Page 199 - Read Online

Galletti et al. Using CTCs in prostate cancer

In the same clinical setting, two other recent studies CTC isolation and downstream molecular
(STAMPEDE trial and LATITUDE trial) indicate a characterization are a powerful tool that has the
significant advantage in survival when abiraterone possibility to grant physicians insight into each
acetate is added to standard ADT [5,6] . These new individual patient’s tumor. Furthermore, repeat sample
results expand the selection of treatment strategies collection could provide the chance of monitoring tumor
in PC, thus prompting the need to identify predictive evolution and could offer the potential to guide therapy.
factors to select ideal candidates for anticipated
therapies. The rarity of CTCs in peripheral whole blood requires
multi-step isolation techniques to maximize the
A greater understanding of the molecular abnormalities capture of cells of malignant origin while minimizing
underlying PC progression and the associated contamination from circulating blood cells that could
mechanisms responsible for treatment resistance mask or limit the clinical utility of CTCs . However,
[13]
may reveal potential biomarkers related to treatment due to the often-intense sample processing during
failure, adding a valuable tool to the clinician’s arsenal. CTC isolation, not all enrichment techniques lend
However, the clinical validation of these molecular themselves to all downstream analyses. For example,
features as predictive biomarkers is still an unmet sample fixation during blood collection or the presence
need, as personalized medicine continues to be of antibody-conjugated magnetic beads may prevent
elusive, due in part to the lack of tumor tissue to profile the implementation of certain assays, such as real
these alterations. time polymerase chain reaction (RT-PCR) or CTC
culture, thereby limiting the type of information that
The use of circulating tumor cells (CTCs) as a “liquid can be extracted from the isolated CTCs. Therefore,
biopsy” to interrogate the molecular profile of single the sample processing involved in CTC enrichment is
patients is extremely encouraging, as these cells of important consideration given the desired biomarker
originate from primary tumor and metastatic sites, analyses that will follow [Figure 1; Table 1]. Even with
providing a comprehensive fingerprint of a given tumor these limitations, the wide variety of isolation methods
at any time during the course of the disease with a currently available allows researchers to perform a
simple blood draw . This is particularly important multitude of downstream assays and reveal important
[7]
in PC, as the primary biopsy tissue available is clinically relevant information from CTCs.
usually collected at diagnosis many years before the
development of metastases and may not mirror the CTC enrichment based on physical properties
biological state of the current disease. A basic approach to enrich CTCs from circulation uses
the physical properties of cancer cells, such as size
Thus, the longitudinal isolation and characterization and density, to differentiate them from the circulating
of CTCs could supply the necessary information to hematopoietic cells. Density-gradient centrifugation
tailor treatment to the individual. The present review effectively separates CTCs from whole blood by
discusses current CTC-enrichment techniques taking advantage of their larger size and distinct
with the specific downstream analyses that can be shape in relation to other components of whole blood.
performed given each method with a particular focus By combining blood with a density-gradient solution
on PC, and the clinical applications that can be guided (e.g. Ficoll-Paque , GE Healthcare Life Sciences)
®
by the molecular and functional analyses of CTCs. and subsequent centrifugation, the blood separates
The most updated results for the use of CTCs to into distinct layers of plasma, mononuclear cells,
investigate the role of potential predictive biomarkers and anucleated cells. CTCs are retained in the
in PC will also be included. mononuclear cell layer with other peripheral blood
mononuclear cells (PBMCs).
FROM RARE CELL CAPTURE TO INSIGHT
INTO PATIENTS’ TUMORS Since physical isolation strategies do not rely upon the
expression of cell surface cancer-specific antigens,
The isolation and analysis of patient-derived CTCs these techniques could effectively capture all CTC
has received enormous attention from the biomedical subtypes including those that may have potentially
community based on their applications towards lost their epithelial features due to epithelial-
personalized therapy [8,9] . It is now established that mesenchymal transition (EMT), a biological process
CTCs offer a suitable source of tumor material as there by which epithelial cells undergo molecular changes
are numerous reports showing that CTC molecular and lose the cohesive interaction among cells
profiles concur with the profiles from metastatic sites down-regulating the expression of common plasma
and primary tumors from the same patient [10-12] . membrane epithelial markers, such as epithelial cell
Journal of Cancer Metastasis and Treatment ¦ Volume 3 ¦ September 27, 2017 191