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The Genomics of Cancer and Why It Matters

by Bradley Miller on October 29, 2009

One of the most harrowing experiences of medical school was during a surgery for a gynecologic oncology patient.  Prior to the operation we had absolutely no idea that this woman’s ovarian cancer had spread – we had only detected a spot on her left ovary.  However, during surgery we discovered that her cancer had metastasized to the lining of her abdomen (something that couldn’t be detected via MRI or CT scan).

Although experience told the surgeon this finding was evidence for a terminal diagnosis, we waited a couple days to inform the patient and her husband of 45 years because the surgeon wanted the pathology report to 100% confirm his suspicion.  After 3 days we finally informed the patient and her husband of the news.  There was really nothing we could do.  It was an absolutely heartbreaking experience.

From my personal perspective this experience, while a harsh reality of medical training, also made me want to learn more and to help save lives.  I spent time at Memorial Sloan Kettering when I could.  During my surgical rotations I usually opted for the cancer operations and office visits.  I’ve posted in the past about the US’s ongoing War on Cancer, but I think the thing that intrigues me about this disease is that there remains so much that we don’t know despite our vast experience with patients and disease.  I get this sense that there remains so much knowledge about the disease locked up in the cancer genome that with newly created DNA technology it’s finally time that we begin to unlock the mysteries of this disease. (Picture above is an electron microscope image of brain cancer cells invading healthy tissues.)

Electron microscope image of a breast cancer cell spreading "pseudopods" as it seeks out its next direction.

Electron microscope image of a breast cancer cell spreading "pseudopods" as it seeks out its next direction.

Indeed, this is one of the main reasons I’m so very excited about the prospect of genomic science – its crossover with cancer research and the promise that holds for better therapies and eventually a cure. Looking specifically at the genomics of cancer, a review article was published in the New England Journal of Medicine last year that summarized the details of what we currently know about cancer.  Just 20 years ago the Nobel Prize was given to two doctors from UCSF for the discovery of what we now call oncogenes.  Think about it this way – all of the cells in our body need signals that tell them when to grow and then signals telling them when to stop growing.  In cancer, the genes that typically tell the cell to grow a little bit faster are completely up-regulated (they cause too much growth) and the genes that typically put the brakes on growth stop working (effectively shutting off the brakes to growth ).  That disease dynamic makes a lot of sense since cancer is essentially the uncontrolled growth of cells.

But since that time much research has happened, and with it has come advances in cancer knowledge.  For instance, we have discovered that there are genes that actually tell cells when to die – to apoptose.  Think of that as the Control-Alt-Delete function of the body.  If something goes completely haywire, then a cell needs to be able to remove itself from the system.  However, if there’s something wrong with the apoptosis gene, then a cell is more likely to grow out of control and become cancer.

The same is true of genes that typically anchor cells to where they are – when haywire, these genes allow the cancer to detach – to metastasize.  Other genes convey an advantage to survive in other specific tissues, thus some cancers display similar traits – always metastasizing to similar, specific organs.  There are several other types of genes also thought to contribute to a cell becoming cancerous.  In a brief time period scientific and medical research went from a very limited knowledge base about  cancer to a very full and greater understanding of how this disease comes in to being.

One of the more interesting aspects is that cancer is now understood to be a disease with multiple genetic mutations.  Before, we would have looked for one or two “cancer genes.”  Today our reality is that cancer is much more complicated than the model of one gene-one cancer.  And this is a good thing.  We now understand that multiple genetic mutations are needed before a cell turns cancerous.  Growth needs to go out of control, the cell needs to split and grow like crazy, and it needs to travel from its home site. Not to mention it also has to elude the immune system!  Healthy individuals get cancerous cells every day – the difference between these people and cancer is an unfortunate set of mutations that leads to full blown cancer.

The cell at center is a cancer cell that is being attacked by the immune system (purplish cells).  You can see one cell in the lower left being a "kamakazi" cell - sacrificing itself against the invading cancer.  Understanding how the immune system helps to fight cancer will be a key understanding in the war on cancer.

The cell at center is a cancer cell that is being attacked by the immune system (purplish cells). You can see one cell in the lower left being a "kamakazi" cell - sacrificing itself against the invading cancer. Understanding how the immune system helps to fight cancer will be a key understanding in the war on cancer.

Ultimately, what this understanding does is help us to discover that which we don’t know – we can better identify areas we didn’t know we needed to know.  As our genetic model for cancer becomes more complicated we’ll begin to better understand the disease and most importantly, make improvements in treatments and save lives. As I’ve said before, all of this research has shown us just how much we don’t know.  We need to take solace in the fact that the more complicated the true cancer genomics model becomes, the closer to savings lives we’ll be.  But there’s a lot of work and research until we make more major breakthroughs.  Fortunately for us, with the improvement in genetic and cellular research we’re closer than we’ve ever been in the past.

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