Expression of p43 in breast cancer tissue, correlation with prognostic parameters

p43 induces IP-10 expression through the JAK-STAT signaling pathway in HMEC-1 cells

p43 is a cofactor of aminoacyl-tRNA synthetase in mammals that effectively inhibits angiogenesis. However, the role of p43 in angiogenesis remains unclear. In the present study, we examined the effects of p43 on angiogenesis using human microvascular endothelial cells-1 (HMEC-1) cells as a model. Our microarray data showed that p43 regulated a number of cytokines, and the majoity of these are involved in the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. IP-10 was previously shown to inhibit angiogenesis and suppress tumor growth via the JAK-STAT signaling pathway in vitro and in vivo. Our results showed that p43 induces both the mRNA and protein expression of IP-10. Furthermore, we demonstrated that p43 exerted an effect on the JAK-STAT signaling pathway by regulating key factors of the pathway. Using a JAK inhibitor, AG490, we studied the effect of p43 on HMEC-1 cells by blocking the JAK-STAT pathway. We found that AG490 inhibited the induction of IP-10 expression by p43, and suppressed the inhibitory effect of p43 on tubule formation and cell migration in HMEC-1 cells. We concluded that p43 inhibits tubule formation and cell migration by inducing IP-10 through the JAK-STAT signaling pathway, and blocking the JAK-STAT pathway with AG490 diminishes the inhibitory effects of p43 on angiogenesis.

Aminoacyl-tRNA synthetase-interacting multifunctional protein 1 suppresses tumor growth in breast cancer-bearing mice by negatively regulating myeloid-derived suppressor cell functions

Myeloid-derived suppressor cells (MDSCs) are one of the most important cell types that contribute to negative regulation of immune responses in the tumor microenvironment. Recently, aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1), a novel pleiotropic cytokine, was identified as an antitumor protein that inhibits angiogenesis and induces antitumor responses. However, the effect of AIMP1 on MDSCs in the tumor environment remains unclear. In the present study, we demonstrated that AIMP1 significantly inhibited tumor growth in 4T1 breast cancer-bearing mice and reduced MDSCs population of tumor sites and spleens of tumor-bearing mice. AIMP1 reduced expansion of MDSCs from bone marrow-derived cells in the tumor-conditioned media. AIMP1 also negatively regulated suppressive activities of MDSCs by inhibiting IL-6 and NO production, and Arg-1 expression. Furthermore, treatment of breast cancer-bearing mice with AIMP1 decreased the capacity of MDSCs to suppress T cell proliferation and Treg cell induction. Western blot and inhibition experiments showed that downregulation of MDSCs functions by AIMP1 may result from attenuated activation of STATs, Akt, and ERK. These findings indicate that AIMP1 plays an essential role in negative regulation of suppressive functions of MDSCs. Therefore, it has a significant potential as a therapeutic agent for cancer treatment.

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.

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.

FBL blood test as a predictive marker of breast cancer in high risk women

The potential use of the ferritin bearing lymphocytes (FBL) blood test which enumerates oncofetal FBL as a biomarker for early breast cancer was explored. Analysis of the FBL positive test results carried out on high risk women who underwent biopsy in 1983-84 was found to be a significant predictor for early breast cancer (relative risk (RR) = 2.9, 95% confidence interval (CI) 1.4-5.8). A group of 635 women from the above study diagnosed in 1983-84 as having no evidence of breast cancer was further traced 8 years later with the aid of the National Cancer Registry. We identified 35 malignancies, including 19 cases of breast cancer. The RR of breast cancer for the FBL positive group was 2.51; 95% CI = 1.04-6.07 while for the other malignancies it was 0.93, 95% CI = 0.30-2.84. All the breast cancer cases in the FBL positive group were of the infiltrative duct carcinoma category and 71% were in early stage. In contrast, in the FBL negative group, 60% of the cases were infiltrative ductal carcinoma and most of them were at stage III. Positive FBL is associated with early manifestation of breast cancer and may be considered as a tool for the screening of breast cancer in high risk women.

The immunosuppressive human placental ferritin subunit p43 is produced by activated CD4+ lymphocytes

Human placental ferritin is an immunosuppressive protein composed of a 43-kDa subunit (p43) and ferritin light chains. Its physiological action seems to be downregulation of the immune response of the mother against her embryo. Elevated levels of p43 in serum are associated with pregnancy, lymphomas, breast cancer, and AIDS. Although it is known that p43 is produced by activated T lymphocytes, the specific T-lymphocyte subset involved is unknown. p43 is measured by enzyme-linked immunosorbent assays with CM-H-9 monoclonal antibody specific for p43. We studied the de novo biosynthesis of p43 by isolated activated CD4+ and CD8+ T lymphocytes in a normal donor and in a patient with elevated levels of p43 in serum. The results indicated that p43 was synthesized by activated CD4+ lymphocytes from the normal donor (0.45% of the total de novo proteins) but that its biosynthesis by CD8+ lymphocytes was below the level of detection. The activated CD4+ lymphocytes from the patient with elevated levels of p43 in serum overproduced p43 (3.8% of the nascent proteins). Since it was shown that a subset of CD8+ lymphocytes has receptors for p43, the latter may be considered an immunoregulatory cytokine produced mainly by activated CD4+ lymphocytes.

Downregulation of lymphocyte mitogenesis by breast cancer-associated p43

Placental isoferritin-associated p43 has proven to induce immune suppression during pregnancy in order to avoid rejection of the fetus' alloantigens by maternal lymphocytes. It has been demonstrated previously that p43 is also synthesized by breast cancer cells and can also be found on the surface of a subpopulation of T cells in women with this disease. Therefore, it was the aim of the present study to investigate if breast cancer-associated p43 has immunosuppressive properties. In 40 women undergoing surgical excision of a suspicious lump in their breast, blood was withdrawn and lymphocytes were isolated. Lymphocyte cultures were incubated with p43 antigen and anti-p43 antibody (CM-H-9). In a second series, lymphocyte mitogenesis was activated by addition of concanavalin A (Con A), Con A + p43 and Con A + anti-p43, respectively. While lymphocytes of breast cancer patients (n = 21) and women with benign breast disease (n = 19) incubated with p43 as well as with anti-p43 antibody did not show any difference in terms of incorporation of [3H]thymidine, activation of lymphocytes by addition of Con A was significantly inhibited after addition of p43 antigen in breast cancer patients compared to women with benign breast disease (P = 0.0178). Analysis of prognostic factors for breast cancer showed that inhibition of lymphocyte mitogenesis was dependent on the degree of tumor differentiation and was significantly higher in well differentiated tumors (GI) compared with more dedifferentiated tumors (GIII). The present study shows that breast cancer-associated antigen p43 is able to induce immune suppression in breast cancer patients but not in women with benign breast disease.