PHA-E is a natural product extracted from red kidney beans, and it has been reported to induce cell apoptosis
by blocking EGFR in lung cancer cells. Because EGF is the major in vivo competitor to PHA-E in clinical application,
PHA-E must be proved that has better affinity to EGFR than EGF. This study would focus on how PHA-E tightly bind to
EGFR and the results would compare with EGF. The adhesion force, measured by AFM, between EGFR and PHA-E was
207.14±74.42 pN that was higher than EGF (183.65±86.93 pN). The equilibrium dissociation constant of PHA-E and
EGF to EGFR was 2.410-9±1.410-9 and 7.310-8±2.710-8, respectively, that could evaluate binding affinity. The result
showed that binding affinity of PHA-E to EGFR was one order higher than EGF to EGFR. In the results of flow cytometer
and confocal microscope, we found binding efficiency of EGF to EGFR was decrease as the concentration of PHA-E increased.
In the analysis of Western blot, treatment of A-549 cells with PHA-E resulted in a dose-dependent decrease in
EGFR phosphorylation. In conclusion, we found that PHA-E had better adhesion force and binding affinity to EGFR than
that of the EGF. The interaction between PHA-E and EGFR could block EGF binding and then inhibit EGFR phosphorylation.
PHA-E could be developed into a new target molecule for lung cancer treatment that could be immobilized on the
drug carrier to guide therapeutic particles to the tumor site.
Keywords: Adhesion force, binding affinity, epidermal growth factor receptor, lung cancer, natural product, phytohemagglutinin
erythroagglutinating, target molecule.
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