Micro-environmental regulation of cancer cell malignancy is one of the most basic cancer life phenomena. However, the study of cellular response to microenvironment has been long focused on signal processes mediated by various chemical factors and their receptors, the study of mechanical forces, another key environmental factor, has been less studied. In recent years, more and more attention has been paid to the physiological and pathological significance of mechanical microenvironment. However, it is still not clear how cells perceive environmental changes and the signal pathways that regulate cell physiological activities. In this study, we identified that low shear stress (LSS) significantly promoted breast cancer cell proliferation. The proliferation was closely associated with mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK) and Yes-associated protein (YAP). Inhibition of ERK or YAP both abolished the LSS-induced proliferation activity of cancer cells. LSS induced ERK phosphorylation and YAP activations, which suggested the involvement of ERK and YAP under LSS treatment. Under LSS, ERK inhibitor U0126 decreased both active YAP and ERK expressions, while YAP inhibitor verteporfin failed to decrease ERK phosphorylation. Further study confirmed that ERK trans-located to nucleus which showed an active state of ERK in LSS-treated group. LSS with verteporfin group showed no differences with LSS-treated group which confirmed ERK and YAP an upstream-downstream cascade. The above results demonstrated that LSS can promote breast cancer cell proliferation through ERK-YAP activation. These results not only highlight a new means of understanding mechanical transmission to cytoplasm mechanisms but also serve as a new basis for developing drug delivery systems for breast cancer treatment. (C) 2019 Elsevier Inc. All rights reserved.