Scientists from Dana-Farber CancerInstitute found some males CancerCells with X and/or Y chromosomes show signs that their X chromosome has been silenced.
Normal mammal cells have one X chromosome. A female cell can choose between two Xs.
The body will randomly turn off an additional X in order to balance the chromosomes of males as well as females. If there is only one X chromosome (as with most male cells), neither the X or the Y need to be activated.
However, some cancer cells break this rule.
These findings were based on publicly available DNA samples taken from patients with cancer around the globe. Analyzing thousands of genomes representing more than 30 different cancers, researchers found the gene responsible for silencing the X chromosome – known as X-inactive specific transcript, or XIST – is highly expressed in a wider variety of cancerous tissues than they’d ever suspected.
This gene is a non-coding sequence of RNA that can be found in placental mammals cells. It plays an important role in silencing genes on Xchromosomes.
Silencing of the X-chromosome in genetic males can be rare, but it is not uncommon. In situations where the chromosomes have been duplicated, it can occur. Klinefelter syndrome(where two or three X chromosomes go hand in hand with a single Y chromosome). It can also happen in scattering cells in the early stages of development and in some cases, in testicular germ-cell tumors.
These sex-related cancers were strong among the 4 per cent of male cancers that have been identified using a silenced version X chromosome.
Surprisingly, 25% of the rest were associated with non-reproductive types of cancers like the skin, brain, lung and thyroid.
“We were shocked by this result because XIST is a transcript commonly used to classify women cancers. We wanted to ensure this was not a result from misannotation.” “Srinivas Viswanathan, a cancer geneticist and oncologist at the Dana-Farber Cancer Institute (Boston), is now available.
“Yet we do see that certain male cancers of different subtypes activates XIST and displays features of X activation.”
Although researchers aren’t certain why this is happening, they do have some ideas. Cancers can spread quickly, which can lead to errors, such as multiple copies of the exact same chromosome. The authors found sometimes two X-chromosomes in male tumor cells.
This could be triggered by X inactivation to preserve genetic stability and allow a cancerous tumor better survive and thrive.
“Another possibility is that there are important genes on theX chromosome which, when silenced allow the cancer to grow. This will be investigated in future studies.” “ Viswanathan.
Scientists don’t often think about how genetic differences can impact cancer treatment and recovery. However, the latest findings indicate that there is a difference in the way cancer cells invade the body and cause damage.
The study was published in Cell Systems.
