Another benefit of dietary fiber The gut microbiome can modulate the immune system and influence the therapeutic response of cancer patients, yet the mechanisms underlying the effects of microbiota are presently unclear. Spencer et al . add to our understanding of how dietary habits affect microbiota and clinical outcomes to immunotherapy. In an observational study, the researchers found that melanoma patients reporting high fiber (prebiotic) consumption had a better response to checkpoint inhibitor immunotherapy compared with those patients reporting a low-fiber diet. The most marked benefit was observed for those patients reporting a combination of high fiber consumption and no use of over-the-counter probiotic supplements. These findings provide early insights as to how diet-related factors may influence the immune response. —PNK

With age, T-cell generation from the thymus is much reduced, yet a substantial naïve T-cell pool is maintained even in aged animals, suggesting that naïve T cells either persist longer or turn over faster to maintain T-cell homeostasis. We found that with age, naïve CD4 T cells became progressively longer-lived. Their longer lifespan did not depend on recognition of self-peptide/class II. Newly generated naïve T cells derived from aged stem cells had a shorter lifespan, like that of young naïve T cells. Conversely, naïve CD4 T cells derived from middle-aged thymectomized mice were longer-lived in vivo, and their development of functional defects was accelerated. These observations suggest that naïve T cells develop their longer lifespan during their sojourn in the periphery. Increased longevity of naïve CD4 T cells correlated well with reduced expression of proapoptotic molecule Bim. We suggest that the intrinsic increase in longevity helps maintain naïve T-cell homeostasis but facilitates the development of functional defects in mice.aging ͉ Bim ͉ T lymphocytes ͉ apoptosis A ging is accompanied by pleiotropic changes in the immune system that lead to dysfunction of cellular and humoral immune responses (1, 2). The progressive decline in functions is associated with increased susceptibilities to infectious disease, autoimmune disease, and cancer (3-5). Naïve CD4 T cells from aged animals exhibit age-related decreases in Ag responsiveness, characterized by weak proliferative response, lower IL-2 production, and a poor ability to help B cells, leading to reduced specific antibody production (6-8). Similar functional defects are observed when aged naïve CD4 T cells are transferred to young hosts (9, 10), indicating that many of the aged-related defects are intrinsic to the naïve CD4 T cells.When depletion of naïve CD4 T cells with an endogenous superantigen (11), by anti-CD4 Ab given systemically, or by lethal irradiation followed by aged bone marrow (BM) reconstitution, leads to reconstitution of naïve T cells in aged mice, the newly generated CD4 T cells function much like cells from young mice, even though they are derived from aged stem cells (10,12,13). This suggests age-associated loss of function occurs primarily while naïve CD4 T cells persist in periphery. However, no particular mechanism(s) leading to such dysfunction has been identified.The size of the naïve T-cell population is determined by the rate of emigration of new naïve T cells from thymus and by homeostatic turnover of T cells in the periphery. T-cell homeostasis has been assumed to be achieved largely by T-cell receptor (TCR) engagement with self-peptide/MHC (14, 15) and homeostatic survival factors, such as 17). Another important component is cellular lifespan, which has often been considered a cell-intrinsic property. The homeostatic equilibriums that regulate the size of the naïve T-cell pool in aged animals may differ from those in young. Thymic involution starts at puberty and causes an abrupt decline of at least 10-fold in new thymic emig...

Striking cell losses occur during late B lymphocyte maturation, reflecting BcR-mediated selection coupled with requisites for viability promoting signals. How selection and survival cues are integrated remains unclear, but a key role for B lymphocyte stimulator (BLyS(TM); trademark of Human Genome Sciences, Inc.) is suggested by its marked effects on B cell numbers and autoantibody formation as well as the B lineage-specific expression of BLyS receptors. Our analyses of the B cell-deficient A/WySnJ mouse have established Bcmd as a gene controlling follicular B cell life span, and recent reports show Bcmd encodes a novel BLyS receptor. Here we show that A/WySnJ B cells are unresponsive to BLyS, affording interrogation of how Bcmd influences B cell homeostasis. Mixed marrow chimeras indicate A/WySnJ peripheral B cells compete poorly for peripheral survival. Moreover, in vivo BrdU labeling shows that (A/WySnJ x BALB/c)F(1) B cells have an intermediate but uniform life span, indicating viability requires continuous signaling via this pathway. Together, these findings establish the BLyS/Bcmd pathway as a dominant mediator of B cell survival, suggesting competition for BLyS/Bcmd signals regulates follicular B cell numbers.

Exosome cargoes are highly varied and include proteins, small RNAs, and genomic DNA (gDNA). The presence of gDNA suggests that different intracellular compartments contribute to exosome loading, resulting in distinct exosome subpopulations. However, the loading of gDNA and other nuclear contents into exosomes (nExo) remains poorly understood. Here, we identify the relationship between cancer cell micronuclei (MN), which are markers of genomic instability, and nExo formation. Imaging flow cytometry analyses reveal that 10% of exosomes derived from cancer cells and <1% of exosomes derived from blood and ascites from patients with ovarian cancer carry nuclear contents. Treatment with genotoxic drugs resulted in increased MN and nExos both in vitro and in vivo. We observed that multivesicular body precursors and exosomal markers, such as the tetraspanins, directly interact with MN. Collectively, this work provides new insights related to nExos, which have implications for cancer biomarker development.

PR1 (VLQELNVTV) is a human leukocyte antigen-A2 (HLA-A2)-restricted leukemiaassociated peptide from proteinase 3 (P3) and neutrophil elastase (NE) that is recognized by PR1-specific cytotoxic T lymphocytes that contribute to cytogenetic remission of acute myeloid leukemia (AML). We report a novel T-cell receptor (TCR)- IntroductionCD8 T cells specific for the human leukocyte antigen-A2 (HLA-A2)-restricted peptides WT1 and PR1, which are derived from the endogenous leukemia-associated antigens Wilms' tumor antigen [1][2][3] and proteinase 3 (P3), respectively, mediate cytotoxicity against acute myeloid leukemia (AML). PR1-specific T cells also contribute to cytogenetic remission of chronic myeloid leukemia (CML) in patients treated with interferon, 4,5 and vaccination with WT1 and PR1 6,7 can induce specific CD8 immunity in patients with myeloid malignancies. These results validate endogenous self-peptides as targets for immunotherapy, including vaccination, adoptive cell therapy, or antibodies that bind peptide/MHC. Such T-cell receptor (TCR)-like monoclonal antibodies (mAbs) may have selective activity against leukemia if target peptide/MHC complexes are aberrantly expressed on leukemia. Furthermore, mAbs are easy to administer and can be dosed frequently, which may increase their effectiveness against high leukemia burdens.Eliciting TCR-like mAbs has been technically challenging, 8 primarily because of the high immunogenicity of HLA molecules in mice. Phage-display libraries, 9 peptide/MHC immunization, 10,11 and the combination of both strategies 8,12 have been used to produce TCR-like mAbs targeting peptides derived from solid-tumor antigens (eg, MAGE, ␤-HCG, TARP, and NY-ESO-1) in the context of HLA-A1 or HLA-A2. [9][10][11]13,14 Although antibody activity against primary tumors has not been well studied, complement-dependent cytotoxicity (CDC) against tumor cell lines has been reported. 11 Some toxin-conjugated antibodies also show activity against tumor cells. 14-16 However, to eradicate cancer, these antibodies must be active against cancerinitiating cells, and TCR-like mAb-induced cytolysis of cancer stem cells has not been reported. Nevertheless, because PR1-specific CTLs suppress leukemia progenitor cells in vitro 17 and because Lin Ϫ CD34 ϩ CD38 Ϫ cells are enriched for leukemia stem cells (LSCs) 18 and can be easily studied, we hypothesized that if an anti-PR1/HLA-A2 antibody could be produced, it may be active against blasts and LSCs from HLA-A2 ϩ AML patients.We report the discovery of 8F4, a novel mAb that binds with high affinity to a conformational epitope of PR1/HLA-A2 and induces dose-dependent cytolysis of myeloid leukemia cells but not normal hematopoietic cells. 8F4 mediates CDC against Lin Ϫ CD34 ϩ CD38 Ϫ LSCs and preferentially inhibits the growth of leukemia progenitor cells. These results justify further study of TCR-like antibodies to verify the differential effects against normal stem cells and LSCs. Biologically significant differences may justify further study of a humanized form o...

Oncolytic viruses selectively lyse tumor cells, disrupt immunosuppression within the tumor and reactivate anti-tumor immunity, but they have yet to live up to their therapeutic potential. Immune checkpoint modulation has been efficacious in a variety of cancer with an immunogenic microenvironment, but is associated with toxicity due to nonspecific T-cell activation. Therefore, combining these two strategies would likely result in both effective and specific cancer therapy. To test the hypothesis, we first constructed oncolytic adenovirus Delta-24-RGDOX expressing the immune co-stimulator OX40 ligand (OX40L). Like its predecessor Delta-24-RGD, Delta-24-RGDOX induced immunogenic cell death and recruit lymphocytes to the tumor site. Compared to Delta-24-RGD, Delta-24-RGDOX exhibited superior tumor-specific activation of lymphocytes and proliferation of CD8+ T cells specific to tumor-associated antigens, resulting in cancer-specific immunity. Delta-24-RGDOX mediated more potent anti-glioma activity in immune-competent C57BL/6 but not immune-deficient athymic mice, leading to specific immune memory against the tumor. In order to further overcome the immune suppression mediated by programmed death-ligand 1 (PD-L1) expression on cancer cells accompanied with virotherapy, intratumoral injection of Delta-24-RGDOX and an anti-PD-L1 antibody showed synergistic inhibition of gliomas and significantly increased survival in mice. Our data demonstrate that combining an oncolytic virus with tumor-targeting immune checkpoint modulators elicits potent in situ autologous cancer vaccination, resulting in an efficacious, tumor-specific and long-lasting therapeutic effect.

CD8+ T cells are master effectors of antitumor immunity, and their presence at tumor sites correlates with favorable outcomes. However, metabolic constraints imposed by the tumor microenvironment (TME) can dampen their ability to control tumor progression. We describe lipid accumulation in the TME areas of pancreatic ductal adenocarcinoma (PDA) populated by CD8+ T cells infiltrating both murine and human tumors. In this lipid-rich but otherwise nutrient-poor TME, access to using lipid metabolism becomes particularly valuable for sustaining cell functions. Here, we found that intrapancreatic CD8+ T cells progressively accumulate specific long-chain fatty acids (LCFAs), which, rather than provide a fuel source, impair their mitochondrial function and trigger major transcriptional reprogramming of pathways involved in lipid metabolism, with the subsequent reduction of fatty acid catabolism. In particular, intrapancreatic CD8+ T cells specifically exhibit down-regulation of the very-long-chain acyl-CoA dehydrogenase (VLCAD) enzyme, which exacerbates accumulation of LCFAs and very-long-chain fatty acids (VLCFAs) that mediate lipotoxicity. Metabolic reprogramming of tumor-specific T cells through enforced expression of ACADVL enabled enhanced intratumoral T cell survival and persistence in an engineered mouse model of PDA, overcoming one of the major hurdles to immunotherapy for PDA.

In 1956, Otto Warburg proposed that the origin of cancer cells was closely linked to a permanent respiratory defect that bypassed the Pasteur effect (i.e., the inhibition of anaerobic fermentation by oxygen). Since then, permanent defects in oxygen consumption that could explain the dependence of cancer cells on aerobic glycolysis have not been identified. Here, we show that under normoxic conditions exposure of leukemia cells to bone marrow-derived mesenchymal stromal cells (MSC) promotes accumulation of lactate in the culture medium and reduces mitochondrial membrane potential (#WM) in both cell types. Notably, the consumption of glucose was not altered in cocultures, suggesting that the accumulation of lactate was the result of reduced pyruvate metabolism. Interestingly, the decrease in #WM was mediated by mitochondrial uncoupling in leukemia cells and was accompanied by increased expression of uncoupling protein 2 (UCP2). HL60 cells fail to increase UCP2 expression, are not uncoupled after coculture, and do not exhibit increased aerobic glycolysis, whereas small interfering RNA-mediated suppression of UCP2 in OCI-AML3 cells reversed mitochondrial uncoupling and aerobic glycolysis elicited by MSC. Taken together, these data suggest that microenvironment activation of highly conserved mammalian UCPs may facilitate the Warburg effect in the absence of permanent respiratory impairment. [Cancer Res 2008;68(13):5198-205]