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Potdar et al. Circulating tumor cells in liquid biopsies

KRT19 was expressed in the ovarian, nasopharyngeal, they are not easily identified, due to their very limited
and prostate cancer samples, whereas its expression numbers. Pantel et al. reviewed the importance of
[26]
was completely absent in samples from all three breast CTCs, including the biological properties of metastatic
cancer patients; and the metastatic genes, MMP1, cells involved in cancer progression, and stated that
MMP2, and MMP9, were expressed in all patients CTC-derived cell lines could be used to develop new
studied, confirming the metastatic potential of these therapeutic targets, and for drug screening. Several
cells. The MMP2 gene was highly expressed in breast investigators have described the development of in
and nasopharyngeal cancer, whereas KCNH2, which vivo and in vitro methods for the isolation of CTCs
is specific for prostate cancer, was faintly expressed in larger numbers from metastatic cancer patients,
only in the sample from the prostate cancer patient for use in research into the role of CTCs in cancer
and its expression was absent from all other samples. progression, [27-29] and with the aim of targeting such
The ICAM gene, which encodes a molecule involved cells to cure cancer; hence CTCs are a topic of intense
in cellular adhesion, was expressed in breast and discussion among oncologists. [25]
prostate cancer samples, but expression was absent
from ovarian and nasopharyngeal cancer samples; Many techniques have been developed and are under
in contrast, the expression of another gene, CADH1, continuous improvement to enhance the efficacy of
encoding the adhesion molecule (cadherin 1), was
completely absent from the samples from all four types
of cancer patients, indicating that cells in liquid biopsies
from metastatic cancer patients were in the EMT
phase, in which they lose their adhesive properties and
become free to move in the blood stream, which may
also explain the high metastatic potential of these cells.

DISCUSSION

In their early stages, the majority of cancers are
asymptomatic, whereas they exhibit rapid growth rates
later in disease progression; therefore, it is difficult to
treat advanced-stage cancer patients, due to spread
of the disease to various organs and tissues. CTCs
[24]
are shed by primary tumors into the vasculature and
[25]
circulate in the blood of cancer patients; however,
Figure 4: Molecular profiling of liquid biopsies (PBMC) of metastatic
cancer patients. PBMC: peripheral blood mononuclear cell

Figure 3: Expression of K18, CD33, CD44, CXCR4 and NOTCH2
genes in circulating tumor cells isolated from culture peripheral Figure 5: Molecular profiling of liquid biopsies (PBMC) of metastatic
blood mononuclear cells of metastatic patients. B indicates black cancer patients. C indicates positive control for respective gene.
sample and B is a blank lane PBMC: peripheral blood mononuclear cell
Journal of Cancer Metastasis and Treatment ¦ Volume 3 ¦ January 23, 2017 11