Targeting aberrant expression of Notch-1 in ALDH cancer stem cells in breast cancer.

We have previously reported that high aldehyde dehydrogenase (ALDH) enzyme activity in breast cancer cells results in breast cancer stem cell (BCSC) properties by upregualting Notch-1 and epithelial mesenchymal markers. This results in chemoresistance in breast cancer. Here, we examined the functional and clinical significance of ALDH expression by measuring the ALDH levels in breast cancer tissues by immunohistochemistry. There was a significantly higher ALDH expression in higher grade breast cancer tumor tissues (Grade- II and III) versus normal breast tissues. Injection of BCSC (ALDH and CD44 /CD22 ) cells resulted in aggressive tumor growth in athymic mice versus ALDH cells. The ALDH and CD44 /CD22 tumors grow rapidly and are larger than ALDH tumors which were slow growing and smaller. Molecularly, ALDH tumors expressed higher expression of Notch-1 and EMT markers than ALDH tumors. Oral administration of the naturally occurring Psoralidin (Pso, 25 mg/kg of body weight) significantly inhibited the growth in ALDH and ALDH tumors as well. Psoralidin inhibited Notch-1 mediated EMT activation in ALDH and ALDH tumors-this confirms our in vitro findings. Our results suggest that Notch-1 could be an attractive target and inhibition of Notch-1 by Psoralidin may prevent pathogenesis of breast cancer as well as metastasis. © 2016 Wiley Periodicals, Inc.