Diagnosis no longer a death sentence
Up until recently, just the thought of cancer could be debilitating.
It was considered a death sentence.
But that is no longer the case, according to molecular pathologist Dr. Rodney Shackelford with Feist-Weiller Cancer Center in Shreveport.
“Things have vastly improved in cancer treatment, and chemotherapy is not as bad as it used to be,” Shackelford said. “If a person thinks they have cancer, they should not let it go because the longer it goes, the less likely it can be treated. But it is not the complete death sentence it was 30 years ago.”
Shackelford said cancer is rarely traced to family history.
“It’s often from environmental factors – like choosing to smoke,” he said. “A low number of people are born with genetics that makes it very likely they will get cancer – about five percent of cancers. Most are caused by either bad luck or environmental factors.”
One gene-related cancer is BRCA 1 mutations. BRCA stands for BReast CAncer susceptibility gene. It increases the risk for getting breast, ovarian and other kinds of cancers at a young age.
Shackelford specifically pointed to actress Angelina Jolie, who had her breasts, ovaries and fallopian tubes removed.
“She had the mutation that made it very likely she would get cancer, if she didn’t have them removed,” he said. “If you have a family history of cancer, often genetic testing is useful.”
Human genome sequencing zeroes in on types of cancer and the best drugs for treatment. What once was an extremely expensive way to determine treatment is becoming more affordable, Shackelford said.
“The first Human Genome was about four billion dollars. We’re down to about three thousand dollars now,” he said. “When it costs less than a thousand dollars, we will probably start sequencing everyone’s genome as part of routine medicine. Then, you’ll be given a piece of paper that says, ‘Here are your chances of getting a particular cancer.’” Then, he said, it will become easier to more carefully monitor a person’s cancer.
Over the last decade, doctors have gone from treating cancer with standard chemotherapy to changing the treatment according to a person’s genetic make-up.
“In lung cancer, there is a gene called ALK, and if you are positive for that gene and cancer, you get a particular drug called crizotinib, and that makes your cancer go away,” Shackelford said.
Discovered in 2007, an ALK mutation is a mutation in a gene called anaplastic lymphoma kinase. It is described as a gene rearrangement – a fusion of two genes known as ALK and echinoderm microtubule-associated protein like 4.
This abnormal (fusion gene) gene in turn codes for an abnormal protein called tyrosine kinase (There are many type of tyrosine kinases.). Tyrosine kinases are enzymes (proteins) that act as chemical messengers, sending signals to the cell’s growth center which tell that cell to divide and multiply.
The medication Xalkori (crizitonib) is an inhibitor of tyrosine kinase. In this case Xalkori binds to the tyrosine kinase receptor on the surface of lung cancer cells and inhibits the abnormal ALK protein.
“Cancer therapy has become very specific, according to the genetics of what you have,” Shackelford said. “For many diseases, they analyze your DNA and then treat you according to what they find in your DNA. The treatment is a lot better with far fewer side effects. Your hair won’t fall out, you won’t be sick to your stomach all the time.”
It’s become standard procedure in most cancer centers, he said. In some ways, all types of cancer can be tracked by genome sequencing.
“In colon cancer, we look for a specific gene called KRAS,” he said. “And we see if that’s mutated or not.
“Chemotherapy is becoming far more specific,” he said. “A lot of these drugs that attack a particular mutation, attack something only found in the cancer, so chemotherapy is often a lot better now, more tolerable and importantly more effective.”
Feist-Weiller is a part of LSU Health Shreveport. It is an academic cancer center where Shackelford is a professor.
–Bonnie Culverhouse
FACTS
• The human genome sequencer is useful for researchers to study genetic mutations and health disparities, as well as to follow patients to better understand the evolution of cancer.
• The genomes of all human beings are 99 percent the same regardless of physical characteristics.
• The technology is an advancement of the 13-year Human Genome Project completed in 2003, in which an army of scientists with super computers managed to create an entire genetic map of the human body. Once scientists knew normal makeup of genes, it became possible to see what is abnormal: mutations that cause cells to multiply uncontrollably.
• Each person begins as a single cell that contains the genetic information to construct every detail of our being. As cells multiply, ultimately reaching more than 100 trillion in a human body, the blueprint is encoded in each cell in a molecule called DNA.
