Cancer stem cell (CSC) research has increased exponentially to gain further insight into the mechanisms underlying both carcinogenesis and chemotherapy resistance. The present study was performed to explore the potential value of a side population (SP) assay for identifying and characterizing putative CSCs among canine lymphoma cells. Canine lymphoma cells from cell lines and clinical samples were subjected to the SP assay consisting of Hoechst 33342 staining and subsequent flow cytometric analysis. The SP assay revealed various amounts of a SP fraction among the canine lymphoma cells. The percentages of SP were not affected by inhibitors of membrane transporters, verapamil hydrochloride, or fumitremorgin C. Most of the canine lymphoma cells expressed high levels of Bmi-1 and membrane transporter proteins such as ABCG2 and phosphorylated (p)-glycoprotein. This investigation lays the groundwork for further studies of the biological behaviors and molecular characteristics of CSCs in cases of canine lymphoma.
Animals ; Benzimidazoles/*metabolism ; Cell Line, Tumor ; Dog Diseases/*diagnosis/drug therapy/pathology ; Dogs ; Flow Cytometry/*methods/veterinary ; Fluorescent Dyes/*metabolism ; Gene Expression Regulation, Developmental ; Lymphoma/diagnosis/drug therapy/pathology/*veterinary ; Neoplastic Stem Cells/drug effects/*metabolism/pathology ; Side-Population Cells/drug effects/*metabolism/pathology

OBJECTIVETo isolate and characterize the side population cells (SP cells) in the lung adenocarcinomas cell line A549.

METHODSThe protein expression of ABCG2 in human lung adenocarcinoma cell line A549 was detected by immunohistochemistry. SP and NSP cells in the cell line A549 were isolated by FACS, and their differentiation was analysed. ABCG2 expression in the two cell subsets was detected by RT-PCR. The cell growth curves, cell division indexes, cell cycles, plate clone formation tests, migration and invasion assays, chemotherapeutic susceptibility tests, tests of the intracellular drug levels, and the tumor cell implantation experiments on nude mice were applied to study the biological properties of the two cell subsets. The expression of ABCG2 in the transplanted tumor in nude mice was detected by immunohistochemistry and RT-PCR.

RESULTSThe positive rate of ABCG2 expression in the A549 cells by immunohistochemistry was 2.13%. SP and NSP cells were isolated by FACS. The SP cells could produce both SP and NSP cells, while NSP cells only produced NSP cells. SP cells expressed ABCG2, but NSP cells did not. The proliferation and migration abilities of the two cell subsets were similar, but the invasion and tumorigenic ability of SP cells was significantly higher than that of NSP cells. The susceptibilities to DDP and its intracellular levels of the two cell subsets were similar, but the susceptibilities to 5-FU, VP16, NVB and GEM and their intracellular levels of NSP cells were significantly higher than those of the SP cells.

CONCLUSIONSSP cells in the human lung adenocarcinomas cell line A549 is enriched with tumor stem cells. An effective way to get lung adenocarcinomas stem cells is to isolate SP cells by FACS.

ATP-Binding Cassette Transporters ; metabolism ; Adenocarcinoma ; pathology ; Animals ; Cell Cycle ; Cell Differentiation ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cell Transformation, Neoplastic ; metabolism ; Fluorouracil ; metabolism ; Humans ; Lung Neoplasms ; pathology ; Mice, Nude ; Neoplasm Proteins ; metabolism ; Neoplasm Transplantation ; Neoplastic Stem Cells ; drug effects ; Side-Population Cells