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.
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 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)
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.
Single cell origin of DU145 colonies. (A) Formation of DU145 colonies from single cells was tracked by time-lapse imaging. (Incucyte) every four hours from initial adherence for two weeks. (B) The number of colonies originating from one or more cells was determined. Colonies which were derived from a single cell upon initial adherence, but merged with other colonies were also determined. Results are displayed as mean ± S.E. from five experiments tracking 40 cells per experiment. (Beaver, C et al. PLOS One, 2014. doi:10.1371/journal.pone.0089834.g005)