# USP28 Promotes Osimertinib Resistance in H1975 NSCLC Cells by Deubiquitinating and Stabilizing SIRT1

## TL;DR

This study shows that USP28 helps lung cancer cells resist a drug called osimertinib by stabilizing a protein called SIRT1, suggesting a new way to treat resistant cancers.

## Contribution

The novel finding is that USP28 promotes osimertinib resistance by deubiquitinating and stabilizing SIRT1 in NSCLC cells.

## Key findings

- USP28 and SIRT1 are upregulated in osimertinib-resistant H1975 cells and NSCLC tissues.
- USP28 stabilizes SIRT1 through deubiquitination, which contributes to osimertinib resistance.
- Targeting the USP28/SIRT1 axis may offer a new therapeutic strategy for overcoming resistance in NSCLC.

## Abstract

Osimertinib (OSI) resistance in non‐small cell lung cancer (NSCLC) remains a significant challenge. This report explored the precise role of USP28 on OSI resistance in NSCLC and identified a functional downstream effector. OSI‐resistant H1975 cells (H1975/OSI) were established by long‐term OSI exposure. USP28 and SIRT1 expression levels were analyzed by quantitative PCR, immunoblotting, and immunohistochemistry. Functional assays included cell viability, colony formation, EdU incorporation, apoptosis analysis, and glycolysis assays. The interaction between USP28 and SIRT1 was confirmed by co‐immunoprecipitation (Co‐IP) assay and SIRT1 protein stability analysis. In vivo validation was performed using H1975/OSI xenograft models. USP28 and SIRT1 were upregulated in H1975/OSI cells and OSI‐resistant NSCLC tissues. USP28 overexpression enhanced cell proliferation and glycolysis, suppressed apoptosis, and conferred OSI resistance in H1975 cells, while its depletion exerted opposite effects in H1975/OSI cells. Mechanistically, USP28 stabilized SIRT1 by deubiquitination. SIRT1 knockdown attenuated the effects of USP28 overexpression, while SIRT1 restoration reversed the phenotype alterations upon USP28 depletion. In vivo, USP28 depletion sensitized H1975/OSI xenografts to OSI treatment. Our study indicates that USP28 promotes OSI resistance in NSCLC by deubiquitinating SIRT1. Targeting the USP28/SIRT1 axis may represent a novel therapeutic approach to overcome OSI resistance in EGFR‐mutant NSCLC.