title: The marine sponge toxin agelasine B increases the intracellular Ca(2+) concentration and induces apoptosis in human breast cancer cells (MCF-7).
abstract: OBJECTIVE
  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 Ca(2+) concentrations were assessed with FURA 2 and by confocal microscopy. Determination of Ca(2+)-ATPase activity was followed by Pi measurements. Changes in the mitochondria electrochemical potential was followed with Rhodamine 123. Apoptosis and DNA fragmentation 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 (IC(50) for MCF-7 = 2.99 μM; SKBr3: IC(50) = 3.22 μM vs. fibroblasts: IC(50) = 32.91 μM), while the IC(50) for PC-3 IC(50) = 6.86 μM. Agelasine B induced a large increase in the intracellular Ca(2+) concentration in MCF-7, SKBr3, and PC-3 cells. By the use of confocal microscopy coupled to a perfusion system, we could observe that this toxin releases Ca(2+) from the endoplasmic reticulum (ER). We also demonstrated that agelasine B produces a potent inhibition of the ER Ca(2+)-ATPase (SERCA), and that this compound induced the fragmentation 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 [Ca(2+)](                               i                            ) after blocking the SERCA activity. The reproduction of the effects of agelasine B on cell viability and on the [Ca(2+)](                               I                            ) obtained on SKBr3 and PC-3 cancer cells strongly suggests the generality of the mechanism of action of this toxin.
authors: Instituto de Estudios Avanzados (IDEA), Carretera Nacional Hoyo de la Puerta, Sartenejas, Baruta, Caracas, Venezuela.
authors: Adriana A
authors: AA
authors: Pimentel
authors: Pimali
authors: P
authors: Felibertt
authors: Felipe
authors: F
authors: Sojo
authors: Laura
authors: L
authors: Colman
authors: Adriana
authors: A
authors: Mayora
authors: May Li
authors: ML
authors: Silva
authors: Hector
authors: H
authors: Rojas
authors: Reinaldo
authors: R
authors: Dipolo
authors: Alírica I
authors: AI
authors: Suarez
authors: Reinaldo S
authors: RS
authors: Compagnone
authors: Francisco
authors: F
authors: Arvelo
authors: Ivan
authors: I
authors: Galindo-Castro
authors: Juan B
authors: JB
authors: De Sanctis
authors: Perla
authors: P
authors: Chirino
authors: Gustavo
authors: G
authors: Benaim