Studying metastatic cancer in a true 3D environment
Growing cells in flat, 2D layers for research has been the norm for around 40 years and is a method with many limitations. Culturing living human cells in 3D spheres has been recently found to be more physiologically relevant to humans. NC3Rs 3Rs Prize runner-up, Professor Shuichi Takayama, University of Michigan USA, describes how this novel method can be applied to metastatic cancer research, screening out drugs that do not work much earlier in the drug discovery process to reduce the number of animals needed overall.
1 – A 384 hanging drop plate. 2 – A researcher pipettes cells and media into each channel, they then hang by surface tension. 3 -Fluorescent image of a prostate cancer spheroid formed in one-to-three days in a a hanging drop. This can remain stable for up to two weeks.
90% of cancer deaths result from metastasis rather than growth of the primary tumour. There is a lack of effective therapies against metastatic cancer, at least in part, because of insufficient animal models and a lack of good and convenient non-animal in vitro models to address the unique nature of metastatic cancer cells and their microenvironment.
Reducing and replacing animal studies is not only important from an animal welfare perspective, but also for enhancing the drug development process. It is said that cancer has been cured many times over in mice, just not for humans. This is understandable given that most anticancer drug testing is done in mice! The goal of my research is to replace as much of this animal testing as possible by using microfluidic and 3D cell-culture models.
While our lab makes a variety of rather complex microfluidic channel-based models of the human body, such systems can be complicated for users to setup for use in high-throughput applications, and for us to disseminate to interested research groups. A project that came out of our efforts to balance physiological relevance, throughput and the need to widely disseminate user-friendly platforms is the development of a new method called the “hanging drop array 3D cell spheroid culture platform”, which was highly-commended in the 2013 NC3Rs 3Rs Prize.
This platform allows us to grow a tiny sphere of different human cell types suspended in a drop of liquid. Unlike a normal “flat” 2D cell culture, the cell spheroid exists in a 3D form – so it behaves much like a group of cells in a human tissue with similar interactions and behaviours, and is therefore more suitable for research into human disease. Different types of cells can be used to create accurate models of different human diseases, so this can replace the need for animals in some stages of drug development.
The research in my lab focuses on developing non-animal in vitro models to mimic metastasised cancer in humans. For example, we have recently shown that these 3D co-culture spheroids that contain prostate cancer cells together with bone cells and blood vessel cells can mimic and behave like bone metastasis. In such environments, the prostate cancer cells grow much slower and are more resistant to conventional anticancer drugs.
What is now required is to improve the physiological relevance even further and to take advantage of these 3D co-culture spheroids by using them in high-throughput screening of potential drugs. In particular, since the prostate cancers are taking on their stealth mode in a “stem cell” environment, we are focusing on investigating combination therapies where conventional anticancer drugs are given after administration of drugs that affect stem cell growth. The idea is to lure out and then hit the hiding cancer cells.
It is important to note that while my lab is currently focused on applying the 3D culture platform for cancer and this blog post has focused on cancer, the physiological 3D cultures enabled by the hanging drop array plates are broadly useful for creating 3D cultures that will help to replace some animal studies for toxicology and immunology.
There is an increasing number of success stories with the 3D culture platform applied to a variety of fields. Given the inexpensive and simple to use format of the systems, we hope the system will catalyse further reduction in animal use in a variety of areas.
Professor Takayama is developing new tools and methods beyond this research to enhance cell-based assays and is open to further discussion.
Tung, Y., Hsiao, A., Allen, S., Torisawa, Y., Ho, M., & Takayama, S. (2011). High-throughput 3D spheroid culture and drug testing using a 384 hanging drop array The Analyst, 136 (3) DOI: 10.1039/c0an00609b
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