Novel triple­positive markers identified in human non­small cell lung cancer cell line with chemotherapy-resistant and putative cancer stem cell characteristics.

Through the specific identification and direct targeting of cancer stem cells (CSCs), it is believed that a better treatment efficacy of cancer may be achieved. Hence, the present study aimed to identify a CSC subpopulation from adenocarcinoma cells (A549) as a model of non­small cell lung cancer (NSCLC). Ιnitially, we sorted two subpopulations known as the triple­positive (EpCAM+/CD166+/CD44+) and triple­negative (EpCAM-/CD166-/CD44-) subpopulation using fluorescence-activated cell sorting (FACS). Sorted cells were subsequently evaluated for proliferation and chemotherapy-resistance using a viability assay and were further characterized for their clonal heterogeneity, self-renewal characteristics, cellular migration, alkaline dehydrogenase (ALDH) activity and the expression of stemness-related genes. According to our findings the triple­positive subpopulation revealed significantly higher (P<0.01) proliferation activity, exhibited better clonogenicity, was mostly comprised of holoclones and had markedly bigger (P<0.001) spheroid formation indicating a better self-renewal capacity. A relatively higher resistance to both 5­fluouracil and cisplatin with 80% expression of ALDH was observed in the triple­positive subpopulation, compared to only 67% detected in the triple­negative subpopulation indicated that high ALDH activity contributed to greater chemotherapy-resistance characteristics. Higher percentage of migrated cells was observed in the triple­positive subpopulation with 56% cellular migration being detected, compared to only 19% in the triple­negative subpopulation on day 2. This was similarly observed on day 3 in the triple­positive subpopulation with 36% higher cellular migration compared to the triple­negative subpopulation. Consistently, elevated levels of the stem cell genes such as REX1 and SSEA4 were also found in the triple­positive subpopulation indicating that the subpopulation displayed a strong characteristic of pluripotency. In conclusion, our study revealed that the triple­positive subpopulation demonstrated similar characteristics to CSCs compared to the triple­negative subpopulation. It also confirmed the feasibility of using the triple­positive (EpCAM+/CD166+/CD44+) marker as a novel candidate marker that may lead to the development of novel therapies targeting CSCs of NSCLC.

Targeting Lung Cancer Stem Cells: Research and Clinical Impacts.

Lung cancer is the most common cancer worldwide, accounting for 1.8 million new cases and 1.6 million deaths in 2012. Non-small cell lung cancer (NSCLC), which is one of two types of lung cancer, accounts for 85-90% of all lung cancers. Despite advances in therapy, lung cancer still remains a leading cause of death. Cancer relapse and dissemination after treatment indicates the existence of a niche of cancer cells that are not fully eradicated by current therapies. These chemoresistant populations of cancer cells are called cancer stem cells (CSCs) because they possess the self-renewal and differentiation capabilities similar to those of normal stem cells. Targeting the niche of CSCs in combination with chemotherapy might provide a promising strategy to eradicate these cells. Thus, understanding the characteristics of CSCs has become a focus of studies of NSCLC therapies.

Isolation and Characterization of Cancer Stem Cells of the Non-Small-Cell Lung Cancer (A549) Cell Line.

Cancer is a major health problem worldwide. The failure of current treatments to completely eradicate cancer cells often leads to cancer recurrence and dissemination. Studies have suggested that tumor growth and spread are driven by a minority of cancer cells that exhibit characteristics similar to those of normal stem cells, thus these cells are called cancer stem cells (CSCs). CSCs are believed to play an important role in initiating and promoting cancer. CSCs are resistant to currently available cancer therapies, and understanding the mechanisms that control the growth of CSCs might have great implications for cancer therapy. Cancer cells are consist of heterogeneous population of cells, thus methods of identification, isolation, and characterisation of CSCs are fundamental to obtain a pure CSC populations. Therefore, this chapter describes in detail a method for isolating and characterizing a pure population of CSCs from heterogeneous population of cancer cells and CSCs based on specific cell surface markers.