Researchers from the Los Angeles-based Terasaki Institute for Biomedical Innovation (TIBI) say they have successfully designed a method for rapid testing large numbers of potential immunotherapy drugs against live tumor cells for accurate and easily analyzable data.

They began by culturing spherical aggregates of breast cancer cells in a custom-fabricated, 3D printed, transparent chip with conical microwells, which were designed for optimum growth and stability of the cellular spheres. Tests performed on the microwells’ cellular spheres confirmed the cells’ viability and their production of T cell de-activating surface proteins, according to the scientists, who published their study (“Cancer-on-a-Chip for Modeling Immune Checkpoint Inhibitor and Tumor Interactions”) in the journal Small.

“Cancer immunotherapies, including immune checkpoint inhibitor (ICI)-based therapies, have revolutionized cancer treatment. However, patient response to ICIs is highly variable, necessitating the development of methods to quickly assess efficacy,” the investigators wrote.

“In this study, an array of miniaturized bioreactors has been developed to model tumor-immune interactions. This immunotherapeutic high-throughput observation chamber (iHOC) is designed to test the effect of anti-PD-1 antibodies on cancer spheroid (MDA-MB-231, PD-L1+) and T-cell (Jurkat) interactions. This system facilitates facile monitoring of T-cell inhibition and reactivation using metrics such as tumor infiltration and interleukin-2 (IL-2) secretion.

“Status of the tumor-immune interactions can be easily captured within the iHOC by measuring IL-2 concentration using a micropillar array where sensitive, quantitative detection is allowed after antibody coating on the surface of the array. The iHOC is a platform that can be used to model and monitor cancer-immune interactions in response to immunotherapy in a high-throughput manner.”

“The features of our microwell-based chip is the key to our successful development of an immunoactive tissue model,” said Wujin Sun, PhD, a faculty member at the Terasaki Institute. “The chip’s transparency allows for direct microscopic observation. And its design allows for high-volume testing, which lends itself well to the rapid screening of immunotherapeutic drugs.”

In order to test the effectiveness of checkpoint inhibitor drugs in activating T cells’ anti-tumor response, the team next considered how a T cell normally behaves during activation. When a T cell is stimulated to attack cellular invaders, it secretes cytokines, which mobilize other immune cells to the invasion site and stimulates the cells to multiply and destroy the invaders. Measurement of these cytokines can therefore indicate the level of a T cell’s activation.

The team then created an automated system to measure cytokine levels using their breast cancer-laden microwell chip. Experiments with this system were performed using anti-checkpoint protein drugs; the results showed that upon incubation of the breast cancer cells with the T cells, cytokine production was increased by the use of the drugs, demonstrating their effectiveness in activating the T cells.

Another way the team used their breast cancer chip was to assess the breast cancer cells’ effect on stimulated T cells. The T cells were fluorescently labeled and added to the breast cancer cells in the microwells; the chip’s transparency allowed direct observation of their cellular interaction using fluorescent microscopy. These breast cancer cells normally cause rupture of the T cells, but experiments conducted with checkpoint inhibitor drugs showed that the drugs increased T-cell viability in the cultures, visually demonstrating how they can counter the effects of T-cell rupture by tumor cell interaction.

The breast cancer chip was also used for the direct observation of how the T cells infiltrated the breast cancer cellular spheres; this type of infiltration is a measure of a T cell’s anti-tumor activity and viability. After labeling each group of cells with separate dyes and mixing them in the chip’s microwells, T-cell infiltration could be directly visualized using high resolution fluorescence microscopy. Experiments conducted with checkpoint inhibitor drugs indicated that there were increased numbers of T cells and deeper penetration into the breast cancer cells in the presence of the drugs.

“Bringing ways to optimize clinical decisions and personalized medicine for patients is a top goal at our institute,” said Ali Khademhosseini, PhD, director and CEO of the Terasaki Institute. “This work is a significant step towards achieving that goal in the realm of cancer immunotherapy.”