| dc.description | Purpose In search for new drugs derived from natural
products for the possible treatment of cancer, we studied
the action of agelasine B, a compound purified from a
marine sponge Agelas clathrodes.
Methods Agelasine B was purified from a marine sponge
Agelas clathrodes and assayed for cytotoxicity by MTT on
two human breast cancer cells (MCF-7 and SKBr3), on a
prostate cancer cells (PC-3) and on human fibroblasts.
Changes in the intracellular Ca2? concentrations were asses-
sed with FURA2 and by confocal microscopy.Determination
of Ca2?-ATPase activity was followed by Pi measurements.
Changes in the mitochondria electrochemical potential was
followed with Rhodamine 123. Apoptosis and DNA frag-
mentation were determined by TUNEL experiments.
Results Upon agelasine B treatment, cell viability of both
human breast cancer cell lines was one order of magnitude
lower as compared with fibroblasts (IC50 for MCF-
7 = 2.99 lM; SKBr3: IC50 = 3.22 lM vs. fibroblasts:
IC50 = 32.91 lM), while the IC50 for PC-3 IC50 =
6.86 lM. Agelasine B induced a large increase in the intra-
cellularCa2?concentration inMCF-7, SKBr3, andPC-3 cells.
By the use of confocal microscopy coupled to a perfusion
system, we could observe that this toxin releases Ca2? from
the endoplasmic reticulum (ER). We also demonstrated that
agelasine B produces a potent inhibition of the ER Ca2?-
ATPase (SERCA), and that this compound induced the frag-
mentation of DNA. Accordingly, agelasine B reduced the
expression of the anti-apoptotic protein Bcl-2 and was able to
activate caspase 8, without affecting the activity of caspase 7.
Conclusions Agelasine B in MCF-7 cells induce the
activation of apoptosis in response to a sustained increase
in the [Ca2?]i after blocking the SERCA activity. The
reproduction of the effects of agelasine B on cell viability
and on the [Ca2?]I obtained on SKBr3 and PC-3 cancer
cells strongly suggests the generality of the mechanism of
action of this toxin. | |
