Journal Article

Induction of macroautophagy in human colon cancer cells by soybean B-group triterpenoid saponins

Allison A. Ellington, Mark Berhow and Keith W. Singletary

in Carcinogenesis

Volume 26, issue 1, pages 159-167
Published in print January 2005 | ISSN: 0143-3334
Published online January 2005 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgh297
Induction of macroautophagy in human colon cancer cells by soybean B-group triterpenoid saponins

More Like This

Show all results sharing this subject:

  • Clinical Cytogenetics and Molecular Genetics

GO

Show Summary Details

Preview

The impact of triterpenoid saponins isolated from soybeans on suppression of colon cancer cell proliferation was evaluated. Experiments were conducted to determine the effects of a purified soybean B-group saponin extract on cell proliferation, cell-cycle distribution and programmed cell death in cultures of human HCT-15 colon adenocarcinoma cells. Treatment of cells with the soyasaponins at concentrations of 25–500 p.p.m. significantly reduced viable cell numbers after 24 and 48 h of exposure. Treatment of cells with 25 and 100 p.p.m. of saponins also resulted in a transient accumulation of cells in the S-phase of the cell cycle that was associated with a significant reduction of cyclin-dependant kinase-2 (CDK-2) activity. More striking was that, when examined by transmission electron microscopy, soyasaponin-treated cells exhibited an ∼4.5-fold increase in cell morphologies characteristic of Type II non-apoptotic programmed cell death (PCD) including numerous autophagic vacuoles, changes that collectively suggest autophagic cell death. In addition, the protein levels of microtubule-associated protein light chain 3 (LC-3), a specific marker of macroautophagy, increased substantially following soyasaponin treatment. Taken together these results thus indicate that soybean saponins, at physiologically relevant doses, can suppress HCT-15 colon cancer cell proliferation through S-phase cell-cycle delay, and can induce macroautophagy, the hallmark of Type II PCD. These findings suggest that B-group soyasaponins may be another colon-cancer suppressive component of soy that warrants further examination as a potential chemopreventive phytochemical.

Keywords: AVi, immature, non-degradative autophagic vacuoles; AVd, mature, degradative autophagic vacuoles; CDK-2, cyclin-dependant kinase 2; CDKI, cyclin-dependent kinase inhibitor; LC-3, microtubule-associated protein light chain 3; 3-MA, 3-methyladenine; MDC, monodansylcadaverine; PCD, programmed cell death

Journal Article.  5933 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.