Exploration of Mechanisms of DrugResistance in a Microfluidic Device andPatient Tissues

Chemoresistance is a major cause of treatment failure in many cancers. However, the lifecycle of cancer cells as they respond to and survive environmental and therapeutic stress isunderstudied. In this study, we utilized a microfluidic device to induce the development ofdoxorubicin-resistant (DOXR) cells from triple negative breast cancer (TNBC) cells within 11days by generating gradients of DOX and medium. In vivo chemoresistant xenograft models,an unbiased genome-wide transcriptome analysis, and a patient data/tissue analysis allshowed that chemoresistance arose from failed epigenetic control of the nuclear protein-1(NUPR1)/histone deacetylase 11 (HDAC11) axis, and high Nupr1 expression correlated withpoor clinical outcomes. These results suggest that the chip can rapidly induce resistant cellsthat increase tumor heterogeneity and chemoresistance, highlighting the need for furtherstudies on the epigenetic control of the NUPR1/HDAC11 axis in TNBC. A total of 1 ×10^5 cells/10 μL was suspended in culture medium, and 1 μL of the solution was gently added to thechip using a pipette with a tip through the cell seeding hole. The hole was plugged with a sterilizedstainless pin, and the chip was incubated at 37 ℃ with 5% CO2 overnight. The next day, 250 μL ofculture medium and culture medium containing 1.5 μM DOX were added to two of the diagonalreservoirs, and 50 μL of culture medium was added to the rest of the diagonal reservoirs. Thefresh culture medium and drug were replaced every day. After 11 days, trypsin (Gibco) was addedto the chip, which was incubated at 37 ℃ for 5 min. The detached cells were flushed out of thechip and collected from the reservoirs by injecting 1 mL of culture medium through the seedinghole with a needle-free syringe. To remove non-resistant cells, the collected cells were grown inmedium containing 0.05 μM DOX for one week