Science Questions

How are translocations related to cancers?

Hello Chris,   My question deals with cancer. I have been hearing on your show that 3-5 mutation in the stem cells leads to cancer (cancers are so different) but working as a cytogenetics in Chicago specifically leukemia. There are many translocations that are linked directly to translocations of the chromsomes. For example the translocation 9; 22 is associated with mainly Chronic Myeloid Leukemia but also is linked to Acute Lymphoid Leukemia. This translocation breaks the BCR and ABL genes that lead to an abnormal tyrosine kinase being formed. How does this agree/disagree with the 3-5 mutation rule that I have been hearing about on the show?   Thank you, James McElherne James McElherne

We posed this question to Elizabeth Murchison from the Wellcome Trust Sanger Institute...

Elizabeth -   Well cancer happens when genes called tumour suppressor genes and oncogenes are mutated and cause the cell to start dividing abnormally.  And this can happen when you get single point mutations in your DNA which mutate an oncogene or a tumour suppressor gene, but they can also occur when two genes can come together abnormally in a translocation and what this can often do is to drive a gene which is not normally active in a particular cell type up to an abnormal level of activity which can sometimes cause the cell to become cancerous.

Chris -   I get it.  So by the chromosomes rearranging themselves, the gene which would normally be off  in a cell can end up being put next to a gene which is normally on in that cell, so the cancer causing gene also gets turned on abnormally and makes the cell misbehave.

Elizabeth -   That type of thing, yes.

May 2010