Tamoxifen-induced rapid death of gper positive cell lines by modulating ras/mapk signaling pathway

Milad Rouhi moghadam,1,* Shahrokh safarian,2 Jason s. carroll,3

1. Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran
2. Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran
3. Cancer Research UK, University of Cambridge, UK

Abstract

Introduction

Breast cancer is the most common cancer in women worldwide. tamoxifen is a nonsteroidal selective estrogen receptor modulator widely used in the endocrine therapy of breast cancer. in some forms of human gper positive breast cancer and in many experimental models of breast cancer progression, signaling through the ras/mapk pathway, in particular, has been implicated as being important in driving cell growth. depending on the duration and its magnitude, the activation of this cascade controls various cell responses.

Methods

Mcf-7 cells were treated with 250µm tamoxifen for 48 hours. the mrna transcript levels for craf, k-ras, mapk1 and gapdh genes were analyzed by a three-step real-time pcr. total rna (2 mg), which was prepared from the cells using the tripure isolation reagent (roche), was used for each rt reaction with the revertaid first strand cdna synthesis kit (thermo scientific) following the manufacturer’s instructions. the fold change of relative gene expression levels was calculated by rest software.

Results

Results from rt-pcr analyses suggested that in er+mcf-7 cells, the erk signaling pathway may be over activated by tamoxifen through ras/mapk signaling axis. we also found that mapk1, craf and k-ras are up-regulated in tamoxifen-treated sample group (in comparison to control group) by a mean factor of 21.333, 27.954 and 1.575, respectively.

Conclusion

Tamoxifen activates gper signaling pathways in er positive cell lines. here we demonstrate a requirement for extracellular signal-regulated protein kinase (erk), a member of the mitogen-activated protein kinase family in mediating tamoxifen-induced apoptosis of human breast cancers. tamoxifen treatment resulted in dose- and time- dependent activation of erk.

Keywords

Tamoxifen, breast cancer, gper, ras/mapk