis of CRC in mice. In this study, we examined the effect of cerulenin on cell proliferation and apoptosis in murine CRC cell lines Colon 26 and CMT 93. Then, the effect of cerulenin on the prevention of growth of liver metastasis lesions in Colon 26 was investigated. Materials and MethodsCerulenin. Cerulenin was obtained from Sigma (St. Louis, MO, USA). For cell culture and i.p. injections, cerulenin was dissolved in acetone at a concentration of 20 mg ⁄ mL and stored at )20°C. In in vitro experiment, 50-200 lM of cerulenin was added to the medium, and cell viability assay and western blot experiments were performed 24 h later. In in vivo experiments,...