# A Double‐Humanized Murine Model in Bladder Cancer: A Novel Preclinical Model for Cancer Immunology Research

## TL;DR

This study introduces a new preclinical model for bladder cancer research that improves tumor growth and allows testing of immune therapies.

## Contribution

The study presents a double-humanized murine model and an optimized protocol for consistent bladder cancer PDX tumor establishment.

## Key findings

- The PDX257S cell line shows faster tumor growth and higher expression of human markers compared to original tumor tissue.
- The double-humanized model minimizes graft-versus-host disease and supports testing of novel immune therapeutics.
- PDX257S exhibits increased mutation burden and altered gene expression relevant to bladder cancer.

## Abstract

Bladder cancer (BC) ranks as the 10th leading cause of cancer‐related deaths in the United States. Despite significant advancements in managing BC, including antibody‐drug conjugates and immune checkpoint blockers, a significant percentage of patients fail these treatments. This underscores the pressing need to develop methods for identifying novel therapeutic targets, predicting therapy responses, and optimizing personalized treatment strategies for patients. Patient‐derived xenograft (PDX) models have the potential to address these challenges. However, these models suffer from limitations, including a consistent rate of tumor acceptance, extended time for tumor growth, and the absence of the donor's immune system.

This study aimed to address these challenges through a comprehensive comparison of different PDX implantation methods, culminating in the establishment of a PDX cell line for utilization in in vivo BC preclinical models. Flow cytometry analysis and total RNA sequencing were used for comparative analysis of original tumor tissue, PDX tumor, and PDX257S cell line.

Tumor tissue processing techniques were optimized to enhance the rate of PDX tumor acceptance and shorten the time to tumor development. Furthermore, a PDX cell line, PDX257S, was successfully established and confirmed to exhibit more aggressive and tumorigenic characteristics compared to the original donor tumor tissue. The PDX257S cell line demonstrated faster tumor growth, higher expression of human epithelial cell adhesion molecule, increased mutation burden in BC‐associated genes, and significant alterations in BC‐related gene expression, compared to the original tumor. The PDX257S cell line was also used to establish a double humanized BC murine model that minimized graft‐versus‐host disease and is a potential platform for testing novel immune therapeutics.

In summary, this study offers an optimized protocol for the consistent establishment of BC PDX tumors. Furthermore, it has also established a novel double‐humanized model, demonstrating the potential for drug screening and clinical prognosis in the context of BC treatment.