Received for publication November 27, 2007.
Revised April 2, 2008.
Accepted for publication April 25, 2008.

_v3 INTEGRIN MEDIATED DRUG RESISTANCE IN HUMAN LARYNGEAL CARCINOMA CELLS IS CAUSED BY GLUTATHIONE DEPENDENT ELIMINATION OF DRUG INDUCED REACTIVE OXIDATIVE SPECIES

Abstract

As a model for determination of the role of integrins in drug resistance, we used _v3 integrin negative human laryngeal carcinoma cell line (HEp2), and three HEp2-derived cell clones with a gradual increase of _v3 integrin expression. The _v3 integrin expression protects cells from cisplatin, mitomycin C and doxorubicin. In HEp2-_v3 integrin expressing cells the constitutive expression of Bcl-2 protein and the level of glutathione (GSH) were increased as compared to HEp2 cells. Pre-treatment of HEp2-_v3 integrin expressing cells with an inhibitor of GSH synthesis, buthionine sulfoximine (BSO), decreased the level of GSH and partially reverted drug resistance to all abovementioned drugs, but did not influence the expression of Bcl-2. Sensitivity to selected anti-cancer drugs didn't change with overexpression of Bcl-2 in HEp2 cells, nor with silencing of Bcl-2 in HEp2-_v3 integrin expressing cells, indicating that Bcl-2 is not involved in resistance mechanism. There was no difference in DNA platination between HEp2 and HEp2-_v3 integrin expressing cells indicating that the mechanism of drug resistance is independent of cisplatin detoxification by GSH. A strong increase of reactive oxidative species (ROS) formation during cisplatin or doxorubicin treatment in HEp2 cells was reduced in HEp2-_v3 integrin expressing cells. Since this increased elimination of ROS could be reverted by GSH depletion, we concluded that multidrug resistance is the consequence of GSH dependent increased ability of _v3 expressing cells to eliminate drug induced ROS.

Key words: Glutathione, Resistance