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Breast cancer stem cells expressing different stem cell markers exhibit distinct biological characteristics

  • Authors:
    • Jun Shao
    • Wei Fan
    • Biao Ma
    • Yiping Wu
  • View Affiliations

  • Published online on: October 27, 2016     https://doi.org/10.3892/mmr.2016.5899
  • Pages: 4991-4998
  • Copyright: © Shao et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

Identification and isolation of breast cancer stem cells (CSCs) based on CD44/CD24 expression and/or enzymatic activity of aldehyde dehydrogenase 1 (ALDH1). However, the differences among the CD44+/CD24‑/low cells, ALDH1+ cells and the overlap between the sub‑populations have not been frequently investigated. Thus, it is imperative to improve the understanding of breast CSC with different stem markers. CD44+/CD24‑/low, ALDH1+ and ALDH1+CD44+/CD24‑/low cell populations were isolated from fresh breast cancer tissues and analyzed by flow cytometry and immunofluorescence. Mammosphere formation, cell proliferation assay and Transwell experiments, were used to analyze self‑renewal, proliferation and invasion, respectively, for each sub‑population. Finally, in vivo experimentation in mice was performed to evaluate the tumorigenic abilities of the sub‑populations. The sub‑populations of CD44+/CD24‑/low, ALDH1+ and ALDH1+CD44+/CD24‑/low in human breast cancer cells, represented the 7.2, 4.6 and 1.5% of the total tumor cell population, respectively. ALDH1+CD44+/CD24‑/low cells had the strongest ability of self‑renewal, invasion, proliferation and tumorigenicity compared with the other sub‑populations (P<0.05). In conclusion, different phenotypes of CD44+/CD24‑/low, ALDH1+ and ALDH1+CD44+/CD24‑/low were isolated and demonstrated that breast CSCs are heterogeneous, and they exhibit distinct biological characteristics. As ALDH1+CD44+/CD24‑/low cells demonstrated the strongest stem‑like properties, it may be a useful specific stem cell marker. The utilization of more reliable biomarkers to distinguish the breast CSC pool will be important for the development of specific target therapies for breast cancer.

Introduction

Breast cancer is the most common cancer in women world wide (1). Although significant progress has been made in early diagnosis and treatment, metastasis cannot be prevented in certain patients. Therefore, breast cancer remains a major public health burden. There is accumulating evidence that cancer stem cells (CSCs) are responsible for tumor initiation, maintenance, invasion, heterogeneity, metastasis and therapy resistance (2,3). In breast cancer, CD44+/CD24−/low is the first convincing marker for identifying and isolating tumorigenic CSCs from non-tumorigenic cancer cells.

Aldehyde dehydrogenase 1 (ALDH1) is a detoxifying enzyme that is associated with the stemness-associated markers, octamer binding transcription factor 4 and Polycomb complex protein BMI-1, and is proven to be a marker of stem/progenitor cells in neural and hematopoietic systems and in the mammary gland (4). Ginestier et al (4) demonstrated that breast cancer cells with increased ALDH activity exhibit stem/progenitor cell properties. It was previously demonstrated that using ALDH1 as a breast CSC marker can further divide the CD44+/CD24−/low cell population into fractions that are tumorigenic (47).

However, within breast cancer cells cultured from fresh human specimens, few studies have analyzed the details of the biological characteristic differences between CD44+/CD24−/low phenotype and high ALDH1 activity cells. Based on this current knowledge, there is evidence to support the hypothesis that the combining CD44/CD24 cell surface expression with ALDH1 activity may be a more accurate method to identify and isolate CSC-like cells within a population of breast cancer cells. Furthermore, it is imperative to improve the understanding of the biological differences among breast CSCs that express different stem cell markers.

The CSC hypothesis has important implications for understanding the basic biology of tumorigenesis. Cells endowed with stem-like properties demonstrate self-renewal and high tumorigenic potential. Current cancer treatments based on tumor regression can kill differentiated tumor cells, while sparing the small CSC population (8). Therefore, the development of more effective cancer therapies may require the targeting, identification, isolation and characterization of CSCs.

In the present study, breast cancer cells from fresh specimens were cultured and the percentage of three different sub-population cells with CD44+/CD24−/low, ALDH1+, and ALDH1+CD44+/CD24−/low phenotypes were analyzed. Additionally, the self-renewal, proliferative, invasive ability of these cells was analyzed in vitro. Finally, the capacity of these cells to generate de novo tumors was also investigated in an in vivo mouse model.

Materials and methods

Dissociation and primary culture of breast cancer cells

Samples of fresh breast cancer specimens were obtained surgically from the primary tumor of one 32-year-old female patient. The samples were dissociated mechanically and enzymatically, based on the triple negative and basal-like pathological type. The samples were dissociated mechanically and enzymatically, based on pathological types that were triple negative and basal-like. No treatment (chemotherapy or endocrine therapy) was given to the patients before the operation and they were treated at the Hubei Cancer Hospital (Wuhan, China) in 2014. Breast cancer cell isolation was performed as previously described (9). The biological specimens were utilized according to the approved institutional review board protocols for research in human subjects. The study was approved by the ethical committee of Wuhan Tongji Hospital (Wuhan, China). All patients provided written informed consent prior to participation in the present study.

Mammosphere suspension culture

Mammosphere culture was performed as previously described (10). Cells from one 32-year-old patient were cultured at 37°C and 5% CO2 a density of 20,000 viable cells/ml in primary culture in serum-free Dulbecco's modified Eagle's medium (DMEM)-F12 medium (Sigma-Aldrich; Merck Millipore, Darmstadt, Germany), which was changed every 2 days. The daily morphological changes of mammospheres were observed under a light microscope. Passaging was performed after 5 days at a density of 5,000 cells/ml.

Immunofluorescence to identify cell phenotype

The procedure was performed as previously described (4). The main steps were as follows: i) Cell preparations, ii) fixation, iii) permeabilization, iv) primary antibody incubation (mouse anti-human CD44, cat. no. BM0321; mouse anti-human CD24, cat. no. BM1723; ALDH1, cat. no. BM3672; Wuhan Boster Biological Technology, Ltd., Wuhan, China), v) secondary antibody incubation [goat anti-mouse IgG phycoerythrin (PE), cat. no. BA1031; rabbit anti-mouse IgG-fluorescein isothiocyanate, cat. no. BA1101; Wuhan Boster Biological Technology, Ltd.], vi) mounting and vii) imaging.

Flow cytometry

The procedure was performed according to the method of Al-Hajj et al (11). The cells were collected by centrifugation, trypsin was added for digestion, serum-free medium was added to terminate the digestion, and a single-cell suspension was obtained. Test tube and control tube were set to adjust the cell concentration, and the number of cells was ≥1×105. Anti-human CD44-phycoerythrin (PE) CY5 (15-0441-81) and anti-human CD24-PE (12-0241-81) antibodies (eBioscience, Inc., San Diego, CA, USA) were added to the test tube, while isotype control antibody was added to the control tube, mixed and incubated at room temperature in the dark for 30 min. Samples were washed twice with PBS, the supernatant was discarded after centrifugation at 200 × g for 5 min at room temperature, and the cells were resuspended in PBS containing 1% paraformaldehyde to fix the cells. Finally, 300 µl PBS was added. The analysis was performed using a FACStarPLUS (BD Biosciences, Franklin Lakes, NJ, USA) flow cytometer.

The ALDEFLUOR kit (Stemcell Technologies, Inc., Vancouver, BC, Canada) was used to isolate the cell population with a high ALDH enzymatic activity. Cells were suspended in serum-free DMEM-F12 medium. ALDEFLUOR assay buffer containing activated ALDEFLUOR substrate (BAAA; 1 µmol/l per 1×106 cells) was added to the cell suspension, mixed and incubated at 37°C for 30 min. The cell suspension was centrifuged, washed with PBS and re-suspended in DMEM-F12 serum-free medium. Then cells were diluted using ALDEFLUOR buffer, adjusting the cell concentration to 1×106 cells/ml. The flow cytometry detection was immediately performed or performed within 24 h at 4°C.

To isolate the ALDH1+CD44+/CD24−/low cells, CD44+/CD24−/low cells were suspended (1×106 cells/ml) in in ALDEFLUOR assay buffer and 5 µl/ml ALDEFLUOR substrate was added to the cell suspension. Then cells were separated as described above.

Analysis of proliferation using MTT

Each cell sub-population and cells in the control group (primary cells without sorting) were re-suspended in DMEM-F12 [1:1; 2% fetal bovine serum (FBS; Gibco Invitrogen; Thermo Fisher Scientific, Inc., Waltham, MA, USA); 20 ng/ml basic fibroblast growth factor; 20 ng/ml epidermal growth factor, 2% B27 and 1% penicillin-streptomycin], and cultured in 96-well plate (approximately 103 cells/well, five wells/group), and then cultured at 37°C. Culture medium (25 µl) was added to each well every 2 days, the MTT assay was performed and the absorbance at 490 nm was measured using a microplate reader (Bio-Rad Laboratories, Inc., Hercules, CA, USA) every 24 h for consecutive 8 days to obtain a curve of the measured values.

Mammosphere formation ability assay

Mammosphere formation rate or cloning efficiency is an important indicator of tumor cell self-renewal ability. The experimental procedure used to compare the cloning efficiency of cells in each sub-population was as follows: A single cell suspension of each sub-population (after sorting) and a non-sorting cell suspension as a control group were re-suspended in serum-free medium containing growth factors (20 ng/ml basic fibroblast growth factor and 20 ng/ml epidermal growth factor; BD Biosciences) to adjust the concentration to 103 cells/ml, and were seeded in 96-well plates. Subsequently, 100 cells were seeded, 25 µl medium containing growth factors was added to each well every 2 days, and breast cancer mammosphere numbers were counted in each well. Breast mammosphere formation rate is calculated as follows: Mammosphere (MS) % = microsphere number/inoculated cells ×100%.

Invasion ability of cells in each sub-population by Transwell assay

The 24-well Transwell chambers (8.0 µm) were placed into the culture plates, pre-warmed serum-free DMEM-F12 medium (300 µl) was added to the chamber and incubated at room temperature for 30 min, and then the medium was removed. The cell suspension was prepared to for experiments, digestion, and the supernatant was discarded following centrifugation and re-suspended with serum-free medium containing 0.2% bovine serum albumin (Gibco Invitrogen; Thermo Fisher Scientific, Inc.). A 200 µl cell suspension (1×105 cells/ml) was added to the Transwell chamber. Another 500 µl DMEM-F12 medium containing 10% FBS was added to the 24-well plate lower chamber, avoiding the formation of air bubbles. The suspension was incubated in a sterile incubator for 24 h. Furthermore, Matrigel was added to coat the upper chamber, while 500 µl complete medium (containing 0.5 mg/ml MTT) was added to the lower house of a 24-well plate, and incubated at 37°C for 4 h before chamber. Next, the chamber was immersed in 500 µl dimethyl sulfoxide and incubated for 10 min. The absorbance was measured on a microplate reader at a wavelength of 490 nm.

In vivo tumorigenicity experiment

The animal experiments were approved by the ethics committee of Hubei Cancer Hospital (Wuhan, China). Female BALB/C-nude mice (n=60; specific-pathogen free; age, 4–6 weeks old; weight, 14–22 g) were purchased from Hunan Slack King of Laboratory Animal Co., Ltd. (Changsha, China). The mice were kept at a temperature of 20–26°C with a relative humidity of 40–70%, with an average of 5 g/100 g weight food and 6–7 ml/100 g weight water per day, with a light/dark cycle of 12 h/12 h. The mice were divided into three batches, and each batch contained four groups with five nude mice in each group. The four groups were represented by the control group, CD44+CD24−/low group, ALDH1+ group and ALDH1+ CD44+CD24−/low group. The tumorigenicity experiments were performed within a laminar flow cabinet. Unsorted primary cells were inoculated in the mice of the control group, while CD44+CD24−/low cells, ALDH1+ cells, and ALDH1+ CD44+CD24−/low cells were inoculated in the mice of the other three groups. The first batch of nude mice were injected with 500 cells per mouse in each group; the second batch was injected with 5,000 cells per mouse, and the third batch was injected with 50,000 cells per mouse. The method of Al-Hajj et al (11), was followed, including the following stages: i) Cell collection; ii) cell mixing; and iii) cell inoculation. A volume of 0.1 ml of cells, was subcutaneously inoculated on one side of the chest of each mouse. Subsequently, the mice were fed under standard conditions for 8 weeks. Mice were monitored once a week, and the tumor dimension was measured and recorded. The mice were sacrificed by cervical dislocation after 8 weeks of monitoring.

Statistical analysis

The results were statistically analyzed using SPSS 13.0 (SPSS Inc., Chicago, IL, USA). The continuous variables are expressed as the mean ± standard deviation. Categorical variables are expressed as frequencies and/or percentages. The data were compared by analysis of variance analysis and followed by least significant difference post hoc analysis. For two independent samples, a t-test was performed. P<0.05 was considered to indicate a statistically significant difference.

Results

CD44+CD24−/low phenotype and ALDH1 activity in breast cancer cells

Flow cytometry analysis enables the separation of different cell populations. As demonstrated in the current study, the proportion of ALDH1+ cells in the breast cancer specimens was 4.6% (Fig. 1A), whereas 7.2% of the population were CD44+CD24−/low phenotype tumor cells (Fig. 1B). Further sorting of the cells by ALDEFLUOR was performed to isolate the population with high ALDH enzymatic activity; 20.8% of these cells were CD44+CD24−/low (Fig. 1C). A small overlap of the two groups, ALDH1+CD44+CD24−/low sub-population, was represented by 1.5% of the total cells.

Difference in the mammosphere formation of different cells population

The sorted CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells in each sub-population were suspended and cultured in serum-free medium. A few mammospheres was observed at 4–5 days, with a diameter of 20–30 µm. Typical mature mammospheres of CD44+CD24−/low cells formed after ~1 week in culture, with a diameter of 80–100 µm (Fig. 2A). For the ALDH1+ and ALDH1+CD44+CD24−/low cells, mammospheres were formed with an increased number and size in the following days (Fig. 2B and C), and remained stable and in shape until 10–12 days. Mammospheres occurred earliest in the ALDH1+CD44+CD24−/low cells after 2 days in serum-free medium and exhibited the largest diameter; up to 110–120 µm (Fig. 2C). Additionally, ALDH1+CD44+CD24−/low cells exhibited the longest stability, starting to disintegrate later than the other sub-groups.

Immunofluorescence findings

Following the suspension of the unsorted primary cells in serum-free medium with growth factors for 7 days, mammospheres were collected, and corresponding fluorescent antibodies were added. Green fluorescence was detected in the cytoplasm of ALDH1+ cell, with no staining in the membrane and the nucleus (Fig. 3B). CD44+CD24−/low cells exhibited brownish/red fluorescence, predominantly in the membrane, although cytoplasmic staining was observed in certain cells (Fig. 3C). Cells exhibiting green fluorescence in the cytoplasm and the brownish/red fluorescence in the membrane (Fig. 3D) indicated the presence of the ALDH1+CD44+CD24−/low sub-population.

Differences in proliferation among the sub-populations

The cells were divided into four groups: Control cells (unsorted primary cells), CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells, using flow cytometry. The proliferation ability of cells in each sub-population was then compared. The number of living cells was subsequently measured by MTT assay (Fig. 4A). After 8 days of culture, the results demonstrated that CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells were continuously proliferating, with no observable of quiescence. On day 8, the values of control, CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells were 0.160±0.005, 0.251±0.005, 0.259±0.007 and 0.279±0.009, respectively. The cell proliferation of the three sub-populations was significantly increased compared with the control group cells (P=0.0113; Fig. 4A), however, there were no significant differences among the three sub-population groups (P=0.151).

Differences in invasion of each cell sub-population

To compare the invasion and migration ability of each cell group, Transwell experiments were conducted. After 48 h in culture, a large number of CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells passed through the Transwell membrane. The MTT absorbance of the control group was 0.48±0.021, and the CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low groups were 1.05±0.058, 1.11±0.036 and 1.56±0.075, respectively. The invasion and migration abilities of CD44+CD24−/low, ALDH1+, and ALDH1+CD44+CD24−/low cells were significantly increased compared with the control group (P=0.0129). Additionally, the invasion and migration abilities of ALDH1+CD44+CD24−/low cells were increased compared with the CD44+CD24−/low and ALDH1+ sub-populations (P=0.0287; Fig. 4B).

Differences in the mammosphere formation rate in each sub-population

At day 8 after suspension, the mammosphere formation rates were 4.80±1.10, 35.70±1.92, 41.50±1.71 and 62.45±2.50% in the control group, CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low groups, respectively. The mammosphere formation rate was significantly increased in the three sub-populations groups compared with the control group (P<0.001). Additionally, the mammosphere formation rate of ALDH1+CD44+CD24−/low cells was significantly increased compared with the other two sub-populations (P=0.0185; Fig. 4C).

Comparison of the tumorigenic ability of each sub-population in vivo

A nude mice tumorigenic experiment was performed to discover the tumorigenicity of the tumor cell sub-populations. Fig. 5A demonstrates a nude mouse bearing a tumor developed following injection of ALDH+CD44+CD24−/low sub-population cells. The batch of nude mice that received an injection of 500 cells of the unsorted control cells, CD44+CD24−/low and ALDH+ sub-populations exhibited no tumor formation after 8 weeks. However, mice that received an injection of 500 ALDH+CD44+CD24−/low sub-population cells demonstrated clear and palpable subcutaneous nodules by week 6, reaching a size of up to 0.36±0.07 cm at week 8, (Fig. 5B). The second batch of nude mice that received an injection of 5,000 cells of the CD44+CD24−/low sub-population exhibited tumor development from the week 6 onward. Nude mice that received an injection of 5,000 cells of the ALDH1+ sub-population exhibited tumor development from week 5 onward, and finally, nude mice that received an injection of 5,000 cells of the ALDH+CD44+CD24−/low sub-population exhibited tumor development from week 2 onward (Fig. 5C). The tumor lengths at week 8 were 0.25±0.04, 0.45±0.05 and 0.97±0.06 cm in the CD44+CD24−/low, ALDH1+ and ALDH+CD44+CD24−/low sub-populations, respectively. Statistical analysis demonstrated that the tumorigenic abilities of the cells in the three sub-populations were significantly increased compared with the control group. The ALDH+CD44+CD24−/low sub-population exhibited the strongest ability of tumor formation and the tumor length was significantly increased compared with the other sub-populations (P=0.0162; Fig. 5C). The third batch of nude mice that received an injection of 50,000 cells of the ALDH+CD44+CD24−/low sub-populations exhibited tumor formation from the week 1 onward, with a fast growth and a large tumors developing (Fig. 5D). Nude mice that received an injection of 50,000 cells of the ALDH+ and of the CD44+CD24−/low sub-populations exhibited tumor formation from week 4 onward, and at week 8, the tumor lengths were 2.10±0.09, 1.10±0.06, 0.85±0.05 and 0.15±0.04 cm in the ALDH+CD44+CD24−/low, ALDH+ and CD44+CD24−/low sub-populations, and the control group, respectively. Statistical analysis demonstrated that the tumorigenic abilities of the cells in the three sub-populations were significantly increased compared with the control group (P<0.05). The ALDH+CD44+CD24−/low sub-population exhibited the strongest tumor formation ability, and the tumor length was significantly increased compared with the other two sub-populations (ALDH+CD44+CD24−/low vs. CD44+CD24−/low, P=0.0074; ALDH+CD44+CD24−/low vs. ALDH1+, P=0.0104), and the comparison among the three sub-populations were significantly different (P=0.010; Fig. 5D).

Discussion

The CSC hypothesis has important implications for understanding the basic biology of tumorigenesis. Cells endowed with stem-like properties demonstrate self-renewal and high tumorigenic potential. Current cancer treatments based on tumor regression can kill differentiated tumor cells, while sparing the small CSC population (8). Therefore, the development of more effective cancer therapies may require the identification, isolation and characterization of CSCs.

In recent years, advances have been made in the research of stem cell markers, including the marker set of CD44/CD24 and ALDH1 (1122) Based on the cell surface markers, Al-Hajj et al (11) isolated the carcinogenic sub-population in breast cancer cells. CD44+/CD24 cells possessed the ability to develop into tumors, whereas the alternate phenotypes failed to form tumors in mice. Ginestier et al (4) observed that breast cancer cells with high ALDH1 activity were able to generate tumors in nude mice with low cell numbers. The previously reported percentages of CD44+/CD24 cells and ALDH1+ vary widely (1122). In the current study, CD44+CD24−/low breast cancer cells were isolated from fresh tissue at a proportion of 7.2% of the total cell population, and ALDH1+ cells at 4.6%. By further sorting, an overlap in the two-sub-population cells was detected, with 1.5% of the total breast cancer cells exhibiting the CD44+CD24−/low phenotype and ALDH1 activity. Immunofluorescence experiments also confirmed the presence of these three sub-populations cells in human breast cancer. The immunohistochemical expression of ALDH1 and its used for clinical prognosis have also been widely explored. High AlDH1 expression is correlated with poor prognosis in various types of cancer (2327). Additionally, by analyzing the CD44+CD24−/low, epithelial specific antigen+, CD133+ and other multiple stem cell markers, Hwang-Verslues et al (15) observed significant differences in the biological characteristics among breast cancer cells with different markers, including CD44+/CD24, ESA+ or CD133+, and even in different pathological types.

By MTT assay and Transwell experiments, the current study demonstrated that there were evident increases in self-renewal, proliferation and invasion ability among the CD44+CD24−/low, ALDH1+ and ALDH1+CD44+CD24−/low cells compared with the unsorted control cells, and ALDH1+CD44+CD24−/low cells were the strongest. Additionally, mammospheres were formed when the cancer cells were cultured in serum-free medium, and after continuous passage culture, they can produce new mammospheres. The difference of self-renewal capacity among these cell populations was also clearly demonstrated. The mammosphere formation rate of ALDH1+CD44+CD24−/low cells was significantly increased compared with the other groups. Increased number and size of mammospheres, as demonstrated in the current study, reflects the typical self-renewal of breast CSCs (16).

Dey et al (17) reported that, after long period in serum-free culture, breast CSCs exhibit difficulties in maintaining their undifferentiated state. With increasing passages, a high-oxygen environment led to telomerase loss, resulting in the aging of stem cells and interfering with the stem cells phenotype, which caused decreased self-renewal ability of the stem cells. In the present study, the cells were, therefore, passaged only 1–2 times to avoid stem cell aging.

In the present study, experiments using a nude mouse tumor model demonstrated that CD44+CD24−/low, ALDH1+, and ALDH1+CD44+CD24−/low breast cancer cells all exhibited tumorigenic ability, however, significant differences between the sub-populations was also observed. Inoculation with 500 ALDH1+CD44+CD24−/low cells formed tumors, whereas, 500 of the other sub-population or control cells did not generate tumors. ALDH1+CD44+CD24−/low cells formed tumors earliest after injection, indicating that this cell population possessed the strongest tumorigenicity. Thus, in-depth study of the biological characteristics of different subsets of breast CSCs may provide a reference for clinical research and tumor treatment.

Previous studies have demonstrated that tumorigenic ALDH1+ cells are biologically aggressive, and their presence tends to be associated with poor patient prognosis. CD44+/CD24−/low cells and ALDH1+ cells are more frequently detected in basal-like tumors (47). In the current study, the primary breast cancer cells were obtained from basal-like tumors. According to the preliminary experiments, ALDH1+ cells were easily detected and isolated from basal-like cancers, however, it was difficult to obtain these cells from other types of tumor. Thus, the primary cells used in the present study were from patients with basal-like breast cancer. Therefore, effort should be made to investigate the expression of stem cell markers in other types of breast cancer.

In conclusion, CD44+/CD24−/low, ALDH1+, and ALDH1+ CD44+/CD24−/low cells have stem/progenitor properties, and are capable of self-renewal and generating tumors. There are distinct biological properties among the three cell sub-population; ALDH1+CD44+/CD24−/low cells exhibit the strongest self-renewal, proliferation, invasion and tumorigenic capacity, indicating that these sub-populations with different markers may potentially not originate from the same stem cells, which is helpful to understand the biological characteristics and heterogeneity of breast CSCs. Diverse phenotypes of CD44+/CD24−/low, ALDH1+ and ALDH1+CD44+/CD24−/low may be used to isolate and identify breast CSCs with distinct levels of heterogeneity, which display distinct biological characteristics. As ALDH1+CD44+/CD24−/low cells exhibited the strongest stem-like properties, it may be useful as a more specific stem cell marker. The utilization of reliable biomarkers to distinguish the breast CSC pool will be important in the development of specific target therapies for breast cancer.

Acknowledgements

This work was supported by Hubei Provincial Health Department (grant no. JX4A07).

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December-2016
Volume 14 Issue 6

Print ISSN: 1791-2997
Online ISSN:1791-3004

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Spandidos Publications style
Shao J, Fan W, Ma B and Wu Y: Breast cancer stem cells expressing different stem cell markers exhibit distinct biological characteristics. Mol Med Rep 14: 4991-4998, 2016.
APA
Shao, J., Fan, W., Ma, B., & Wu, Y. (2016). Breast cancer stem cells expressing different stem cell markers exhibit distinct biological characteristics. Molecular Medicine Reports, 14, 4991-4998. https://doi.org/10.3892/mmr.2016.5899
MLA
Shao, J., Fan, W., Ma, B., Wu, Y."Breast cancer stem cells expressing different stem cell markers exhibit distinct biological characteristics". Molecular Medicine Reports 14.6 (2016): 4991-4998.
Chicago
Shao, J., Fan, W., Ma, B., Wu, Y."Breast cancer stem cells expressing different stem cell markers exhibit distinct biological characteristics". Molecular Medicine Reports 14, no. 6 (2016): 4991-4998. https://doi.org/10.3892/mmr.2016.5899