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Int J Oncol. 2008 Mar;32(3):683-8.

Dexamethasone interferes with trastuzumab-induced cell growth inhibition through restoration of AKT activity in BT-474 breast cancer cells.

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Division of Medical Oncology and Molecular Respirology, Faculty of Medicine, Tottori University, Yonago 683-8504, Japan.


The combination of trastuzumab with paclitaxel (PTX) is an important option for the treatment of HER2-positive breast cancer. Dexamethasone (Dex) premedication is routinely used in the treatment with PTX. The interactions among Dex, PTX and trastuzumab were evaluated in BT-474 cells. Dex interfered with trastuzumab-induced cell growth inhibition without clear effects on PTX-induced cytotoxicity. Trastuzumab dephosphorylated retinoblastoma protein (pRB). Dex restored this trastuzumab-induced dephosphorylation of pRB and released trastuzumab-induced G1 arrest. Trastuzumab suppressed AKT activity without affecting ERK activity. A specific inhibitor for the phosphatidylinositol 3-kinase/AKT pathway, LY294002, inhibited cell growth and AKT and pRB phosphorylation. Dex restored the trastuzumab-induced suppression of AKT without affecting ERK activity. It was concluded that Dex interferes with trastuzumab-induced cell growth inhibition, at least partially, through the restoration of trastuzumab-induced AKT suppression and subsequent pRB dephosphorylation in BT-474 breast cancer cells. These observations support the development of new chemotherapeutic regimens without glucocorticoid premedication.

[Indexed for MEDLINE]

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