By NIKKI SCHWAB

Suntans, cigarettes and chemicals are sometimes cancer culprits, but viruses too can be behind these deadly diseases.

While scientists have understood this link for nearly a century, scores of Americans are now finding out about this connection thanks to television commercials for Gardasil, the vaccine that prevents human papillomavirus, which can cause cervical cancer in women.

“I just found out that cervical cancer is caused by certain types of a common virus–HPV, human papillomavirus,” a miffed actress says in the TV advertisement.

HPV, a common sexually transmitted disease, and other viruses are responsible for the onset of different cancers.

How cervical cancer works

Cancer is a disorder of cell growth. Normally, when cells are abnormal the body tells them to stop growing and they die. Cells have checkpoints which control their growth, but when a person has cancer, these protections are overcome and the cells are hijacked, explained Dr. Mark Schiffman, head of the human papillomavirus research unit at the National Cancer Institute’s Division of Cancer Epidemiology and Genetics.

Schiffman said it’s similar to the movie Alien — in that a virus comes in, snatches the cells and mutates them so that they turn into something bigger and uglier.

“The virus is keeping the cell from turning into just flaking skin and falling off, it keeps it from dying,” Schiffman said.

The idea that a virus could cause cancer became prevalent after 1910 when scientist Peyton Rous experimented with hens with tumors. He would remove their tumors, mash them up and give them to other hens, which would also grow tumors. This was the first instance in which a virus was found to cause a tumor, according to Dr. Patrick Moore, the director of the Molecular Virology Program at the University of Pittsburgh Cancer Institute.

“This helped in figuring out what genes caused cancer, genes that were associated with these animal tumor viruses, but as of the early 1980s no virus had been found that clearly caused a human cancer. That changed with several discoveries, one was HPV,” Moore said.

HPV, hepatitis B and human herpesvirus-8 are viruses now linked to cervical cancer, liver cancer and Kaposi sarcoma, a cancer prevalent in AIDS patients.

While most people are concerned about HPV, Dr. Robert Edwards, the director of Gynecological Cancer Research at the University of Pittsburgh Medical Center, explained the majority of people with HPV would not get cancer.

“HPV doesn’t usually cause a lot of issues,” Edwards said.

Risks and Results

Over half of sexually active adults are infected with HPV at some point in their lives.

“So any woman who has had sex with a man is at fairly significant risk of having the vagina and cervix colonized with this particular risk,” Edwards said.

This prevalence is shocking to some and condoms only cut the risk down by half.

“I think people are shocked that their pap is abnormal,” Edwards said. “I have had many patients in my practice who have had one sexual partner.”

There are more than 100 varieties of HPV, of which more than 30 are transmitted through sexual contact.

Two types, HPV-16 and HPV-18, are responsible for about 70 percent of cases of cervical cancer worldwide, according to the National Institutes of Health. There are 13 other types that account for the other 30 percent of cancer-causing HPV.

Also HPV-6 and HPV-11 cause about 90 percent of genital warts in men and women.

In most people, HPV clears, or goes away; but if HPV persists, it becomes a problem. The virus is associated with not just cervical, but vulva, vagina, penis and throat cancer.

While men can get some cancers from HPV, they are usually asymptomatic carriers, and there is no good way to test them for the virus.

In the United States, 10,000 women are affected with high-risk HPV and 4,000 will die from cervical cancer. In the world, it is the second leading female cancer killer with half a million women diagnosed and 200,000 deaths per year. The median age that cervical cancer is diagnosed is 48, according to the National Cancer Institute.
HPV is a paradox, being both common and serious.

“How do you explain to people that it is the most common sexually transmitted agent, but at the same time, if it’s persistent, it can be very dangerous,” Schiffman said. “It is both common and very serious, and that’s a difficult health message.”

In almost all instances that a woman continues to be infected by the virus, it develops into pre-cancer and then cancer, but not every time.

“HPV is not gonorrhea. It’s one of those things that almost everyone gets exposed to and unfortunately, we can’t predict who is going to have a problem with it,” Edwards said.

Researchers are trying to figure out why HPV persists in some and not others. They’ve investigated smoking as a possibility because it affects the immune system. Scientists have also noticed people who have chronic infections due to Chlamydia, another sexually transmitted disease, have a higher chance of developing cancer, according to Schiffman.

Vaccine’s effectiveness

Researchers have developed Gardasil, the vaccine that was approved in June by the Food and Drug Administration, for use in women ages 9 to 26.

Gardasil vaccinates women against the two types of HPV that cause 70 percent of cervical cancer and the two types that produce most genital warts. The vaccine, which is administered in three doses over six months, does not work against the other 13 types of cancer-causing HPV.

Also, if a woman is already infected with the virus, the vaccine is ineffective, which is why doctors recommend girls get vaccinated before they become sexually active.

“Before you become sexually active, you are almost guaranteed that the vaccine is going to be effective,” Edwards said. Edwards has helped Gardasil’s maker, Merck, with public relations for the vaccine.

A concern expressed among parents when Gardasil debuted was that they would have to discuss sex with their daughters.

Edwards said this doesn’t have to be the case.

“I think the emphasis of this as an STD is probably the wrong approach,” Edwards said. “This is an anti-cancer vaccine, it’s going to prevent cancer from developing, it has the potential to wipe out cancer from populations that are immunized.”

Schiffman, who helped develop Gardasil, wasn’t as positive about the new vaccine.

The National Cancer Institute researcher said there are still a lot of things scientists don’t know about the vaccine. They don’t know how long it lasts in people, so they don’t know how often it should be administered.

“Mainly, we don’t know if it is worth it,” Schiffman said.

Also, by vaccinating girls against only some types of the virus and not every type, Schiffman said he is concerned that screening programs could become less meaningful because doctors would be looking for “fewer needles in the haystack.”

Dr. James Goedert, chief of the viral epidemiology branch of the National Cancer Institute, said people should be aware that the vaccine works against 70 percent, not 100 percent, of cancer-causing HPV.

“You don’t want to have the misunderstanding that you are completely protected,” Goedert said.

A Merck spokesperson said the company chose to focus on HPV-16 and HPV-18 because they cause the most cancers.

Merck is currently studying whether the vaccine is effective in protecting women against the other 30 percent of HPV types that cause cancer because some of the types are closely related. The company is also researching if Gardasil would protect men from getting HPV.

Schiffman added that the vaccine is intended primarily for use in third world countries, which lacks good health care. There, women are not able to go to a gynecologist for a yearly Pap smear, which is the current screening process for cervical cancer.

“There is no reason why we need the vaccine in the United States,” Schiffman said.

Goedert said the vaccine would have a much bigger impact in Africa or South America, where large-scale Pap test programs don’t exist, but said Merck’s intention was to sell it to people in wealthier nations.

“It was developed by private industry for people who would pay for it,” Goedert said.

Schiffman said while Merck is putting millions of dollars into advertising Gardasil, doctors should hold off on attempting to vaccinate the masses until more studies can be done.

“I just don’t think policy should be made in the absence of knowledge,” Schiffman said. “I’m just somebody who doesn’t want to do harm in public health.”

Cancer vaccine success stories

However, at least one cancer-causing virus has become less prevalent because of a vaccine. Hepatitis B can lead to liver cancer if the virus persists. The disease, which primarily affects people in Southeast Asia, has been diminished because of vaccination programs in Taiwan and in some parts of China, but is still a health threat in these regions, according to Goedert.

Like HPV, most of the time when people are infected with hepatitis B, they recover from it. In about 95 percent of cases this is true. However, one way the disease can spread is from mother to child. When children are infected as infants, they are at the greatest risk of hanging on to the virus so that it will cause cirrhosis, or scarring, of the liver and liver cancer.

“Cirrhosis and liver cancer occur because of the damage to the liver cells from the virus and then the effort of the body to repair the cells causes the scarring,” Goedert said.

Also, alcoholism can aid a hepatitis-B positive person in developing liver cancer.

Screening programs today are mostly targeted toward pregnant women, so children can get vaccinated early. There aren’t many treatment options for people with liver cancer. Doctors have transplanted livers, or if caught early enough, surgeons can remove cancerous section of the organ, according to Goedert.

A more recently discovered form of hepatitis, hepatitis C, can also cause liver cancer, but this form doesn’t have a vaccine yet.

Goedert said in the next few years, researchers might be able to develop a vaccine that would eradicate hepatitis C. This discovery may be helpful with human immunodeficiency virus research also because both hepatitis C and HIV are RNA viruses, which means, they, like the common flu, mutate often.

HIV doesn’t cause cancer by itself, but can help one type of herpes virus turn into Kaposi sarcoma, according to Moore of the Molecular Virology Program at Pitt.

Kaposi sarcoma originates from human herpesvirus-8 and is often seen in HIV-positive patients. Human herpesvirus-8 is a sexually transmitted disease, but is not the same herpes that causes cold sores or genital herpes. It is sometimes transmitted by blood, and in Africa, researchers are not sure how it is transmitted.

While Kaposi sarcoma may not sound familiar to most, it is the disease Tom Hank’s character suffers from in the movie “Philadelphia,” and there were huge outbreaks of it in New York City and California’s gay community during the onset of the HIV/AIDS epidemic in the 1980s.

Because of the HIV outbreak in Africa, Kaposi sarcoma has become the most common tumor in Sub-Saharan Africa and will continue to become even more of a public health concern, Moore said. The cancer creates a slow growing tumor, which can be surgically removed but often causes a large open sore.

“But we could do much better if we had a vaccine, that’s extremely important,” Moore said.

Because Kaposi sarcoma mainly affects Africa and not the United States and Europe, resources are slim to develop a vaccine. However, now that people are beginning to know about HPV and understand the vital link between cancer and viruses, things may change, Moore said.

“One could hope that that will spill over to some other virus-caused cancers as well,” he said.

Edwards too agreed that the future looks promising for those studying this link.

“I don’t think there is any doubt that we will find that more cancers will be caused by viruses,” Edwards said.

“Which is exciting because theoretically you can prevent them with vaccination. It’s a lot cheaper than trying to treat people with chemotherapy and a lot less morbid,” he said.