Abstract
Colorectal cancer (CRC) is both the third most common and deadliest cancer in the United States. Despite recent
advances in treatment, the 5-year survival rate remains poor due to multiple factors including delayed diagnosis,
chemoresistance, and disease heterogeneity. Altered expression of enteroendocrine protein signaling
components consisting of Fibroblast Growth Factor Receptor 4 (FGFR4), its ligand Fibroblast Growth Factor 19
(FGF19), and co-receptor Klotho Beta (KLB) recently have been implicated in various cancers. Specific to CRC,
the role of KLB remains elusive, although FGF19 and FGFR4 have more established oncogenic functions. An
objective of this proposed research is to delineate KLB’s function in CRC. The work is predicated on the analysis
of CRC RNA-seq data from The Cancer Genome Atlas (TCGA) database consistently showing significant
repression in CRC generally and across all subtypes. Collectively, it is necessary to further investigate and
validate KLB’s role in CRC, focusing on how KLB modulates oncogenic FGFR4-FGF19 signaling in the larger
context of epithelial-mesenchymal transition (EMT) and tumorigenesis. Thus, our overall hypothesis is that KLB
demonstrates tumor suppressor properties in CRC by negatively regulating oncogenic, EMT-promoting
FGFR4-FGF19 signaling. Specific Aim 1 will test the hypothesis by analyzing detailed clinical parameters via
informatics to assess the prognostic value of KLB deficiency in CRC and reveal its impact on tumor dynamics in
vitro and in vivo. Our preliminary data reveals tumor-suppressor-like properties of KLB as its expression is directly
associated with treatment success, microsatellite stability, survivability and inversely with pathologic stage.
Additionally, KLB downregulation occurs as early as the adenoma stage further supported by a CRC cell line
panel showing global KLB repression which directly correlated with differentiation status. Finally, KLB expression
was enhanced in two separate in vitro CRC models of differentiation and its transgenic overexpression was
associated with increased cellular organization and polarization of HT29 cells compared to CrisprCas9-induced
knock down. Specific Aim 2 will investigate KLB’s mechanism of action by testing FGFR4-FGF19 signaling as
the major effector pathway through which KLB affects CRC. In support of this Aim, we present compelling new
preliminary evidence showing that KLB expression positively correlates with Farnesoid-X-Receptor (FXR), a
known tumor suppressor and target of FGFR4 signaling, within the clinical data thereby indicating possible
crosstalk. Additionally, chemical agonism of FXR induces KLB expression in Caco2 cells in vitro. By performing
these studies, we expect to (i) Establish KLB’s clinical implications in CRC, and (ii) Demonstrate that KLB affects
CRC mechanistically through regulation of FGFR4-FGF19 signaling. Overall, this study will establish a tentative
role for KLB in CRC and how its presence impacts oncogenic FGFR4-FGF19 signaling. The ultimate goal of this
proposal is to utilize KLB expression to predict prognosis, treatment response and serve as a potential
therapeutic target for improving CRC patient outcomes.