Functional drug screens on intact patient tumor samples are a promising approach to identify the best therapy for individual patients. The response of patient cancer tissue biopsies to drugs (or drug combinations) is highly dependent on the tumor microenvironment (TME), which consists of a variety of resident and infiltrating host cells, secreted factors, and extracellular matrix proteins. However, current methods to assess drug responses of individual tissue samples rely on techniques that require the partial or complete disassociation of the TME, often resulting in inaccurate predictions of drug effects later observed in the patients. For instance, tumor spheroids have gain popularity for high-throughput drug screening assays. The spheroids are generated by disassociating cells from patient tissue biopsies and culture in a special matrix to create cell-cell and cell-matrix 3-D interactions. Yet, spheroids retain only a limited amount of TME, underscoring the need for new high-throughput drug testing platforms.
In collaboration with the Gujral lab in the Human Biology Division, the Folch lab at the UW Bioengineering Department has developed a microfluidics platform that delivers minuscule amounts of drugs to small tissue biopsies, called “cuboids.” In the microfluidic device, the cuboids flow through microchannels containing dispersed wells that trap the cuboids for culture and multi-drug exposures. The group recently published a proof-of-concept study using this platform in the Royal Society of Chemistry journal, Lab on a Chip. With this platform, the scientists aim to streamline direct-in-human drug testing to predict drug responses in humans accurately and shorten the time frames for drug development. Dr. Albert Folch, a principal investigator in the study, added: “We have demonstrated a new miniature tissue format that is both intact, regularly-sized, and easy to array in large numbers in a multi-well format (e.g., for drug testing). We believe that this opens the possibility, until now impossible, of directly screening drugs in human tissues, bypassing animal testing.”
In the study, the cuboids were generated by cutting live biopsy specimens from mouse liver and glioma cell-derived xenograft flank tumors into thousands of similarly-sized cuboidal-shaped pieces measuring 400 μm × 400 μm × 400 μm; this size is large enough to preserve TME but adequately small to maintain nutrient delivery and viability and ensure proper flow in the microfluidic device. The cuboids’ small size allows for maximization of small-sized clinical samples, which are often difficult to obtain, and needed for multiple purposes, including diagnostic histologic examination, immunohistochemistry, and molecular studies. To validate the cuboids’ integrity and viability, the researchers visualized the 3D tissue microenvironment using open-top light-sheet (OTLS) microscopy of fixed and optically-cleared liver cuboids. They identified distinct cell types in the liver, vascular, and liver-specific structures, demonstrating the tissue sample’s integrity. Moreover, examination of the glioma cuboids via immunostaining revealed continued proliferation, minimal cell death, and the presence of endothelial and immune cells, demonstrating the cuboids’ viability and functionality.
Finally, using glioma cuboids, the researchers evaluated the effects of different cisplatin concentrations, a cytotoxic chemotherapy drug. After two days of treatment, significant cell death –relative to non-treated cuboids– in most of the concentrations tested was observed, underscoring the system’s utility for drug testing. In summary, this study combined micro-dissected tumor cuboids and microfluidics to facilitate drug testing in intact tissues that better preserve the tissue microenvironment. Dr. Folch shared future directions using the cuboid platform: “We are preparing much larger-throughput format platforms (such as 384-well platforms) that can trap and accommodate the large numbers of cuboids that we obtain from each tiny tumor. We have heard a lot of the promise of the tumor spheroid/organoid technology – in a sense, our cuboids are the “next-generation spheroids” because our cuboids are directly taken from the patient without any major disruption of the tumor microenvironment, so we believe we can recapitulate the drug-tumor interactions very faithfully.”
Horowitz LF, Rodriguez AD, Au-Yeung A, Bishop KW, Barner LA, Mishra G, Raman A, Delgado P, Liu JTC, Gujral TS, Mehrabi M, Yang M, Pierce RH, Folch A. (2020) Microdissected “cuboids” for microfluidic drug testing of intact tissues. Lab Chip. doi: 10.1039/d0lc00801j. Epub ahead of print. PMID: 33174580.
This work was supported by grants from the National Cancer Institute; a pilot grant from Juno Therapeutics; an Innovation grant from CoMotion at the University of Washington; a Hong Kong Research Grant Council; an International Scholars award from the Consejo Nacional de Ciencia y Tecnología of Mexico; a Department of Defense Prostate Cancer Research Program; and the National Science Foundation Graduate Research Fellowship Program.
Fred Hutch/UW Cancer Consortium members Albert Folch, Robert Pierce, and Taran Gujral contributed to this research.