HPV (Human papilloma virus) is a common virus that will affect at least 80% of males and females at some point in their life. In fact, anyone who has some sort of sexual contact is susceptible to being infected by HPV. Although, in most people, infection by HPV does not lead to any symptoms, in some cases it can cause diseases of the genital area like warts, cervical cancer and cancers of the vulva, vagina and anus.
Until the early 1990s, most cases of cancer in the back of the throat (orthopharyngeal cancer) occurred in 50-year-old smokers and drinkers and were blamed on alcohol and tobacco consumption. However, in recent years throat cancer has become more and more prominent in younger individuals who appear to maintain a healthy lifestyle, avoid smoking and drinking and are physically active. Now, Maura Gillison, an oncologist from John Hopkin’s University, has uncovered a possible cause for this rise in throat cancer cases, in younger, otherwise healthy individuals. In her studies, she has demonstrated that, surprisingly, HPV can be a hidden cause for a great number of throat cancers yearly, worldwide. But how has she managed to establish a link between a virus that is known to affect the genital area and cancer of the throat?
Linking HPV to throat cancer
In 1996, alerted by a passing comment of a colleague that there was HPV present in a cell line developed from an tumor in the throat, Maura Gillison started to examine weather this virus could be a cause for throat cancer. When analyzing many samples from patients with head and neck cancer, she realized that at least 25% of the samples were infected with HPV. From her studies, it seemed that by infiltrating into healthy human cells and integrating into their DNA, HPV DNA produced two very potent proteins that are known to cause cancer (oncoproteins). Although Gillison came up with these intriguing results in 2000, many oncologists were still skeptical about this correlation. Therefore, Gillison went on to perform a very long and painstaking population study that lasted seven years, where she compared cancer patients to healthy individuals. Over these seven years, she collected tissue samples from 300 individuals and when she finally sat down to analyze the data she had collected, was faced with irrefutable evidence proving her initial theory that HPV infection can be the cause of throat cancer. In fact, the data indicated that people with head and neck cancer were 15 times more likely to be infected with HPV in their mouths and throats than those without. In the years after her population study was published, Gillison also showed that HPV positive cancer patients seemed to have many oral sex partners, but did not have a lot to do with smoking and drinking, which was the opposite for throat cancer patients who were found to be HPV negative. Thus, the cause in these two cases of throat cancer seemed to be very different. By then, all doubts about the link between HPV and throat cancer pathogenesis had faded…
Is HPV vaccination the solution to eradicating HPV induced throat cancer?
Normally, patients with throat cancer are treated with chemotherapy and radiation. However, this treatment has severe side-effects and may not be necessary in patients where throat cancer is caused by HPV. In these type of patients, maybe a different more milder therapy would be indicated. In fact, maybe this type of throat cancer could even be prevented by using the HPV vaccination. This type of vaccination is already available on doctor’s shelves and is used to prevent cervical cancer. The major problem with this solution at the moment is that there is no actual evidence that this will work. For cervical cancer, doctors are able test cells taken from the cervix during a routine cancer screening. However, for the throat, a more invasive procedure would be required, where a tonsillectomy would have to be preformed on every patient in a vaccination trial. Nevertheless, Gillison is still hopeful and believes that her findings about HPV as a cause of throat cancer will help physicians treat this disease and eventually prevent it with the HPV vaccine. There are not many cases, in terms of cancer, where the underlying molecular mechanisms have been identified, she says.