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Prolonged Drug Selection of Breast Cancer Cells and Enrichment of Cancer Stem Cell Characteristics.

ABSTRACT: Background: Cancer stem cells are presumed to have virtually unlimited proliferative and self-renewal abilities and to be highly resistant to chemotherapy, a feature that is associated with overexpression of ATP-binding cassette transporters. We investigated whether prolonged continuous selection of cells for drug resistance enriches cultures for cancer stem-like cells. Methods: Cancer stem cells were defined as CD44+/CD24– cells that could self-renew (ie, generate cells with the tumorigenic CD44+/CD24– phenotype), differentiate, invade, and form tumors in vivo. We used doxorubicin-selected MCF-7/ADR cells, weakly tumorigenic parental MCF-7 cells, and MCF-7/MDR, an MCF-7 subline with forced expression of ABCB1 protein. Cells were examined for cell surface markers and side-population fractions by microarray and flow cytometry, with in vitro invasion assays, and for ability to form mammospheres. Xenograft tumors were generated in mice to examine tumorigenicity (n = 52). The mRNA expression of multidrug resistance genes was examined in putative cancer stem cells and pathway analysis of statistically significantly differentially expressed genes was performed. All statistical tests were two-sided. Results: Pathway analysis showed that MCF-7/ADR cells express mRNAs from ABCB1 and other genes also found in breast cancer stem cells (eg, CD44, TGFB1, and SNAI1). MCF-7/ADR cells were highly invasive, formed mammospheres, and were tumorigenic in mice. In contrast to parental MCF-7 cells, more than 30% of MCF-7/ADR cells had a CD44+/CD24– phenotype, could self-renew, and differentiate (ie, produce CD44+/CD24– and CD44+/CD24+ cells), and overexpressed various multidrug resistance-linked genes (including ABCB1, CCNE1, and MMP9). MCF-7/ADR cells were statistically significantly more invasive in Matrigel than parental MCF-7 cells (MCF-7 cells = 0.82 cell per field and MCF-7/ADR = 7.51 cells per field, difference = 6.69 cells per field, 95% confidence interval = 4.82 to 8.55 cells per field, P<.001). No enrichment in the CD44+/CD24– or CD133+ population was detected in MCF-7/MDR. Conclusion: The cell population with cancer stem cell characteristics increased after prolonged continuous selection for doxorubicin resistance.

ORGANISM(S): Homo sapiens

PROVIDER: GSE24460 | GEO | 2011/09/26

SECONDARY ACCESSION(S): PRJNA132705

REPOSITORIES: GEO

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Project description:Background: Cancer stem cells are presumed to have virtually unlimited proliferative and self-renewal abilities and to be highly resistant to chemotherapy, a feature that is associated with overexpression of ATP-binding cassette transporters. We investigated whether prolonged continuous selection of cells for drug resistance enriches cultures for cancer stem-like cells. Methods: Cancer stem cells were defined as CD44+/CD24– cells that could self-renew (ie, generate cells with the tumorigenic CD44+/CD24– phenotype), differentiate, invade, and form tumors in vivo. We used doxorubicin-selected MCF-7/ADR cells, weakly tumorigenic parental MCF-7 cells, and MCF-7/MDR, an MCF-7 subline with forced expression of ABCB1 protein. Cells were examined for cell surface markers and side-population fractions by microarray and flow cytometry, with in vitro invasion assays, and for ability to form mammospheres. Xenograft tumors were generated in mice to examine tumorigenicity (n = 52). The mRNA expression of multidrug resistance genes was examined in putative cancer stem cells and pathway analysis of statistically significantly differentially expressed genes was performed. All statistical tests were two-sided. Results: Pathway analysis showed that MCF-7/ADR cells express mRNAs from ABCB1 and other genes also found in breast cancer stem cells (eg, CD44, TGFB1, and SNAI1). MCF-7/ADR cells were highly invasive, formed mammospheres, and were tumorigenic in mice. In contrast to parental MCF-7 cells, more than 30% of MCF-7/ADR cells had a CD44+/CD24– phenotype, could self-renew, and differentiate (ie, produce CD44+/CD24– and CD44+/CD24+ cells), and overexpressed various multidrug resistance-linked genes (including ABCB1, CCNE1, and MMP9). MCF-7/ADR cells were statistically significantly more invasive in Matrigel than parental MCF-7 cells (MCF-7 cells = 0.82 cell per field and MCF-7/ADR = 7.51 cells per field, difference = 6.69 cells per field, 95% confidence interval = 4.82 to 8.55 cells per field, P<.001). No enrichment in the CD44+/CD24– or CD133+ population was detected in MCF-7/MDR. Conclusion: The cell population with cancer stem cell characteristics increased after prolonged continuous selection for doxorubicin resistance. PARALLEL study design with 4 samples Parental MCF-7 cell line versus Doxorubicin Resistant MCF-7 cell sublines Biological replicates: 2 parental controls, 2 drug resistant, independently grown and harvested. agent:Selection agent is multi-step doxorubicin selection: MCF7226ng, MCF7262ng biological replicate: MCF71, MCF72 biological replicate: MCF226ng, MCF7262ng

Project description:Tumorigenic breast cancer cells characterized by CD44 expression and low or undetectable CD24 levels (CD44+/CD24-/low) may be resistant to chemotherapy and therefore responsible for cancer relapse. Paired breast cancer core biopsies before and after neoadjuvant chemotherapy or lapatinib were obtained and as single cell suspensions stained using antibodies against CD24, CD44, and lineage markers, and then analyzed by flow cytometry. Mammosphere (MS) formation in culture was compared before and after treatment. Global gene expression differences between cancer cells bearing CD44+/CD24-/low cells and all other sorted cells, and between cancer MS and the primary bulk invasive cancers were analyzed. We report that CD44+/CD24-/low tumorigenic breast cancer cells were intrinsically chemoresistant - chemotherapy led to increased CD44+/CD24-/low cells, increased self-renewal capacity on MS assays, and enhanced tumorigeneicity in immunocompromised SCID/Beige mice. Conversely, in patients with HER2 overexpressing tumors, the EGFR/HER2 tyrosine kinase inhibitor, lapatinib decreased CD44+/CD24-/low cells, with the majority of these patients after conventional therapy achieving pathologic complete response, a validated surrogate marker for long-term survival. Gene transcription pathways that underlie chemoresistant, MS-forming CD44+/CD24-/low cells involve genes belonging to stem cell self-renewal, Wnt signaling, and early development pathways. Experiment Overall Design: Cells from human breast tumors were grown as mammospheres (MS). Experiment Overall Design: Isolated single cell suspensions from primary breast cancers were plated onto non-adherent (polyhema-coated) plastic, counted with a hematocytometer, and 20,000 cells were then seeded into a 6-well ultra-low attachment plate supplemented with 2mL MEGM, with the addition of 2 mL of freshly unfrozen MEGM every 3-4 days. Gene expression profiles were taken of both MS and primary bulk tumors and compared with each other.

Project description:Tumorigenic breast cancer cells characterized by CD44 expression and low or undetectable CD24 levels (CD44+/CD24-/low) may be resistant to chemotherapy and therefore responsible for cancer relapse. Paired breast cancer core biopsies before and after neoadjuvant chemotherapy or lapatinib were obtained and as single cell suspensions stained using antibodies against CD24, CD44, and lineage markers, and then analyzed by flow cytometry. Mammosphere (MS) formation in culture was compared before and after treatment. Global gene expression differences between cancer cells bearing CD44+/CD24-/low cells and all other sorted cells, and between cancer MS and the primary bulk invasive cancers were analyzed. We report that CD44+/CD24-/low tumorigenic breast cancer cells were intrinsically chemoresistant â chemotherapy led to increased CD44+/CD24-/low cells, increased self-renewal capacity on MS assays, and enhanced tumorigeneicity in immunocompromised SCID/Beige mice. Conversely, in patients with HER2 overexpressing tumors, the EGFR/HER2 tyrosine kinase inhibitor, lapatinib decreased CD44+/CD24-/low cells, with the majority of these patients after conventional therapy achieving pathologic complete response, a validated surrogate marker for long-term survival. Gene transcription pathways that underlie chemoresistant, MS-forming CD44+/CD24-/low cells involve genes belonging to stem cell self-renewal, Wnt signaling, and early development pathways. Experiment Overall Design: Human breast tumor samples were sorted using flow cytometry to select for cells that were CD44+ and CD24-. Gene expression profiles of these cells were compared with profiles of the other sorted cells (CD24+ and CD44-/CD24-). Experiment Overall Design: Core biopsies of primary breast tumors were taken and placed immediately in cold RPMI-1640 supplemented with 10% heat-inactivated newborn calf serum (HINCS, Invitrogen, Carlsbad, CA). Within an hour, the samples were minced and then digested in 10-15 mL of MEGM with 250-300 units/mL collagenase at 370C. The samples were filtered, washed, and then subjected to hypotonic shock to lyse red blood cells. About 106 single cells were re-suspended, incubated for 15 min at 40C with anti-CD44 (APC), anti-CD24 (FITC), and anti-lineage cocktail antibodies (PE-conjugated anti-CD2, CD3, CD10, CD16, CD18, CD31 and CD 140B) (Pharmingen, San Diego, CA) using the manufacturerâs suggested concentrations. The cells were then washed twice, re-suspended with the viability dye propidium iodide, and analyzed using Dako MoFlo flow cytometry. Side- and forward- scatter were used to eliminate debris and cell doublets, and the Lin- cells were further analyzed by CD44 and CD24 markers.

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Prolonged Drug Selection of Breast Cancer Cells and Enrichment of Cancer Stem Cell Characteristics.

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