Diminished expression of placental isoferritin p43 component in first trimester abnormal pregnancies

The novel C24D synthetic polypeptide inhibits binding of placenta immunosuppressive ferritin to human T cells and elicits anti-breast cancer immunity in vitro and in vivo

Immune tolerance mechanisms supporting normal human pregnancy are exploited by breast cancer and other malignancies. We cloned from human placenta and breast cancer cells the novel human immunomodulator named placenta immunosuppressive ferritin (PLIF). PLIF is composed of a ferritin heavy chain-like domain and a novel cytokine-like domain, named C48. Both intact PLIF and C48 inhibit T cell proliferation. Blocking PLIF by specific antibodies in a tolerant breast cancer model in nude mice resulted in tumor cell apoptosis and rejection. This prompted us to study active immune preventive strategies targeting PLIF activity. Currently, we report on the design and synthesis of the novel C24D polypeptide, which inhibits the binding of PLIF to T cells and therefore inhibits the immune suppressive effect of PLIF. The effect of C24D on the generation of anti-breast cancer cytotoxic T lymphocytes (CTLs) was studied in vitro in cultures of MCF-7 (HLA-A2(+)) or T47D (HLA-A2(-)) breast cancer cells incubated with peripheral blood mononuclear cells (PBMCs) from healthy blood donors. We found that C24D treatment exclusively induced development of CTLs. On reactivation by their specific target cells, the CTLs secreted interferon-γ and induced target apoptosis. Anti-MCF-7 CTLs were cross-cytotoxic to MDA-MB-231 (HLA-A2(+)) triple-negative breast cancer but not to T47D. Moreover, C24D treatment in vivo inhibited the growth of MCF-7 tumors engrafted in immune-compromised nude mice transfused with naïve allogeneic human PBMCs. Our results demonstrate that C24D treatment breakdown breast cancer induced tolerance enabling the initiation of effective anti-tumor immune response.

Ferritin and FasL (CD95L) mediate density dependent apoptosis in primary rat hepatocytes

Based on a recent description of an apoptosis stimulating property for hepatocyte derived isoferritins, this investigation demonstrates that ferritin, released in vitro from hepatocytes substantially contributes to density dependent apoptosis in primary hepatocytes and is significantly (P < or = 0.05) inhibited by anti-H-ferritin antibody rH02. Furthermore, total protein release and albumin secretion rapidly decline in a time and density dependent mode under serum-free conditions, whereas ferritin secretion, which is upregulated at initial stages of primary culture is not affected by cell density. Supplementation with dexamethasone (DEX) or proliferative stimulation by epidermal growth factor (EGF) and insulin strongly suppresses density dependent apoptosis. Both regimens have previously been shown to inhibit isoferritin mediated apoptosis in hepatocytes, most likely by interrupting proapotitc mitochondrial signalling. Finally, FasL/Fas also participates in density dependent apoptosis, since apoptosis is significantly (P < or = 0.005) reduced in high density cultures supplemented with an anti-FasL antibody. This antibody has also been shown to neutralise ferritin mediated apoptosis in primary hepatocytes, suggesting a linkage of ferritin and Fas in density dependent apoptosis. In conclusion, ferritin contributes to apoptosis in primary hepatocytes in an autocrine, density dependent mode, involving Fas stimulation and proapoptotic mitochondrial signalling. With respect to liver physiology, these findings may indicate that ferritin plays a yet unrecognised role as an acute phase signalling molecule in early stages of tissue repair and liver regeneration, and may also be responsible for the limited ability to propagate human hepatocytes in culture and the limited expansion of donor cells in the recipient liver upon cell transplantation.

Antibodies to placental immunoregulatory ferritin with transfer of polyclonal lymphocytes arrest MCF-7 human breast cancer growth in a nude mouse model

The recently cloned human gene named "placental immunoregulatory ferritin" (PLIF) is a pregnancy-related immunomodulator. Recombinant PLIF and its bioactive domain C48 are immune-suppressive and induce pronounced IL-10 production by immune cells. PLIF is expressed in the placenta and breast cancer cells. Blocking PLIF in pregnant mice by anti-C48 antibodies inhibited placental and fetal growth and modulated the cytokine network. It has been revealed that anti-C48 treatment inhibited MCF-7 tumor growth in nude mice. However, this significant effect was observed only in those transfused with human peripheral blood mononuclear cells. Blocking PLIF in tumor-engrafted human immune cell transfused mice resulted in massive infiltration of human CD45+ cells (mainly CD8+ T cells), both intratumorally and in the tumor periphery, and a significant number of caspase-3+ cells. In vitro, anti-C48 treatment of MCF-7 tumor cells cocultured with human lymphocytes induced a significant increase in interferon-gamma secretion. We conclude that blocking PLIF inhibits breast cancer growth, possibly by an effect on the cytokine network in immune cells and on breakdown of immunosuppression.

Ferritin-a mediator of apoptosis?

Previously we have demonstrated an apoptosis inducing activity for a rat hepatocyte conditioned medium (CM) presumably mediated by acidic isoferritins. Here, we present support for this assumption since isoferritins purified from different rat hepatocyte CM significantly enhanced the frequency of apoptotic cells in primary rat hepatocytes, an effect completely inhibited by a neutralizing anti-H-ferritin antibody. The apoptosis induction appears to be related to a 43 kDa ferritin subunit contained in the isoferritins released from primary hepatocytes, presumably representing a ferritin heavy/light chain heterodimer. In addition, these isoferritins immunologically crossreact with antibodies raised against placental isoferritin p43-PLF (which also contains a 43 kDa ferritin subunit) and melanoma-derived H-chain ferritin, representing ferritin isoforms which reveal immunomodulatory properties. Furthermore, p53 and FasL are upregulated upon isoferritin treatment in a time dependent mode, and apoptosis induction can be suppressed by neutralizing anti-FasL antibodies. Proapoptotic Bid is upregulated too and translocated into mitochondria in primary hepatocytes exposed to the isoferritins purified from the CM. Finally, epidermal growth factor (EGF) and dexamethasone (DEX), which counteract proapoptotic mitochondrial signalling, almost completely abolished the proapoptotic effect of the hepatocyte derived isoferritins. In conclusion, our findings demonstrate that acidic isoferritins with homology to immunomodulatory ferritin isoforms (p43-PLF, melanoma-derived-H-chain ferritin) are released from hepatocytes in vitro, and are able to stimulate upregulation of p53 and mediate apoptosis involving Fas (CD95) signalling as well as addressing the intrinsic mitochondrial proapoptotic pathway.

PLIF, a novel human ferritin subunit from placenta with immunosuppressive activity

Ferritin is a ubiquitous iron storage protein existing in multiple isoforms composed of 24 heavy and light chain subunits. We describe here a third ferritin-related subunit cloned from human placenta cDNA library and named PLIF (placental immunomodulatory ferritin). The PLIF coding region is composed of ferritin heavy chain (FTH) sequence lacking the 65 C-terminal amino acids, which are substituted with a novel 48 amino acid domain (C48). In contrast to FTH, PLIF mRNA does not include the iron response element in the 5'-untranslated region, suggesting that PLIF synthesis is not regulated by iron. The linkage between the FTH and C48 domains created a restriction site for EcoRI. PLIF protein was found to localize in syncytiotrophoblasts of placentas (8 weeks of gestation) at the fetal-maternal interface. Increased levels of PLIF transcript and protein were also detected in the breast carcinoma cell lines T47D and MCF-7 but not in the benign corresponding cell line HBL-100. In vitro, PLIF was shown to down-modulate mixed lymphocyte reactions and to inhibit the proliferation of peripheral blood mononuclear cells stimulated with OKT3. The accumulated data indicate that PLIF is an embryonic immune factor involved in down-modulating the maternal immune recognition of the embryo toward anergy. This mechanism may have been adapted by breast cancer cells over expressing PLIF.