Creation of a Patient-Derived Xenograft (PDX) Model for Breast Cancer Bone Metastasis in Zebrafish

Ren Watanabe^*
*Correspondence: Ren Watanabe, Department of Molecular Cell Biology, Osaka University Graduate School of Medicine, Suita 565-0871, Japan, Email:

Introduction

Breast cancer remains one of the most prevalent forms of cancer worldwide, with a significant number of patients developing metastatic disease. Among the various sites where breast cancer can metastasize, bones are particularly common and challenging targets. Bone metastases can lead to severe complications, including pain, fractures and reduced quality of life. Traditional models for studying cancer metastasis often fall short in recapitulating the complexities of human tumors and their interactions with the microenvironment. Consequently, there is a pressing need for innovative and more representative experimental models to study breast cancer metastasis, especially in the context of bone [1].

Patient-Derived Xenografts (PDXs) have emerged as a powerful tool in cancer research, allowing for the direct transplantation of human tumor tissues into immunocompromised mice. This approach retains the heterogeneity and architectural features of the original tumor, making PDXs a valuable resource for studying tumor biology, drug response and metastasis. However, the use of mice can be resource-intensive and time-consuming. In recent years, zebrafish models have gained traction as an alternative for cancer research. Their transparent embryos and rapid development offer unique advantages for observing tumor growth and metastasis in vivo. The combination of PDX models and zebrafish presents an exciting opportunity to investigate breast cancer bone metastasis in a more accessible and visually tractable system. This paper aims to explore the creation of a PDX model of breast cancer bone metastasis in zebrafish, detailing the methods, implications and potential applications of this innovative approach. By integrating PDX technology with zebrafish models, researchers can gain insights into the metastatic process, evaluate therapeutic interventions and enhance our understanding of tumor behavior in a human-like context .

Breast cancer is characterized by its heterogeneity, encompassing a range of molecular subtypes, each with distinct biological behaviors and clinical outcomes. The propensity for breast cancer cells to metastasize to bones is influenced by several factors, including the tumor microenvironment, the presence of specific receptors and the release of signaling molecules that facilitate the colonization of bone. Metastatic breast cancer cells can interact with bone cells, including osteoblasts and osteoclasts, leading to a destructive cycle that exacerbates bone degradation and tumor growth. Bone metastasis is associated with significant morbidity, impacting patient survival and quality of life. Understanding the mechanisms underlying bone metastasis is crucial for developing effective therapeutic strategies aimed at preventing or treating metastatic disease [2].

Description

PDXs have revolutionized cancer research by providing a more accurate representation of human tumors in preclinical studies. In a PDX model, tumor fragments from a patient are implanted into immunocompromised mice, allowing the tumor to grow and maintain its original characteristics. This model retains the genetic, histological and functional features of the patient’s tumor, making it an invaluable tool for personalized medicine. PDXs offer several advantages, including capturing the diversity of tumor cell populations found in the original tumor, enabling researchers to study variations in response to treatment and evaluating the efficacy of new therapies to provide insights into how individual tumors may respond to different treatments. Furthermore, by monitoring the growth and spread of the implanted tumor, researchers can investigate the mechanisms of metastasis in a controlled environment.

Zebrafish have become increasingly popular in cancer research due to their unique biological characteristics. The transparent embryos of zebrafish allow for real-time imaging of tumor progression and metastasis, providing insights into the dynamic processes of cancer spread. Key advantages of using zebrafish include rapid development, allowing the study of cancer progression over a short time frame, the ability to easily manipulate the zebrafish genome, which enables researchers to study the effects of specific genes on tumor behavior and the capacity for high-throughput screening of drugs, making them valuable for evaluating potential therapeutic agents [3].

The integration of PDX technology with zebrafish models presents a novel approach to studying breast cancer bone metastasis. This method involves several steps. First, tumor samples are obtained from patients with metastatic breast cancer, specifically targeting tumors with a known propensity for bone metastasis. These tumors are processed into small fragments suitable for implantation. Zebrafish are maintained under standard conditions and embryos are collected for experimentation, typically at 24-48 Hours Post-Fertilization (hpf), a stage that allows for ease of injection and visualization. Tumor fragments are then implanted into the yolk sac or the circulation system of the zebrafish embryos, achieved through microinjection techniques that allow for precise placement of the tumor tissue.

Once the tumor fragments are implanted, real-time imaging techniques, such as fluorescence microscopy, are employed to monitor tumor growth and metastatic spread within the zebrafish model. This approach allows researchers to observe how the implanted tumor interacts with the host microenvironment, particularly in the context of bone tissues. Using this PDX-zebrafish model, researchers can explore various aspects of metastatic mechanisms in breast cancer, including cell migration, by observing the movement of cancer cells from the primary site to distant sites to identify factors that facilitate or inhibit cell migration. The model also allows for the study of how tumor cells interact with surrounding bone cells and the implications for tumor growth and bone degradation, as well as the efficacy of different therapeutic agents, which can be tested in real-time, providing valuable insights into potential treatments for bone metastasis [4].

The creation of a PDX model for breast cancer bone metastasis in zebrafish has several applications. By using patient-derived tumors, researchers can tailor treatments based on the specific characteristics of an individual’s cancer, leading to more personalized approaches in cancer therapy. Additionally, the model can be utilized for screening potential drugs that target metastatic behavior, helping to identify novel therapeutic strategies. Researchers can also investigate molecular changes associated with metastasis, aiding in the identification of biomarkers that predict disease progression.

While the PDX-zebrafish model offers numerous advantages, certain limitations must be acknowledged. For instance, the size of zebrafish limits the complexity of the tumor microenvironment compared to mammalian models. Additionally, the immune system of zebrafish differs from that of humans, which may influence tumor behavior and therapeutic responses. Future research should focus on optimizing the PDX-zebrafish model, including improving the engraftment efficiency of tumor fragments and refining imaging techniques to enhance the resolution of metastasis monitoring. Collaborative efforts between cancer biologists, pharmacologists and geneticists will be crucial in advancing this model and uncovering novel insights into breast cancer bone metastasis [5].

Conclusion

The creation of a Patient-Derived Xenograft (PDX) model for breast cancer bone metastasis in zebrafish represents a significant advancement in cancer research. By combining the strengths of PDX technology with the unique advantages of zebrafish models, researchers can gain valuable insights into the mechanisms underlying metastatic disease. This innovative approach not only enhances our understanding of breast cancer biology but also paves the way for the development of personalized therapeutic strategies. As we continue to explore the complexities of cancer metastasis, the integration of diverse models will be essential for translating findings into effective treatments and improving outcomes for patients with metastatic breast cancer. Future studies utilizing this PDX-zebrafish model will undoubtedly contribute to the ongoing efforts to combat this challenging disease, offering hope for improved therapeutic interventions and patient care.

Acknowledgement

None.

Conflict of Interest

None.

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