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e23005 Background: The microenvironment is a central regulator of cancer biology. While the contribution of fibroblasts has been largely studied, the role of endothelial cells as regulators of cancer cell behavior is still poorly understood. As in a diverse spectrum of physiological processes in normal tissue, endothelial cells may exert a similar regulatory control in cancer progression and metastasis. Methods: To characterize the functional effects of endothelial-cancer interaction we focused on an in vitro co-culture model. Results: Co-culturing human umbilical venous endothelial cells (HUVEC) with SKBR-3 breast cancer cells induced morphological changes with epithelial-mesenchymal transition traits (EMT) and a significantly increased migratory and invasive potential. This activity leading to an elongated phenotype, expression of mesenchymal markers and pro-migratory gene sets in SKBR-3 was contained in HUVEC conditioned medium. The pro-migratory effect on SKBR-3 was significantly more pronounced when the supernatant was obtained from a sub-confluent and highly proliferative endothelial cell culture than from a confluent and resting endothelial cell layer. To identify the secreted regulatory molecules, we analyzed the supernatant of sub-confluent and confluent endothelial cells by quantitative MS proteomics (SILAC analysis). Eight candidate proteins significantly more secreted in conditioned medium from confluent HUVEC represented potential inhibitors of migration. Among them NIDOGEN1 was found to be necessary and sufficient for the inhibition of EMT and migration in SKBR-3. Stimulation of SKBR-3 with supernatant from sub-confluent HUVEC increased p-STAT3 levels in SKBR-3. Silencing nidogen1 in confluent HUVEC re-activated phosphorylation of STAT3 indicating that NIDOGEN1 inhibits the promigratory STAT3 pathway. The STAT3 pathway and migration were also inhibited by overexpression of nidogen1 in MDA-MB-231 LM2 cells.When injected in the mammary fat pad of nude mice these cells formed significantly less lung metastases than controls (p < 0.01). Conclusions: We identified NIDOGEN1 as a novel regulator of endothelial control over cancer cell migration, invasion and metastasis.

e22014 Background: The microenvironment is a central regulator of tumor biology. While the contribution of fibroblasts has been largely studied, the role of endothelial cells as regulators of cance...

10515 Background: Bone metastasis is a main cause of morbidity in breast cancer. Since breast cancer is a heterogeneous disease, the interactions of cancer cells with the skeletal host cells might ...

503 Background: The effects of tumor-endothelial interaction on global gene expression in breast cancer are not yet well characterized. We hypothesized that gene expression signatures induced by tumor-endothelial interaction might be of clinical relevance. Methods: To this aim we set up an ex vivo co-culture model with human benign and a panel of 6 malignant breast epithelial cells in combination with human venous and microvascular endothelial cells and determined associated gene expression changes with cDNA microarrays. Pretreatment gene expression profiles of 295 early stage breast cancers from the Netherlands Cancer Institute with a median follow up of 12.6 years allowed evaluating in vitro effects in vivo. Results: The most prominent response to co-culture was the induction of a set of “M-phase cell cycle” genes in a subset of breast cancer co-cultures, which were absent in co-cultures with normal breast epithelial cells. While in monoculture tumor cells containing the stem cell like CD44+/CD24- signature showed a lower expression of the “M-phase cell cycle” genes than the CD44-/CD24+ cells, in the co-cultures with CD44+/CD24- cells these genes were induced. Interestingly, these tumor cells co- expressed a set of angiogenic factors such as VEGF, PTN, and FGF12 mRNA at significantly higher levels. In vivo, the expression of the gene set derived from the co-culture was remarkably coherent providing a basis for segregation of tumors into two groups. In a univariate analysis, early stage tumors with high expression levels (n= 137) of “M-phase cell cycle” genes had a significantly lower distant metastasis-free survival (p=1.8e-5) (50 % at 10 years) and overall survival rate (p= 5e-9) (52 % at 10 years) than tumors with low expression levels (n= 158) (metastasis-free survival: 73 %; overall survival: 84 % at 10 years). Conclusions: Our results suggest that the interaction of tumor cells expressing the CD44+/CD24- stem cell like signature, implicating a low proliferative potential, with endothelial cells might explain the unexpected and paradoxical association of the CD44+/CD24- signature with highly proliferative tumors with an unfavorable prognosis. Multiple co-expressed angiogenic factors represent potentially interesting additional therapeutic targets. No significant financial relationships to disclose.

e18500 Background: TTFields (tumor treating fields) are low intensity, intermediate frequency, alternating electric fields which slow the growth of solid tumors in-vivo, and have shown promise in pilot clinical trials in patients with advanced solid tumors. TTFields are a regional treatment which acts both by interfering with microtubules polymerization and by physical disruption of the cell structure during cytokinesis. It has been shown previously that TTFields sensitize non-small cell lung cultures to Pemetrexed. In-Vivo, TTFields did not increase pemetrexed related toxicity. Methods: A prospective trial was performed in 14, pretreated, stage IIIb-IV, NSCLC patients. Patients with brain metastases were excluded, as were patients with abnormal marrow, kidney, liver or cardiac functions. Patients with history of clinically significant arrhythmias or those having pacemakers were excluded as well. Patients received Pemetrexed 500mg/m2 IV q3w together with daily TTFields (12 h/day) using a portable medical device (NovoTTF-100L). The device generated 2 direction (AP and Lat), 150 kHz TTFields. Patients were followed every three weeks and had a lung CT every 9 weeks. The primary endpoint was the safety and tolerability of the NovoTTF-100L device in combination with pemetrexed. Results: The 14 patients received an average of 4 courses of pemetrexed (Range 1–9) and a cumulative TTFields treatment time of 182 weeks. The device was well tolerated as indicated in the device log files which showed an average daily use of 11±1 hours. There were no device-related, nor pemetrexed-related SAEs. In addition, no unexpected abnormalities were evident in the lab tests or EKGs, done every 3 weeks for all patients. There were no reports of arrhythmias. The only device related AE seen in all patients was dermatitis under the electrodes. This improved with meticulous skin care, topical steroid use and in extreme cases oral steroids. One patient (7.6%) had a CR, 1 a PR (7.6%), 9 SD (69.2%) and 3 PD (23%). 77% of patients were progression free at 12 weeks and the 6 month survival was 89%. Conclusions: TTFields are well tolerated when given together with pemetrexed. The excellent safety profile and initial efficacy results reported here justify further clinical testing. [Table: see text]

10006 Background: Perturbations in cell-cell interaction are a key feature of cancer. However, the systematic effects of cell-cell interaction on global gene expression in cancer are largely unexplored. We hypothesized that gene expression signatures induced by cell-cell interaction might be of clinical relevance. Methods: We simulated tumor-stroma interaction in vitro by systematically co-cultivating each of 7 different breast cancer cell lines with stromal fibroblasts from 3 different sites, and determined associated gene expression changes with cDNA microarrays. A dataset of pretreatment gene expression profiles from 295 early stage breast cancers (stage 1 and 2) with a median follow up of 12.6 years allowed us to evaluate the prognostic significance of the gene expression signatures of specific cell-cell interactions derived from our ex vivo models. Results: The most prominent response to epithelial-mesenchymal interaction was an induction of interferon-response genes (IRG), observed in 4 of the 7 breast cancer cell lines in co-culture with fibroblasts, but not in normal mammary epithelial cells. In response to close contact with these breast cancer cells, the fibroblasts secreted type I interferons, which, in turn, induced expression of the IRG in the tumor cells. Immunohistochemical analysis of human breast cancer tissues showed that Stat1, the key transcriptional activator of the IRG, and itself an IRG, was expressed in a subset of the cancers, with a striking pattern of elevated expression in the cancer cells in contact with, or close proximity to, the tumor stroma - paralleling the response seen in our ex vivo model. In vivo, expression of the IRGs was remarkably coherent, providing a basis for segregation of the 295 early-stage breast cancers into two groups by unsupervised hierarchical clustering with the IRG. Tumors with high expression levels (n=161) of IRG were associated with significantly shorter overall survival; 59% at 10 years versus 80% at 10 years for tumors with low expression levels (n=134) (log-rank p=0.001). Conclusions: Our results suggest that an interaction between some breast cancer cells and stromal fibroblasts can induce an interferon response, and that this response may be associated with a greater propensity for tumor progression. No significant financial relationships to disclose.