The marine sponge toxin agelasine B increases the intracellular Ca2+ concentration and induces apoptosis in human breast cancer cells (MCF-7)

• Published in: Cancer chemotherapy and pharmacology Vol. 69; no. 1; pp. 71 - 83
• Main Authors: Pimentel, Adriana A., Felibertt, Pimali, Sojo, Felipe, Colman, Laura, Mayora, Adriana, Silva, May Li, Rojas, Hector, Dipolo, Reinaldo, Suarez, Alírica I., Compagnone, Reinaldo S., Arvelo, Francisco, Galindo-Castro, Ivan, De Sanctis, Juan B., Chirino, Perla, Benaim, Gustavo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-01-2012; Springer
• Subjects: Antineoplastic agents; Biological and medical sciences; Cancer Research; Gynecology. Andrology. Obstetrics; Mammary gland diseases; Medical sciences; Medicine; Medicine & Public Health; Oncology; Original Article; Pharmacology. Drug treatments; Pharmacology/Toxicology; Tumors; Thapsigargin; Agelasine B; Calcium; SERCA; Natural products; Breast disease; Inorganic element; Marine environment; Established cell line; Tumor cell; Human; Animal origin; Natural product; Breast cancer; Malignant tumor; Concentration; Mammary gland diseases; Toxin; Cell death; Porifera; Sponge; Intracellular; Invertebrata; Cancer; Apoptosis
• ISSN: 0344-5704; 1432-0843
• DOI: 10.1007/s00280-011-1677-x

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 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.