We maintain that a thorough and rigorous analysis of trafficking of EGFR ligands in polarized epithelial cells will continue to provide important insights into basic cell biology and the pathogenesis of colorectal cancer (CRC). The current grant cycle has been a period of significant productivity with 39 manuscripts and 4 reviews published that cite this grant. Simply stated, we intend to demonstrate that in the colon TGFA is beneficial and EREG is harmful. Endogenous TGFA acts to maintain colonic homeostasis;it stabilizes NKD2 to ensure its efficient delivery to the basolateral surface. After delivering TGFA to the basolateral surface, NKD2 binds and degrades DVL-1 (a positive regulator of Wnt signaling) so as to maintain tight regulation of canonical Wnt signaling. Loss of NKD2 is a frequent late event in CRC, and induction of NKD2 in Caco-2 cells initiates a program of goblet cell differentiation. Whereas TGFA mRNA is decreased in CRC, EREG expression is increased. Overexpression of EREG in colon cancer has been linked to metastasis. We show that tyrosine (Y)156 in the cytoplasmic tail of EREG regulates its basolateral trafficking and have identified multiple interacting partners. Remarkably, EREG(Y156A) is completely missorted to the apical surface of polarized MDCK cells, and the cells are morphologically and functionally transformed. We propose two aims to elucidate the divergent roles of TGFA and EREG in normal colon and CRC.
Aim 1. Test the hypothesis that NKD2 acts as a tumor suppressor. We will elucidate the mechanism by which induction of NKD2 in Caco-2 cells results in goblet cell differentiation. Using mice we recently generated, we will determine whether loss of NKD2 in Wnt-dependent (AOM) and Wnt-independent (Smad3-/-) colonic tumors results in more advanced tumors. We also propose to examine post-transcriptional regulation of NKD2 as part of a long-term therapeutic strategy to treat CRC by regulated re-expression of NKD2.
Aim 2. Identify factors (and their underlying mechanisms of action) that regulate EREG basolateral trafficking and signaling. Using wild-type EREG and EREG (Y156A), we propose to elucidate mechanisms underlying the invasive phenotype of apically redirected EREG. Finally, we will test the hypothesis that EREG is a """"""""metastasis promoter"""""""" by attempting to prevent lung metastasis in a syngeneic mouse colon cancer model through elimination of EREG.

Public Health Relevance

Through a detailed analysis of NKD2 as a potential tumor suppressor and the role of EREG in promoting metastasis, these studies will provide new insights into the pathogenesis of colorectal cancer (CRC) (and possibly other solid tumors). We expect that the results of these studies will guide approaches to enhance the expression of NKD2 as a potential therapeutic strategy and increase the efficacy of cetuximab in the treatment of patients with CRC.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA046413-26
Application #
8628051
Study Section
Tumor Cell Biology Study Section (TCB)
Program Officer
Salnikow, Konstantin
Project Start
1988-05-01
Project End
2017-02-28
Budget Start
2014-03-01
Budget End
2015-02-28
Support Year
26
Fiscal Year
2014
Total Cost
$454,495
Indirect Cost
$163,152
Name
Vanderbilt University Medical Center
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
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