Up-regulation of cathepsin S expression by HSP90 and 5-HT7 receptor-dependent serotonin signaling correlates with triple negativity of human breast cancer.

Our findings suggest CTSS as a candidate target for development of a strategy to inhibit breast cancer invasion, and indicate that HSP90 and 5-HT7 (regulators of CTSS) should be considered as alternative targets for the management of TNBC invasion and metastasis.