Compelling efficacy on intervention of
tumorigenesis by nonsteroidal anti-inflammatory drugs (
NSAIDs) has been documented intensively. However, the toxicities related to
cyclooxygenase (COX) inhibition resulting in suppression of physiologically important
prostaglandins limit their clinical use for human
cancer chemoprevention. A novel derivative of the
NSAID sulindac sulfide (SS), referred as
sulindac sulfide amide (SSA), was recently developed, which lacks COX inhibitory activity, yet shows greater suppressive effect than SS on growth of various
cancer cells. In this study, we focus on the inhibitory activity of SSA on
breast tumor cell motility, which has not been studied previously. Our results show that SSA treatment at non-cytotoxic concentrations can specifically reduce
breast tumor cell motility without influencing
tumor cell growth, and the mechanism of action involves the suppression of TGFβ signaling by directly blocking Smad2/3 phosphorylation. Moreover, miR-21, a well-documented oncogenic
miRNA for promoting
tumor cell
metastasis, was also found to be involved in inhibitory activity of SSA in
breast tumor cell motility through the modulation of TGFβ pathway. In conclusion, we demonstrate that a non-COX inhibitory derivative of
sulindac can inhibit
breast tumor metastasis by a mechanism involving the TGFβ/miR-21 signaling axis.