RECENT CAPABILITY AND PERFORMANCE ENHANCEMENTS OF THE WHOLE-CORE TRANSPORT CODE nTRACER

The whole-core transport code nTRACER has made many advances in recent years. Several innovative cross section treatment methods were developed, a new axial transport solver was introduced for stabilizing the 2D/1D scheme, and substantial computational enhancements were achieved using NVIDIA CUDA and Intel Math Kernel Library (MKL). In addition, gamma transport solver was implemented to predict the power distributions more physically, and the flexibility of the restart calculation was improved using an offline processing code nTIG (nTRACER Input Generator). This paper is the compilation of the recent progresses in nTRACER developments.

Modification of the HER2/NEU-derived tumor antigen GP2 improves induction of GP2-reactive cytotoxic T lymphocytes

GP2 (IISAVVGIL), the p654-662 HER2/neu-derived tumor antigen, induces HLA-A2-restricted cytotoxic T lymphocytes (CTL) reactive to various epithelial cancers. The binding affinity of GP2 for HLA-A2, however, is very low. To improve the immunogenicity of GP2, we tested 10 different amino acid substitutions into GP2 at the C- and N- terminus. Five out of 10 modified peptides, especially those containing phenylalanine at position 1 (1F), showed a significantly improved binding affinity to HLA-A2. 1F-based modified peptides were well recognized by GP2-specific CTL. These peptides were used to stimulate peripheral blood lymphocytes from HLA-A2 healthy donors using peptide-pulsed autologous dendritic cells (DC). After 3 or more weekly stimulations, CTL activity against GP2 pulsed T2 (T2-GP2) and HER2/neu-overexpressing tumor cells was measured in (51)Cr release and IFN-gamma secretion assays. The modified peptides significantly enhanced GP2-specific CTL activity in some donors. In particular, the peptide with phenylalanine at position 1, leucine at position 2 and valine at position 10 (1F2L10V) maximized the CTL activity against both T2-GP2 and HER2/neu-positive tumor cells. Peptide 1F2L10V increased not only the binding affinity to HLA-A2 but also improved recognition of GP2. These data suggest that DC + modified GP2 may improve immune therapies for the treatment of HER2/neu overexpressing tumors.

Loss of T-cell receptor-CD3zeta and T-cell function in tumor-infiltrating lymphocytes but not in tumor-associated lymphocytes in ovarian carcinoma

BACKGROUND

Impaired T-cell function has been noted in tumor-infiltrating lymphocytes (TIL). Recently, loss of function was found to be associated with modifications in T-cell receptor complex (TCR)-mediated signaling. A common feature is loss or reduced expression levels of the signaling chain, TCRzeta. We evaluated whether loss of function in TIL and tumor-associated lymphocytes (TAL) from patients with ovarian cancer is associated with changes in TCRzeta expression, and which factors can cause these defects.

METHODS

TIL and TAL were isolated from multiple patients and evaluated for their proliferative capacity by stimulation with a polyclonal stimulus. In addition, expression of TCRzeta and CD3epsilon was evaluated in fresh TIL and TAL by the Western blot technique. Finally, various conditions within a tumor environment were tested for their effect on TCRzeta and CD3epsilon.

RESULTS

TIL, but not TAL, were significantly impaired in their proliferative response, even when both populations were derived from the same patient (P <.05). Reduced proliferation levels were associated with loss of expression of TCRzeta but not of CD3epsilon. Exposure of normal T cells to relative ischemia or heat shock, or culture in medium without IL-2, did not significantly reduce expression of TCRzeta compared with CD3epsilon. However, coculture of T cells with tumor-derived macrophages or tumor-derived factors led to a selective loss of TCRzeta compared with CD3epsilon (P <.05). Further analysis suggested that oxides such as hydrogen peroxide secreted by macrophages may be responsible for loss of TCRzeta and high molecular weight factors secreted by certain tumors.

CONCLUSIONS

TIL but not TAL show impaired T-cell function, which is associated with loss of TCRzeta. In addition to macrophages secreting oxides, loss of TCRzeta may be caused by tumor-derived soluble factors.

Expression and function of galectin-3, a beta-galactoside-binding protein in activated T lymphocytes

A soluble beta-galactoside-binding lectin, galectin-3 has been shown to be involved in cell adhesion and activation of immune cells. Although galectin-3 is known to be expressed in various types of cells, it has not been shown whether galectin-3 is expressed in T lymphocytes. We present evidence here that galectin-3 is expressed in activated murine T lymphocytes including CD4+ and CD8+ T cells but not in resting T cells. Galectin-3 expression was induced by anti-CD3 mAb or mitogen and enhanced by common gamma-chain signaling cytokines, IL-2, IL-4, and IL-7, in activated T lymphocytes, whereas the inflammatory cytokines including TNF-alpha and IFN-gamma did not. Galectin-3 expression and proliferation were down-regulated by withdrawal of IL-2 and gamma irradiation. Antisense but not sense phosphorothioated oligonucleotides for galectin-3 inhibited galectin-3 expression and blocked proliferation of T cells significantly. This study suggests that up-regulation of galectin-3 plays an important role in proliferation of activated T lymphocytes.

Immunohistochemical detection of galectin-3 in canine gastric carcinomas

Galectin-3 was detected immunohistochemically in nine canine gastric carcinomas. In normal gastric tissue adjacent to the neoplasms, the gastric epithelial cells showed faint immunolabelling for galectin-3, but in all the tumours the neoplastic cells showed moderate to strong immunolabelling. Galectin-3 was localized in the cytoplasm of the normal mucosal cells, whereas it was found in both the cytoplasm and the nucleus of the neoplastic cells. Positive cells typically exhibited dark brown coloration of the nucleus or cytoplasm, without background labelling. The results suggest that galactin-3 has a pathophysiological role in canine gastric carcinoma.

Soluble MUC1 secreted by human epithelial cancer cells mediates immune suppression by blocking T-cell activation

Solid tumors may secrete factors that mediate immune suppression in patients. We investigated the effect of supernatants from 25 human tumor cell lines on T-lymphocytes from healthy donors. A profound inhibition of proliferation, cytokine secretion and cytotoxic activity was seen when T-cells were cultured in concentrated tumor supernatants from 6 cell lines fractionated into high (>100 kDa) m.w. molecules. Interestingly, the inhibitory effects were reversed when the tumor supernatant was removed. Cell cycle studies of inhibited T-cells showed most of them were growth arrested in the G(0)/G(1) phase similar to naïve T-cells. In addition, these T-cells did not express IL2-receptors and expression of CD54 (ICAM-1) and CD58 (LFA-3) resembled that of resting T-cells. Protein gel electrophoresis of the tumor supernatants and western blot analysis demonstrated the presence of soluble MUC1 in the inhibitory tumor supernatants but not in control supernatant. Most importantly, depletion of soluble MUC1 by immunoprecipitation from the tumor supernatants neutralized the inhibitory effects on T-lymphocytes. Therefore, our results show that MUC1 shed by cultured epithelial tumor cells mediates inhibition of T-cell proliferation and function by inducing cell growth arrest.

Local secretion of IFN-gamma induces an antitumor response: comparison between T cells plus IL-2 and IFN-gamma transfected tumor cells

Previously we described that the adoptive transfer of tumor-infiltrating lymphocytes (TIL) + interleukin-2 (IL-2) leads to eradication of established methylcholanthrene (MCA)-105 fibrosarcoma pulmonary metastases in a congenic murine model. The in vivo efficacy of TIL was associated with their ability to secrete interferon-gamma (IFN-gamma), and to a lesser extent granulocyte-macrophage colony-stimulating factor. The local secretion of these cytokines resulted in recruitment of naive host immune cells to the tumor and eventually in a successful host antitumor immune response. In the present study, to further evaluate the role of IFN-gamma in the induction of a host antitumor immune response, we compared the treatment efficacy of adoptively transferred T cells and IFN-gamma gene transfected tumor cells (MCA-105/IFN-gamma) as delivery systems of IFN-gamma. Treatment with TIL-IL-2 or irradiated MCA-105/IFN-gamma induced a similar reduction in pulmonary metastases of MCA-105 tumor. In contrast, irradiated wild-type MCA-105 or TIL from IFN-gamma gene knockout mice did not cause tumor eradication. MCA-105 tumor-bearing mice treated with MCA-205/IFN-gamma showed a partial reduction in the number of pulmonary metastases. Histologically, lungs of successfully treated mice showed that initially activated macrophages expressing inducible nitric oxide synthase (iNOS) and dendritic cells infiltrated the tumor bed. Subsequently, CD4+ and CD8+ T cells infiltrated tumors. The therapeutic efficacy of IFN-gamma transfected tumor cells was eliminated when either CD4+ T cells or CD8+ T cells were depleted. These results suggest that local secretion of IFN-gamma induces a tumor-specific host antitumor immune response mediated through activated macrophages, dendritic cells, and tumor-specific T cells. This may be a common component of successful immunotherapy.

Tumor-specific cytokine release by donor T cells induces an effective host anti-tumor response through recruitment of host naive antigen presenting cells

We recently reported that tumor eradication induced by immunotherapy (IT) in a congenic mouse model using tumor infiltrating lymphocytes (TIL) + recombinant interleukin-2 (rIL-2) is dependent on recruitment of naive host immune cells at the tumor sites. The recruitment of host immune cells was induced mainly through a local secretion of interferon-gamma (IFN-gamma) produced by donor T cells. We now further investigated how a non-specific inflammatory response progresses to a host T-cell-mediated tumor-specific response. In cross-over experiments using MCA-105 and MCA-205 sarcoma tumors, pulmonary metastatic disease was eradicated only in mice treated with tumor-matched TIL + rIL-2. In vitro, TIL stimulated with the tumor of origin secreted relatively high levels of IFN-gamma and granulocyte-macrophage colony stimulating factor (GM-CSF) compared to TIL stimulated with mismatched tumor cells. In lungs of tumor-bearing mice treated with matched TIL + rIL-2, significant increases in the percentages of IFN-gamma, GM-CSF and tumor necrosis factor-alpha (TNF-alpha) positive cells were detected, as well as of macrophages, natural killer (NK) cells and dendritic cells. Depletion of macrophages or NK cells did not inhibit the efficacy. In contrast, depletion of dendritic cells partially inhibited the efficacy of the treatment. Combined depletion of dendritic cells and macrophages abrogated more than 80% of the efficacy. Our data suggest that successful IT may require 3 steps: (1) release of inflammatory cytokines by donor TIL after restimulation by tumor cells; (2) infiltration of host immune cells in response to local cytokine production; and (3) activation of tumor-specific host immune cells by dendritic cells and to a lesser extent by macrophages.