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Author ORCID Identifier
Date Available
8-19-2028
Year of Publication
2026
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Medicine
Department/School/Program
Molecular and Cellular Biochemistry
Faculty
Tianyan Gao
Abstract
The spatiotemporal control of cell signaling requires a balancing act of protein kinases and phosphatases. Hyperactivation of signaling downstream receptor tyrosine kinases (RTKs) is one of the most common mechanisms leading to oncogenic transformation in numerous cancer types. Although the activation process of RTKs has been extensively studied, the inactivation mechanisms mediated by tyrosine phosphatase are less understood. PTPRF, protein tyrosine phosphatase receptor type F, belongs to class I R2A subfamily of protein tyrosine phosphatases (PTP) that utilizes a cysteine-based catalytic mechanism to remove the phosphate group from tyrosine residues. In this study, we investigated the functional importance of PTPRF in controlling MET signaling in colon cancer.
The bioinformatics analysis of the human TCGA-COAD RNA-seq and the CPTAC colon cancer proteome datasets reveals that the expression of PTPRF mRNA and protein is significantly decreased in tumor samples compared to normal tissues. To determine the effect of PTPRF downregulation in colon cancer cells, we generate PTPRF knockout cells using CRISPR-mediated gene deletion and doxycycline-inducible PTPRF knockdown cells using shRNA-mediated gene silencing. Our studies show that loss of PTPRF expression results in an increase in the phosphorylation of MET receptor upon HGF stimulation. Co-immunoprecipitation experiments indicate that PTPRF interacts with the MET receptor/GAB1 complex. Interestingly, re-expression of wild-type, but not catalytically inactive mutant, PTPRF attenuates the HGF-stimulated phosphorylation of c-MET and GAB1 in PTPRF knockout cells, suggesting a phosphatase activity-dependent regulation. Intriguingly, the phosphorylation of AKT and ERK downstream of MET activation remain unchanged in PTPRF depleted cells. Instead, silencing PTPRF leads to increased activation of FAK and PAK, key regulators of cell motility. Consistently, we show that PTPRF downregulation promotes migration and invasive cell growth in vitro. Moreover, genetic and pharmacological inhibition of PAK1/2/3 blocks the migratory advantage conferred by PTPRF loss. Furthermore, decreased PTPRF expression renders colon cancer cells more sensitive to PAK inhibitor-induced growth inhibition.
Taken together, these results identify PTPRF as a novel phosphatase that negatively regulates the MET/FAK/PAK signaling axis to control cell motility. Importantly, PTPRF downregulation may play an important role in promoting tumor progression in colon cancer. Our findings will help guide the future development of targeted therapeutic options by using PTPRF as a new biomarker.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2026.377
Archival?
Archival
Funding Information
This work was supported by NIH grant R01GM150200 (TG). Carolina Galeano-Naranjo was partially supported by supplemental funding to NIH grant R01CA133429.
Recommended Citation
Galeano-Naranjo, Carolina, "MOVING TARGETS: THE ROLE OF PTPRF IN REGULATING C-MET SIGNALING AND CELL MIGRATION IN COLORECTAL CANCER" (2026). Theses and Dissertations--Molecular and Cellular Biochemistry. 81.
https://uknowledge.uky.edu/biochem_etds/81
