Fra-1 et cancer du sein (analyse de son rôle dans le contrôle de la progression tumorale et mécanismes responsables de sa surexpression dans les cancers du sein les plus invasifs)

MONTPELLIER-BU Médecine UPM (341722108) / SudocPARIS-BIUP (751062107) / SudocMONTPELLIER-BU Médecine (341722104) / SudocSudocFranceF

Mechanisms underlying differential expression of interleukin-8 in breast cancer cells.

We have recently reported that interleukin-8 (IL-8) expression was inversely correlated to estrogen receptor (ER) status and was overexpressed in invasive breast cancer cells. In the present study, we show that IL-8 overexpression in breast cancer cells involves a higher transcriptional activity of IL-8 gene promoter. Cloning of IL-8 promoter from MDA-MB-231 and MCF-7 cells expressing high and low levels of IL-8, respectively, shows the integrity of the promoter in both cell lines. Deletion and site-directed mutagenesis of the promoter demonstrate that NF-kappaB and AP-1 and to a lesser extent C/EBP binding sites play a crucial role in the control of IL-8 promoter activity in MDA-MB-231 cells. Knockdown of NF-kappaB and AP-1 activities by adenovirus-mediated expression of an NF-kappaB super-repressor and RNA interference, respectively, decreased IL-8 expression in MDA-MB-231 cells. On the contrary, restoration of Fra-1, Fra-2, c-Jun, p50, p65, C/EBPalpha and C/EBPbeta expression levels in MCF-7 cells led to a promoter activity comparable to that observed in MDA-MB-231 cells. Our data constitute the first extensive study of IL-8 gene overexpression in breast cancer cells and suggest that the high expression of IL-8 in invasive cancer cells requires a complex cooperation between NF-kappaB, AP-1 and C/EBP transcription factors

Apoptosis and p53 are not involved in the anti-tumor efficacy of (125)I-labeled monoclonal antibodies targeting the cell membrane.: Running title: 125I-RIT-induced cell death mechanisms

International audienceINTRODUCTION: (125)I-labeled monoclonal antibodies ((125)I-mAbs) can efficiently treat small solid tumors. Here, we investigated the role of apoptosis, autophagy and mitotic catastrophe in (125)I-mAb toxicity in p53(-/-) and p53(+/+) cancer cells. METHODS: We exposed p53(-/-) and p53(+/+) HCT116 cells to increasing activities of internalizing (cytoplasmic location) anti-HER1 (125)I-mAbs, or non-internalizing (cell surface location) anti-CEA (125)I-mAbs. For each targeting model we established the relationship between survival and mean nucleus absorbed dose using the MIRD formalism. RESULTS: In both p53(-/-) and p53(+/+) HCT116 cells, anti-CEA (125)I-mAbs were more cytotoxic per Gy than anti-HER1 (125)I-mAbs. Sensitivity to anti-CEA (125)I-mAbs was p53-independent, while sensitivity to anti-HER1 (125)I-mAbs was higher in p53(-/-) HCT 116 cells, suggesting that they act through different signaling pathways. Apoptosis was only induced in p53(+/+) HCT116 cells and could not explain cell membrane radiation sensitivity. Inhibition of autophagy did not modify the cell response to (125)I-mAbs. By contrast, mitotic death was similarly induced in both p53(-/-) and p53(+/+) HCT116 cells by the two types of (125)I-mAbs. We also showed using medium transfer experiments that γ-H2AX foci were produced in bystander cells. CONCLUSION: Cell membrane sensitivity to (125)I-mAbs is not mediated by apoptosis and is p53-independent. Bystander effects-mediated mitotic death could be involved in the efficacy of (125)I-mAbs binding cell surface receptors

The human Mullerian inhibiting substance type II receptor as immunotherapy target for ovarian cancer. Validation using the mAb 12G4

International audienceOvarian cancer has the highest mortality rate among gynecologic malignancies. The monoclonal antibody 12G4 specifically recognizes the human Mullerian inhibiting substance type II receptor (MISRII) that is strongly expressed in human granulosa cell tumors (GCT) and in the majority of human epithelial ovarian cancers (EOC). To determine whether MISRII represents an attractive target for antibody-based tumor therapy, we first confirmed by immunohistochemistry with 12G4 its expression in all tested GCT samples (4/4) and all, but one, EOC human tissue specimens (13/14). We then demonstrated in vitro the internalization of 12G4 in MISRII(high)COV434 cells after binding to MISRII and its ability to increase the apoptosis rate (FACS, DNA fragmentation) in MISRII(high)COV434 (GCT) and MISRII(medium)NIH-OVCAR-3 (EOC) cells that express different levels of MISRII. A standard (51)Cr release assay showed that 12G4 mediates antibody-dependent cell-meditated cytotoxicity. Finally, in vivo assessment of 12G4 anti-tumor effects showed a significant reduction of tumor growth and an increase of the median survival time in mice xenografted with MISRII(high)COV434 or MISRII(medium)NIH-OVCAR-3 cells and treated with 12G4 in comparison to controls treated with an irrelevant antibody. Altogether, our data indicate that MISRII is a new promising target for the control of ovarian GCTs and EOCs. A humanized version of the 12G4 antibody, named 3C23K, is in development for the targeted therapy of MISRII-positive gynecologic cancers

Effect of tyrosine kinase inhibitor STI571 on the kinase activity of wild-type and various mutated c-kit receptors found in mast cell neoplasms.

Systemic mastocytosis (SM) is a rare disease caused by an abnormal mast cell accumulation in various tissues. Two classes of constitutive activating c-kit mutations are found in SM. The most frequent class occurs in the catalytic pocket coding region with substitutions at codon 816 and the other in the intracellular juxtamembrane coding region. Therefore, kinase inhibitors that block mutated c-kit activity might be used as therapeutic agents in SM. Here, we show that STI571 inhibits both wild-type and juxtamembrane mutant c-kit kinase activity, but has no effect on the activity of the D816 V mutant. Accordingly, STI571 selectively decreases the survival of normal mast cell and of mast cell lines either with juxtamembrane c-kit mutations, but not that of tumoral mast cell from patient with SM or of mast cell lines with the D816 V mutation. Therefore, STI571 is not a good candidate to treat SM and specific kinase inhibitors should be designed to inhibit constitutive activating mutations at codon 816

The anti-tumor efficacy of 3C23K, a glyco-engineered humanized anti-MISRII antibody, in an ovarian cancer model is mainly mediated by engagement of immune effector cells

International audienceOvarian cancer is the leading cause of death in women with gynecological cancers and despite recent advances, new and more efficient therapies are crucially needed. Müllerian Inhibiting Substance type II Receptor (MISRII, also named AMHRII) is expressed in most ovarian cancer subtypes and is a novel potential target for ovarian cancer immunotherapy. We previously developed and tested 12G4, the first murine monoclonal antibody (MAb) against human MISRII. Here, we report the humanization, affinity maturation and glyco-engineering steps of 12G4 to generate the Fc-optimized 3C23K MAb, and the evaluation of its in vivo anti-tumor activity. The epitopes of 3C23K and 12G4 were strictly identical and 3C23K affinity for MISRII was enhanced by a factor of about 14 (KD = 5.5 × 10-11 M vs 7.9 × 10-10 M), while the use of the EMABling® platform allowed the production of a low-fucosylated 3C23K antibody with a 30-fold KD improvement of its affinity to FcγRIIIa. In COV434-MISRII tumor-bearing mice, 3C23K reduced tumor growth more efficiently than 12G4 and its combination with carboplatin was more efficient than each monotherapy with a mean tumor size of 500, 1100 and 100 mm3 at the end of treatment with 3C23K (10 mg/kg, Q3-4D12), carboplatin (60 mg/kg, Q7D4) and 3C23K+carboplatin, respectively. Conversely, 3C23K-FcKO, a 3C23K form without affinity for the FcγRIIIa receptor, did not display any anti-tumor effect in vivo. These results strongly suggested that 3C23K mechanisms of action are mainly Fc-related. In vitro, antibody-dependent cytotoxicity (ADCC) and antibody-dependent cell phagocytosis (ADCP) were induced by 3C23K, as demonstrated with human effector cells. Using human NK cells, 50% of the maximal lysis was obtained with a 46-fold lower concentration of low-fucosylated 3C23K (2.9 ng/ml) than of 3C23K expressed in CHO cells (133.35 ng/ml). As 3C23K induced strong ADCC with human PBMC but almost none with murine PBMC, antibody-dependent cell phagocytosis (ADCP) was then investigated. 3C23K-dependent (100 ng/ml) ADCP was more active with murine than human macrophages (only 10% of living target cells vs. about 25%). These in vitro results suggest that the reduced ADCC with murine effectors could be partially balanced by ADCP activity in in vivo experiments. Taken together, these preclinical data indicate that 3C23K is a new promising therapeutic candidate for ovarian cancer immunotherapy and justify its recent introduction in a phase I clinical trial

Oestrogen signalling inhibits invasive phenotype by repressing RelB and its target BCL2.

International audienceAberrant constitutive expression of c-Rel, p65 and p50 NF-kappaB subunits has been reported in over 90% of breast cancers. Recently, we characterized a de novo RelB NF-kappaB subunit synthesis pathway, induced by the cytomegalovirus (CMV) IE1 protein, in which binding of p50-p65 NF-kappaB and c-Jun-Fra-2 AP-1 complexes to the RELB promoter work in synergy to potently activate transcription. Although RelB complexes were observed in mouse mammary tumours induced by either ectopic c-Rel expression or carcinogen exposure, little is known about RelB in human breast disease. Here, we demonstrate constitutive de novo RelB synthesis is selectively active in invasive oestrogen receptor alpha (ERalpha)-negative breast cancer cells. ERalpha signalling reduced levels of functional NF-kappaB and Fra-2 AP-1 and inhibited de novo RelB synthesis, leading to an inverse correlation between RELB and ERalpha gene expression in human breast cancer tissues and cell lines. Induction of Bcl-2 by RelB promoted the more invasive phenotype of ERalpha-negative cancer cells. Thus, inhibition of de novo RelB synthesis represents a new mechanism whereby ERalpha controls epithelial to mesenchymal transition (EMT)