Combined Phytochemicals Synergistically Restrain Breast Cancer in Cultured Cells and Xenograft Mice
Phytochemicals, the secondary plant metabolites present in variety of foods, have been considered excellent candidates to develop an effective approach to overcome tumor heterogeneity and drug resistance in breast cancer. However, the big gap between the concentrations of phytochemicals having antitumor effects in vitro studies and the plasma level of phytochemicals in humans undermines the phytochemicals in anti-breast cancer application. The aims of this study are to screen novel combinations of phytochemicals synergistically restrain breast cancer, and investigate underlying molecular mechanisms in cells and mice. Through performing pairwise combination screens from 12 selected phytochemicals with great potency in anti-breast cancer based on cell proliferation assay, we identified two active combinations: combination of luteolin (LUT, 30μM) and indole-3-carbinol (I3C, 40μM), and LUT (30μM) and curcumin (CUR, 20μM) synergistically and selectively inhibited the cell proliferation of estrogen receptor alpha positive (ERα+) MCF7 cells, and triple-negative breast cancer (TNBC) BT-549 and MDA-MB-231 cells only receptively, while the individual chemicals exhibit less effect at the selected concentrations. Consistently, combined LUT and I3C (LUT10mg/kg/day + I3C20mg/kg/day) and combined LUT and CUR (LUT 10mg/kg/day + CUR 20mg/kg/day) by ip injection every other day for 4-5 weeks synergistically suppressed tumor growth in ERα+ and TNBC xenograft mice respectively. Our further analyses show that the synergistic anti-breast cancer effect by combination of LUT and I3C was mediated by reducing CDK4 to induce growth arrest in G1 cell cycle and by degrading ERα proteins in cultured cells and xenograft mice. Our RNA-seq transcriptome analysis revealed that combination LUT and CUR synergistically activated type I interferon (IFN) signaling and suppressed Transforming growth factor beta (TGF-β) signaling in TNBC xenografts. The combination of LUT and CUR dramatically triggered the phosphorylation at STAT1 Tyr701 (Y701) residue and increased interferon-stimulated gene OAS1 expression. In addition, this combination also synergistically decreased onco-proteins levels of BRD4 MYC, NTOCH1, which are required to maintain stem cell properties, tumor clonal evolution and drug resistance development. In conclusion, taking a combination of LUT and I3C, LUT and CUR may be an effective, safe approach to prevent/treat breast cancer in humans after clinical trials.
Molecular biology|Cellular biology|Biochemistry
"Combined Phytochemicals Synergistically Restrain Breast Cancer in Cultured Cells and Xenograft Mice"
ETD Collection for Tennessee State University.