Anticancer alkaloid lamellarins inhibit protein kinases

Abstract

Lamellarins, a family of hexacyclic pyrrole alkaloids originally isolated from marine invertebrates, display promising anti-tumor activity. They induce apoptotic cell death through multi-target mechanisms, including inhibition of topoisomerase I, interaction with DNA and direct effects on mitochondria. We here report that lamellarins inhibit several protein kinases relevant to cancer such as cyclin-dependent kinases, dual-specificity tyrosine phosphorylation activated kinase 1A, casein kinase 1, glycogen synthase kinase-3 and PIM-1. A good correlation is observed between the effects of lamellarins on protein kinases and their action on cell death, suggesting that inhibition of specific kinases may contribute to the cytotoxicity of lamellarins. Structure/activity relationship suggests several paths for the optimization of lamellarins as kinase inhibitors.

Keywords: CK1; DYRK-1A; GSK-3; cyclin-dependent kinases; kinase inhibitor; lamellarin.

Figure 1.

Dose- and time- dependent induction of cell death by lamellarin N. (A) Neuroblastoma SH-SY5Y cells were treated with lamellarin N at various concentrations. Cell death was measured by LDH release, cell survival was assessed by the MTS reduction assay, and caspase 3 activity was monitored as DEVDase activity. MTS and LDH assay were carried out 48 hours after treatment with lamellarin N. The caspase assay was carried out 24 hours after treatment. (B) Kinetics of cell survival, cell death and caspases activation following exposure of SH-SY5Y cells to 1 μM lamellarin N. Average of 3 independent experiments performed in triplicate. The standard deviation (±SD) is indicated by error bars.

Figure 2.

Lamellarin N triggers PARP cleavage, p53 & p21^CIP1 upregulation, but not Mcl-1 down-regulation. SH-SY5Y cells treated at time 0 with 1 μM lamellarin N. Cells were harvested at different time-points and protein extracted for SDS-PAGE followed by Western blot analysis using antibodies directed against PARP, p53, p21^CIP1, or Mcl-1, as described in the materials and methods section. β-actin was used as loading control. “Ctrl” denoted untreated sample after 10 hours.