Directed cell motion in response to an external chemical gradient occurs in
many biological phenomena such as wound healing, angiogenesis, and cancer
metastasis. Chemotaxis is often characterized by the accuracy, persistence, and
speed of cell motion, but whether any of these quantities is physically
constrained by the others is poorly understood. Using a combination of theory,
simulations, and 3D chemotaxis assays on single metastatic breast cancer cells,
we investigate the links among these different aspects of chemotactic
performance. In particular, we observe in both experiments and simulations that
the chemotactic accuracy, but not the persistence or speed, increases with the
gradient strength. We use a random walk model to explain this result and to
propose that cells' chemotactic accuracy and persistence are mutually
constrained. Our results suggest that key aspects of chemotactic performance
are inherently limited regardless of how favorable the environmental conditions
are