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Review

Role of circulating tumor cells in future diagnosis and therapy of cancer

Pravin D. Potdar, Navjeet Kaur Lotey
Department of Molecular Medicine and Biology, Jaslok Hospital and Research Centre, Mumbai 400026, Maharashtra, India.
Correspondence to: Dr. Pravin D. Potdar, Department of Molecular Medicine and Biology, Jaslok Hospital and Research Centre, 15 Dr. G. Deshmukh
Marg, Mumbai 400026, Maharashtra, India. E-mail: ppotdar@jaslokhospital.net

ABSTRACT
Circulating tumor cells (CTCs) have become a blistering topic of discussion for oncologists because of their tremendous potential
in the diagnosis and treatment of cancer. Over the past few years, they have been doled with quite an amount of research in this
area understanding that CTCs are shed from tumors and circulate in the bloodstream. This process can also occur at an early stage
of cancer. The major limitation in isolation of CTCs is their availability in limited numbers. Hence, many techniques have been
developed and are under continuous improvement to enhance their effi cacy of CTC isolation and enumeration. They have shown
their potentiality to not just indicate the presence of a tumor but also to provide us with its core information. They have also
proven to be useful in detecting minor subgroups of cells present in the primary tissue which might eventually be the cause of
treatment resistance or relapse of the disease. Hence, detecting and characterizing CTCs can defi nitely become an inevitable step
in treating solid tumor malignancies. In this review, we have tried to comprehend the basics of CTCs including isolation, detection,
characterization, and molecular mechanism of their circulation in the blood stream. We have mostly focused on the signifi cance
of CTCs in diagnosis and therapies of four most common types of cancers, namely, breast, prostate, lung, and colorectal. This
review provides the coverage of most of the advancements with regards to different tumor malignancies and their probable use in
predicting outcomes of the disease to realize the concept of personalized medicine.
Key words: Cancer stem cells, circulating tumor cells, epithelial to mesenchymal transition, metastasis, molecular markers,
personalized medicine

Introduction continuation of the same treatment only worsens the
condition, therefore, there is a need of extremely specifi c
Cancer is a collective term for uncontrolled malignant and targeted therapy which can help the survival of
tumor growth taking place in any tissue of the body. patients in such situations. It is increasingly becoming a
[4]
More than 100 types of cancers are known till date, some prerequisite to take a “fi ngerprint” of a given tumor and
of them being more common in specifi c genders such as then proceed with a “tailor-made” treatment. Circulating
in case of women; breast cancer is of the most common tumor cells (CTCs) can provide us with the required
whereas in men, prostate cancer is quite common. information and pave a new avenue in future cancer
[1]
Other types of cancer like lung, colon, blood, lymph are therapies.
found in both men and women. Surgery, radiotherapy,
chemotherapy are the established treatments for cancer Mechanism of Cancer Development
which also constitute signifi cant side effects. However,
there is still a long way to go to constitute 100% Most cancer remains asymptomatic at early stages and
effi cacious results because of heterogeneity and resistant start showing up signs only in later stages of development.
of tumor cells to available therapies of cancer. Each of It is diffi cult to treat the patient in advanced stages of
[2]
the subtypes responds differently to the treatment and cancer, because the tumor spreads itself in various tissues
makes it diffi cult to attain a replete cytogenic response. of the body which is referred as invasion and metastasis
[5]
Cancers are also known for attaining complex diversity of cancer. The actual trigger which initiates this process
which makes it diffi cult for clinicians to choose the remains obscure. However, CTC-based technologies
treatment procedure. Some prevalent mutations or may predict the pathway of metastasis. A malignant
[3]
the ones attained during the course of treatment may tumor cell has many cell cycle pathways abnormally
also result resistance to the therapy. In such cases, regulated. Initially, the epithelial cells of a primary tumor
infest nearby blood or lymphatic vessels and circulate
Access this article online in them as shown in Figure 1. Of the many altered
pathways in these cells, one of them is the production of
Quick Response Code: a protein called matrix metalloproteinase (MMP). Upon
[6]
Website:
www.jcmtjournal.com metastasis of a tumor cell, it breaks from the main tumor
and enters the extracellular space which is mainly made
up of collagenous fi bers. The tumor cells secrete MMP,
DOI:
10.4103/2394-4722.158803 which breaks collagen fi bers as well as the basement
membrane surrounding the blood and lymph vessels.
44 Journal of Cancer Metastasis and Treatment ¦ Volume 1 ¦ Issue 2 ¦ July 15, 2015 ¦