Effect Of Timp-1 Overexpression On Endocrine Sensitivity Of Mcf-7 Er Positive Human Breast Cancer Cells In Vitro

Abstract Background: A large proportion of ER-positive breast cancer patients are offered endocrine therapy following surgery for primary breast cancer. However, many of these patients do not benefit from the treatment. Currently, no markers exist to predict whether or not an ER positive breast cancer patient will respond to endocrine therapy. Thus, additional predictive markers need to be identified to ensure a more tailored treatment. In this regard, recent clinical studies have demonstrated that high serum levels of TIMP-1 are associated with a poor response to tamoxifen or letrozole in ER positive patients with metastatic disease (Lipton et al., JCO 2008). The purpose of the present study was to investigate the association between TIMP-1 and endocrine therapy by using an in vitro approach.Tamoxifen has been shown to induce apoptosis in human breast cancer cells in vitro and TIMP-1 has been shown to inhibit drug induced apoptosis.Materials and Methods: We stably transfected the human breast carcinoma cell line MCF-7 S1 with the human TIMP-1 gene and established single cell clones expressing different levels of TIMP-1. The sensitivity of these cells to estradiol, tamoxifen and 4-hydroxy tamoxifen was compared using the crystal violet assay. For the estradiol experiments, cells were grown in RPMI 1640 supplemented with 10% DCC-stripped FCS and without phenol red and for the tamoxifen/4-hydroxy tamoxifen experiments cells were grown in RPMI supplemented with 10% FCS. Cells were grown in their maintenance medium. Experimental media was added at day two, at a cell density of 20-30%, renewed at day five, and cell number determination was performed at day seven., In all experiments the mean value for each treatment was estimated from triplicate or quadruplicate independent wells and expressed in percentage relative to cells treated only with vehicle.Results: TIMP-1 overexpresing cells grew with a distinct morphology with more well circumscribed cells, and adapted faster to stripped serum than wild type and vector control MCF-7 cells. Independent of TIMP-1 production, all cell lines demonstrated estradiol sensitivity and inhibition of growth by either tamoxifen or 4-hydroxy tamoxifen.Conclusions: This in vitro study shows that overexpression of TIMP-1 in MCF-7 cells did not change the sensitivity of endocrine treatment of the cells. This is in contrast to our experiments with the same cells demonstrating decreased sensitivity to chemotherapy of TIMP-1 overexpresing cells. Moreover, our results are in contrast to those published by Lipton et al., JCO 2008, showing that patients with metastatic breast cancer and high serum TIMP-1 levels had a reduced benefit from endocrine therapy. On the other hand, the present results are supported by our recent finding that TIMP-1 cancer cell immunoreactivity is not associated with benefit from adjuvant tamoxifen therapy in ER-positive breast cancer patients (Bjerre et al., 2009) Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2029.