Friday, December 9, 2011

Single protein stops cell division in cancer

Rapid cell division is one of the main problems in cancer. Their rate of replicating themselves is so high, that it starts damaging their surroundings. Cancer therapies mainly focus on stopping growth, mostly by non-specific toxins that also hamper healthy cells. A newly discovered protein was found to play a role in cell division, and seems effective in killing cancer cells. Clinical trials are now needed to assess whether it is any use for cancer patients. It does seem a promising new weapon in our arsenal against cancer.

The mitotic spindle
STARD9 is a protein involved with cell division, but more specifically with building the so-called mitotic spindle. This is a structure that the cell uses to pull chromosomes apart, so that each copy goes to a different daughter cell during the process of cell division. STARD9 functions as some sort of molecular motor for the whole process, and if the cell lacks it, the failure of separating the chomosomes, that carry our DNA, eventually leads to death. It's one of the few molecules that, when it's not present, can actually cause cell death during cell division.

Cancer therapy
STARD9 can be used as a target in targeted cancer therapy. Depleting the protein caused rapid death of cancer cells when it was tested in the laboratory. When patients are given an inhibitor, it could destroy the tumour. However, the mitotic spindle is part of the normal cell division process, so healthy cells will also be affected. But because cancer cells divide much more rapidly, they will be suffering the worst, which could make low doses, that do not cause a lot of side-effects, effective. Cancer is very hard to treat, because failure to kill every single cell could result in new tumours, so clinical trials with real patients have to confirm whether it is a useful anti-cancer drug

STARD9 depletion therapy has been touted as an effective medicine in certain cancer types. It can be used in combination with conventional chemotherapy, in which the latter can be administered in a low dose. Mixing it into a cocktail of cancer drugs could bring the side-effects down, however they will probably not be perfect.

The cell cycle
The mitotic spindle is part of the cell cycle. This cycle describes the stages a cell goes through when it wants to divide itself, which is the basis of growth for an organism. At each part of the cell cycle, there are checkpoints, that validate whether a cell can go into the next stage. The mitotic spindle does not arrive until very late in the cycle, when the DNA is already replicated for each daughter cell. Cancer cells are known to have a dysfunctional cell cycle, in which the checkpoints do not work, and division occurs too rapid.
Different stages in cell division. The mitotic spindle is found during mitosis.
An alternative
There are more therapies in development that focus around the cell cycle, which is a logical target in a disease that focuses around abnormally fast growth. A new class of drugs inhibits RAF, which is an enzyme involved with the cell cycle. This could prove to be an addition to the STARD9 treatment, as both therapies combined could work in a synergistic way. 

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