A human breast cancer cell line (MCF7/WT) was selected for resistance to etoposide (VP-16) by stepwise exposure to 2-fold increasing concentrations of this agent. The resulting cell line (MCF7/VP) was 28-, 21-, and 9-fold resistant to VP-16, VM-26, and doxorubicin, respectively. MCF7/VP cells also exhibited low-level cross-resistance to 4'-(9-acridinylamino)-methanesulfon-m-anisidide, mitoxantr...

A human breast cancer cell line (MCF7/WT) was selected for resistance to etoposide (VP-16) by stepwise exposure to 2-fold increasing concentrations of this agent. The resulting cell line (MCF7/VP) was 28-, 21-, and 9-fold resistant to VP-16, VM-26, and doxorubicin, respectively. MCF7/VP cells also exhibited low-level cross-resistance to 4'-(9-acridinylamino)methanesulfon-m-anisidide, mitoxantro...

A human breast cancer cell line (MCF7/WT) was selected for resistance to etoposide (VP-16) by stepwise exposure to 2-fold increasing concentrations of this agent. The resulting cell line (MCF7/VP) was 28-, 21-, and 9-fold resistant to VP-16, VM-26, and doxorubicin, respectively. MCF7/VP cells also exhibited low-level cross-resistance to 4'-(9-acridinylamino)methanesulfon-m-anisidide, mitoxantro...

The WTH3 gene's biological characteristics and relationship to multidrug resistance (MDR) were investigated further. Results showed that WTH3 was mainly located in the cytosol and capable of binding to GTP. In addition, WTH3's promoter function was significantly attenuated in MDR (MFC7/AdrR) relative to non-MDR (MCF7/WT) cells. Advanced analyses indicated that two mechanisms could be involved i...

BACKGROUND In human breast cancer, a growth status switched from estrogen-dependent to growth factor-dependent is a critical step during development of acquired tamoxifen resistance. However, the molecular mechanisms underlying this switch remain poorly understood. The Wilms' tumor suppressor gene, WT1, encodes a zinc-finger protein WT1 that functions as a transcription regulator. High levels o...

MCF7 human breast cancer cells have been studied extensively as a model for hormonal effects on breast cancer cell growth and specific protein synthesis. Because the proliferative effect of natural estrogen is considered the hallmark of estrogen action, it was proposed that this property be used to determine whether a substance is an estrogen. The E-screen assay, developed for this purpose, is ...

Increased activation of ERK signaling has been reported in breast cancer models of acquired tamoxifen resistance. Here, we examined the expression of Mitogen-Activated Protein Kinase Phosphatases (MKPs) 1 and 2 following tamoxifen treatment and the effects of MKP-1/MKP-2 overexpression on tamoxifen sensitivity. Treatment of MCF7 breast cancer cells with tamoxifen increased MKP-2, but not MKP-1,...

Objective(s):Multidrug resistance (MDR) of cancer cells is a major obstacle to successful chemotherapy. Overexpression of breast cancer resistance protein (BCRP) is one of the major causes of MDR. In addition, it has been shown that PI3K/Akt signaling pathway involves in drug resistance. Therefore, we evaluated the effects of novel approaches including siRNA directed against BCRP and targeted t...

Gefitinib inhibits the ATP-binding site of the tyrosine kinase associated with the epidermal growth factor receptor. It is conceivable that gefitinib may inhibit functions of ATP-binding cassette (ABC) transporters by binding at their ATP-binding sites. The aim of this study is to systematically explore the combined effect of gefitinib and chemotherapeutic agents in gefitinib-insensitive multid...

BACKGROUND Multidrug resistance is a major obstacle in the successful therapy of breast cancer. Studies have proved that this kind of drug resistance happens in both human cancers and cultured cancer cell lines. Understanding the molecular mechanisms of drug resistance is important for the reasonable design and use of new treatment strategies to effectively confront cancers. RESULTS In our st...