Herceptin Research Today is a free monthly online journal that collates and summarizes the latest research about Herceptin, including details on side-effects, breast cancer, treatment, therapy.

HER2 signaling downregulation by trastuzumab and suppression of the PI3K/Akt pathway: an unexpected effect on TRAIL-induced apoptosis.

Dubská L, Andera L, Sheard MA

Department of Laboratory Medicine, Masaryk Memorial Cancer Institute, Zluty Kopec 7, 656 53 Brno, Czech Republic. dubska@mou.cz

We investigated whether HER2 downregulation by trastuzumab modulates the responsiveness of breast cancer cells to TNF-related apoptosis-inducing ligand (TRAIL). Interestingly, in contrast to increased response to TRAIL in SKBr3 cells, trastuzumab decreased the susceptibility of BT474 cells to TRAIL. This decrease was also observed after exogenous inhibition of PI3-K/Akt kinase, but not MAPK/ERK kinase (MEK)/mitogen-activated protein kinase (MAPK). In BT474 cells, but not SKBr3 cells, inhibition of the HER2/phosphatidylinositol 3' kinase (PI3K)/Akt pathway resulted in downregulation of the pro-apoptotic receptors TRAIL-receptor 1 (TRAIL-R1) and TRAIL-R2. TRAIL-induced caspase-8 activation, Bid processing, drop of DeltaPsi(m), and poly ADP-ribose polymerase (PARP) cleavage but not in caspase-9 activation, and these events were inhibited in HER2/PI3K/Akt-suppressed BT474 cells, which on the other hand exhibited downregulation of Bcl-xL and increased response to mitomycin C. We show that HER2/PI3K/Akt pathway may play a specific pro-apoptotic role in certain cell type by inducing TRAIL-R1 and -R2 expression and thereby enhancing responsiveness to TRAIL.

Published 26 July 2005 in FEBS Lett, 579(19): 4149-58.
Full-text of this article is available online (may require subscription).

© 2004-2008 Herceptin Research Today. All Rights Reserved.