Anastrozole and RU486: Effects on estrogen receptor α and Mucin 1 expression and correlation in the MCF-7 breast cancer cell line

Anastrozole and RU486 are shown to reduce hormone-responsive breast cancer progression when used as adjuvant treatments to surgical intervention, however, a high incidence of cancer recurrence remains. Estrogen receptor alpha (ERα) and Mucin 1 (MUC1), a glycoprotein, are both implicated in breast cancer progression. We assessed whether Anastrozole and RU486 treatment affects the expression of, and relationship between, ERα and MUC1 in the ERα+ MUC1+ MCF-7 breast cancer cell line. MCF-7 cells, treated with physiological concentrations of either Anastrozole or RU486 for 18 h or 72 h, were subjected to immunolocalization of both markers. CellProfiler software was used to quantify intensity for statistical analyses. ERα expression increased at both time periods following treatment. MUC1 expression increased with RU486-treatment at both times, whereas Anastrozole induced increased MUC1 expression at 72 h only. The biomarkers demonstrated increased point association at 72 h within treatment groups despite MUC1 diverging from correlation with ERα. We propose that tumor progression is independent of MUC1 and ERα correlation. These preliminary results indicate that withdrawal of adjuvant treatment may result in residual cell populations expressing increased ERα and MUC1. This phenotype may allow enhanced estrogenic and metastatic capacity influencing cancer recurrence, a hypothesis we are investigating further.