Page 55 - Read Online

Characterization and Molecular Profi ling of remain in the circulation. There are reports suggesting
CTCs that CTCs bearing mutations, such as upregulation of
CD47, help them in escaping attack by natural killer
We have discussed various CTCs enrichment techniques cells and macrophages. Similarly, downregulation of
which are being used for isolation of CTCs from chaperone protein-calreticulin again helps them to dodge
metastatic cancer patients. However, none of them has the immune system. [47,48] Schölch et al. in their studies
[49]
achieved much of quantitative success. The results have have referred this state as an “immune-evasive” to the
shown a great amount of variation from 10% to 90% period between EMT and MET in circulation. Thus,
of isolated CTCs and hence, it is crucial to analyze the overall it seems that CTCs have very evolved mechanisms
collected cells for their quantity as well as their exact to maintain and express their invasive aggressive nature
phenotype. A numerical indication of collected CTCs by surpassing the body’s natural immune system.
may not be able to reveal the true picture of the type
of cells isolated from cancer patients. Similarly, tumor CTCs in Breast Cancer Diagnosis and
cells can undergo a variety of changes and be present in Treatment
heterogeneous subpopulations. Hence, a mere number of
CTCs can lead to faulty conclusions. Therefore, there is Breast cancer is one of the most common types of
a need for true characterization of these isolated CTCs cancer detected in women. Last two decades, due to
cells to come to logical conclusions. Molecular profi ling early diagnosis and advancement in treatment protocols,
of these isolated cells will crystallize the picture, as it breast cancer mortality has been considerably reduced.
reveals the true nature of the isolated CTCs cells. However, there is no hope of survival when patient
condition progresses to the metastatic stage. Recent
A fundamental process in EMT, down-regulates studies have shown that CTCs which are shed from
E-cadherin, which can be attained by many transcriptional tumor are mediator of metastatic dissemination and form
factors. Most of the molecular markers that have been micrometastasis at distant organs. Due to advancement
[39]
[50]
isolated for characterizing CTCs are EMT indicators. in technology, several methods have been established
During EMT process, a metastatic cell goes through a to isolate CTCs from metastatic breast cancer patients.
lot of modifi cations at cellular and molecular levels and CTCs derived from breast cancer patients are among
many genes undergo transcriptional alterations. Some the most extensively studied for diagnosis and treatment
[39]
of these genes play a role in initiating the effect of EMT of breast cancer. There is a direct co-relation of
[50]
while others play a role in regulating and maintaining CTCs with disease prognosis and survival has been
its transited state. The other factors like infl ammatory reported in many cases. It has been shown that if
cytokines and physical changes in the tumor there is more number of CTCs, there are less chances
microenvironment also play a role in EMT promotion. of survival. The progression of the disease and its
[39]
[50]
TWIST1 and TWIST2 genes are most strongly expressed response to treatment can be very well-monitored by
genes in EMT process which are responsible for inducing characterizing CTCs which are disseminated from
transformation alone or in co-operation with other the primary tumor. It has shown that the presence of
factors such as TGFβ, Wnt, Notch, etc. E-cadherin is CTCs, despite of ongoing treatment, is an indicative of
[40]
one of the most important proteins for maintaining the worse overall survival. Hence, it is very important to
[51]
epithelial nature of cells. Snail1 and Snail2 suppress the characterize CTCs for better understanding of this disease
transcription of E-cadherin as well as Zeb1 and Zeb2 progression and cure. [51]
genes. This results into downregulation of E-cadherin, Due to large size and few numbers of CTCs in blood
which leads to initiation of EMT process. [41,42] Other circulation of metastatic breast cancer patients, the
gate keeper’s genes of epithelial state, such as alpha and isolation and enumeration of captured CTCs have proven
gamma catenins are also been down-regulated along with to be of prognostic value in breast cancer evaluation
downregulation of E-cadherin in this process. [43,44]
and treatment. One of technologies presently in use is
Induction of certain mesenchymal characters during EMT the CellSearch system, which works on a principle
®
process requires upregulation of two extracellular matrix of selecting CTCs as per the positive expression for
proteins, that is, vimentin and fi bronectin in these cells EpCAM and cytokeratin (CK) protein on the surface
which escape the barriers of local tissue and proceeded of these cells. Although it has proven greatly useful
[52]
for invasion. Similarly, other genes such as N-cadherin, and reproductive, it may limit the selection due to EMT
CD44, intergrin β6 are also implicated for proper transition process. CTCs which have undergone EMT
migration of these cells. [43-46] Even understanding the will show downregulation of epithelial markers including
mutational changes, abnormal size, and characteristics EpCAM. In some cases, it has been observed that
[52]
of CTCs, scientists are still pondering over the fact that HER2-positive metastatic breast cancer shows the
these cells are able to survive in an environment which presence of EpCAM negative CTCs. Hence, EpCAM
[53]
is totally hostile for them. It is postulated that out of the independent methods could fetch an increase in number
several hundred CTCs shed by the tumor, only a few of capture of CTCs. Second, detecting CTCs on the

48 Journal of Cancer Metastasis and Treatment ¦ Volume 1 ¦ Issue 2 ¦ July 15, 2015 ¦