What is metastasis and why does it matter?

In order to fully comprehend metastasis, it is crucial to understand the mechanism of tumors. These are essentially an abnormal mass of cells developed as a result of their damaged capacity of contact inhibition. It can be visualized as a swelling.

Tumors are primarily of two distinct kinds, i.e, benign and malignant. The characteristic that helps distinguish between the two is their capacity to metastasize. Since the latter of the two is capable of invading neighboring tissues, spreading to other parts of the body, and expressing possibility of recurrence post removal, it is termed as metastatic. While benign tumors very rarely require extensive medical treatment, malignant pose a threat to multiple organs of the body system simultaneously and therefore require constant medical attention and care.

Malignant tumors essentially translate to ‘badly born’ tumors that lack a immune cells constituting sack outline around them, which desegregates them from the rest of the body and allows them to travel throughout the body via the blood stream. However, what makes their treatment difficult is not limited to the prospect of their mobility. The tumor cell that breaks away from the primary mass and travels to several other lymph nodes of the body further divides to produce tumor mass and these locations. In order to do the same, it must be able to survive the following:

  1. They have to be able to break away from the original tumor and enter the bloodstream or lymph system, which can carry them to another part of the body.
  2. They need to attach to the wall of a blood or lymph vessel and move through it into a new organ.
  3. They need to be able to grow and thrive in their new location.
  4. They need to be able to avoid attacks from the body’s immune system.

After having gone through the challenging stages of mobility, the tumor cell produces a cell mass that is slightly differing in expression from the primary tumor. This in turn creates difficulty in administering an efficient detection, diagnosis and treatment of the cancer.

Since detection is the primary and most crucial step towards the removal of cancerous tumors, it must be performed with extreme precision.

What are the limitations posed by the current detection machinery?

The secret to an increased cancer cure rate lies in accurate and early diagnosis of malignant tumors.

Malignant tumors more often than ever begin as an undetectable mass of micrometastatic tumor. Statistically placed, 3% of the 13 million cancers diagnosed annually have an undetected site of origin.

The presently extensive use of optical imaging like tomography, magnetic resonance imaging and nuclear-based imaging techniques for detection of cancerous tumors is based on the use of luminescent or fluorescent reporter genes or injectable fluorescent or luminescent probes (radioactively labelled DNA or RNA sequences that have an affinity for specific biomarkers that are probably present in the cancerous tumor.) That provide the possibility to study tumor features even by means of fluorescence and luminescence imaging.

The clinical use of optical imaging is however highly debatable given several limitations and risks involved in the procedural dyes, quantum dots and rays employed:

1) Signal loss

2) High background interference

3) Unacceptable cytotoxicity

4) Inefficiency of probe molecules upon accumulation in cancerous tissue

5) Many target specific biomarkers may not be present in a patient’s cancer

What are nanodiamonds and how do they surpass the limitations posed by the optical imaging techniques?

Nanodiamonds are diamonds with a size less than one micrometre, and are chemically designed to facilitate cancer detection.

Nanodiamonds are developed from diamond dust by inducing colour centres through certain chemical changes. Diamond dust invariably has nitrogen impurities. When a molecule of this is subjected to high energy radiation, a carbon atom from the structure is eliminated, post which the molecule is subjected to extremely high temperatures in order to shift the vacancy created adjacent to the nitrogen impurity. This nitrogen-vacancy centre accounts for a point defect in the atom and shows the property of photoluminescence.

They can be used for cancer detection based on the magnetic characteristics of electron spins at N-V centres, allowing the nanodiamonds to provide as innately non-toxic, stable and therefore more efficient replacements for probes in MRIs. In presence of magnetic fields, nanodiamonds fluctuate in light intensity and can therefore be used as blinkers to reduce background tissue noise, effectively and stably indicating presence of cancerous region.

Nanodiamonds are superior to optical probes because:

1) Brightness

2) Signal stability

3) Biocompatability to eliminate cytotoxicity

4) Reduced background noise

The above images are from rounds of experimentation on lymph nodes of laboratory rats by a 2013 biotechnology start–up Bikanta. They aim to demarcate the difference between efficiency of optical imaging and nanodiamonds in cancer tumor detection, and promote the idea of the latter.

Conclusively, nanodiamonds carry commendable potential to transform the realm of cancer tumor detection and subsequent diagnosis and treatment. These nanodiamonds can further be coated to enable their binding to specific body molecules like antibodies. This chemical property can be exploited to implement delivery of antineoplastic drug to affected individual tumor cells for their effective recovery. If it proves fruitful at all stages of laboratory testing, it can provide as a tool to detect cancer at stages early enough for elimination of cancer from almost all infected bodies, changing the demography of the disease for the better.

Aastha Munjal
Published 28th December 2016