Esophageal adenocarcinoma (EAC) is an aggressive carcinoma with intrinsic resistance to current therapies and poor clinical outcome. Gastro esophageal reflux disease (GERD), a chronic pathological condition in which the esophagus is exposed to acidic gastric juice mixed with bile salts, is the main risk factor for the development of Barrett's esophagus, a glandular metaplasia that carries a high risk for progression to esophageal adenocarcinoma. Our preliminary data has shown that AXL is a pro-survival protein that protects cancer cells against genotoxic DNA damaging events such as exposure to acidic bile salts and chemotherapeutics. Based on these novel preliminary data, we plan to investigate the mechanistic and biological roles of AXL in mediating response to genotoxic acidic bile-salts and DNA damaging drugs, and determine the clinical and therapeutic potential of AXL in EAC. Supported by preliminary data, we hypothesize that loss of p53 mediates up-regulation of AXL protein in EAC. The overexpression of AXL provides important pro-survival, pro-invasion, and malignant transformation activities by regulating the protein levels of both nuclear and cytosolic c-ABL in response to genotoxic stress. This hypothesis will be tested by pursuing three specific aims: 1) Investigate the role of p53 in regulating AXL protein level; 2) Investigate the role of AX in regulating c-ABL function in Barrett's and EAC cells; 3) Determine the clinical significance and therapeutic potential of AXL in EAC.
In Aim 1, the molecular mechanisms by which p53 negatively regulates AXL protein expression will be investigated.
In Aim 2, studies will be undertaken to determine the role of AXL in regulating cytosolic c-ABL protein expression and stability. Additionally, the role of AXL in regulating c- ABL-dependent cell survival, invasion, an malignant transformation will be examined.
In Aim 3, a comprehensive study will be undertaken to examine the clinical and histopathological parameters associated with AXL and c-ABL protein expressions in human EAC, using IHC analysis of normal, premalignant, and EAC tissue microarrays. Also, the potential of AXL as a therapeutic target will be evaluated using the AXL inhibitor R428/BGB324 or genetic knockdown alone, or in combination with cisplatin, docetaxel, or oxaliplatin in pre- clinical settings (xenograft mouse model). The approach is innovative because it is based on an innovative hypothesis that proposes the AXL-ABL axis as an important player in Barrett's carcinogenesis, mechanistic studies of AXL and c-ABL relevant to their combined tumorigenic functions, advanced methodologies, and the potential development of novel targeted therapy in EAC. The proposed research is significant because it fills in a critical gap in our understanding of the functions of AXL in EAC. Upon completion of the proposed research, we will have a better understanding of the biology of EAC which could provide new translational opportunities that facilitate the development of better therapeutic and prognostic approaches.

Public Health Relevance

The identification of a novel mechanism of esophageal tumorigenesis mediated by the AXL receptor tyrosine in response to acidic bile-salts is expected to provide new translational opportunities that facilitate the development of better therapeutic and prognostic approaches.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Molecular Pathobiology Study Section (CAMP)
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Yassin, Rihab R
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Vanderbilt University Medical Center
United States
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