In Canton, professor explains link between HPV and cancer
By ROGER MILLER
CANTON -- A dimly lit bar might not be the first place one would expect to find a scientific presentation taking place, but that’s exactly what happened at the Blackbird Café recently, where Clarkson University Biology Professor Craig Woodworth explained to an audience of 23 community members, health professionals, and fellow researchers the link between human papilloma virus (HPV) and cancer.
Woodworth has just received a grant from the National Institute of Health to research why cervical cancer only develops on a narrow range of tissue on the cervix.This talk was one of a series talks organized by Clarkson University known as “Science Cafes” that are meant to spread science, philosophy and other forms of knowledge out into the public. St. Lawrence University Associate Professor of Biology helped organize this event.
According to the Center for Disease Control, HPV is directly related to cervical cancer, which is only second to breast cancer in the number of cases reported each year.
While HPV is most strongly linked to cervical cancer, it has also been tied to a number of other cancers that are highly prevalent in men such as penile, anal and head and neck, and oral cancers.
While there are over 100 distinct types of HPV that can cause warts around the body, Woodworth explained that only 10 have been linked to cancer, with 70 percent of all cervical cancer being caused by just two types, known simply as 16 and 18.
Papilloma viruses are not just limited to humans though. Almost every closely studied mammal and even some birds and reptiles have been found to be susceptible to variations of the virus.
“The virus cannot be spread from animals to humans, though,” said Woodworth. “You can only be infected through skin to skin contact with other humans.”
What makes HPV’s link to cancer confusing is the fact that researchers still don’t know why some people develop cancer from the virus and why some don’t. There is also no cure for HPV once you have it.
“Approximately 20 million Americans have HPV and another 6 million become infected every year,” said Woodworth. “So why don’t we all have warts all over our body?”
The answer, he said, lies in our generally strong immune systems, which normally fight off the viruses enough to stop them from producing warts. That said, the CDC warns that HPV can be passed on regardless of whether someone shows symptoms or not.
While researchers don’t know exactly what causes some people to develop cancer from HPV, Woodworth cited a number of risk factors including pregnancy or prolonged birth control use, a compromised immune system, sexual activity before the age of 18, having many sexual partners, smoking tobacco, receiving an organ transplant, and having other sexually transmitted diseases.
What researchers do know is how HPV can become cancerous once it has infected a susceptible victim.
Some viruses like human immunodeficiency virus (HIV) and HPV have this nasty ability to insert chunks of their DNA into their host’s DNA – tricking the victim’s cells into helping the virus.
When HPV is persistent and doesn’t get killed by the host’s immune system, Woodworth said, it allows the virus to integrate two bits of DNA, genes called E6 and E7, that can produce two particularly harmful proteins. These viral proteins in turn stop the infected cells from producing proteins that suppress tumors and cell growth. Only the high-risk types of HPV possess these genes.
“Think of cells like Indy race cars,” Woodworth said. “They need pit stops and checkpoints to refuel, and repair any damaged parts. These viral proteins block the normal checkpoints of cells so that instead of being able to repair itself, the cell starts dividing out of control and accumulates damaging mutations that drive the cell towards cancer.”
The reason HPV does this, he said, is to trick its host into producing more skin to house newly replicated viruses – we know them as warts.
HPV can only survive and reproduce in the lowest layers of the skin, Woodworth said – away from the best defenses of our immune system. From there the virus hitches a ride inside the skin cells that gradually divide and move up towards the surface where they die and flake off.
“Once an HPV infected cell reaches the skin’s surface, however, it erupts even more little viruses onto the skin,” he said.
This is where warts come into play; the virus has to trick the body into producing more skin so that all those new viruses have homes to move in to.
Of course not everyone who gets warts will develop cancer, said Woodworth; most types of HPV, including the common genital warts, don’t have the capacity. The kinds of HPV that carry a high risk for cancer can actually be very hard to detect without tests.
Fortunately, said Woodworth, most cancers related to HPV are easily preventable and treatable as long as the virus is detected early.
“Early detection is key,” he said. “PAP smears have dramatically reduced the incidence of cervical cancer worldwide”
Woodworth then displayed a map that highlighted in red and orange which regions of the world still had the most cases of cervical cancer, most of Africa, South America and India.
The reason, said Woodworth, was that these countries not only had poor or developing health care systems, but also had high levels of other diseases like AIDS that directly compromise the immune system.
In the U.S., however, he said researchers have developed a new screening test that can detect even the minutest traces of HPV DNA in the body.
“If women test negative for HPV, the screening interval may be increased to five years,” said Woodworth. “There is little to no chance of cervical cancer forming if you are not HPV positive.”
Although it’s expensive at $400, he said, getting vaccinated against the most common cancer-causing types of HPV is an even better way for women and men to guard themselves against most kinds of HPV-related cancers.
Woodworth said the vaccine works by introducing a harmless version of the virus into the body so that the immune system can build up a defensive response before the real thing comes knocking on the door.
“The HPV vaccine can’t cure existing infections, though,” he said. “It must be taken before infection happens.”
While various forms of the vaccine like Gardasil and Cervarix have been highly effective at preventing the most common types of HPV infections and cancers, Woodworth said there are still problems with the vaccine.
“Its expensive, so who gets the most HPV? Poor people who can’t afford the vaccine or the regular screenings.”
Another problem is that the vaccine only protects against 70 percent of cancer causing HPV, so Woodworth said women still have to get PAP smears to detect the other 30 percent of dangerous viruses.
“It’s also unclear how long the vaccine lasts,” he said. “But it lasts at least eight years and is more effective if all three shots were administered within 6 months.”
Perhaps the most beguiling problem with HPV vaccinations is the political one.
“The vaccine should be given to young girls and boys before they become sexually active,” Woodworth said, “and some people are opposed to this because they think it will encourage risky sexual behavior.”
The question of whether this claim is true or not was actually partly answered last October by a study conducted by the American Academy of Pediatrics that found that vaccinating 12-year-old girls did not affect their sexual behavior later in life, as measured by pregnancies and other sexually transmitted diseases contracted.
As for the connection between vaccines and autism, Woodworth said that a study claiming a connection has been retracted and disclaimed by scientists as false, and that the CDC publicly stated that the HPV vaccine is entirely safe for boys and girls.
When audience members asked him for advice concerning the vaccine, however, Woodworth said he was in no position to give personal advice.
“I’m not a physician, I’m just a researcher presenting some information,” he said, advising them to speak to their own doctor about the vaccine.
Aside from personal questions, there were many other comments and questions throughout the talk concerning everything from the science of the virus and cancer to the politics that sometimes gets twisted up in the science.
Christine Schrauth is a regular attendee of these talks in the upstairs bar of the Blackbird.
“They’re all just very, very well presented and the questions are as interesting as the presentation itself.”
At times, the bar even felt like a classroom with a bunch of curious students. Unlike a regular classroom, however, some of the students were drinking wine and beer.
If interested in attending a future science café, go to www.clarkson.edu/sciencecafe/ to check the schedule and locations.
Roger Miller is a freelance writer living in Canton.