Download A 3-D look at cell division in cancer stem cells

A 3-D look at cell division in cancer stem cells
Stem Cell Biology
Hong-Wu Xin, Itzhak Avital, and colleagues, National Cancer Institute, National Institutes of Health
Dr. Hong-Wu Xin from the National Cancer Institute in Bethesda, Md., led a team of researchers who used Imaris software to
study a unique type of cell division in cancer stem cells and to observe how cells undergoing this type of cell division interact with
their microenvironment.
Studies have suggested that gastrointestinal cancers may develop in tissues containing stem cells that undergo a specific type of
cell division called asymmetric cell division with non-random chromosomal cosegregation (ACD-NRCC). During ACD-NRCC,
each stem cell chromosome conserves a template DNA strand during asymmetric cell division, which prevents the accumulation
of mutations from DNA replication errors.
“It is important to understand the mechanisms of ACD-NRCC
in gastrointestinal cancer cells because it may provide the
basis for novel cancer therapy against cancer stem cells,” Dr.
Xin says.
Studying live cells
Previous studies examining ACD-NRCC used fixed cells, and
thus couldn’t examine the gene expression involved in ACDNRCC. Dr. Xin’s team isolated live cells undergoing ACDNRCC to study with confocal microscopy and other analysis
methods. The 3-D rendering capability of Imaris was a key part
of this research.
The investigators used confocal microscopy to acquire 30 to 50
slices at 0.38-micron intervals. They then used Imaris software
for 3D rendering of the Z-stacks. The researchers used a
cutting plane to expose internal surfaces or made outer
surfaces semi-transparent so that they could clearly observe
nuclei position. The 3D images revealed two nuclei in the same
cytoplasmic space without intervening cytoplasmic membrane
during ACD-NRCC. This image analysis confirmed that ACDNRCC does occur in a subpopulation of gastrointestinal cancer
cells.
An arrested dividing cell shows asymmetric segregation of
chromosomes (red). Images courtesy of Hong-Wu Xin.
Other analysis revealed that ACD-NRCC can be regulated by the Wnt pathway, although more work is needed to better
understand Wnt’s role in this type of cell division. Also, the researchers found that other cells in the cancer niche — which is
made of surrounding non-stem cells — can alter the behavior of stem cells undergoing ACD-NRCC in a way that does not require
cell-to-cell contact.
“Our findings provided the first molecular pathway map of ACD-NRCC, which may have implications on future targeted cancer
therapy against cancer stem cells,” Dr. Xin says.
Three dimensional confocal microscopy images showing human liver cancer cells undergoing ACD-NRCC. Cells undergoing potential ACD-NRCC
incorporated both nucleotides (green and red) into only one of the daughter cells’ nuclei while the other nucleus incorporated only one nucleotide
(red).
In other work, the researchers have also shown that label-retaining cancer cells undergo active ACD-NRCC, express
pluripotency genes, and initiate tumors with only 10 cells (Stem Cells, 2012). Label-retaining cancer cells are relatively resistant
to chemotherapy (Annals of Surgery, 2013), targeted cancer therapy (GUT, 2013), and reported anti-CSC drugs (submitted). “We
are searching for novel cancer drugs that can overcome the label-retaining cancer cells resistance, or abrogate the resistance of
cancer stem cells,” Dr. Xin says.
Research Paper: Xin HW, Ambe CM, Ray S, Kim BK, Koizumi T, Wiegand GW, Hari D, Mullinax JE, Jaiswal KR, Garfield SH,
Stojadinovic A, Rudloff U, Thorgeirsson SS, Avital I. Wnt and the Cancer Niche: Paracrine Interactions with Gastrointestinal
Cancer Cells Undergoing Asymmetric Cell Division. J Cancer 2013; 4(6):447-457.