Wednesday, May 11, 2011

The biology of cancer treatment (Part 2 of 3)

Continuing from yesterday, remember that we defined four cell functions, plus DNA repair, that "break" as tumor cells progress toward dangerous metastatic behavior.

1) Cell growth control
2) Programmed cell suicide
3) Blood vessel formation
4) Cell mobility

We'll pick up today where we left off: with programmed cell suicide.

Programmed cell suicide
Cells are "smart." They sense when their internal (molecular) processes have gone awry. And when they sense that they have become abnormal, for whatever reason, they initiate a process that results in their own orderly death. When it's working properly, programmed cell suicide ("apoptosis"... pronounced ay'-pop-toh-sis) kills cells that are becoming cancerous.

But when mutations occur in genes critical for programmed cell death, then the cell becomes more dangerous. It isn't able to kill itself when it senses it is growing too fast or cell processes are "out of whack." It's likely that when both cell growth control (step 1) and programmed cell suicide (step 2) are broken, a small tumor can form.

Blood vessel formation
A cell with broken growth signaling and broken programmed cell suicide can form a small tumor, but it can't get very large and it can't move to other parts of the breast or body. The reason is that the tumor needs blood to grow larger. Normal cells can't create blood vessels/capillaries to both feed themselves and provide a means of transport.

That brings up the next cell process that goes awry in cancer cells: blood vessel formation ("angiogenesis"... pronounced an-gee-oh-gen'-a-sis). Cancer cells receive DNA mutations that actually turn on cell processes that result in the attraction or formation of blood vessels. Once this third type of mutation occurs, the tumor can grow larger. But it's still likely that the cells stay confined to the main tumor.

Cell mobility
Normal healthy cells stay where they are in the body. They are immobile. Cancer cells gain the ability to physically move in the body tissues, including into blood vessels that transport them to other locations in the body. The fourth cell function that goes haywire in cancer cells is cell mobility.

Cell mobility can be caused by genes breaking or by genes becoming abnormally activated. But with this final cell process broken, we now have a cancer cell that: 1) is growing and dividing rapidly, 2) can't kill itself, 3) has attracted blood vessels (nutrient supply lines) and grow into a larger tumor, and 4) that can move around the body. This is a dangerous cell.

Tomorrow: How DNA repair fits in, and relating all this to breast cancer treatment

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