Abstract

Introduction: It is well documented that using antihormonal therapy with tamoxifen significantly improves the survival rate of women with oestrogen-receptor positive (ER+) breast tumours. However, the development of resistance to tamoxifen as a primary therapy and disease reoccurrence limits its clinical benefit. This therapeutic failure has revived interest in the breast cancer stem cell (BCSC), since stem cells were reported to be resistant to antihormonal therapy. Stemness” genes expression increases in undifferentiated cells. However, the role of their expression in breast cancer is still poorly defined. The aim of this study was to examine the role of stemness proteins in breast cancer cell lines and anti-hormonal therapy resistance.

Method: MCF-7, MCF-7/tamoxifen resistant (TAMR) and MDA-MB238 cells were cultured, with relevant hormonal therapy to calculate ED50 and incubated in 5% CO2 incubator at 37°C. Quantitative and qualitative immunophenotyping of cells was achieved using fluorescein isothiocyanate (FITC) labelled antibodies reactive with NANOG, SOX2, OCT4 and CD44.

Result: MDA-MB238 cells showed significant expression of NANOG (70%), CD44 (85%) SOX2 (68%) and OCT3-4 (50%) compared with MCF-7(12%, 4%, 15% and 10% respectively). However the MCF-7 TAMR demonstrated lower expression of NANOG (45%), CD44 (60%), SOX2 (60%) and OCT3/4 (55%) compared with MDA-MB238.

Conclusion: Stemness” proteins are highly expressed in breast cancer cells resistant to tamoxifen therapy. There is association between the expression of Stemness” proteins level and the development and progression of breast cancer resistance to tamoxifen therapy