# Establishment and Characterization of a Brain Parenchymal Metastatic Cell Line AlmoR1 Derived From an NSCLC Patient With EGFR‐TKI Resistance

## TL;DR

A new cell line, AlmoR1, derived from a brain metastasis of an NSCLC patient resistant to EGFR-TKIs, is established to study drug resistance mechanisms and develop new treatments.

## Contribution

The novel NSCLC brain metastasis cell line AlmoR1 exhibits resistance to third-generation EGFR-TKIs and high tumorigenicity in an orthotopic brain model.

## Key findings

- AlmoR1 is a novel NSCLC brain metastasis cell line with EGFR exon 19 deletion and resistance to almonertinib and osimertinib.
- The cell line shows high tumorigenicity in an orthotopic brain tumor model, with 75% tumor formation in live systems.
- AlmoR1 can be used to study mechanisms of intracranial resistance and develop new therapies for EGFR-TKI-resistant brain metastases.

## Abstract

Non‐small cell lung cancer patients with EGFR mutation have a high rate of brain metastases, and EGFR tyrosine kinase inhibitors (TKIs) are the principal therapeutic approach. However, acquired targeted therapy resistance is the main reason for EGFR‐TKIs' treatment failure. At present, the mechanism of intracranial acquired targeted therapy resistance is limited, mainly due to the lack of a cell line that can be used for its study.

A brain parenchymal metastatic sample that progressed after third‐generation EGFR‐TKI treatment was used to establish a cell line named AlmoR1. The genetic characteristics of the cell line were evaluated by short tandem repeat (STR) profiling and whole‐exome sequencing analysis. The phenotypic characteristics were characterized by CCK8, western blot, HE staining, immunohistochemistry (IHC), and orthotopic brain tumor model.

The cell line we successfully established, AlmoR1, can be passed in vitro stably. STR analysis revealed it was a novel NSCLC BM cell line. It harbors the EGFR E746_A750del (ex19del) mutation, and the IC50 to almonertinib and osimertinib of AlmoR1 was significantly higher than that of sensitive cells. In our orthotopic brain tumor model construction with AlmoR1 cells, 75% (3/4) tumor formation can be observed in the living system.

These data suggest that the established cell line, AlmoR1, preserved the resistance to broad third‐generation EGFR‐TKIs and good tumorigenicity in an intracranial orthotopic model, so that it can serve as a new tool to elucidate the pathogenesis, explore new treatment methods, and conduct the development of new drugs for targeted therapy resistance of brain metastases.