Proteomic and Phosphoproteomic Analyses Reveal the Oncogenic Role of PTK7-NDRG1 Axis in Non-small-cell Lung Cancer Cell Resistance to AZD9291

Epidermal growth factor receptor
tyrosine kinase inhibitors
(EGFR-TKIs)
are the most important chemotherapeutics for non-small-cell lung cancer
(NSCLC) therapy. The resistance to EGFR-TKIs is one of the biggest
obstacles to NSCLC outcome. In this study, taking advantage of phospho-
and proximal proteomic techniques, we analyzed the network rearrangement
in cell lines responding to AZD9291 treatment and found that cell-cell
adhesion was dramatically enhanced in AZD9291-resistant cells. Further
analysis revealed that protein tyrosine kinase 7 (PTK7) expression
was significantly elevated. Knockdown or overexpression assays showed
that PTK7 played a critical role in improving cell adhesion, which
enhanced drug resistance. Because PTK7 is a membrane-localized pseudokinase,
the proximal labeling probe BirA* was fused to reveal PTK7-interacting
proteins. We found that PTK7 interacted with and stabilized NDRG1,
which is located predominantly adjacent to adherens junctions. Downregulation
of PTK7 or NDRG1 eliminated the resistance of H1975-resistant (H1975-R)
and PC9-resistant (PC9-R) cells to AZD9291, suggesting that the PTK7-NDRG1
axis might be a potential target to eliminate the EGFR-TKI resistance
during NSCLC therapy.