In vitro inhibitory properties of sesquiterpenes from Chloranthus serratus on cell motility via down-regulation of LIMK1 activation in human breast cancer.

BACKGROUND: LIM kinase 1 plays an important role in tumor cell invasion and metastasis by regulating architecture of actin cytoskeleton, and inhibiting activity of this kinase may be a promising strategy to prevent cancer cells from distant spread. In our previous studies, we found several extracts from the medical herbs in genus Chloranthus to exhibit anti-metastatic effects.

PURPOSE: The aim of this study is to find LIMK1 inhibitors from Chloranthus serratus, a medical herb from genus Chloranthus and to evaluate their effects on cell motility.

METHODS: Three sesquiterpenes, chloranthalactone E (compound 1), serralactone A (compound 2, SERA is used in the further testing), and 8β, 9α-dihydroxylindan-4(5), 7(11)-dien-8α, 12-olide (compound 3) were isolated from Chloranthus serratus, and the anti-LIMK1 activities of these compounds were investigated by kinase-Glo® luminescent kinase assay. Then, the anti-LIMK1 properties of SERA were verified by kinase-Glo® luminescent kinase assay and western blot assay. The effects of SERA on F-actin polymerization and cell migration were investigated by Phalloidin dying, AP 48 chamber system and ORIS™ cell migration assay. Furthermore, the inhibitory effects of SERA on LIMK1 were confirmed by overexpression of LIMK1 and small interfering RNA (siRNA) mediated gene silencing.

RESULTS: we reported here that among the three sesquiterpenes, SERA showed significantly inhibition on LIMK1 activity, and the IC50 values on MDA-MB-231 and MDA-MB-468 cells were 3.14 μM and 4.64 μM, respectively. Furthermore, it was also found that SERA significantly suppressed LIMK1 and cofilin1 phosphorylation, F-actin polymerization and also cell migration. Data from LIMK1 overexpression and RNA interfering assay confirmed that the inhibitory effects of SERA on LIMK1 was antagonized and enhanced by the overexpression and knockdown of LIMK1.

CONCLUSION: collectively, it was concluded that SERA exhibited significant inhibitory effects on breast cancer cells migration, and these effects of this sesquiterpene are due to its properties reducing the activation of LIM kinase 1.