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IL-28 is a recently described antiviral cytokine. In this study, we investigated the biological effects of IL-28 on tumor growth to evaluate its antitumor activity. IL-28 or retroviral transduction of the IL-28 gene into MCA205 cells did not affect in vitro growth, whereas in vivo growth of MCA205IL-28 was markedly suppressed along with survival advantages when compared with that of controls. When the metastatic ability of IL-28-secreting MCA205 cells was compared with that of controls, the expression of IL-28 resulted in a potent inhibition of metastases formation in the lungs. IL-28-mediated suppression of tumor growth was mostly abolished in irradiated mice, indicating that irradiation-sensitive cells, presumably immune cells, are primarily involved in the IL-28-induced suppression of tumor growth. In vivo cell depletion experiments displayed that polymorphonuclear neutrophils, NK cells, and CD8 T cells, but not CD4 T cells, play an equal role in the IL-28-mediated inhibition of in vivo tumor growth. Consistent with these findings, inoculation of MCA205IL-28 into mice evoked enhanced IFN-γ production and cytotoxic T cell activity in spleen cells. Antitumor action of IL-28 is partially dependent on IFN-γ and is independent of IL-12, IL-17, and IL-23. IL-28 increased the total number of splenic NK cells in SCID mice and enhanced IL-12-induced IFN-γ production in vivo and expanded spleen cells in C57BL/6 mice. Moreover, IL-12 augmented IL-28-mediated antitumor activity in the presence or absence of IFN-γ. These findings indicate that IL-28 has bioactivities that induce innate and adaptive immune responses against tumors.

Modulation of surface T cell antigen receptor (TCR) expression is an important mechanism for the regulation of immune responses and the prevention of T cell hyperactivation and autoimmunity. The TCR is rapidly internalized after antigen stimulation and then degraded in lysosomes. However, few of the molecules involved in this process have been identified. We demonstrate that the lysosomal protein LAPTM5 negatively regulated surface TCR expression by specifically interacting with the invariant signal-transducing CD3zeta chain and promoting its degradation without affecting other CD3 proteins, CD3epsilon, CD3delta, or CD3gamma. TCR downmodulation required the polyproline-tyrosine motifs and the ubiquitin-interacting motif of LAPTM5. LAPTM5 deficiency resulted in elevated TCR expression on both CD4(+)CD8(+) thymocytes and spleen T cells after CD3 stimulation, as well as enhanced T cell responses in vitro and in vivo. These results identify a lysosomal protein important for CD3zeta degradation and illustrate a unique mechanism for the control of surface TCR expression and T cell activation.

A novel cytokine interleukin‐27 (IL‐27), composed of p28 and Epstein‐Barr virus‐induced gene 3 (EBI3), is produced from activated dendritic cells and is involved in an early phase of T‐helper type I differentiation. We examined whether Colon 26 murine colon carcinoma cells that were retrovirally transduced with the p28‐linked EBI3 gene (Colon 26/IL‐27) could produce antitumor effects in inoculated mice. Although proliferation in vitro of Colon 26/IL‐27 cells was not different from that of parent cells, syngeneic BALB/c mice rejected Colon 26/IL‐27 tumors inoculated and subsequently acquired tumor‐specific protective immunity. In contrast, mice inoculated with Colon 26 cells transduced with either the p28 or EBI3 gene developed tumors and survival of the mice remained the same as that of the mice inoculated with parent cells. Syngeneic nude mice developed Colon 26/IL‐27 tumors, but the growth was retarded compared to that of parent tumors. Depletion of natural killer cells from nude mice with anti‐asialo GM1 antibody diminished the growth retardation of Colon 26/IL‐27 tumors. Survival of severe combined immunodeficient mice that received subcutaneous inoculation of Colon 26/IL‐27 cells was not different from that of the immunodeficient mice inoculated with parent cells. Interferon‐γ was produced from CD4+ and CD8+ T, and natural killer cells of the mice that rejected Colon 26/IL‐27 tumors and cytotoxic activity against Colon 26 cells were also detected from the mice. These data collectively suggest that expressed IL‐27 in tumors produces T cell‐dependent and‐independent antitumor effects and is a possible therapeutic strategy for cancer. ©2005 Wiley‐Liss, Inc.

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The distinction between sarcomatoid mesothelioma and fibrous pleuritis is difficult based on histology, especially when the amount of tumor tissue examined via biopsy is small and immunohistochemical examination is inconclusive. We studied the usefulness of deletion of p16 with fluorescence in situ hybridization (FISH) and p16 hypermethylation with polymerase chain reaction for the diagnosis and prognosis of malignant pleural mesothelioma (MPM). We analyzed 50 MPMs, including 22 sarcomatoid mesothelioma cases and 10 fibrous pleuritis cases. We set the cutoff value of homozygous deletion pattern as 14.4% based on FISH signaling patterns using samples of fibrous pleuritis. The percentage of homozygous deletion pattern was higher than 14.4% in 55.6% of the epithelioid mesotheliomas (10/18) and in all of the sarcomatoid mesotheliomas (22/22). Methylation of p16 was observed in 7 (20.6%) of 34 informative cases. p16 FISH analysis can be a reliable test for distinguishing between sarcomatoid mesothelioma and fibrous pleuritis and a prognostic factor for MPM.

Somatic hypermutation of Ig variable region genes is initiated by activation-induced cytidine deaminase; however, the activity of multiple DNA polymerases is required to ultimately introduce mutations. DNA polymerase (Pol ) has been implicated in mutations at A͞T, but polymerases involved in C͞G mutations have not been identified. We have generated mutant mice expressing DNA polymerase (Pol ) specifically devoid of polymerase activity. Compared with WT mice, Polq-inactive (Polq, the gene encoding Pol ) mice exhibited a reduced level of serum IgM and IgG1. The mutant mice mounted relatively normal primary and secondary immune responses to a T-dependent antigen, but the production of high-affinity specific antibodies was partially impaired. Analysis of the J H4 intronic sequences revealed a slight reduction in the overall mutation frequency in Polq-inactive mice. Remarkably, although mutations at A͞T were unaffected, mutations at C͞G were significantly decreased, indicating an important, albeit not exclusive, role for Pol activity. The reduction of C͞G mutations was particularly focused on the intrinsic somatic hypermutation hotspots and both transitions and transversions were similarly reduced. These findings, together with the recent observation that Pol efficiently catalyzes the bypass of abasic sites, lead us to propose that Pol introduces mutations at C͞G by replicating over abasic sites generated via uracil-DNA glycosylase.abasic site ͉ low-fidelity DNA polymerase ͉ activation-induced cytidine deaminase ͉ uracil-DNA glycosylase

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