Regulation of transcription factor E2F3a and its clinical relevance in ovarian cancer.

Recently we showed an integral epidermal growth factor receptor (EGFR)-E2F3a signaling path, in which E2F3a was found to be essential in EGFR-mediated proliferation in ovarian cancer cells. The present work evaluates the clinical relevance of this novel axis and of E2F3a itself in a large set of 130 ovarian cancer specimens. For this purpose E2F3a and its counterpart, E2F3b, were measured by RT-PCR and activated EGFR was assessed by immunohistochemistry. When compared with healthy control tissue, both E2F3 isoforms were overexpressed in the cancers, but only E2F3a expression correlated with tumor stage (ρ=0.349, P=0.0001) and residual disease (ρ=0.254, P=0.004). Univariate survival analyses showed E2F3a and activated EGFR to be associated with poor PFS and OS. Furthermore, a strong, positive correlation between activated EGFR and E2F3a expression was shown (P=0.0001). We further identified two EGFR-independent mechanisms that regulate E2F3a expression, namely one, acting by promoter methylation of miR-34a, which by its physical interaction with E2F3a transcripts causes their degradation, and the second based on 6p22 gene locus amplification. MiRIDIAN-based knockdown and induction of miR-34a evidenced a direct regulatory link between miR-34a and E2F3a, and the tumor-suppressive character of miR-34a was documented by its association with improved survival. Although, 6p22 gene locus amplification was detected in a significant number of ovarian cancer specimens, 6p22 ploidy was not relevant in predicting survival. In Cox regression analysis, E2F3a, but not activated EGFR or miR-34a expression, retained independent prognostic significance (PFS: hazards ratio 3.785 (1.326-9.840), P=0.013; OS: hazards ratio 4.651 (1.189-15.572), P=0.013). These clinical findings highlight the relevance of E2F3a in the biology of ovarian cancer. Moreover, identification of EGFR-independent mechanisms in E2F3a control can be helpful in explaining the non-responsiveness of therapeutic EGFR targeting in ovarian cancer.

L1CAM-integrin interaction induces constitutive NF-kappaB activation in pancreatic adenocarcinoma cells by enhancing IL-1beta expression.

L1 cell adhesion molecule (L1CAM) overexpression is often associated with bad prognosis in various human carcinomas. Recent studies also suggest a role of L1CAM in pancreatic ductal adenocarcinomas (PDAC). To further address its contribution, we expressed functional domains of L1CAM in PT45-P1 PDAC cells. We found that L1CAM that is full length (L1-FL), but neither the soluble ectodomain (L1ecto) nor the cytoplasmic part (L1cyt), could enhance cell proliferation or tumour growth in mice. Expression of L1-FL resulted in constitutive activation of NF-kappaB, which was abolished by L1CAM knockdown. We showed that the expression of IL-1beta was selectively upregulated by L1-FL, and increased IL-1beta levels were instrumental for sustained NF-kappaB activation. IL-1beta production and NF-kappaB activation were abolished by knockdown of alpha5-integrin and integrin-linked kinase, but insensitive to depletion of L1CAM cleavage proteinases. Supporting these data, PT45-P1 cells transduced with an L1CAM mutant deficient in integrin binding (L1-RGE) did not support the described L1-FL functions. Our results suggest that membranous L1CAM interacts with RGD-binding integrins, leading to sustained NF-kappaB activation by IL-1beta production and autocrine/paracrine signalling. The unravelling of this novel mechanism sheds new light on the important role of L1CAM expression in PDAC cells.

L1 cell adhesion molecule (L1CAM) as a pathogenetic factor in endometriosis.

BACKGROUND: Endometriosis is a benign and progressive disease with a high prevalence. Women with endometriosis, especially with atypical endometriosis, have a higher probability for developing ovarian cancer compared with women without endometriosis. The L1 cell adhesion molecule (L1CAM) is over expressed in ovarian and endometrial carcinomas and is associated with a bad prognosis. Here, we have analysed L1CAM expression in endometriosis. METHODS AND RESULTS: In our study with the samples from 79 patients with, and 37 patients without, endometriosis, we found that endometriosis cell lines and short-term cultures of endometrium from women with endometriosis expressed L1CAM at the mRNA and protein level. Quantitative RT-PCR analysis showed that L1CAM was expressed at significantly higher level in the epithelial compartment from patients with endometriosis compared with healthy controls (P = 0.0126). By immunohistochemical staining, 15 of 31 ovarian endometriotic lesions (48%) were shown to have L1CAM-positive staining. Of these 15 L1CAM-positive samples, 13 were atypical endometriotic lesions. Soluble L1 present in the conditioned medium of epithelial endometrium cultures from women with endometriosis was able to stimulate neurite outgrowth as measured in a chicken ganglion assay. CONCLUSIONS: We propose that L1CAM could promote endometriosis development by increasing enervation and aggravation. L1CAM expression is higher in atypical endometriosis compared with normal endometriosis.

The cytoplasmic part of L1-CAM controls growth and gene expression in human tumors that is reversed by therapeutic antibodies.

L1 cell adhesion molecule (L1-CAM) is a transmembrane cell adhesion molecule involved in cell migration and axon guidance in the developing nervous system. L1 is also overexpressed in ovarian and endometrial carcinomas and is associated with a bad prognosis. In carcinoma cell lines, L1 overexpression augments cell motility, tumor growth in mice and induces expression of Erk-dependent genes. Here, we show that a mutation in the cytoplasmic portion of L1 (T1247A, S1248A) abrogates Erk activation, blocks cell migration on extracellular matrix proteins and did not augment tumor growth in non-obese diabetic/severe combined immuno-deficient mice. In cells expressing mutant L1, the induction of Erk-dependent genes such as beta3-integrin, cathepsin-B and several transcription factors is eliminated and the invasive phenotype is abrogated. L1 antibodies showed similar effects. They prevented Erk activation and interfered with the Erk-dependent gene expression pattern. These findings provide a rationale for the mode of action of L1 antibodies and suggest that interference with L1 function could become a valuable target for therapy.

Ectodomain shedding of L1 adhesion molecule promotes cell migration by autocrine binding to integrins.

The L1 adhesion molecule plays an important role in axon guidance and cell migration in the nervous system. L1 is also expressed by many human carcinomas. In addition to cell surface expression, the L1 ectodomain can be released by a metalloproteinase, but the biological function of this process is unknown. Here we demonstrate that membrane-proximal cleavage of L1 can be detected in tumors and in the developing mouse brain. The shedding of L1 involved a disintegrin and metalloproteinase (ADAM)10, as transfection with dominant-negative ADAM10 completely abolishes L1 release. L1-transfected CHO cells (L1-CHO) showed enhanced haptotactic migration on fibronectin and laminin, which was blocked by antibodies to alpha v beta 5 and L1. Migration of L1-CHO cells, but not the basal migration of CHO cells, was blocked by a metalloproteinase inhibitor, indicating a role for L1 shedding in the migration process. CHO and metalloproteinase-inhibited L1-CHO cells were stimulated to migrate by soluble L1-Fc protein. The induction of migration was blocked by alpha v beta 5-specific antibodies and required Arg-Gly-Asp sites in L1. A 150-kD L1 fragment released by plasmin could also stimulate CHO cell migration. We propose that ectodomain-released L1 promotes migration by autocrine/paracrine stimulation via alpha v beta 5. This regulatory loop could be relevant for migratory processes under physiological and pathophysiological conditions.

In vivo activation and expansion of T cells by a bi-specific antibody abolishes metastasis formation of human melanoma cells in SCID mice.

Bi-specific antibody fragments (bAB) are used in tumour therapy as a means to redirect and to strengthen effector cell function. It would be of great therapeutic advantage if, in addition, recruitment, expansion and the state of activity of effector cells are influenced by targeting through a bAB. This question was explored in the melanoma-bearing SCID mouse. The chemically coupled Fab' fragments of an anti-CD3 and an anti-p97 monoclonal antibody (MAB) were characterized in vitro for dual binding specificity and support of lymphokine-activated-killer-cell (LAKC) cytotoxicity towards a highly aggressive human melanoma line, which was significantly increased and exceeded levels of antibody-dependent cellular cytotoxicity observed in the presence of the anti-p97 MAB. The in vivo efficacy was tested in the SCID mouse: 5, 10 and 15 days after i.p. application of tumour cells, mice received LAKC (2 x 10(7)) together with bAB (150-100 microg). The application of bAB was repeated at days 20 and 25. Application of LAKC to melanoma-bearing SCID mice prolonged the mean survival time from 22 days of the untreated control group to 41 days. Anti-p97 did not exert any additive effect. In the presence of bAB, melanoma cells did not grow in 3 out of 8 mice. The mean survival time of the 5 mice developing tumours was 45 days. Importantly, none of the mice receiving bAB developed metastases, which were seen in 100% of animals receiving tumour cells or tumour cells plus LAKC or tumour cells plus LAKC plus anti-p97. As revealed by LAKC recovered from the SCID mice, the efficacy of the bAB was based on prolonged persistence of CD8-positive cells as well as on expansion and activation of CD4-positive cells, which was observed only in bAB-treated tumour-bearing mice. The efficiency in recruiting cytotoxic and, in particular, helper T cells suggests bAB as a valuable additive in immunotherapeutic treatment of melanoma patients.