It remains generally accepted that colorectal cancer (CRC) results from the accumulation of genetic events within the epithelial compartment. Unresolved issues include (1) whether the order of these genetic events matter (e.g., APC vs KRAS), (2) whether cancers can initiate from multiple distinct cells of origin, (3) the relationship between the normal colonic stem cell and the cells that function to maintain the tumor and (4) the contribution of the local environment to the neoplastic process. We hypothesize that colonic tumor initiation and progression is highly dependent upon the origin of the cell that incurs the relevant mutagenic events, as well as the regulation of growth and clonal selection of particular progeny that emanate from tumor-initiating cells. We have demonstrated that there are distinct normal colonic progenitor populations marked by expression of two specific cell surface markers, Lrig1 and Lgr5. Although the precise relationship between cells expressing these two markers is unknown, these two bona fide stem cell markers exhibit overlapping, yet distinct, expression patterns in both normal colon and in ApcMin/+ tumors. Of note, Lrig1 is induced by EGFR signaling and acts to negatively regulate EGFR signaling, whereas Lgr5 is a canonical Wnt target of unknown function. We have generated inducible Lrig1-CreERT2 mice, and our collaborator Hans Clevers has provided us with inducible Lgr5-EGFP-IRES-CreERT2 animals that allow for the specific activation of Cre recombinase within distinct colonic stem cell populations. We will use these mice to determine the importance of cell-of-origin in colon cancer initiation and progression. In addition, we have identified a gene, Slc26a3, that is selectively expressed in the differentiated compartment of the colon, and we have generated Slc26a3-CreERT2 mice that will allow us to resolve whether colonic tumors arise from the "top down" or "bottom up."

Public Health Relevance

The cell in the colon which gives rise to colorectal cancer is unknown. We have generated novel genetically engineered mice that will allow us to answer this question. These results may allow us to determine whether colon cancer stem cells exist and their relationship to normal colonic stem cells, leading to identification of the colon cancer cell-of-origin and the colon cancer stem cell and offering exciting new therapeutic options.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA151566-03
Application #
8204978
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Salnikow, Konstantin
Project Start
2010-07-01
Project End
2014-12-31
Budget Start
2012-01-01
Budget End
2012-12-31
Support Year
3
Fiscal Year
2012
Total Cost
$376,724
Indirect Cost
$64,177
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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