Seeing is believing: How imaging orthotopic models might pave the way for bladder cancer breakthroughs

Over 70% of cases of bladder cancer (BC) are initially diagnosed at non-muscle-invasive stages (NIMBC). These are typically managed through local treatments like intravesical instillation. Therefore, subcutaneous models may not be applicable for research in NMIBC. Moreover, the microenvironment of BC within the bladder diverges from that in the subcutaneous region. Similarly, in cases of the metastases or muscle-invasive stages of bladder cancer (MIBC), subcutaneous models rarely show spontaneous progression to the later stage of the disease or lack the ability to metastasize. Therefore, there is a need for developing new in vivo bladder cancer models for preclinical drug development.

Orthotopic BC models are generated by seeding tumor cells directly into the organ of origin. They recapitulate the essential features of tumor growth in the natural microenvironment and demonstrate spontaneous invasion and metastasis, making them an ideal model for:

• Studying tumorigenesis: Observing tumor development within the bladder
• Investigating mechanisms of disease: Understanding how cancer cells behave in the bladder environment
• Evaluating treatment: Testing new drugs at different stages of the disease, including relapse.

Our established models of BC include NMIBC and MIBC subtypes from the MB49_luc, MB49_luc2F7, or MBT-2 cell lines. Here we will discuss in more details the establishment and characterization of the MB49_luc orthotopic model. More information on all our currently established bladder cancer models can be found in our Factsheet.

At Reaction Biology, we use a minimally invasive approach to deliver bladder cancer cells into bladder cavity of C57BL/6 mice. The tight junctions of urothelial cells prohibit the instilled cancer cells from attaching. As part of our protocol, we prime the bladder walls with poly-L-lysine to facilitate optimal adhesion of the cancer cells, akin to preparing a canvas before painting.

Figure: Schematic representing the workflow for establishing a bladder wall instillation model

Historically, orthotopic models had to be sacrificed at multiple time points to evaluate the tumor load. Thanks to advances in molecular biology and optical imaging, it has become possible to track the tumor progression within the animal in real-time.

Once implanted into the bladder, whole body luminescent images are overlayed on photographic images to follow tumor growth. This approach not only reduces animal use and associated costs, but also enables animals to be more accurately randomized to treatment arms, and tumor tracking can be performed non-invasively without animal termination.

We have successfully transduced 11 different clones from the MB49 BC cell line with that we have used to establish a collection of orthotopic bladder cancer models with different growth characteristics and immune profiles. To maintain the highest quality of data, each cancer cell clone used to establish the orthotopic model is validated for growth and luminescence in vitro and is checked for in vivo luminescence over time and terminal tumor weight.

Figure: Representative in vivo luminescent signal in different clones of NMIBC bladder wall instillation models (left) Average luminescence for different clones (n=5) 7 days post inoculation (right).

Moreover, our flow cytometry analysis for measuring TILs infiltration and T cell proliferation has identified differences between immune cell infiltration between tumor clones allowing you to select from hotter or colder tumor models for downstream analysis. Our comprehensive approach ensures that you’re equipped with the best tools to advance your bladder cancer research and develop superior treatments.

Figure: Characterization of MB49_luc clones used to establish NMIBC bladder wall instillation model. This data shows the analysis of tumor-infiltrating lymphocytes (TILs) and T cell proliferation profile using flow cytometry.

Our standard service extends beyond in vivo luminescence data. In addition to terminal tumor weight measurements, we offer a robust program of clinical observations throughout the study. The observation data can provide valuable insights that complement the bioluminescent data and aid in a more complete understanding of the effect of your clinical candidate on tumor burden and overall animal health.

Furthermore, we understand the critical role of regulatory compliance in drug development. Our team of experienced medical writers can translate your research findings into clear, concise, and IND-ready study reports. These reports meet all the necessary requirements set forth by regulatory agencies, ensuring a smooth path towards clinical trials and ultimately, new treatment options for bladder cancer patients.

By combining innovative research with powerful orthotopic models, Reaction Biology is committed to accelerating the development of new and effective bladder cancer treatments. Together, we can rewrite the future of bladder cancer therapy.