Feeder Cell Detachment in Drug Response Profiling of Leukemia Cell Coculture Can Be Prevented by Conditioned Medium

Determining drug sensitivity in tumor cells ex vivo is a frequently used method not only in leukemia cell research but also serves as an indispensable tool for searching for alternative treatment strategies for leukemia patients unresponsive to classical treatment. The drug response profiling (DRP) method based on fluorescence imaging of leukemia cells cocultured with a monolayer of mesenchymal stromal cells (MSC) and treated with antileukemia drugs currently represents one of the most powerful methods well suited for simultaneous screening of multiple drugs with significantly reduced numbers of cells and time required to perform the test. Moreover, the coculture of leukemia cells with MSC simulates the situation in the bone marrow and thus improves the prediction accuracy of drug sensitivity in vivo. However, the addition of leukemia cells frequently leads to MSC detachment from the well bottom, which disturbs automated image analysis and, in the end, may lead to imprecise DRP results.

The MSC detachment, either mild or strong, was observed in 27.8% of our experiments. To overcome this phenomenon, we introduced a simple solution for effectively preventing the MSC detachment. It is based on the addition of MSC-conditioned medium to leukemia cells-MSC coculture. This method improvement reduced the proportion of experiments impaired by the strong MSC detachment from 16.7% to 3.3%. Importantly, implementing MSC-conditioned medium had no adverse effect on the leukemia cell viability or drug response.

Upgrading the DRP method with the simple step of addition of MSC-conditioned medium to the leukemia cells-MSC coculture significantly reduces cases of MSC detachment without interfering with any advantages of this DRP method, including its feasibility for high-throughput screening.