# CIB2 mediates acquired gefitinib resistance by inducing ZEB1 expression and epithelial-mesenchymal transition

## TL;DR

This study shows that CIB2 contributes to resistance to gefitinib in lung cancer by promoting EMT through ZEB1, offering a potential new target for treatment.

## Contribution

The study identifies CIB2 as a novel mediator of gefitinib resistance through ZEB1-induced EMT in lung cancer.

## Key findings

- High CIB2 levels in resistant cells correlate with gefitinib resistance.
- CIB2 promotes EMT by upregulating ZEB1, increasing resistance to gefitinib.
- FOSL1 regulates CIB2 expression, linking it to resistance mechanisms.

## Abstract

EGFR-TKIs have been used as frontline treatment in patients with advanced non-small cell lung cancer (NSCLC) suffering from the EGFR mutation. Gefitinib, the first-generation EGFR-TKI, has greatly improved survival rates in lung cancer patients, whereas acquired gefitinib resistance is still a critical issue that needs to be overcome. In our research, high expression levels of CIB2 were found in gefitinib-resistant lung cancer cells. CIB2 knockout rendered gefitinib-resistant cells more sensitive to gefitinib, and overexpression of CIB2 in parental cells was sufficient to induce more resistance to gefitinib. Inhibition of CIB2 in gefitinib-resistant lung cancer cells significantly induced cell apoptosis. To clarify the major molecular mechanism by which CIB2 increases gefitinib resistance, we demonstrated that raised CIB2 in lung cancer cells promoted epithelial-to-mesenchymal transition (EMT) through upregulation of ZEB1. Moreover, FOSL1 transcriptionally regulated CIB2 expression. Finally, CIB2 rendered tumors resistant to gefitinib treatment in vivo. Our results explored a new mechanism: upregulated CIB2 promoted EMT through ZEB1 to regulate gefitinib resistance, which could be a candidate therapeutic target for overcoming acquired resistance to EGFR-TKIs in NSCLC patients.