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Galletti et al. Using CTCs in prostate cancer

capture cells of epithelial origin and proved efficient independent manner. The device can then release the
in isolating CTCs from different tumor types [43] . enriched live CTCs, which can be used for standard
Improvements to the fluid dynamics within the CTC- cytopathologic evaluations, RNA or DNA-based
chip led to the development of the herringbone- analysis and to generate CTC-derived cell culture [36,50] .
chip, which generates microvortices to multiply
the number of interactions between CTCs and the All of the approaches described above isolate CTCs
antibody-coated chip surface [44] . The geometrically from a tube of peripheral blood collected from the
enhanced differential immunocapture chip employs patient. The GILUPI CellCollector is a medical guide
®
a 3D geometry with microposts functionalized with wire functionalized with anti-EpCAM antibodies
a monoclonal antibody to the cell-surface antigen that is designed to capture CTCs directly from the
PSMA to enhance the capture of CTCs from PC circulating blood of patients after it is inserted in the
patients [45] . All these microfluidic devices have been cubital vein of patients for 30 min. This device can
shown to capture live cells that can be used for interact with an estimated 1.5-3 liters of blood [51] , and
many subsequent molecular assays (IF, FISH, DNA has the advantage of being able to isolate live CTCs
or RNA sequencing), including CTC in vitro culturing from volumes of blood larger than what usually
and ex-vivo drug treatment [46] . reported in the literature and obtained from patients
with either localized or advanced PC [52,53] .
The novel microscale platform VERSA (Versatile
Exclusion-Based Rare Sample Analysis) optimizes CTC isolation techniques are constantly seeing new
the potentially harmful washing, cell transfer, and and improved methods to separate these rare tumor
centrifugation steps of many microfluidic devices cell populations from other nucleated blood cells.
by coupling EpCAM-coated paramagnetic particles Particular emphasis has been given to methods that
(PMPs) with immiscible barriers that aid in the move away from antigen-dependent capture and can
removal of contaminating PBMCs and unbound PMPs isolate live CTCs, regardless of the expression of
through surface tension over gravity at the microscale specific surface markers, like EpCAM, as cells with
on the single device . This innovative approach low or complete loss of expression of EpCAM likely
[47]
demonstrates very versatile and is able to perform hold clinically meaningful information . In addition
[36]
different assays, as it can either isolate live cells for to enabling a diverse array of downstream biomarker
subsequent nucleic acid extraction and analysis, or analyses, live CTCs can also be expanded through
perform cell fixation and immunofluorescence directly culturing methods or organoid development, opening
within the wells of the device, which is engineered for new exciting scenarios in tumor biology [54,55] . Organoids
CTC microscopy. originating from CRPC CTCs have been successfully
generated and reproduce some of the major molecular
In order to avoid the pitfalls of selecting for CTCs features commonly found in the primary tumor, such
based on positive expression of epithelial markers, as expression of SPYNK1, STEAP1 and TMPRSS2,
negative depletion techniques have emerged that confirming CTCs are a precious readily available
target and remove the contaminating leukocytes, thus source of tumor material that can be used to generate
allowing the enrichment of a pool of heterogeneous in vitro PC models to explore and understand disease
subpopulations of CTCs.
pathogenesis and progression .
[55]
RosetteSep™ Circulating Epithelial Tumor Cells
enrichment kit (STEMCELL™ Technologies) employs CTC AS SOURCE OF TUMOR TISSUE FOR
anti-CD45/anti-glycophorin A antibody complexes that BIOMARKER INVESTIGATION
create crosslinks between red blood cells and white
blood cells (immunorosettes), that are then eliminated The biomarker-based approach has considerably
by gradient-based separation, leaving behind a CTC- transformed the treatment strategies of cancer,
enriched cell population . A major benefit of this improving response rates and overall survival;
[48]
approach is the possibility to enrich live CTCs, without however, the availability of tumor tissue is required to
sample fixation, allowing live cell studies such as study and understand the biology of these biomarkers
development of CTC-derived xenografts (PDX) and and to follow the evolution of these molecular
gene expression profiling . alterations over time.
[49]
The CTC iChip captures CTCs using the two-stage Using CTCs as source of tumor material to
process of deterministic lateral displacement, inertial characterize the molecular profile of the disease
focusing and magnetophoresis to achieve leukocyte represents the most significant and exciting impact
depletion and CTC enrichment, in an antibody for the clinical practice, especially in the current era
Journal of Cancer Metastasis and Treatment ¦ Volume 3 ¦ September 27, 2017 195