ABCG2, a novel antigen to sort luminal progenitors of BRCA1- breast cancer cells

Abstract

IntroductionTumor-initiating cells (TICs), aka “cancer stem cells”, are believed to fuel tumors and to sustain therapy resistance and systemic metastasis. Breast cancer is the first human carcinoma in which a subpopulation of cells displaying a specific CD44+/CD24-/low/ESA+ antigenic phenotype was found to have TIC properties. However, CD44+/CD24-/low/ESA+ is not a universal marker phenotype of TICs in all breast cancer subtypes. The aim of this study was to identify novel antigens with which to isolate the TIC population of the basal-A/basal-like breast cancer cell lines.MethodsWe used polychromatic flow-cytometry to characterize the cell surface of several breast cancer cell lines that may represent different tumor molecular subtypes. We next used fluorescence-activated cell sorting to isolate the cell subpopulations of interest from the cell lines. Finally, we explored the stem-like and tumorigenic properties of the sorted cell subpopulations using complementary in vitro and in vivo approaches: mammosphere formation assays, soft-agar colony assays, and tumorigenic assays in NOD/SCID mice.ResultsThe CD44+/CD24+ subpopulation of the BRCA1-mutated basal-A/basal-like cell line HCC1937 is enriched in several stemness markers, including the ABCG2 transporter (i.e., the CD338 antigen). Consistently, CD338-expressing cells were also enriched in CD24 expression, suggesting that coexpression of these two antigenic markers may segregate TICs in this cell line. In support of ABCG2 expression in TICs, culturing of HCC1937 cells in ultra-low adherent conditions to enrich them in precursor/stem-cells resulted in an increase in CD338-expressing cells. Furthermore, CD338-expressing cells, unlike their CD338-negative counterparts, displayed stemness and transformation potential, as assessed in mammosphere and colony formation assays. Lastly, CD338-expressing cells cultured in ultra-low adherent conditions maintained the expression of CD326/EpCAM and CD49f/α6-integrin, which is a combination of antigens previously assigned to luminal progenitors.ConclusionCollectively, our data suggest that CD338 expression is specific to the tumor-initiating luminal progenitor subpopulation of BRCA1-mutated cells and is a novel antigen with which to sort this subpopulation.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-213) contains supplementary material, which is available to authorized users.

Induced Expression of Cancer Stem Cell Markers ALDH1A3 and Sox-2 in Hierarchical Reconstitution of Apoptosis-resistant Human Breast Cancer Cells

“…HCC1937 DNA contains the 916 C→T mutation of TP53 resulting in the termination codon at 306 a.a., and lacks the normal wild-type BRCA1 [43]. HCC1937 cells may have the potential to be luminal progenitor cells because overexpression of GATA3 was induced in apoptosis-resistant cells in our study, which is consistent with the recent consensus that basal cell tumors are derived from luminal progenitor cells [17, 20]. …”

Anti-Cancer Phytometabolites Targeting Cancer Stem Cells

“…Additionally, ABCG2 protein expression was directly associated with the migration and invasion ability of U251 glioma stem-like cells [52]. Similarly, a direct association with increased ABCG2 expression was also observed in CD44 + CD24 - low ESA + cells obtained from metastatic breast cancer [53]. The expression of ABCB5 was associated with tumor progression and relapse of oral cancer squamous cell carcinoma.…”

Aminopeptidase N (APN/CD13) as a target molecule for scirrhous gastric cancer

“…Several studies reported that ABCG2 is a more reliable cell surface marker to identify CSCs [16][17][18][19][20], we then examined whether ABCG2 would be useful for the identification of CSCs in scirrhous gastric cancers. However, ABCG2 expressed weakly only on HSC-58 and 44As3 but not on HSC-44PE and 58As1 (Fig.…”

“…We then investigated whether a population of HSC-58 cells that express high ALDH activity could also express any of the cell surface CSC candidates identified above. HSC-58 cells were evaluated by flow cytometry using a fluorescent substrate for assay of ALDH activity and using PE-conjugated antibodies against cell surface molecules such as CD44, ABCG2 and CD13 [4,9,[15][16][17][18][19][20]. The population of cells that was strongly positive for ALDH also expressed high levels of CD13 (Fig.…”