# Targeting PLK1 potentiates the antitumor efficacy of EGFR-TKIs through inhibiting the JAK1/STAT3 pathway

## TL;DR

Combining PLK1 inhibitors with EGFR-TKIs may improve cancer treatment by overcoming drug resistance in lung cancer patients.

## Contribution

This study reveals a new mechanism of resistance to EGFR-TKIs and proposes a novel combination therapy involving PLK1 inhibition.

## Key findings

- High PLK1 expression correlates with STAT3 activation and poor survival in EGFR-mutant NSCLC patients.
- Combining PLK1 inhibitors with EGFR-TKIs reverses resistance and induces tumor regression in preclinical models.
- PLK1 and STAT3 form a feedback loop that contributes to EGFR-TKI resistance.

## Abstract

Despite the rapid development of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in recent decades, resistance remains a significant challenge in managing advanced non-small cell lung cancer (NSCLC). Elucidating the mechanisms underlying EGFR-TKI resistance and developing novel strategies are therefore crucial. In this study, we investigated the role of polo-like kinase 1 (PLK1) in EGFR-mutant NSCLC and evaluated the therapeutic potential of combining EGFR-TKIs with PLK1 inhibitors. We demonstrated that high PLK1 expression correlates with STAT3 signaling activation and decreased survival probability in EGFR-mutant NSCLC patients. Subsequent studies revealed that PLK1 inhibitors effectively reversed the activation of STAT3 induced by EGFR-TKIs. When used in combination with EGFR-TKIs, they promoted cell apoptosis, inhibited cell proliferation in vitro, and induced tumor regression in animal models. Mechanistically, our data demonstrated that PLK1 regulated STAT3 activity through protein-protein interactions and JAK1-mediated phosphorylation, while STAT3 reciprocally regulated PLK1 transcription, establishing a positive feedback loop between these signaling molecules. This PLK1/STAT3 loop was further reinforced by FGFR1 upregulation and directly linked to EGFR-TKI resistance. Targeting this axis with combinatorial inhibitors exerted synergistic anti-tumor effects, suppressing proliferation and migration in osimertinib-resistant models. In conclusion, concurrent inhibition of EGFR and FGFR1/STAT3/PLK1 signaling pathways provides a promising therapeutic strategy for NSCLC patients with EGFR mutations, enhancing efficacy and overcoming resistance.