Background & Aims Adenosine mediates immune suppression and is generated by the ectonucleotidases CD39 (ENTPD1) and CD73 that are expressed on vascular endothelial cells and regulatory T cells (Treg). Although tumor-infiltrating immune cells include Foxp3+ Treg, it is not clear whether local adenosine generation by Treg promotes tumor growth in a CD39-dependent manner. In this study, we have examined the impact of CD39 expression by Treg on effector immune cell responses to hepatic metastases in vivo. Methods and Results A model of hepatic metastatic cancer was developed with portal vein infusion of luciferase-expressing melanoma B16/F10 cells and MCA38 colon cancer cells in wild type and mutant mice null for Cd39. Chimeric mice were generated by bone marrow transplantation (BMT) using Cd39 null or wild type (wt) C57BL6 donors and irradiated recipient mice. We demonstrate that hepatic growth of melanoma metastatic tumors was strongly inhibited in mice with Cd39 null vasculature or in wild type mice with circulating Cd39 null bone marrow-derived cells. We show functional CD39 expression on CD4+Foxp3+ Treg suppressed anti-tumor immunity mediated by NK cells in vitro and in vivo. Lastly, inhibition of CD39 activity by POM-1 (polyoxometalate-1), a pharmacological inhibitor of NTPDase activity, significantly inhibited tumor growth (P < .001). Conclusions CD39 expression on Treg inhibits NK activity and is permissive for metastatic growth. Pharmacological or targeted inhibition of CD39 enzymatic activity may find utility as an adjunct therapy for secondary hepatic malignancies.

The purpose of this study was to clarify the factors linked to recurrence of small hepatocellular carcinomas, up to 3 cm in diameter, after hepatectomy. Fifty patients with small hepatocellular carcinomas who underwent hepatectomy between 1976 and 1988 were observed for possible recurrence for at least 2 yr. These patients were divided into two groups: 20 patients who had recurrence within 2 yr and 30 patients who had no recurrence within 2 yr. The recurrence pattern was analyzed by hepatic angiography. Statistical analysis by the chi 2 test and stepwise logistic regression showed that the risk factors linked to recurrence were (a) tumor diameter greater than 2.2 cm, (b) intracapsular infiltration of tumor cells, (c) tumor location deep in the liver, (d) macroscopical and microscopical tumor invasion into the portal vein and (e) tumor invasion into the portal vein or intrahepatic metastasis. When patients diagnosed with small hepatocellular carcinomas have any of these risk factors, postoperative adjuvant therapy and follow-up should be particularly carefully considered, since these patients are at high risk for early recurrence.

Osteoarthritis in the knees, which can be caused by meniscal defect, constitutes an increasingly common medical problem. Repair for massive meniscal defect remains a challenge owing to a lack of cell kinetics for the menisci precursors in knee joint. The synovium plays pivotal roles during the natural course of meniscal healing and contains mesenchymal stem cells (MSCs) with high chondrogenic potential. Here, we investigated whether intra-articular injected synovium-MSCs enhanced meniscal regeneration in rat massive meniscal defect. To track the injected cells, we developed transgenic rats expressing dual luciferase (Luc) and LacZ. The cells derived from synovium of the rats demonstrated colony-forming ability and multipotentiality, both characteristics of MSCs. Hierarchical clustering analysis revealed that gene expression of meniscal cells was closer to that of synovium-MSCs than to that of bone marrow-MSCs. Two to 8 weeks after five million Luc/ LacZ1 synovium-MSCs were injected into massive meniscectomized knee of wild-type rat, macroscopically, the menisci regenerated much better than it did in the control group. After 12 weeks, the regenerated menisci were LacZ positive, produced type 2 collagen, and showed meniscal features by transmission electron microscopy. In in-vivo luminescence analysis, photons increased in the meniscusresected knee over a 3-day period, then decreased without detection in all other organs. LacZ gene derived from MSCs could not be detected in other organs except in synovium by real-time PCR. Synovium-MSCs injected into the massive meniscectomized knee adhered to the lesion, differentiated into meniscal cells directly, and promoted meniscal regeneration without mobilization to distant organs.

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IFN-λ 1, -λ 2 and -λ 3 have been discovered as the latest members of the class II cytokine family and shown to possess antiviral activity. Murine B16 melanoma and Colon26 cancer cells were transduced with mouse IFN-λ to determine whether IFN-λ possesses antitumor activity. Overexpression of IFN-λ induced cell surface MHC class I expression and Fas/CD95 Ag, induced significant caspase-3/7 activity, and increased p21Waf1/Cip1 and dephosphorylated Rb (Ser780) in B16 cells in vitro. IFN-λ expression in tumor cell lines markedly inhibited s.c. and metastatic tumor formation in vivo compared with mock transfections (p &lt; 0.05). Moreover, IFN-λ expression induced lymphocytic infiltrates, and an Ab-mediated immune cell depletion assay showed that NK cells were critical to IFN-λ-mediated tumor growth inhibition. Hydrodynamic injection of IFN-λ cDNA successfully targeted liver metastatic foci of Colon26 cells, and moderately decreased the mortality of mice with tumors. IFN-λ overexpression in the liver increased NK/NKT cells and enhanced their tumor-killing activity, and suggested the activation of innate immune responses. Thus, IFN-λ induced both tumor apoptosis and NK cell-mediated immunological tumor destruction through innate immune responses. These findings suggested that local delivery of IFN-λ might prove a useful adjunctive strategy in the clinical treatment of human malignancies.