Intracellular signaling in the induction of apoptosis in a human breast cancer cell line by water extract of Mekabu.
BACKGROUND
We previously reported that water extract of Mekabu, a kind of seaweed, induced apoptosis in a human breast cancer cell line. In the present study we investigated intracellular signaling in apoptosis, with a focus on caspases.


METHODS
Mekabu extract, obtained with ultrapure water, was used to induce apoptosis in a human breast cancer cell line, MDA-MB231, and DNA fractionation was investigated by flow cytometry and electrophoresis. In addition, using the caspase detection kit Caspa Tag, activation of caspases 3, 6, 8, and 9 was observed under a fluorescence microscope. Furthermore, using antibodies to caspases 3, 8, 9, and Bid, we conducted a protein analysis by Western blotting to determine the activation of these substances.


RESULTS
Obvious ladder formation demonstrating DNA fractionation was seen, confirming that Mekabu extract induced apoptosis. In the fluorescence microscope observations, activation of caspases 3, 6, and 8, but not caspase 9, was seen. Activated caspases 3 and 8 were detected in the Western blotting analysis, but no proteins of activated caspase 9 or Bid were detected.


CONCLUSIONS
Mekabu extract activates caspases 3, 6, and 8 and contributes to intracellular signaling to induce apoptosis in a human breast cancer cell line. This signaling is not via the mitochondria.
Sekiya
Masanori
M
Second Department of Surgery, Nagoya University School of Medicine, Nagoya 466-8550, Japan. endocrina@ybb.ne.jp
Funahashi
Hiroomi
H
Tsukamura
Kyosuke
K
Imai
Tsuneo
T
Hayakawa
Akemi
A
Kiuchi
Tetsuya
T
Nakao
Akimasa
A
D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000473:pathology*; D020169:Caspases / Q000378:metabolism*; D018736:DNA Adducts; D004249:DNA Damage; D005260:Female; D006801:Humans; D010936:Plant Extracts / Q000494:pharmacology*; D012624:Seaweed / Q000737:chemistry*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D018736:DNA Adducts; D010936:Plant Extracts; D020169:Caspases