Andrew Chow

Adoptive transfer of T-cell precursors enhances T-cell reconstitution after allogeneic hematopoietic stem cell transplantation.

Immunoincompetence after allogeneic hematopoietic stem cell transplantation (HSCT) affects in particular the T-cell lineage and is associated with an increased risk for infections, graft failure and malignant relapse. To generate large numbers of T-cell precursors for adoptive therapy, we cultured mouse hematopoietic stem cells (HSCs) in vitro on OP9 mouse stromal cells expressing the Notch-1 ligand Delta-like-1 (OP9-DL1). We infused these cells, together with T-cell–depleted mouse bone marrow or purified HSCs, into lethally irradiated allogeneic recipients and determined their effect on T-cell reconstitution after transplantation. Recipients of OP9-DL1–derived T-cell precursors showed increased thymic cellularity and substantially improved donor T-cell chimerism (versus recipients of bone marrow or HSCs only). OP9-DL1–derived T-cell precursors gave rise to host-tolerant CD4+ and CD8+ populations with normal T-cell antigen receptor repertoires, cytokine secretion and proliferative responses to antigen. Administration of OP9-DL1–derived T-cell precursors increased resistance to infection with Listeria monocytogenes and mediated significant graft-versus-tumor (GVT) activity but not graft-versus-host disease (GVHD). We conclude that the adoptive transfer of OP9-DL1–derived T-cell precursors markedly enhances T-cell reconstitution after transplantation, resulting in GVT activity without GVHD.

Glucocorticoid-Induced TNF Receptor Family Related Gene Activation Overcomes Tolerance/Ignorance to Melanoma Differentiation Antigens and Enhances Antitumor Immunity

Glucocorticoid-induced TNF receptor family related protein (GITR) is present on many different cell types. Previous studies have shown that in vivo administration of an anti-GITR agonist mAb (DTA-1) inhibits regulatory T cells (Treg)-dependent suppression and enhances T cell responses. In this study, we show that administration of DTA-1 induces >85% tumor rejection in mice challenged with B16 melanoma. Rejection requires CD4+, CD8+, and NK1.1+ cells and is dependent on IFN-γ and Fas ligand and independent of perforin. Depletion of Treg via anti-CD25 treatment does not induce B16 rejection, whereas 100% of the mice depleted of CD25+ cells and treated with DTA-1 reject tumors, indicating a predominant role of GITR on effector T cell costimulation rather than on Treg modulation. T cells isolated from DTA-1-treated mice challenged with B16 are specific against B16 and several melanoma differentiation Ags. These mice develop memory against B16, and a small proportion of them develop mild hypopigmentation. Consistent with previous studies showing that GITR stimulation increases Treg proliferation in vitro, we found in our model that GITR stimulation expanded the absolute number of FoxP3+ cells in vivo. Thus, we conclude that overall, GITR stimulation overcomes self-tolerance/ignorance and enhances T cell-mediated antitumor activity with minimal autoimmunity.

MiR-145 inhibits cell proliferation of human lung adenocarcinoma by targeting EGFR and NUDT1.

MicroRNAs (miRNAs) are emerging as important modulators in cellular pathways and they appear to play a key role in tumorigenesis. MiR-145 is downregulated in several human malignancies, including lung cancer, but the responsible molecular mechanisms remain unclear. We previously reported that restoration of hsa-miR-145 inhibits cancer cell growth in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation. This study showed that hsa-miR-145 targets EGFR and nucleoside diphosphate linked moiety X-type motif 1 (NUDT1 or MTH1) in lung adenocarinoma cells. The mRNA expressions of EGFR and NUDT1 were significantly downregulated after miR-145 transfection in human lung adenocarcinoma cells. Our results demonstrated miR-145 in the negative regulation of EGFR and NUDT1 expressions at both mRNA and protein levels. Further analysis showed that miR-145 has the ability to inhibit cell proliferation on transfected lung adenocarcinoma cells over three time points (24, 48 and 72 hours). Upregulation of miR-145 appeared to be an important gene regulation mechanism for the proliferation of lung adenocarcinoma cells and it correlated strongly with the downregulation of EGFR and NUDT1. Interestingly, our study revealed that the altered proliferation in lung cancer cells is not accompanied by changes in apoptosis. Our findings provided new insight into the complex regulating pathway comprising of miR-145, EGFR, NUDT1 and other unknown factors which function in cell proliferation but not in apoptosis. Understanding miR-145’s targets and its regulating pathways may lead to new therapeutic strategies for lung adenocarcinoma.

STAT-3 and ERK 1/2 phosphorylation are critical for T-cell alloactivation and graft-versus-host disease

Graft-versus-host disease (GVHD) is a serious complication of allogeneic bone marrow transplantation, and donor T cells are indispensable for GVHD. Current therapies have limited efficacy, selectivity, and high toxicities. We used a novel flow cytometry technique for the analysis of intracellular phosphorylation events in single cells in murine BMT models to identify and validate novel GVHD drug targets.(1-7) This method circumvents the requirement for large numbers of purified cells, unlike western blots. We defined a signaling profile for alloactivated T cells in vivo and identified the phosphorylation of ERK1/2 and STAT-3 as important events during T-cell (allo)activation in GVHD. We establish that interference with STAT-3 phosphorylation can inhibit T-cell activation and proliferation in vitro and GVHD in vivo. This suggests that phospho-specific flow cytometry is useful for the identification of promising drug targets, and ERK1/2 and STAT-3 phosphorylation in alloactivated T cells may be important for GVHD.

IFN-γ and Fas Ligand Are Required for Graft-versus-Tumor Activity against Renal Cell Carcinoma in the Absence of Lethal Graft-versus-Host Disease

To determine the mechanisms of graft-versus-tumor (GVT) activity in the absence of graft-versus-host disease (GVHD) against a solid tumor, we established two allogeneic bone marrow transplantation models with a murine renal cell carcinoma (RENCA). The addition of 0.3 × 106 donor CD8+ T cells to the allograft increased the survival of tumor-bearing mice without causing GVHD. The analysis of CD8+ T cells deficient in cytotoxic molecules demonstrated that anti-RENCA activity is dependent on IFN-γ and Fas ligand (FasL), but does not require soluble or membrane-bound TNF-α, perforin, or TRAIL. Recipients of IFN-γ−/− CD8+ T cells are unable to reject RENCA compared with recipients of wild-type CD8+ T cells and, importantly, neither group develops severe GVHD. IFN-γ−/− CD8+ T cells derived from transplanted mice are less able to kill RENCA cells in vitro, while pretreatment of RENCA cells with IFN-γ enhances class I and FasL expression and rescues the lytic capacity of IFN-γ−/− CD8+ T cells. These results demonstrate that the addition of low numbers of selected donor CD8+ T cells to the allograft can mediate GVT activity without lethal GVHD against murine renal cell carcinoma, and this GVT activity is dependent on IFN-γ and FasL.

Fc-Mediated Anomalous Biodistribution of Therapeutic Antibodies in Immunodeficient Mouse Models

A critical benchmark in the development of antibody-based therapeutics is demonstration of efficacy in preclinical mouse models of human disease, many of which rely on immunodeficient mice. However, relatively little is known about how the biology of various immunodeficient strains impacts the in vivo fate of these drugs. Here we used immunoPET radiotracers prepared from humanized, chimeric, and murine mAbs against four therapeutic oncologic targets to interrogate their biodistribution in four different strains of immunodeficient mice bearing lung, prostate, and ovarian cancer xenografts. The immunodeficiency status of the mouse host as well as both the biological origin and glycosylation of the antibody contributed significantly to the anomalous biodistribution of therapeutic monoclonal antibodies in an Fc receptor-dependent manner. These findings may have important implications for the preclinical evaluation of Fc-containing therapeutics and highlight a clear need for biodistribution studies in the early stages of antibody drug development.Significance: Fc/FcγR-mediated immunobiology of the experimental host is a key determinant to preclinical in vivo tumor targeting and efficacy of therapeutic antibodies. Cancer Res; 78(7); 1820-32. ©2018 AACR.

Abstract 1189: MiR-145 inhibits cell proliferation of human lung adenocarcinoma by targeting EGFR and NUDT1

MicroRNAs (miRNAs) are emerging as important modulators in cellular pathways and they appear to play a key role in tumorigenesis. MiR-145 is downregulated in several human malignancies, including lung cancer, but the responsible molecular mechanisms remain unclear. We previously reported that restoration of hsa-miR-145 inhibits cancer cell growth in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation. This study showed that hsa-miR-145 targets EGFR and nucleoside diphosphate linked moiety X-type motif 1 (NUDT1 or MTH1) in lung adenocarinoma cells. The mRNA expressions of EGFR and NUDT1 were significantly downregulated after miR-145 transfection in human lung adenocarcinoma cells. Our results demonstrated miR-145 in the negative regulation of EGFR and NUDT1 expressions at both mRNA and protein levels. Further analysis showed that miR-145 has the ability to inhibit cell proliferation on transfected lung adenocarcinoma cells over three time points (24, 48 and 72 hours). Upregulation of miR-145 appeared to be an important gene regulation mechanism for the proliferation of lung adenocarcinoma cells and it correlated strongly with the downregulation of EGFR and NUDT1. Interestingly, our study revealed that the altered proliferation in lung cancer cells is not accompanied by changes in apoptosis. Our findings provided new insight into the complex regulating pathway comprising of miR-145, EGFR, NUDT1 and other unknown factors which function in cell proliferation but not in apoptosis. Understanding miR-145s targets and its regulating pathways may lead to new therapeutic strategies for lung adenocarcinoma.