Enteric Glia is New Biological Target to Block Drug Resistance in Colon Cancer

PROJECT SUMMARY/ABSTRACT
Resistance to anti-cancer therapies largely explains the abysmal 5-year survival rate of patients with advanced
colon cancer. Traditional chemotherapy regimens have been designed to efficiently stop proliferation and initiate
apoptosis in cancer cells, but have failed to appreciate the pro-chemoresistance signals emanating from cells
surrounding the tumor. We have identified a novel cellular component of the tumor microenvironment: the enteric
glial cells (EGC). We and others have shown over the last 15 years that EGC are potent inducers of barrier
function and healing in a healthy colon. Recently we have demonstrated that the EGC network substantially
infiltrates human colon adenocarcinomas and promotes cancer stem cell tumor-forming abilities via a paracrine
PGE2-EP4 pathway. Nevertheless, whether EGC impact colon cancer resistance to chemotherapy remains
unknown. Our preliminary studies indicate that EGC protect cancer stem cells against apoptosis induced by
chemotherapeutic drugs, allowing for enhanced tumor formation and growth despite the chemotherapy
treatment. We also have evidence that this is (1) dependent on activation of the MRN-ATM pathway - a central
player in DNA repair- in cancer cells and (2) exacerbated by EGC activation with chemotherapy. Using mass
spectrometry analyses, we have identified FSTL3 as a novel EGC-derived factor and generated preliminary
results implicating FSTL3 in EGC chemoprotective effects. Therefore, we propose to test the hypothesis that “in
response to chemotherapeutic drugs, EGC release larger amounts of FSTL3 in the tumor microenvironment,
which enhances cancer stem cell chemoresistance and allows for tumor formation and growth by promoting DNA
repair driven by the MRN-ATM pathway”. Specific Aim 1 will determine whether EGC promote cancer stem cell
resistance to chemotherapies via the release of FSTL3. Specific Aim 2 will test whether EGC protective effects
are mediated by increased DNA repair as a result of activation of the MRN-ATM pathway. Specific Aim 3 will
determine whether blocking FSTL3 production in EGC sensitizes colon tumors to chemotherapies in vivo.
Studies will use translationally relevant primary cultures of human EGC and cancer cells, 3D co-culture platforms,
orthotopic co-engraftment in immunodeficient mice, murine models of colon carcinogenesis, transgenic mice
allowing for chemogenetic activation of EGC (GFAP-hM3Dq) and inducible gene targeting in EGC (GFAP-
CreERT2), in addition to cutting-edge molecular profiling using single cell RNA seq and mass spectrometry
studies to identify the pro-chemoresistance factor(s) (and in particular FSTL3) and pathway(s) involved. These
studies will not only improve our understanding of the cellular and molecular mechanisms driving colon cancer
chemoresistance but will also demonstrate the therapeutic potential of developing strategies combining targeted
therapies against EGC-derived FSTL3 and traditional chemotherapy regimens.