Metabolic coupling between a single tumor cell and fibroblasts on microdroplet array chips.

Metabolic coupling between tumor cells and fibroblasts critically regulates tumor aggressiveness including matrix metalloproteinase-9 (MMP-9) activities via nitric oxide (NO)-mediated pathways. It remains a fundamental challenge to reveal the interactions between tumor cells and fibroblasts at the single cell level. Here we report a microdroplet array platform that enables co-encapsulating a single tumor cell and fibroblasts for the studies of cell-to-cell interactions. We have investigated an inducible nitric oxide synthase (iNOS)-dependent metabolic coupling between tumor cells (HeLa and MCF-7) and fibroblasts (3T3-L1), in which fibroblasts markedly enhance tumor-cell MMP-9 activities via NO signaling. Inhibition with L-NAME effectively disrupts this coupling and markedly reduces MMP-9 activities. Our results obtained using microchips reveal phenotype-dependent correlations between fibroblast lipid droplet accumulation and tumor-cell aggressiveness, highlighting how metabolic competition and enzymatic regulation jointly shape tumor-stroma crosstalk at the single-cell level.