frank_davis (frank_davis) wrote,
frank_davis
frank_davis

Human Papillomavirus

One of  the effects on me of antismoking mendacity has been to make me not only question whether secondhand smoke is a health threat - that's easy -, but to also question whether smoking causes lung cancer. After all, if they're lying about the former, they're probably lying about the latter too. But if smoking doesn't cause lung cancer, what does?

I have been interested to learn that, in the past 20 years or so, it has been established that cervical cancer is caused by Human Papillomavirus, HPV, which infects epidermis and mucous membranes of humans. This  makes cervical cancer an infectious disease - and a sexually transmitted disease - for which vaccines can be (and have been) prepared.

There are a whole family of Human Papillomaviruses, with over one hundred different variant types currently known, and of these HPV 16 and HPV 18 are the ones associated with cervical cancer. Virtually all cases of cervical cancer reveal HPV infection. So also do some anal and vaginal and penile cancers.

The story of the discovery of the role of HPV in cervical cancer seems to be one of those classic tales of the lone, persistent researcher bucking conventional wisdom and following his own nose. Harald zur Hausen was born in Germany in 1936, and devoted his life to work in the field of virology. He contributed to research that showed that the Epstein-Barr virus could transform normal cells into cancer cells. In the 1970s he isolated HPV 6 in genital warts, finding a way of identifying viruses in human tumours. In 1983 he identified HPV 16 in cervical cancer tumours, and in 1984 he identified HPV 18, sparking controversy. By 1991, other studies confirmed that HPV was the cause of cervical cancer.  In 2006 - 23 years after zur Hausen first identified HPV in cervical cancer - a vaccine finally became available. In 2008, he was awarded a Nobel Prize for Medicine. Of this long delay, he was to say:

“People became sceptical about the role of papilloma viruses in cancers. Pharmaceutical companies were not interested in the story any more, because this period created such confusion. I got a bit frustrated in this period and could not hide it. Cervical cancer is one of the major cancers worldwide, and it kills relatively young women. If our original conviction that this virus must be causative had been carried through, we would have made an earlier start on a vaccine.”

The virus seems to work by gradually shutting down the body's normally efficient natural defences over a long period of time. Women may be infected with HPV between the ages of 15 and 22, but only develop cervical cancer between the ages of 40 and 45, some 20-30 years later.

As ever, before HPV was discovered, smoking was originally fingered as a risk factor for cervical cancer. Cervical cancer was found to be more common among prostitutes than among nuns. Prostitutes also smoke more than nuns, and this is one of the reasons which smoking became a risk factor for cervical cancer. From Velvet Glove, Iron Fist:

Smoking, like herpes, was not the cause of cervical cancer, it was simply more common amongst women who were sexually active and, therefore, more likely to be infected with HPV. Had the Italian doctor [Rigoni-Stern] looked at tobacco use, he would have observed that smoking was more common amongst prostitutes than amongst nuns. He might also have noted that prostitutes were more likely to drink alcohol, have children and be atheists. But none of these things caused cervical cancer; they were just more common amongst prostitutes. 
 
But although smoking has been - and still is - advanced as a risk factor for cervical cancer, zur Hausen is convinced that HPV infection is all that's needed to account for it.

Other factors such as smoking make cancers more likely, but zur Hausen believes that the papilloma virus will do it alone, given time. “People say that the papilloma virus is a necessary but not a sufficient factor. We here are deeply convinced that this statement is wrong; that the virus is necessary and in quite a number of instances is also sufficient..."

There remains some doubt over whether HPV is the sole cause of cervical cancer, but zur Hausen is dismissive:

A few scientists still report cervical cancer without papilloma virus. zur Hausen will believe it when he sees it. “I frequently ask colleagues to provide us with tumour samples which are in their opinion negative and we have never got any.” 

If HPV can be shown to cause cancer by infecting mucous membranes of sexual organs, might it also be capable of infecting the mucous membranes of mouth and throat and lungs? Lung Cancer Blog, 21 July 2009, suggests exactly this:

According to the authors of a study published in the journal Lung Cancer, HPV may even be the 2nd most important cause of lung cancer after smoking... As the link between HPV and cervical cancer was discovered by finding HPV in cervical cancer cells, HPV has been found in roughly 20-25% of lung cancers in the United States. 

But this turns out to be just the average. Far higher figures have been found elsewhere:

Overall, the mean incidence of HPV in lung cancer was 24.5%. While in Europe and the America the average reported frequencies were 17% and 15%, respectively, the mean number of HPV in asian lung cancer samples was 35.7%. There was a considerable heterogeneity between certain countries and regions. Particular high frequencies of up to 80% were seen in Okinawa (Japan) and Taichung (Taiwan).

Even the average figures of 25% are remarkable. 80% is quite astonishing. It suggests that most lung cancers in Japan and Taiwan are caused by HPV rather than smoking or anything else. Why the difference between Japan and America? Is HPV more common in the Far East than in the West? Or do the Japanese and Taiwanese have more accurate HPV tests? Or might it be that in the West, where the medical establishment has long since convinced itself that smoking causes lung cancer, it's not felt necessary to test lung cancer tissues for HPV? Why bother with some new-fangled test when you already know the cause?
 
So here is a cancer virus which is now recognised as the cause of cervical cancer, and which is also showing up in anal and vaginal cancer, and now mouth and throat and lung cancer. Might it be that all cancers will one day be proved to be caused by cancer viruses?

It has only been about 15 years since HPV was established as the cause of cervical cancer. Presumably it was only when that had happened that other cancers began to be investigated. And so the study of HPV in other cancers must be lagging behind the cervical cancer studies.

In the circumstances, it's remarkable that in 15 years HPV has been shown not only to be the cause of cervical cancer, but also to be present in about a quarter -  and sometimes much more - of cases of many other cancers. As HPV testing improves, and new types of HPV are found, it's not implausible to imagine that HPV may  be found to be the principal cause not just of 25% of lung cancers, but of almost all of them. 

What a storm that would cause! After all, it has been 'known' for 60 years that smoking causes lung cancer. Sir Richard Doll used to assert that 90% of lung cancer was caused by smoking. What if it now turns out that lung cancer is a sexually transmitted disease just like AIDS or syphilis or gonorrhoea? And is a disease that reached epidemic proportions at the same time and for exactly the same reasons as they did - a relaxation of sexual mores, and the breakdown of marriage and the family?

It may well turn out that the present global war on tobacco and upon smokers will prove to have been launched just before tobacco was finally acquitted of causing lung cancer. Which is a bit like invading Iraq just before it was proved that it possessed none of the weapons of mass destruction which had been used to justify its invasion.
 
Addendum

Retrovirus Linked to Aggressive Prostate Cancer

A New Germ Theory
Tags: cancer, hpv
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