The esophageal epithelium contains proliferating basal cells that undergo differentiation as they migrate towards the luminal surface, where they slough off due to apoptosis. The epithelium is renewed continuously, but it is this constant state of renewal that makes the epithelium so susceptible to injurious insults, such as infection, acid reflux, radiation, chemotherapy, and ischemia. Peptide growth factors such as epidermal growth factor (EGF) and insulin-like growth factor (IGF)-I regulate esophageal epithelial cell proliferation, growth, migration, differentiation, and apoptosis. They also play a critical role in pathological processes such as carcinogenesis. Amongst the IGF binding proteins, IGFBP-3 is a major negative regulator of the bioactivities of IGF. Both IGF-I and IGF-II are implicated in esophageal cancer. The present proposal focuses upon insulin like growth factor binding protein-3 (IGFBP-3). IGFBP-3 binds insulin-like growth factors (IGFs) and regulates their bioactivities. IGFBP-3 is induced by hypoxia and suppressed by EGFR as shown by us. In the esophagus, IGFBP-3 is often upregulated in preneoplastic lesions and frequently overexpressed in invasive adenocarcinomas and squamous cell carcinomas with concurrent EGFR overexpression. However, the biological role(s) of IGFBP-3 and the mode of its regulation are not known in esophageal tumors. Our fundamental hypothesis is that IGFBP-3 plays a critical role in esophageal tumor growth under hypoxic conditions in the microenvironment. When the esophageal epithelium is maintained in a physiological milieu in the presence of growth factors (e.g. EGF) and a normal level of oxygen, IGFBP-3 is inactive and permissive for the full activation of the IGF-signaling pathway. However, in esophageal tumors, hypoxia fosters IGFBP-3 induction. IGFBP-3 gene is transcriptionally activated by hypoxia inducible factor (HIF). IGFBP-3 mRNA is translated in cap-dependent as well as cap-independent manners, while the latter is activated under severe hypoxic conditions to permit selective IGFBP-3 protein synthesis. Once expressed and secreted, IGFBP-3 neutralizes IGF and exerts antiproliferative or proapoptotic effects in tumor cells. However, in a subset of esophageal tumor cells, which have adapted to a hypoxic microenvironment, such tumor cells can proliferate autonomous of IGF even in the presence of IGFBP-3. Inhibition of IGF signaling by IGFBP-3 may benefit tumor cells by suppressing cellular anabolic activities to make them dormant in the absence of sufficient oxygen supply and energy sources. This hypothesis will be pursued through the following interrelated Specific Aims since it is important to understand the role and regulation of IGFBP-3 in esophageal tumor biology: (1) Specific Aim 1: To determine the role of IGFBP-3 in esophageal tumor biology;(2) Specific Aim 2: To elucidate the role of HIF1a in the transcriptional regulation of IGFBP-3;and (3) Specific Aim 3: To determine how hypoxia regulates the translation of IGFBP-3.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Gastrointestinal Cell and Molecular Biology Study Section (GCMB)
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Hamilton, Frank A
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University of Pennsylvania
Internal Medicine/Medicine
Schools of Medicine
United States
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Kagawa, S; Natsuizaka, M; Whelan, K A et al. (2015) Cellular senescence checkpoint function determines differential Notch1-dependent oncogenic and tumor-suppressor activities. Oncogene 34:2347-59
Muir, Amanda B; Dods, Kara; Noah, Yuli et al. (2015) Esophageal epithelial cells acquire functional characteristics of activated myofibroblasts after undergoing an epithelial to mesenchymal transition. Exp Cell Res 330:102-10
Natsuizaka, Mitsuteru; Kinugasa, Hideaki; Kagawa, Shingo et al. (2014) IGFBP3 promotes esophageal cancer growth by suppressing oxidative stress in hypoxic tumor microenvironment. Am J Cancer Res 4:29-41
Naganuma, Seiji; Whelan, Kelly A; Natsuizaka, Mitsuteru et al. (2012) Notch receptor inhibition reveals the importance of cyclin D1 and Wnt signaling in invasive esophageal squamous cell carcinoma. Am J Cancer Res 2:459-75
Kalabis, Jiri; Wong, Gabrielle S; Vega, Maria E et al. (2012) Isolation and characterization of mouse and human esophageal epithelial cells in 3D organotypic culture. Nat Protoc 7:235-46
Natsuizaka, Mitsuteru; Naganuma, Seiji; Kagawa, Shingo et al. (2012) Hypoxia induces IGFBP3 in esophageal squamous cancer cells through HIF-1?-mediated mRNA transcription and continuous protein synthesis. FASEB J 26:2620-30
Ohashi, Shinya; Natsuizaka, Mitsuteru; Naganuma, Seiji et al. (2011) A NOTCH3-mediated squamous cell differentiation program limits expansion of EMT-competent cells that express the ZEB transcription factors. Cancer Res 71:6836-47
Ohashi, Shinya; Natsuizaka, Mitsuteru; Nakagawa, Hiroshi (2011) MMP7 and activation of IGF-1R: a new insight into anti-EGFR therapeutic resistance in metastatic colorectal cancer. Cancer Biol Ther 11:184-7
Natsuizaka, Mitsuteru; Ohashi, Shinya; Wong, Gabrielle S et al. (2010) Insulin-like growth factor-binding protein-3 promotes transforming growth factor-{beta}1-mediated epithelial-to-mesenchymal transition and motility in transformed human esophageal cells. Carcinogenesis 31:1344-53
Ohashi, Shinya; Natsuizaka, Mitsuteru; Wong, Gabrielle S et al. (2010) Epidermal growth factor receptor and mutant p53 expand an esophageal cellular subpopulation capable of epithelial-to-mesenchymal transition through ZEB transcription factors. Cancer Res 70:4174-84

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