Esophageal cancer is the eighth most common malignancy, and one of the leading causes of cancer-related deaths worldwide. The overall 5-year survival rate of patients with esophageal cancer remains low at 10% to 40% due to late diagnosis, metastasis, and resistance of the tumor to radiotherapy and chemotherapy. NF-κB is involved in the regulation of cell growth, survival, and motility, but little is known about the role of this signaling pathway in the tumorigenesis of human esophageal squamous cell carcinoma (ESCC), the most common form of esophageal cancer. This study aims to explore the functions of NF-κB in human ESCC progression and to determine whether targeting the NF-κB signaling pathway might be of therapeutic value against ESCC. Our results from human ESCC cell lines and ESCC tissue indicated that NF-κB is constitutively active in ESCC. Exposure of ESCC cells to two NF-κB inhibitors, Bay11-7082 and sulfasalazine, not only reduced cancer cell proliferation, but also induced apoptosis and enhanced sensitivity to chemotherapeutic drugs, 5-fluorouracil, and cisplatin. In addition, Bay11-7082 and sulfasalazine suppressed the migration and invasive potential of ESCC cells. More importantly, the results from tumor xenograft and experimental metastasis models showed that Bay11-7082 had significant antitumor effects on ESCC xenografts in nude mice by promoting apoptosis, and inhibiting proliferation and angiogenesis, as well as reduced the metastasis of ESCC cells to the lungs without significant toxic effects. In summary, our data suggest that NF-κB inhibitors may be potentially useful as therapeutic agents for patients with esophageal cancer. [Mol Cancer Ther 2009;8(9):2635-44]

Id-1 (inhibitor of differentiation or DNA binding) is a helix-loophelix protein that is overexpressed in many types of cancer including esophageal squamous cell carcinoma (ESCC). We previously reported that ectopic Id-1 expression activates the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in human esophageal cancer cells. In this study, we confirmed a positive correlation between Id-1 and phospho-AKT (Ser473) expressions in ESCC cell lines, as well as in ESCC on a tissue microarray. To investigate the significance of Id-1 in esophageal cancer progression, ESCC cells with stable ectopic Id-1 expression were inoculated subcutaneously into the flank of nude mice and were found to form larger tumors that showed elevated Ki-67 proliferation index and increased angiogenesis, as well as reduced apoptosis, compared with control cells expressing the empty vector. The Id-1-overexpressing cells also exhibited enhanced metastatic potential in the experimental metastasis assay. Treatment with the PI3K inhibitor LY294002 attenuated the tumor promotion effects of Id-1, indicating that the effects were mediated by the PI3K/AKT signaling pathway. In addition, our in vitro experiments showed that ectopic Id-1 expression altered the expression levels of markers associated with epithelial-mesenchymal transition and enhanced the migration ability of esophageal cancer cells. The Id-1-overexpressing ESCC cells also exhibited increased invasive potential, which was in part due to PI3K/AKTdependent modulation of matrix metalloproteinase-9 expression. In conclusion, our results provide the first evidence that Id-1 promotes tumorigenicity and metastasis of human esophageal cancer in vivo and that the PI3K inhibitor LY294002 can attenuate these effects. ' UICCKey words: Id-1; PI3K/AKT; esophageal; tumorigenicity; metastasis Esophageal cancer is the 8th most common cancer and the 6th most frequent cause of cancer death in the world.1 Despite modern multimodality therapy, the overall 5-year survival rate of patients with esophageal cancer remains low partly due to rapid progression, and local and distant metastasis at diagnosis. [2][3][4] Understanding the mechanisms involved in the progression of esophageal cancer is the key to effective treatment. A recent immunohistochemical study of esophageal squamous cell carcinoma (ESCC) showed that aberrant expression of Id-1 (inhibitor of differentiation or DNA binding) is associated with tumor invasion and metastasis.5 Id-1 is a helix-loop-helix (HLH) protein, which heterodimerizes with the basic helix-loop-helix transcription factors and inhibits them from DNA binding, therefore regulating gene transcription.6 It is overexpressed in many types of human cancer, 7 and its expression levels in uterine cervical, 8 breast, 9 prostate, 10 and lung 11 cancers are associated with cancer progression and poor prognosis.We previously reported that Id-1 induced esophageal cancer cell proliferation 4 and activation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B ...

Purpose: To investigate the autocrine/endocrine role of Id1-induced insulin-like growth factor-II (IGF-II) in esophageal cancer, and evaluate the potential of IGF-II-and IGF-type I receptor (IGF-IR)-targeted therapies.Experimental Design: Antibody array-based screening was used to identify differentially secreted growth factors from Id1-overexpressing esophageal cancer cells. In vitro and in vivo assays were performed to confirm the induction of IGF-II by Id1, and to study the autocrine and endocrine effects of IGF-II in promoting esophageal cancer progression. Human esophageal cancer tissue microarray was analyzed for overexpression of IGF-II and its correlation with that of Id1 and phosphorylated AKT (p-AKT). The efficacy of intratumorally injected IGF-II antibody and intraperitoneally injected cixutumumab (fully human monoclonal IGF-IR antibody) was evaluated using in vivo tumor xenograft and experimental metastasis models.Results: Id1 overexpression induced IGF-II secretion, which promoted cancer cell proliferation, survival, and invasion by activating AKT in an autocrine manner. Overexpression of IGF-II was found in 21 of 35 (60%) esophageal cancer tissues and was associated with upregulation of Id1 and p-AKT. IGF-II secreted by Id1-overexpressing esophageal cancer xenograft could instigate the growth of distant esophageal tumors, as well as promote metastasis of circulating cancer cells. Targeting IGF-II and IGF-IR had significant suppressive effects on tumor growth and metastasis in mice. Cixutumumab treatment enhanced the chemosensitivity of tumor xenografts to fluorouracil and cisplatin.