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(Cancer) Target Acquired

February 21, 2011

Eva Gusnowski

Aptamers to battle stations.  Target acquired.  Get ready to enter.  Endocytosis commencing.  Prepare to kill in 3.  2.  1.  Go.

Cancer is an incredible monster.  It results from the transformation of your own cells, DNA and proteins into something that works against you and attacks from the inside out. 

 

Eva Gusnowski, CSC targeting, RNA aptamer


Most people are aware of some basic classifications of different types of cancer: benign, meaning it’s staying in one place, and malignant, meaning it’s spreading to other areas of the body.  Cancer cells can also be present as free cells in the body, such as in the case of leukemias and blood cancers.  Other times, cancers can be present as solid tumors. 

Although cancer of any sort is difficult to fight, solid tumors pose a specific set of challenges.  This is because the cells at the center of the tumor are often protected from conventional chemical chemotherapy drugs because of their position in the tumor, and sometimes their capability to pump anticancer drugs out of the cell itself.  Additionally, most conventional anticancer treatments attack any dividing cells present in the body: healthy non-cancerous tissue is therefore vulnerable to the drugs.

However, cancer research is taking immeasurable leaps forward.  Much like embryonic stem cells are able to give rise to a population of cells, cancer cells are now believed to rise from cancer stem cells (CSCs).  Elimination of CSCs could therefore prevent repopulation of cancers after chemotherapy, and actually curing the cancer.  It was discovered that many solid tumor cancer cells overexpress a protein called epithelial cell adhesion molecule (EpCAM).  This protein has also been determined as a marker for CSCs. 

 

scientific american, CSC targeting, RNA aptamer



Essentially what this means is that a protein that is quite specific to CSCs has been identified.  Theoretically, if we could attach an anticancer compound or small radioactive molecule to something that recognizes the EpCAM target, we might be able to kill only cancer cells, and not healthy tissue.  But how can this targeting be achieved?

The way the immune system recognizes invaders is through antibodies.  Antibodies are able to specifically recognize only a single or very specific set of targets, and were the first avenue used to try and target the EpCAM protein on CSCs.  However, antibody production can be pretty expensive, and one of the previous problems remained: getting the antibody into the center of the tumors. 

 

Eva Gusnowski, CSC targeting, RNA aptamer



New research out of Wei Duan’s lab at Deakin University may have found a cheap and effective solution for targeting CSCs.  They have found a small sequence of RNA bases (called an aptamer) that specifically binds to EpCAM and is efficiently internalized by the cancer cell.  The hope is that the aptamer can be used in a guided missile-like system, and can be exploited to either detect cancer at much earlier stages than is currently possible (if it was, for example, linked to a dye molecule) or could be used to specifically kill cancer cells (if the aptamer was linked to a toxic chemical or a small radioactive molecule).  These “medical smart bombs” could therefore be used to target cancer at its root, and may eventually lead us to the ever-elusive cure for cancer.  Here’s hoping.

Our very own biological soldiers.  Aptamers: we salute you. 
 

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