A secreted form of the major histocompatibility complex class II-associated invariant chain inhibiting T cell activation

Evaluating Anticancer and Immunomodulatory Effects of Spirulina (Arthrospira) platensis and Gamma-Tocotrienol Supplementation in a Syngeneic Mouse Model of Breast Cancer

Nutrition can modulate host immune responses as well as promote anticancer effects. In this study, two nutritional supplements, namely gamma-tocotrienol (γT3) and Spirulina, were evaluated for their immune-enhancing and anticancer effects in a syngeneic mouse model of breast cancer (BC). Five-week-old female BALB/c mice were fed Spirulina, γT3, or a combination of Spirulina and γT3 (Spirulina + γT3) for 56 days. The mice were inoculated with 4T1 cells into their mammary fat pad on day 28 to induce BC. The animals were culled on day 56 for various analyses. A significant reduction (p < 0.05) in tumor volume was only observed on day 37 and 49 in animals fed with the combination of γT3 + Spirulina. There was a marked increase (p < 0.05) of CD4/CD127+ T-cells and decrease (p < 0.05) of T-regulatory cells in peripheral blood from mice fed with either γT3 or Spirulina. The breast tissue of the combined group showed abundant areas of necrosis, but did not prevent metastasis to the liver. Although there was a significant increase (p < 0.05) of MIG-6 and Cadherin 13 expression in tumors from γT3-fed animals, there were no significant (p > 0.05) differences in the expression of MIG-6, Cadherin 13, BIRC5, and Serpine1 upon combined feeding. This showed that combined γT3 + Spirulina treatment did not show any synergistic anticancer effects in this study model.

The role of macrophage migration inhibitory factor in autoimmune liver disease

The role of the cytokine, macrophage migration inhibitory factor (MIF), and its receptor, CD74, was assessed in autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC). Two MIF promoter polymorphisms, a functional -794 CATT5-8 microsatellite repeat (rs5844572) and a -173 G/C single-nucleotide polymorphism (rs755622), were analyzed in DNA samples from over 500 patients with AIH, PBC, and controls. We found a higher frequency of the proinflammatory and high-expression -794 CATT7 allele in AIH, compared to PBC, whereas lower frequency was found in PBC, compared to both AIH and healthy controls. MIF and soluble MIF receptor (CD74) were measured by enzyme-linked immunosorbent assay in 165 serum samples of AIH, PBC, and controls. Circulating serum and hepatic MIF expression was elevated in patients with AIH and PBC versus healthy controls. We also identified a truncated circulating form of the MIF receptor, CD74, that is released from hepatic stellate cells and that binds MIF, neutralizing its signal transduction activity. Significantly higher levels of CD74 were found in patients with PBC versus AIH and controls.

CONCLUSIONS

These data suggest a distinct genetic and immunopathogenic basis for AIH and PBC at the MIF locus. Circulating MIF and MIF receptor profiles distinguish PBC from the more inflammatory phenotype of AIH and may play a role in pathogenesis and as biomarkers of these diseases.

A novel regulatory pathway for autoimmune disease: binding of partial MHC class II constructs to monocytes reduces CD74 expression and induces both specific and bystander T-cell tolerance

Treatment with partial (p)MHC class II-β1α1 constructs (also referred to as recombinant T-cell receptor ligands - RTL) linked to antigenic peptides can induce T-cell tolerance, inhibit recruitment of inflammatory cells and reverse autoimmune diseases. Here we demonstrate a novel regulatory pathway that involves RTL binding to CD11b(+) mononuclear cells through a receptor comprised of MHC class II invariant chain (CD74), cell-surface histones and MHC class II itself for treatment of experimental autoimmune encephalomyelitis (EAE). Binding of RTL constructs with CD74 involved a previously unrecognized MHC class II-α1/CD74 interaction that inhibited CD74 expression, blocked activity of its ligand, macrophage migration inhibitory factor, and reduced EAE severity. These findings implicate binding of RTL constructs to CD74 as a key step in both antigen-driven and bystander T-cell tolerance important in treatment of inflammatory diseases.

Tocotrienol-Rich Fraction from Palm Oil and Gene Expression in Human Breast Cancer Cells

Vitamin E is important not only for its cellular antioxidant and lipid-lowering properties, but also as an antiproliferating agent. It has also been shown to contribute to immunoregulation, antibody production, and resistance to implanted tumors. It has recently been shown that tocotrienols are the components of vitamin E responsible for growth inhibition in human breast cancer cells in vitro as well as in vivo through estrogen-independent mechanisms. Although tocotrienols act on cell proliferation in a dose-dependent manner and can induce programmed cell death, no specific gene regulation has yet been identified. In order to investigate the molecular basis of the effect of a tocotrienol-rich fraction (TRF) from palm oil, we performed a cDNA array analysis of cancer-related gene expression in estrogen-dependent (MCF-7) and estrogen-independent (MDA-MB-231) human breast cancer cells. The human breast cancer cells were incubated with or without 8 mug/mL of tocotrienols for 72 h. RNA was subsequently extracted and subjected to reverse transcription before being hybridized onto cancer arrays. Tocotrienol supplementation modulated significantly 46 out of 1200 genes in MDA-MB-231 cells. In MCF-7 cells, tocotrienol administration was associated with a lower number of affected genes. Interestingly, only three were affected in a similar fashion in both cell lines: c-myc binding protein MM-1, 23-kDa highly basic protein, and interferon-inducible protein 9-27 (IFITM-1). These proteins are most likely involved in the cell cycle and can exert inhibitory effects on cell growth and differentiation of the tumor cell lines. These data suggest that tocotrienols are able to affect cell homeostasis, possibly independent of their antioxidant activity.

Tocotrienol-rich fraction from palm oil affects gene expression in tumors resulting from MCF-7 cell inoculation in athymic mice

It has recently been shown that tocotrienols are the components of vitamin E responsible for inhibiting the growth of human breast cancer cells in vitro, through an estrogen-independent mechanism. Although tocotrienols act on cell proliferation in a dose-dependent manner and can induce programmed cell death, no specific gene regulation has yet been identified. To investigate the molecular basis of the effect of tocotrienols, we injected MCF-7 breast cancer cells into athymic nude mice. Mice were fed orally with 1 mg/d of tocotrienol-rich fraction (TRF) for 20 wk. At end of the 20 wk, there was a significant delay in the onset, incidence, and size of the tumors in nude mice supplemented with TRF compared with the controls. At autopsy, the tumor tissue was excised and analyzed for gene expression by means of a cDNA array technique. Thirty out of 1176 genes were significantly affected. Ten genes were downregulated and 20 genes up-regulated with respect to untreated animals, and some genes in particular were involved in regulating the immune system and its function. The expression of the interferon-inducible transmembrane protein-1 gene was significantly up-regulated in tumors excised from TRF-treated animals compared with control mice. Within the group of genes related to the immune system, we also found that the CD59 glycoprotein precursor gene was up-regulated. Among the functional class of intracellular transducers/effectors/modulators, the c-myc gene was significantly down-regulated in tumors by TRF treatment. Our observations indicate that TRF supplementation significantly and specifically affects MCF-7 cell response after tumor formation in vivo and therefore the host immune function. The observed effect on gene expression is possibly exerted independently from the antioxidant activity typical of this family of molecules.

Genomic expression programs and the integration of the CD28 costimulatory signal in T cell activation

Optimal activation of T cells requires effective occupancy of both the antigen-specific T cell receptor and a second coreceptor such as CD28. We used cDNA microarrays to characterize the genomic expression program in human peripheral T cells responding to stimulation of these receptors. We found that CD28 agonists alone elicited few, but reproducible, changes in gene expression, whereas CD3 agonists elicited a multifaceted temporally choreographed gene expression program. The principal effect of simultaneous engagement of CD28 was to increase the amplitude of the CD3 transcriptional response. The induced genes whose expression was most enhanced by costimulation were significantly enriched for known targets of nuclear factor of activated T cells (NFAT) transcription factors. This enhancement was nearly abolished by blocking the nuclear translocation of NFATc by using the calcineurin inhibitor FK506. CD28 signaling promoted phosphorylation, and thus inactivation, of the NFAT nuclear export kinase glycogen synthase kinase-3 (GSK3), coincident with enhanced dephosphorylation of NFATc proteins. These results provide a detailed picture of the transcriptional program of T cell activation and suggest that enhancement of transcriptional activation by NFAT, through inhibition of its nuclear export, plays a key role in mediating the CD28 costimulatory signal.