"Colon cancer could also be triggered by viruses"

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Viruses and Co. have long been discussed as cancer triggers. So is the life-threatening illness as contagious as a cold? The Nobel laureate and discoverer of the papilloma virus Prof. Harald zur Hausen gives answers in the interview.

Prof. Harald zur Hausen

Prof. Harald zur Hausen headed the German Cancer Research Center in Heidelberg for 20 years, where he continues to conduct research. In 2008 he received the Nobel Prize in Medicine for the discovery of the papilloma virus.

Mr. zur Hausen, when did you first get the idea that cancer could have something to do with viruses?

That was when I was a medical student. It was then that I learned that bacteria that are infected by bacteriophages occasionally take up the genetic material of these viruses and change their properties. It is assumed, for example, that the formation of poison in diphtheria or cholera bacteria was caused by such viral, genetic elements. This gave me the idea that it could be the same with cancer: you take in genetic material from viruses and that is what ultimately causes cancer. My original idea of ​​the process was a bit naive, but the basic idea has not left me to this day.

Wasn't that hypothesis very provocative at the time?

Not really. At that time it was already known that some cancers in animals are caused by viruses. But no human example was known until 1965.

The Epstein-Barr virus, the causative agent of Pfeiffer's glandular fever, was then discovered in two rare tumor diseases ...

Yes, with Burkitt's lymphoma, a child tumor in Africa, and throat cancer in southern China. The decisive factor for me was that we were able to detect the virus genome in the tumor cells. That prompted me to keep looking for tumor viruses.

It then took another 20 years until you hit the bull's eye and were able to isolate human papilloma viruses (HPV).

We found HPV 16 and HPV 18 at the time. About 70 percent of cervical cancers contain one of these two types of virus.

Do these viruses actually trigger cancer?

Yes. We were able to show that the genome of the virus is usually built into the DNA of the cell. And that very specific genes of these viruses are active in tumor cells, the so-called E6 and E7 genes. It was later discovered that these two genes can promote cell growth - that is, they are the crucial cancer genes.

80 percent of adults will become infected with these types of HPV at some point in their life. But not all of them get cancer. Why?

There must also be changes in the cell's genetic make-up, so-called mutations. Because when the virus incorporates its DNA into the host cell's genetic make-up, the body's own cell police normally prevent the information from being read and virus proteins from being produced. If that does happen, the immune system recognizes the intruder and destroys the cell before the virus can transform the cell into a cancer cell. Only when this control fails does cancer develop - but the virus is a necessary component for this.

One way to protect yourself from HPV infection is to get vaccinated. A new vaccine helps against nine different types of viruses. Does it make sense to ask the doctor specifically about this vaccine?

In any case. The previous vaccine works against types 16 and 18 and thus in 70-80 percent of cases. With the new vaccine you can achieve over 90 percent protection.

Not as many can be vaccinated as one might wish ...

The vaccination rate is insanely low. The vaccination is safe. For every hundred thousand vaccine doses there is just one incident, then an allergy to the virus protein.

The vaccination only makes sense if you are not infected yet. And it is recommended before the first sexual contact. How else can you protect yourself?

The safest thing to do is not to have sexual intercourse. However, if both partners are not infected in a partnership, there is of course no risk. Condoms reduce the risk of infection by 40 percent, but do not provide absolute protection. The reason: unlike, for example, an AIDS infection, transmission can also take place in women via the external genitalia.

However, cervical cancer is not the only cancer that is caused by viruses.

That's correct. It is currently estimated that around 20 percent of cancers are related to infections - viruses, bacteria or parasites. I think the number is actually much higher. We suspect, for example, that colon cancer and breast cancer are also triggered by pathogens.

Can you give any other examples of infection-related cancers?

This is also known, for example, for liver cancer or stomach cancer. In addition to cervical cancer, the papilloma viruses can also cause penile cancer, anal tumors, vaginal cancer or tumors in the head and neck area.

In liver cancer there is a link to hepatitis viruses. Can the hepatitis vaccination protect?

Yes, this protection option has been known for a longer time with hepatitis viruses than with papilloma viruses. More than 20 years ago, all newborn children in Taiwan were vaccinated against hepatitis B. It has been shown that vaccination not only protects children from infection, but also from liver cancer. The virus is transmitted through blood or other body fluids such as semen or saliva.

You and your team are currently looking for carcinogens in beef. Have you found what you are looking for?

Yes, we found infectious particles in meat - they are probably viruses. It has long been known that red meat promotes colon cancer. And we suspect that these pathogens are behind it. But I can't reveal more yet.

Is it theoretically conceivable that cancer cells themselves are transmitted as infectious particles?

Such cases are actually known - but so far only from the animal kingdom. The so-called sticker sarcoma affects the reproductive organs of dogs and is transmitted through sexual contact. The infectious agent here is the tumor cell itself, which then continues to grow in the new host. It has changed its surface properties in the course of the cancer evolution in such a way that it is no longer recognized by the immune system. Similar examples can be found in the Australian bagwolf and a specific type of clam. However, I hardly believe that such a case also exists in humans. This would have long been discovered for more common tumors. It might be conceivable for very rare forms of cancer.

Can you get infected from a cancer patient?

Usually not. Because in the cancer cells the virus is changed in such a way that no one infects it again. So family and friends do not need to be afraid of close contact with a cancer patient. Liver cancer is an exception. The hepatitis virus can also be transmitted from cancer patients. For example, the surgical instruments here can be infectious after a tumor operation.

However, there is a risk of infection with most precancerous stages, which the carrier often does not even know that he has them. And: You can become infected with a cancer-causing pathogen in someone who is completely healthy himself and may never even notice his infection.

You have dealt with cancer for much of your life. What have you done yourself to prevent the disease? For example, do you do sports?

I play chess. Otherwise, I go to regular checkups and eat consciously. But I do eat a steak when I feel like it.

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