Delphinidin Inhibits HER2 and Erk1/2 Signaling and Suppresses Growth of HER2-Overexpressing and Triple Negative Breast Cancer Cell Lines.
Bottom Line: Delphinidin is a polyphenolic compound found in many brightly colored fruits and vegetables.MAPK signaling was partially reduced in triple negative cells and ER-negative chemically transformed MCF10A cells after treatment with delphinidin.In addition, delphinidin induced a significant level of apoptosis in HER2-overexpressing cells in association with reduced HER2 and MAPK signaling.
Affiliation: Departments of Pharmacology.
Delphinidin is a polyphenolic compound found in many brightly colored fruits and vegetables. Delphinidin is also the major bioactive component found in many dietary supplements that are currently consumed as complementary cancer medicine including pomegranate extract. The purpose of the current study was to determine the in vitro biological effects of delphinidin on established breast cancer cell lines of varying molecular subtypes in comparison to non-transformed breast epithelial cells. We examined cell proliferation, apoptosis, and growth inhibition in response to delphinidin using a tetrazolium salt-based assay, DNA fragmentation assay, and anchorage-independent growth assay. In comparison to vehicle control, delphinidin inhibited proliferation (P < 0.05), blocked anchorage-independent growth (P < 0.05), and induced apoptosis (P < 0.05) of ER-positive, triple negative, and HER2-overexpressing breast cancer cell lines with limited toxicity to non-transformed breast epithelial cells. MAPK signaling was partially reduced in triple negative cells and ER-negative chemically transformed MCF10A cells after treatment with delphinidin. In addition, delphinidin induced a significant level of apoptosis in HER2-overexpressing cells in association with reduced HER2 and MAPK signaling. Since delphinidin is often consumed as a complementary cancer medicine, the effect of delphinidin on response to specific HER2-targeted breast cancer therapies was examined by proliferation assay. Results of these drug combination studies suggested potential antagonism between delphinidin and HER2-directed treatments. In summary, the data presented here suggest that single agent delphinidin exhibits growth inhibitory activity in breast cancer cells of various molecular subtypes, but raise concerns regarding potential drug antagonism when used in combination with existing targeted therapies in HER2-overexpressing breast cancer.
No MeSH data available.
Related in: MedlinePlus
Mentions: To better examine the anti-cancer effects of delphinidin, we chemically transformed the MCF10A breast epithelial cell line by treating cells chronically with 100 nM of the dietary carcinogen PhIP, which has been shown to induce mammary carcinoma in rats.15 After 3 months of PhIP exposure, duplicate cultures of MCF10A.PhIP cells and corresponding control DMSO-maintained MCF10A cells were grown in matrigel for 4–6 weeks. MCF10A.PhIP cells were either treated with 50 μg/mL delphinidin or DMSO. MCF10A.DMSO cells formed very few colonies (Fig. 4A), consistent with the fact that this cell line is not transformed. In contrast, MCF10A.PhIP cells showed significant anchorage-independent colony formation, indicating that PhIP had transformed MCF10A cells, with 6-fold higher colony counts versus MCF10A.DMSO (Fig. 4B). Importantly, delphinidin treatment suppressed growth of MCF10A.PhIP cells. Thus, delphinidin inhibited anchorage-independent growth of the chemically transformed MCF10A.PhIP cell line. To determine if ER status of MCF10A cells had changed after PhIP exposure, MCF10A parental, DMSO control, and PhIP-transformed cells were examined by Western blot for ER in comparison to ER-positive MCF-7 cells (Fig. 4C). PhIP exposure did not alter ER expression. Finally, since PhIP was previously shown to mediate transformation by activating Erk1/2 signaling,16 MCF10A cells were stimulated with 100 nM PhIP in the absence or presence of delphinidin, and examined by Western blotting for Erk1/2 phosphorylation (Fig. 4D). While PhIP induced phosphorylation of Erk1/2, co-treatment with delphinidin prevented activation of Erk1/2 signaling. Thus, while delphinidin showed limited activity in non-transformed parental MCF10A and control MCF10A.DMSO cells, anchorage-independent growth and Erk1/2 signaling were significantly inhibited by delphinidin in PhIP-transformed MCF10A cells.
No MeSH data available.