Mechanisms of Gefitinib-mediated reversal of tamoxifen resistance in MCF-7 breast cancer cells by inducing ER? re-expression.

ABSTRACT: Estrogen receptor (ER)-positive breast cancer patients may turn ER-negative and develop acquired drug resistance, which compromises the efficacy of endocrine therapy. By investigating the phenomenon that gefitinib can re-sensitise tamoxifen (TAM)-resistant MCF-7 breast cancer cells (MCF-7/TAM) to TAM, the present study verified that gefitinib could reverse the acquired drug resistance in endocrine therapy and further explored the underlying mechanism.ER?-negative MCF-7/TAM cells were established. Upon treating the cells with gefitinib, the mRNA and protein levels of ER? and ER?, as well as the expression of molecules involved in the MAPK pathway, were examined using the RT-PCR and immunocytochemistry. The RT-PCR results showed that the mRNA levels of ER? and ER? in MCF-7/TAM cells were up-regulated following gefitinib treatment; specifically, ER? was re-expressed, and ER? expression was up-regulated. The expression of molecules involved in the MAPK pathway, including RAS, MEK1/2, and p-ERK1/2, in MCF-7/TAM cells was significantly up-regulated, compared with MCF-7 cells. After the gefitinib treatment, the expression levels of MEK1/2 and p-ERK1/2 were significantly down-regulated. ER? loss is the primary cause for TAM resistance. Gefitinib reverses TAM resistance primarily by up-regulating the ER? mRNA level and inducing the re-expression of ER?. The MAPK pathway plays a key role in ER? re-expression.

SUBMITTER: Zhang X 

PROVIDER: S-EPMC4314651 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature