Breast cancers are classified into different types and sub-types. Are there any methods available to classify breast cancer based on mutations in the gene?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4656721/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5009820/
Thank You, Sabine Strehl
I have seen these article, but none of the articles specifically says particular genes are significantly mutated in subtypes
Dear Snijesh,
Have you seen this one?
http://www.nature.com/nature/journal/v490/n7418/full/nature11412.html?foxtrotcallback=true
the databases by the cancer genome atlas are deposited here:
https://cancergenome.nih.gov/cancersselected/breastductal
https://cancergenome.nih.gov/cancersselected/breastlobular
@Masha Savelieff
I have seen these articles too... But, Is it possible to say an individual has got breast cancer if we find somatic mutations in those specific genes.
Dear Snijesh,
The short answer is no. if a person has those specific mutations, it does not mean they have cancer. it only means they have a risk to develop cancer.
However, it is actually not such a simple question, and the answer as a result is also not that straightforward. My expertise is in glioma, not breast cancer, just to keep in mind.
If a healthy person has one of these somatic mutations, and depending on which one it is, and what other co-mutations they have... this translates into risks for developing breast cancer. But unless the person has developed a tumor, you cannot say an individual has breast cancer just because they have the mutation. Having the mutation is a measure of the risk or chance of developing cancer. You've probably heard of BRCA1 for example. Carriers of certain BRCA1 mutations have a high risk to develop breast cancer among others.
The reason the answer is complex is because risk of developing cancer depends one what mutation the individual has. Some mutations are "driver mutations" and are the originating problem which drives tumor formation and clonal heterogeneity. Other somatic mutations that sequencing studies find evolve during tumor growth. A mutation in one of those genes may not increase risk of cancer on their own. But they also may. It is difficult to know.
I didn't share this paper last time, it is more recent and discusses driver mutations:
https://www.ncbi.nlm.nih.gov/pubmed/27135926
The other part of the answer is that focusing on somatic mutations in coding-genes is limiting. Most papers have examined this. Recently, a paper came out for mutations in non-coding regions which have regulatory functions. This is also becoming increasingly important area of research:
https://www.ncbi.nlm.nih.gov/pubmed/28658208
@Masha Savelieff
Thank you for an explanatory answer....
A positive thing from your answer I can figure out is:
We can not tell whether an individual has got breast cancer or not?
But we can predict the risk or chance of getting breast cancer for an individual. Right?
The upcoming technology early detection of cancer using liquid biopsy is based on identifying mutation in circulating tumor cells (ctDNA). But, according to the aforesaid concept is it possible to detect cancer early?
Dear Snijesh,
The ctDNA is an area much less explored in glioma, which is my area... however I am aware of them. These cells are shed from a tumor and then detected in the blood. So this means the tumor has already formed and is starting to grow. Of course, ctDNA does have the potential to be used for early detection. How early, and with how much accuracy and sensitivity, this is still being determined.
However, the presence of ctDNA implies a tumor has already formed, even though it may still be small. So with regards to your earlier question, simply having the somatic mutation does not mean an individual already has cancer. But the presence of ctDNA could imply that a tumor has formed.
That being said, it is not possible at present to detect when a oncogenic somatic mutation has occurred in an individual. unlike germ line mutations, somatic mutations will only occur in a particular cell. that cell may or may not become cancerous.
Did this clarify it for you?
@Masha Savelieff
Ya almost clarified..... You mentioned another important point here "somatic mutations will only occur in a particular cell".
When we are taking the samples from breast tissue rather than some other region or blood, the detection will be more accurate. So, by applying this logic we can predict the risk factor (Low, High or Intermediate) for an individual for getting breast cancer based on mutation profile. Am I right here?
Thanks
@Snijesh,
Sorry for my late reply, I didn't see an email notification that you'd added an answer to the thread.
For germline mutations, if you biospy tissue, and profile genetic mutations, some may be associated with increased risk of breast cancer, such as BRCA1. But inheritable BRCA1 mutations only account for a fraction of all breast cancers.
For somatic mutations, unless a tumor has already formed, there is no way to biopsy for them because you cannot identify where in the body the mutations are. For a cell that acquires an oncogenic somatic mutation, either it remains nonmalignant, or it transforms. If it transforms, then a tumor grows, and then it can be biopsied and genetically profiled. At this point however, there is no need to calculate chances of getting cancer because the cancer has already formed.
however if a cell acquires oncogenic somatic mutations but does not transform, there is no way to identify where that cell is in order to profile it genetically and calculate risk.
For cancer diagnosis, at present, early detection is key unless it is germline mutation which can be identified and risk assessed.
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