Understanding cancer stem cell biology with real-time live-cell analysis

Cancer cells lack the strict cell cycle regulation present in normal tissues, giving them a ‘competitive advantage’ when it comes to growth and proliferation. One or more significant changes to signaling pathways – affecting growth ligands, their corresponding receptors or cytosolic signaling molecules –result in the so-called cancer stem cells responsible for tumor development and relapse.

The IncuCyte® live-cell analysis system has been used to evaluate and verify the key properties of cancer stem cells, including self-renewal, differentiation, chemoresistance, dormancy, colony forming and survival under serum starvation.

Differentiation

Time-lapse studies using IncuCyte® live-cell analysis provide a clear picture of cellular differentiation, enabling cell populations to be monitored over several days.

Freeze frames from a time-lapse movie showing SORE6+ cells generating SORE6- offspring. MCF10Ca1h cultures enriched for SORE6+ cells followed by time-lapse imaging. In frame 1 (t = 6 hr), the single-headed arrow marks a small cluster of SORE6+ cells (cluster 1) and the double-headed arrow marks a doublet of SORE6+ and SORE6- cells (cluster 2). Frame 2 (t = 78 hr) shows that cluster 1, after undergoing several symmetric self-renewing divisions, has begun to generate SORE6- cells around the periphery of the colony. Cluster 2 has now generated a colony on the right that is predominantly SORE6-, suggesting the SORE6- cells may proliferate faster than the SORE6+ cells. Frame 3 (t = 94 hr) and frame 4 (t = 112 hr) show that when cluster 2 expands to contact cluster 1, there is a rapid loss of SORE6+ cells in cluster 1. The group of predominantly SORE6+ cells marked by the dashed line in the top left of frame 4 has migrated in from outside of the field. Scale bar, 200 μm. (Tang, B et al. Stem Cell Reports, 2015, 4, 155-169. doi:  10.1016/j.stemcr.2014.11.002)

Chemoresistance

Chemoresistance is a major challenge in the treatment of many cancers – such as glioblastoma and epithelial ovarian cancer – due to the rapid recurrence of aggressive, chemoresistant tumors. A number of studies point to resistance mechanisms within a small subpopulation of tumor cells being responsible for this behavior.

SORE6+ cells are relatively resistant to chemotherapeutics. Cultures of MCF10Ca1h cells after two days of treatment with doxorubicin (50 nM) or paclitaxel (25 nM) showing selective killing of SORE6- cells, imaged using IncuCyte live-cell analysis system. Scale bar, 200 μm. (Tang, B et al. Stem Cell Reports, 2015, 4, 155-169. doi:  10.1016/j.stemcr.2014.11.002)

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Colony formation

IncuCyte live-cell analysis allows cancer stem cells to be identified and tracked across multiple generations, to check the proportion of colonies that arise from single cells.