Betulin induces mitochondrial cytochrome c release associated apoptosis in human cancer cells

Abstract

We examined whether betulin, a naturally abundant compound, has anticancer functions in human cancer cells. The results showed that betulin significantly inhibited cell viability in cervix carcinoma HeLa cells, hepatoma HepG2 cells, lung adenocarcinoma A549 cells, and breast cancer MCF-7 cells with IC(50) values ranging from 10 to 15 microg/mL. While betulin exhibited only moderate anticancer activity in other human cancer cells such as hepatoma SK-HEP-1 cells, prostate carcinoma PC-3, and lung carcinoma NCI-H460, with IC(50) values ranging from 20 to 60 microg/mL, it showed minor growth inhibition in human erythroleukemia K562 cells (IC(50) > 100 microg/mL). We further investigated the mechanism of anticancer activity by betulin, using HeLa cells as an experimental model. Betulin (10 microg/mL) induces apoptotic cell death, as evidenced by morphological characteristics such as membrane phosphatidylserine translocation, nuclear condensation/fragmentation, and apoptotic body formation. A kinetics analysis showed that the depolarization of mitochondrial membrane potential and the release of mitochondrial cytochrome c occurred as early as 30 min after treatment with betulin. Betulin, unlike its chemical derivative betulinic acid, did not directly trigger mitochondrial cytochrome c release in isolated mitochondria. Importantly, Bax and Bak were rapidly translocated to the mitochondria 30 min after betulin treatment. The sequential activation of caspase-9 and caspase-3/-7 and the cleavage of poly(ADP-ribose) polymerase (PARP) were observed behind those mitochondrial events. Furthermore, specific downregulation of either caspase-9, Bax, or Bak by siRNA effectively reduced PARP cleavage and caspase-3 activation. Taken together, the lines of evidence demonstrate that betulin triggers apoptosis of human cancer cells through the intrinsic apoptotic pathway.

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Effects of Novel All-Trans Retinoic Acid Retinamide Derivatives on the Proliferation and Apoptosis of Human Lung Adenocarcinoma Cell Line A549 Cells

“…This suggests that part of the antitumor activity of N-(3-tri‰uoromethyl-phenyl) retinamide may be mainly mediated by promoting the apoptosis of A549 cells. The mechanism of the MAPK pathway may be aŠected by Bcl-2 family protein expression, 15,16) which promotes the release of cytochrome c and aŠects the expression of the caspase family, 17) ultimately leading to apoptosis.…”

Apoptosis of Breast Cancer Cells: Modulation of Genes for Glycoconjugate Biosynthesis and Targeted Drug Delivery

“…Targeting mitochondria as a cancer therapeutic strategy is of interest in recent years. Besides recognition of inhibitors of GSL biosynthesis ( l -PPMP, d -PPMNP, and d -PDMP) and DNA biosynthesis (cisplatin) in our laboratory (Basu et al 2004a, b, c ;Ma et al 2004 ;Boyle et al 2006 ) several other different chemicals have been tested as apoptosis inducing agents (via intrinsic mitochondrial or extrinsic receptor pathways) in breast cancer cells Patil et al 2010 ;Banerjee et al 2010Banerjee et al , 2011Shirure et al 2011 ;Cazet et al 2010 ;Jada et al 2008 ;Domingo-Domenech et al 2008 ;Nakagawa et al 2007 ;Nakajima et al 2007 ;Sato-Cerrato et al 2005 ;Balabhadrapatharuni et al 2005 ;Hatasukari et al 2003 ;Chung et al 2002 ;Hansen et al 2000 ;Fromigue et al 2003 ;Elton et al 2000 ;Distefano et al 1998 ;Han et al 1998 ;Schwartz et al 1997 ;Sarkar et al 2007 ;Singh et al 2009 ;Lu et al 2006 ;Somers-Edgar and Rosegren 2009 ;Neuzil et al 2007 ;Fulda et al 1997 ;Li et al 2010a ;Chaouki et al 2010 a;Mullauer et al 2011a ;Kessler et al 2007a ;Laszczyk 2009 ;Bzesk et al 2006a ;Goldoni et al 2008 a;Ellerby et al 1999 ) .…”