What is Sarcoma
& Clear Cell Sarcoma?
What is a cancer?
We are each made up of many trillions of cells. Each cell has a defined role and they work together to make up the organs and tissues of our body. Our cells are regularly dividing, both as we grow, and to replace old dying cells, but this process is normally kept under very tight control. A cancer arises when one cell goes wrong and starts to multiply uncontrollably, invading into the space around it and growing into other parts of the body at the expense of normal healthy cells. This can happen if the genetic code, which is stored in the cell’s DNA and instructs everything it does, gets damaged. Such damage can either result from agents in the environment that directly injure DNA, like UV light or chemicals in cigarette smoke, or it can occur randomly as the cell divides and makes small errors whilst copying its genetic code. Once a cancer starts growing and the cells within it begin multiplying rapidly the likelihood of more errors occurring increases, and gradually the cells look less and less like the normal cell they started from.
What is clear cell sarcoma?
The name sarcoma is a broad term that refers to many different types of cancer growing from cells in the ‘connective tissues’ in the body. This includes cancers of bone, cartilage, fat, tendons and blood vessels. There are therefore many subtypes of sarcoma, each of which is a very different disease in its own right. Clear cell sarcoma is a rare cancer that grows from a tendon, usually in an arm or leg, and predominantly affects young adults from 20 to 40 years old. It often grows very slowly initially and so can be easily mistaken for other, more benign, lumps and bumps. However, even in this early stage the cancer very often spreads from the tendon it started in to other parts of the body, in particular to the lungs.
Cancer cells in clear cell sarcoma are almost always found to have a very specific type of damage to their genetic code, called a chromosomal translocation, and this is likely to be the initial driver for the disease. DNA is a long string of repeating molecules that encodes our genetic makeup. In each of our cells our DNA is split into 23 matched pairs of these strings, called chromosomes. A chromosomal translation occurs when two of these strings get damaged and break in half, then are stitched back together in the wrong order. This can have dire consequences if it leads to genes that tell the cell to divide being excessively switched on, as is the case with the translocations that occur in clear cell sarcoma.
What treatments are available for clear cell sarcoma?
If a clear cell sarcoma is identified early on then it may be possible to cut it out with surgery or by amputation of the limb in which it is growing. This might be accompanied by radiotherapy to the surrounding area to increase the chances of killing any remaining cancer cells that were not successfully removed. However, if the cancer has spread to other parts of the body, then it is no longer possible to cure the disease with surgery. Even if no spread is detected at the time of diagnosis it is possible that small numbers of cells, too small to see, have already spread, and so even when surgery appears successful the cancer can sometimes come back at a later date.
For other types of cancer that have spread throughout the body there are usually several different drugs that can be tried, including chemotherapies, which target cells that are dividing fast, and immunotherapies, which boost the immune system’s ability to fight the cancer. Unfortunately, clear cell sarcomas usually do not respond well to any of these treatments. There remains a need for new and more effective treatments.
What research is being conducted?
As clear cell sarcoma is a very rare disease there is little ongoing research focused exclusively on this disease. However, patients with clear cell sarcoma can often be included in clinical trials that accept multiple different types of cancer. Similarly, preclinical laboratory research sometimes includes clear cell sarcoma as part of broader projects looking at many different cancers. Three current areas of research most pertinent to clear cell sarcoma are:
Testing of medicines that block certain molecules, called kinases, that drive cells to grow and divide and which are switched on by the gene rearrangement in clear cell sarcoma.
Investigating the underlying genetic damage (mutations) present in clear cell sarcoma cells that might contribute to the initiation or progression of disease.
Investigating whether the immune system could be exploited or boosted to recognize and attack clear cell sarcoma cells.
Whilst research into other more common cancers can sometimes be relevant to clear cell sarcoma, each particular type of cancer is unique with important differences in the fundamental processes driving disease. Better understanding of these processes is essential for the identification of effective targets for treatment. By supporting research focused on clear cell sarcoma we hope to further the understanding, and ultimately improve the treatment, of this devastating and neglected disease.