Colorized transmission electron micrograph of papillomavirus virions (blue), which replicate exclusively in body surface tissues, such as on the hands, the soles of the feet,
the mucous membranes, and the genitals.

A Stealthy Stalker

A Conversation About HPV with Dr. Richard Hayes and Dr. Brian Schmidt
Human papillomavirus (HPV)—the most common sexually transmitted disease and one of the oldest known viruses—
affects at least 50% of men and women. Most people will never know they have HPV, and in 90% of cases the body’s
immune system fights off the infection within two years. Of the more than 40 subtypes of HPV, however, some cause
cancer of the cervix, the genitals, the anus, and the oropharynx, which includes the base of the tongue, the tonsils,
the soft palate (back of the mouth), and the walls of the throat. In this region of the throat and mouth, cancer is on
the rise, particularly in men. The HPV vaccine, designed to prevent the viral infection that leads to cancer, is currently
recommended for girls, and increasingly for boys, before they become sexually active. Richard Hayes, DDS, PhD, MPH,
professor of environmental medicine, director of the Division of Epidemiology, and associate director for population
sciences at the NYU Cancer Institute at N YU Langone Medical Center, and Brian Schmidt, MD, DDS, PhD, professor
of oral and maxillofacial surgery, director of the Bluestone Center for Clinical Research at NYU College of Dentistry, are
trying to better understand the behavior of HPV and how it can lead to cancer.

What is HPV, and when did it start to infect
large portions of the population?
Dr. Hayes: HPV is a virus transmitted
sexually from one person to another.
Humans have been exposed to HPV for
thousands, perhaps millions, of years.
Though cervical cancer seems more
common now, mortality rates from cervical
cancer were much higher back in the
1920s and 1930s, before the Pap smear was
developed in the 1950s to screen for it.
Which types of HPV are more common in men
vs. women?
Dr. Schmidt: It’s important to understand that
some types of HPV cause simple warts and
others can cause cancer. The types that cause
cervical cancer are HPV-16, -18, -31, and -45.
Men are obviously not at risk for cervical
cancer, but there are associations with penile
and anal cancer also caused by HPV-16 and
-18. Cancer of the oropharynx is almost
always caused by type -16.
How exactly does HPV lead to cancer?
Dr. Hayes: The virus takes over the machinery
of cell replication, leading cells to multiply in
an uncontrolled fashion. The ability to do this
is attributed to the viral E6 and E7 proteins
that interfere with the capacity of two human
tumor suppressor proteins, p53 and pRb,
respectively, to regulate growth of infected
human cells.
HPV-16 (the same type that causes
cervical cancer) has been associated with
a significant rise in head and neck cancers.
What are some of the risk factors and
preventive measures?
Dr. Schmidt: To prevent HPV-negative
tumors, reducing alcohol and tobacco use is
critical. With HPV, the only way to prevent it
is to get vaccinated, but you have to vaccinate
kids at 10 or 11—before they’re sexually
active. The only other way is to limit sexual
contacts involving oral-genital sex. Though
using condoms is important, they are not
100% effective against HPV.
Head and neck cancers caused by HPV are more
treatable and have a significantly higher survival
rate. Why is that?
Dr. Hayes: HPV-positive oropharyngeal cancers
respond better to induction chemotherapy
than HPV-negative cancers. The reasons are
not entirely understood, but it may be due to
differences in epidemiologic profiles (younger
age and lower smoking and drinking) of the
patients and differences in the biology of
the tumors, possibly including lower rates of
genomic damage and the presence of immune
responses to HPV antigens.
Can you screen and test for early signs of cancer of
the head and neck, especially in at-risk patients?
Dr. Schmidt: In the same way that cervical
cancer develops, oral cancer develops through
dysplasia, the abnormal development of cells. If
a patient has an oral lesion, we’ll often biopsy it
and follow the patient carefully. Only 10 to 20%
of cases of dysplasia go on to become cancerous,
and we have no way of predicting who will be
among the 40,000 new cases of oropharyngeal
cancer we see each year.

page 9 | news & views web extra
September/October 2011

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