Fluorescent Proteins as Visible In Vivo Sensors - Progress in Molecular Biology and Translational Science - page 397

6.5. Imaging of nuclear - cytoplasmic dynamics, proliferation,
and cell death of cancer cells in the portal vein area
Human HCT-116 colon cancer and MMT cells were injected in the PV of
nude mice. Both cell lines were labeled with GFP in the nucleus and RFP
in the cytoplasm. The cells were observed intravitally in the liver at the
single-cell level using the Olympus OV100 system. Most HCT-116-
GFP-RFPcells remained in sinusoids near peripheral PVs.Only a small fraction
of the cancer cells invaded the lobular area. Extensive clasmocytosis of the
HCT-116-GFP-RFP cells occurred within 6 h. The number of apoptotic
cells rapidly increased within the PV within 12 h of injection. Apoptosis
was readily visualized in the dual-color cells by separation of nucleus
and cytoplasm. The data suggest rapid death of HCT-116-GFP-RFP cells
in the PV. In contrast, dual-color MMT-GFP-RFP cells injected into the
PVmostly survived in the liver of nudemice 24 h after injection.Many surviv-
ing MMT-GFP-RFP cells showed invasive figures with cytoplasmic protru-
sions. The cells grew aggressively and formed colonies in the liver. However,
when the host mice were pretreated with cyclophosphamide, the HCT-
116-GFP-RFP cells also survived and formed colonies in the liver after PV
injection. These results suggest that a cyclophosphamide-sensitive host cellular
system attacked the HCT-116-GFP-RFP cells but could not effectively kill
the MMT-GFP-RFP cells. 31

6.6. Imaging the effect of cyclophosphamide on cancer cells
quiescence, proliferation, and death in blood vessels
Intravascular proliferation, extravasation, and colony formation by cancer
cells, which are critical steps of metastasis, can be enhanced by pretreatment
of host mice with cyclophosphamide. In contrast, in the un-pretreated mice,
most cancer cells remained quiescent in vessels without extravasation.
HT1080 human fibrosarcoma cells, labeled in the nucleus with GFP and
in the cytoplasm with RFP, were injected into the epigastric cranialis vein
of nude mice. Twenty-four hours before cancer cell injection,
cyclophosphamide was administered i.p. Double-labeled cancer cells were
imaged at the cellular level in live mice with the Olympus OV100 system.
Cyclophosphamide appeared to interfere with a host process that
inhibited intravascular proliferation, extravasation, and extravascular colony
formation. Cyclophosphamide did not directly affect the cancer cells, as cy-
clophosphamide had been cleared by the time the cancer cells were injected.
These results demonstrate an important, unexpected “opposite effect” of
chemotherapy that enhances critical steps in malignancy rather than