Abstract
Lung cancer is among the most lethal malignancies with a high metastasis and recurrence rate. Recent studies indicate that tumors contain a subset of stem-like cancer cells that possess certain stem cell properties. Herein, we used Hoechst 33342 dye efflux assay and flow cytometry to isolate and characterize the side population (SP) cells from human lung cancer cell line NCI-H460 (H460). We show that the H460 SP cells harbor stem-like cells as they can readily form anchorage-independent floating spheres, possess great proliferative potential, and exhibit enhanced tumorigenicity. Importantly, the H460 SP cells were able to self-renew both in vitro and in vivo. Finally, we show that the H460 SP cells preferentially express ABCG2 as well as SMO, a critical mediator of the Hedgehog (HH) signaling, which seems to play an important role in H460 lung cancer cells as its blockage using Cyclopamine greatly inhibits cell-cycle progression. Collectively, our results lend further support to the existence of lung cancer stem cells and also implicate HH signaling in regulating large-cell lung cancer (stem) cells.
Highlights
It has long been appreciated that most tumors are heterogeneous containing a spectrum of phenotypically different cell types
Work in the past decade indicates that various human solid tumors contain functionally divergent tumor cells with subpopulations possesing high tumorigenic potential and being able to reconstitute the phenotypic and histologic heterogeneity of the parent tumor when transplanted in immunodeficient mice
Such subsets of tumor cells that possess enhanced tumorigenic capacity have been operationally called tumor-initiating cells or cancer stem cells (CSC), which have been reported in most solid tumors [1,2]
Summary
It has long been appreciated that most tumors are heterogeneous containing a spectrum of phenotypically different cell types. The lung cancer stem cells have been reported in long-term cultures as well as in xenografts and primary patient tumors. CCK-8 proliferation experiment (see Method) revealed higher proliferative potential in the SP cells compared to the non-SP cells (Fig. 2C).
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