Mikiko Fukui

Increased expression of MUC1 in advanced pancreatic cancer

BackgroundMUC1 is associated with tumor invasion and metastasis, and is expressed in pancreatic cancer with a high frequency. This study explored whether MUC1 expression affected the survival of patients with pancreatic cancer.MethodsTissue specimens obtained from 70 patients with invasive ductal carcinoma of the pancreas, in pTNM stage III or IV, were immunostained with the anti-MUC1 monoclonal antibody DF3. The results of immunostaining were determined to be positive when more than 50% of the total cancer cells were positively stained. Association of the expression of the DF3 epitope with clinicopathological parameters or patients’ survival was statistically evaluated.ResultsThe incidence of positivity of MUC1 expression was 55.7% (39/70) and this incidence was significantly higher in pTNM stage IV than in stage III (odds ratio [OR], 4.015; 95% confidence interval [CI], 1.459–11.0541; P = 0.0076). As there was a clear difference in overall survival between pTNM stages III and IV (P = 0.0016), the effect of MUC1 expression on survival was separately evaluated in each stage. It was shown that the expression of MUC1 was associated with unfavorable overall survival in stage IV (P = 0.0197).ConclusionsOur data suggest that the expression of MUC1 may be related to the progression of pancreatic cancer.

Anti-tumor activity of dendritic cells transfected with mRNA for receptor for hyaluronan-mediated motility is mediated by CD4+ T cells

Receptor for hyaluronan-mediated motility (RHAMM) is overexpressed in various tumors with high frequency, and was recently identified as an immunogenic antigen by serologic screening of cDNA expression libraries. In this study, we explored whether RHAMM is a potential target for dendritic cell (DC) immunotherapy. We constructed a plasmid for transduction of in vitro-transcribed mRNAs into DCs to efficiently transport the intracellular protein RHAMM into MHC class II compartments by adding a late endosomal/lysosomal sorting signal to the RHAMM gene. Immunization of mice with modified RHAMM mRNA-transfected DCs (DC/RHAMM) induced killing activity against RHAMM-positive tumor cells in splenocytes. To examine whether CD4+ and/or CD8+ T cells were required for this antitumor immunity, an anti-CD4 or anti-CD8 antibody was administered to mice after immunization with DC/RHAMM. Depletion of CD4+ T cells significantly diminished the induction of tumor cell-killing activity in splenocytes, whereas CD8+ T cell depletion had no effect. We then investigated the therapeutic effect of DC/RHAMM in a 3-day tumor model of EL4. DC/RHAMM was administered to mice on days 3, 7 and 10 after EL4 tumor inoculation. The treatment markedly inhibited tumor growth compared to control DCs. Moreover, antibody-mediated depletion of CD4+ T cells completely abrogated the therapeutic effect of DC/RHAMM, whereas depletion of CD8+ T cells had no effect. The results of this preclinical study indicate that DCs transfected with a modified RHAMM mRNA targeted to MHC class II compartments can induce CD4+ T cell-mediated antitumor activity in vivo.

Therapeutic effect of dendritic cells loaded with a fusion mRNA encoding tyrosinase-related protein 2 and enhanced green fluorescence protein on B16 melanoma.

Dendritic cells (DCs) loaded with messenger RNA (mRNA) have been proposed to be useful for inducing specific cytotoxic T lymphocytes against tumor antigens. It is now also apparent that tumor antigen-specific T cell tolerance limits the efficacy of active immunotherapy. To improve the efficacy of mRNA-loaded DCs, we constructed a fusion mRNA encoding tyrosinase-related protein 2 (TRP2), which has a late endosomal/lysosomal sorting signal and enhanced green fluorescence protein (EGFP), and evaluated its effect in a murine melanoma model. C57BL/6 mice were challenged subcutaneously (s.c.) with 3 × 105 B16 tumor cells, and 3 and 10 days later, 3 × 105 DCs loaded with mRNA (DC/mRNA) were injected s.c. in the vicinity of the tumor site. Treatment with DC/TRP2 mRNA or DC/TRP2-EGFP mRNA significantly inhibited tumor growth compared to DC/PBS on day 17 after B16 challenge (DC/PBS vs. DC/TRP2 mRNA, p = 0.0411; DC/PBS vs.DC/TRP2-EGFP mRNA, p = 0.0253), whereas no antitumor effect was observed in mice treated with DC/EGFP mRNA or DC/TRP2 peptide. Moreover, the survival rate in mice immunized with DC/TRP2 mRNA or DC/TRP2-EGFP mRNA was significantly improved as compared with that in mice receiving DC/PBS (DC/PBS vs. DC/TRP2 mRNA, p = 0.0228; DC/PBS vs. DC/TRP2-EGFP mRNA, p = 0.0049). Depletion of CD4+ T cells or CD8+ T cells with antibody administration completely abrogated the therapeutic effectiveness of DC/TRP2-EGFP mRNA, suggesting the induction of a T cell immune response against the B16 tumor.

Evaluation of an mRNA Lipofection Procedure for Human Dendritic Cells and Induction of Cytotoxic T Lymphocytes against Enhanced Green Fluorescence Protein

We utilized an mRNA lipofection procedure in human dendritic cells (DCs) and attempted to induce cytotoxic T lymphocytes (CTLs) against enhanced green fluorescence protein (EGFP). EGFP mRNA was transfected into phytohemagglutinin (PHA)-stimulated lymphocytes or adherent peripheral blood mononuclear cell-derived DCs using a liposomal reagent. Lipofection efficiency was measured by flow cytometry. In PHA-stimulated lymphocytes, increasing concentrations of liposome or mRNA increased EGFP expression levels by up to 64.4%, but caused a decrease in cell viability. A similar trend was also observed in DCs. For 70% DC viability, the concentration of liposomes was 24 µl/ml, and the mRNA concentration was 6 µg/ml. Under these conditions, ELISPOT and 51Cr release assays were performed on CD8+ T cells stimulated twice with EGFP mRNA-transfected DCs. The number of interferon-γ-producing cells was increased when the CD8+ T cells were cocultured for 24 h with PHA-stimulated lymphocytes transfected with EGFP mRNA. The level of specific lysis of EGFP mRNA-transfected DCs also increased to approximately 80%, with an effector to target ratio of 40:1. These data suggest that EGFP is immunogenic for human T cells, confirming that our lipofection procedure may be of use for inducing specific CTLs.