Selectively Targeting Breast Cancer Stem Cells by 8-Quinolinol and Niclosamide

Abstract

Cancer maintenance, metastatic dissemination and drug resistance are sustained by cancer stem cells (CSCs). Triple negative breast cancer (TNBC) is the breast cancer subtype with the highest number of CSCs and the poorest prognosis. Here, we aimed to identify potential drugs targeting CSCs to be further employed in combination with standard chemotherapy in TNBC treatment. The anti-CSC efficacy of up to 17 small drugs was tested in TNBC cell lines using cell viability assays on differentiated cancer cells and CSCs. Then, the effect of 2 selected drugs (8-quinolinol -8Q- and niclosamide -NCS-) in the cancer stemness features were evaluated using mammosphere growth, cell invasion, migration and anchorage-independent growth assays. Changes in the expression of stemness genes after 8Q or NCS treatment were also evaluated. Moreover, the potential synergism of 8Q and NCS with PTX on CSC proliferation and stemness-related signaling pathways was evaluated using TNBC cell lines, CSC-reporter sublines, and CSC-enriched mammospheres. Finally, the efficacy of NCS in combination with PTX was analyzed in vivo using an orthotopic mouse model of MDA-MB-231 cells. Among all tested drug candidates, 8Q and NCS showed remarkable specific anti-CSC activity in terms of CSC viability, migration, invasion and anchorage independent growth reduction in vitro. Moreover, specific 8Q/PTX and NCS/PTX ratios at which both drugs displayed a synergistic effect in different TNBC cell lines were identified. The sole use of PTX increased the relative presence of CSCs in TNBC cells, whereas the combination of 8Q and NCS counteracted this pro-CSC activity of PTX while significantly reducing cell viability. In vivo, the combination of NCS with PTX reduced tumor growth and limited the dissemination of the disease by reducing circulating tumor cells and the incidence of lung metastasis. The combination of 8Q and NCS with PTX at established ratios inhibits both the proliferation of differentiated cancer cells and the viability of CSCs, paving the way for more efficacious TNBC treatments.

Extracellular vesicles secreted by triple‐negative breast cancer stem cells trigger premetastatic niche remodeling and metastatic growth in the lungs

“…CSC were obtained by fluorescence-activated cell sorting (FACS) from the MDA-MB-231 ALDH1A1:tdTomato model, previously described and validated by our group 12 along with other breast cancer cell lines for example, MCF-7 33 and HCC1806. 38 Briefly, cells were stably transfected with a vector expressing the reporter tdTomato fluorescent protein under the control of the CSC ALDH1A1 promoter. This strategy allows the fluorescent tagging of ALDH1A1 expressing CSC, while nonfluorescent cells represent the DCCs subpopulation.…”

3D Bioprinted Tumor-Stroma Models of Triple-Negative Breast Cancer Stem Cells for Preclinical Targeted Therapy Evaluation

“…Primary HBFs were purchased from Innoprot (Derio, Spain), and human breast MDA-MB-231, MCF-7, and THP-1 cell lines were obtained from American Type Culture Collection. MDA-MB-231 ALDH/tdTomato CSCs were generated as previously described. − Briefly, this process involved the stable transfection of MDA-MB-231 cells with a vector expressing the tdTomato fluorescent protein under the regulatory control of the ALDH1A1 promoter specific to CSC, facilitating fluorescent labeling and isolation of CSCs expressing ALDH1A1. CSC subpopulations from MDA-MB-231 ALDH/tdTomato were isolated according to their tdTomato expression in a fluorescent-activated cell sorter Aria cell sorter (BD Biosciences, Franklin Lakes, NJ). − All cell lines were cultured in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum and 1% penicillin/streptomycin (Fisher Scientific) and cultured under standard tissue culture conditions at 37 °C with 5% CO 2 .…”