Fluorescent Proteins as Visible In Vivo Sensors - Progress in Molecular Biology and Translational Science - page 392

TME formation resulting from the liver metastasis was observed using an
Olympus OV100 small animal fluorescence imaging system. HCT-116
cells formed tumor colonies in the liver 28 days after cell transplantation
to the spleen. GFP-expressing host cells were recruited by the metastatic
tumors as visualized by fluorescence imaging. A desmin-positive area in-
creased around and within the liver metastasis over time, suggesting that
cancer-associated fibroblasts (CAFs) were recruited by the liver metastasis
which have a role in tumor progression. 21
3.2. Multicolor palette of the TME
Six different implantation models were used to image the TME using
multiple colors of fluorescent proteins: (I) RFP- or GFP-expressing
HCT-116 human colon cancer cells were implanted subcutaneously in
the cyan fluorescent protein (CFP)-expressing nude mice. CFP stromal
elements from the subcutaneous TME were visualized interacting with
the RFP- or GFP-expressing tumors. (II) RFP-expressing HCT-116 cells
were transplanted into the spleen of CFP-nude mice, and experimental
metastases were then formed in the liver. CFP stromal elements from
the liver TME were visualized interacting with the RFP-expressing tumor.
(III) RFP-expressing HCT-116 cancer cells were transplanted in the tail
vein of CFP-expressing nude mice, forming experimental metastases in
the lung. CFP stromal elements from the lung were visualized interacting
with the RFP-expressing tumor. (IV) In order to visualize two different
tumors in the TME, GFP-expressing and RFP-expressing HCT-116 can-
cer cells were co-implanted subcutaneously in CFP-expressing nude mice.
A three-color TME was formed subcutaneously in the CFP mouse, and
CFP stromal elements were visualized interacting with the RFP- and
GFP-expressing tumors. (V) In order to have two different colors of
stromal elements, GFP-expressing HCT-116 cells were initially injected
subcutaneously in RFP-expressing nude mice. After 14 days, the tumor,
which consisted of GFP cancer cells and RFP stromal cells derived from
theRFP-nudemouse,washarvested and transplanted into the CFP-
nude mouse. CFP stromal cells invaded the growing transplanted tumor
containing GFP cancer cells and RFP stroma. (VI) Mouse mammary
tumor(MMT)ce lsexpressingGFPinthenucleusandRFPinthe
cytoplasm were implanted in the spleen of a CFP-nude mouse. Cancer
cells were imaged in the liver 3 days after cell injection. The dual-
color dividing MMT cells and CFP hepatocytes, as well as CFP