3D imaging reveals divergent effects of two cancer drugs

Researchers at Uppsala University have developed a transparent three-dimensional approach to Cell Painting that can resolve the responses of individual cells inside small clusters of bowel cancer cells. In a study published in Nature Communications, the team tested 52 cancer drugs and found that 5-fluorouracil and olaparib produced nearly indistinguishable effects when the cells were grown in a flat layer, but clearly different effects when the same cells formed minispheres. The distinction became visible only when the researchers analyzed each cell separately rather than treating an entire sphere as one image. Follow-up experiments linked the divergence to activation of the p53 cellular stress-response pathway, offering a way to identify drug behaviors that conventional two-dimensional screens may conceal.

The method builds on Cell Painting, a high-content imaging technique used in drug discovery to capture cellular changes across multiple cellular structures. It labels major components such as nuclei, mitochondria and the internal scaffolding with stains that can be imaged under a microscope. For this study, the researchers first grew bowel cancer cells as small three-dimensional spheres in standard laboratory plates. They then made the minispheres transparent with a solution of sugar and glycerol, allowing the microscope to image cells located deeper inside the clusters. Thousands of measurements of cell shape and structure could then be collected at single-cell resolution while retaining the three-dimensional environment in which the drugs were tested.

That combination addresses a central limitation of existing screening approaches. Cells can behave differently when they grow in three dimensions, yet many screening methods either examine flat cultures or collapse a complete three-dimensional sample into a single summary image. The adapted Cell Painting workflow preserves the detail of individual cells without giving up the throughput needed to test many compounds at once. In the reported comparison, 5-fluorouracil, a chemotherapy, and olaparib, a targeted cancer drug, looked almost alike in conventional flat cultures. Their profiles separated in minispheres, but only when the investigators inspected the cells individually; whole-sphere views did not show the difference.

Follow-up experiments produced a counterintuitive result. Although 5-fluorouracil caused less DNA damage than olaparib, it was more effective at preventing the cancer cells from dividing. Measurements of gene activity indicated that the chemotherapy activated the p53 pathway more strongly. The p53 pathway is a central stress-response system, and the study therefore associated the drugs’ different effects in three dimensions with distinct cellular responses, even though their effects in two-dimensional cultures appeared similar. The experiments were conducted in two cancer cell lines under laboratory conditions, so the results do not establish how either drug acts in patients.

The approach was also tested beyond the laboratory where it was developed through collaboration with colleagues at AstraZeneca, which the researchers described as a useful test of whether the method could be adopted by other laboratories. Images, data and code from the study were made openly available. The authors now hope to extend the imaging strategy to more complex three-dimensional models, including organoids grown from patient tissue. The work is presented as a peer-reviewed imaging-analysis study rather than a clinical trial, and its immediate contribution is methodological: it shows that making three-dimensional samples transparent can expose drug-dependent responses at the individual-cell level that would otherwise remain hidden in flat cultures or averaged tissue-scale measurements.

Subject of Research: Single-cell Cell Painting analysis of drug responses in three-dimensional colorectal cancer minispheres

Article Title: Transparent minispheres reveal that some look-alike cancer drugs part ways in 3D

Article References: Transparent minispheres reveal that some look-alike cancer drugs part ways in 3D. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Cell Painting, 3D spheroids, drug screening, 5-fluorouracil, olaparib, p53 pathway, cancer cells, high-content imaging, morphological profiling, Transparent, minispheres, reveal