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Cancer Research

Flow Cytometric Detection of Newly-formed Breast Cancer Stem Cell-like Cells After Apoptosis Reversal

Published: January 26th, 2019



1School of Life Sciences, The Chinese University of Hong Kong, 2State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, 3Key Laboratory for Regenerative Medicine, Ministry of Education, The Chinese University of Hong Kong, 4Centre for Novel Biomaterials, The Chinese University of Hong Kong

Here, we present a protocol to isolate apoptotic breast cancer cells by fluorescence-activated cell sorting and further detect the transition of breast non-stem cancer cells to breast cancer stem cell-like cells after apoptosis reversal by flow cytometry.

Cancer recurrence has long been studied by oncologists while the underlying mechanisms remain unclear. Recently, we and others found that a phenomenon named apoptosis reversal leads to increased tumorigenicity in various cell models under different stimuli. Previous studies have been focused on tracking this process in vitro and in vivo; however, the isolation of real reversed cells has yet to be achieved, which limits our understanding on the consequences of apoptosis reversal. Here, we take advantage of a Caspase-3/7 Green Detection dye to label cells with activated caspases after apoptotic induction. Cells with positive signals are further sorted out by fluorescence-activated cell sorting (FACS) for recovery. Morphological examination under confocal microscopy helps confirm the apoptotic status before FACS. An increase in tumorigenicity can often be attributed to the elevation in the percentage of cancer stem cell (CSC)-like cells. Also, given the heterogeneity of breast cancer, identifying the origin of these CSC-like cells would be critical to cancer treatment. Thus, we prepare breast non-stem cancer cells before triggering apoptosis, isolating caspase-activated cells and performing the apoptosis reversal procedure. Flow cytometry analysis reveals that breast CSC-like cells re-appear in the reversed group, indicating breast CSC-like cells are transited from breast non-stem cancer cells during apoptosis reversal. In summary, this protocol includes the isolation of apoptotic breast cancer cells and detection of changes in CSC percentage in reversed cells by flow cytometry.

Cancer has been a leading cause of death, causing heavy burden to countries worldwide1. Breast cancer ranks high both in terms of incidence and mortality in female patients among all types of cancer1. Due to the cancer heterogeneity, a combination of drugs is usually used in chemotherapy to achieve cancer cell death2,3,4. However, since common chemotherapeutic drugs often target DNA5,6, protein synthesis7,8 and/o....

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1. Preparation of Breast Non-stem Cancer Cells

  1. Culture MCF-7 and MDA-MB-231 cells in 10 mL of phenol red-free Roswell Park Memorial Institute (RPMI) 1640 medium supplemented with 10% heat-inactivated fetal bovine serum (FBS) in a 100 mm dish. Culture T47D in 10 mL of phenol red-free RPMI 1640 medium supplemented with 2 mM L-glutamine, 10% heat-inactivated FBS, and 1% v/v Penicillin-Streptomycin (PS) in a 100 mm dish. Culture cells at 37 °C in a 5% CO2/95% air cell culture incu.......

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In order to observe the transition from breast non-stem cancer cells to breast CSC-like cells, a first sorting of CD44-/CD24+ breast cancer cells were needed. For the MCF-7 cell line, which has around 0.15% cells with CSC markers in the original population (Figure 1), this step helped exclude the possibility of CSC enrichment during apoptosis reversal. On the contrary, if there were no cells with CSC markers in the original population, s.......

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This protocol describes a direct and clear way for detecting the transition of breast non-stem cancer cells into breast CSC-like cells as a result of apoptosis reversal. Confirmation of the CSC properties of these reversed cells could be assisted by using in vitro mammosphere formation assay and in vivo xenograft transplantation in immunodeficient mice18,24,26,27,

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This work was supported by the Innovative Technology Fund of Innovation Technology Commission: Funding Support from the State Key Laboratory of Agrobiotechnology (CUHK), the Lo Kwee-Seong Biomedical Research Fund and the Lee Hysan Foundation. Y.X. was supported by the postgraduate studentship from the CUHK.


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Name Company Catalog Number Comments
MCF-7 American Type Culture Collection (ATCC) HTB-22
MDA-MB-231 American Type Culture Collection (ATCC) HTB-26
T47D American Type Culture Collection (ATCC) HTB-133
0.05% trypsin-EDTA Invitrogen 25300054
0.25% trypsin-EDTA Invitrogen 25200072
Alexa Fluor 680 annexin V conjugate Invitrogen A35109
bovine serum albumin USB 9048-46-8
CaCl2 · 2H2O Sigma-Aldrich C-5080
CellEvent caspase-3/7 green fluorescent dye Invitrogen C10423
dimethyl sulfoxide Sigma-Aldrich D2650
Fc block Miltenyi Biotec 130-059-901
fetal bovine serum Invitrogen 16000044 heat-inactivated
Hoechst 33342 Invitrogen H3570
L-glutamine Invitrogen 25030081
Mitotracker Red CMXRos Invitrogen M7512
monoclonal antibodies against human CD24 BD Biosciences 555428 PE Clone:ML5
monoclonal antibodies against human CD44 BD Biosciences 560531 PERCP-CY5.5 Clone:G44-26
NaCl Sigma-Aldrich 31434
paclitaxel Sigma-Aldrich T7402
PE Mouse IgG2a, κ Isotype Control BD Biosciences 554648 Clone:G155-178 (RUO)
Penicillin-Streptomycin Invitrogen 15070-063
PerCP-Cy5.5 Mouse IgG2b, κ Isotype Control BD Biosciences 558304 Clone:27-35
phosphate buffered saline Thermo Fisher Scientific 21600010
propidium iodide Invitrogen P1304MP
Roswell Park Memorial Institute 1640 medium Invitrogen 11835055 phenol red-free
sodium azide Sigma-Aldrich S2002
staurosporine Sigma-Aldrich S4400
100 mm culture dish Greiner Bio-One 664160
12-well tissue culture plates Thermo Fisher Scientific 150628
Cell Strainer 40-μm nylon mesh BD Biosciences 08-771-1
FACSuite software bundle v1.0 BD Biosciences 651360
FACSVerse BD Biosciences 651155
FluoView FV1000 confocal microscope Olympus IX81 60X objective
FV10-ASW Viewer software Ver.4.2b Olympus -
round-bottom polystyrene 12 × 75 mm tubes BD Biosciences 352003
S3e sorter Bio-Rad 1451006

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