Effect of Wnt5a on drug resistance in estrogen receptor-positive breast cancer

Abstract BackgroundIt was previously reported by us that Wnt5a-positive breast cancer can be classified as estrogen receptor (ER)-positive breast cancer and its prognosis is worse than that of Wnt5a-negative breast cancer. Herein, the molecular mechanisms underlying the poor prognosis of Wnt5a-positive breast cancer patients were examined. MethodsA total of 151 consecutive ER-positive breast cancer patients who underwent resection between January 2011 and February 2014 were enrolled. DNA microarray and pathway analyses were performed conducted using MCF-7 cells stably expressing Wnt5a (MCF-7/Wnt5a(+)). Based on the results, cell viability and drug sensitivity assays as well as mutation analysis , were performed using culture cells and breast cancer tissue. The relationship between Wnt5a and the PI3K–AKT–mTOR signaling pathway was examined.ResultsThe relapse-free survival rate in patients with Wnt5a-positive breast cancer was significantly lower than that in patients with Wnt5a-negative breast cancer ( P = 0.047). DNA microarray data indicated that only the cytochrome P450 (CYP) pathway was significantly upregulated in MCF-7/Wnt5a(+) cells ( P = 0.0440). MCF-7/Wnt5a(+) cells showed reduced sensitivity to the metabolic substrates of CYP, tamoxifen ( P < 0.001), and paclitaxel ( P < 0.001). PIK3CA mutations were unrelated to Wnt5a expression in breast cancer tissue and culture cells.ConclusionsIn ER-positive breast cancer, Wnt5a upregulated the CYP metabolic pathway; additionally, it inhibited the sensitivity to tamoxifen and paclitaxel, which constitute the standard treatment options for ER-positive breast cancer. Wnt5a could be involved in the poor prognosis of ER-positive breast cancer independently of the PI3K–AKT–mTOR signaling pathway.