Researchers have found the cells at the origin of cervical cancer, in a discovery that could offer new ways to prevent and treat the disease, according to a US-published study.
Most cases of cervical cancer are known to be caused by specific strains of human papillomavirus, but now researchers know the specific group of cells that HPV targets, said the study in the Proceedings of the National Academy of Sciences.
Moreover, when they are removed from the cervix they do not appear to regenerate, said the study by scientists at Brigham and Women's Hospital, Harvard Medical School and the Agency for Science Technology and Research (A-STAR) in Singapore.
The cells can become cancerous when infected with HPV while other cells in the cervix often do not, said senior author Christopher Crum, director of women's and prenatal pathology at Brigham and Women's Hospital in Massachusetts.
Cells located near opening of the cervix
They also have a particular gene expression that is the same as found in aggressive cervical tumours, which could allow doctors to differentiate benign lesions from dangerous pre-cancers.
"We have discovered a discrete population of cells that are located in a specific area of the cervix that could be responsible for most, if not all, of HPV-associated cervical cancers," said Crum, who was joined by researchers Wa Xian from A-STAR and Frank McKeon of Harvard Medical School. Michael Herfs, a postdoctoral fellow at Brigham and Women's, was the lead author.
The cells are located near the opening of the cervix, in a transition area between the uterus and the vagina known as the squamo-columnar junction.
The findings build on the group's previous research that identified the origin of a rare and sometimes cancerous change in certain cells in the oesophagus, at a junction between the tube that carries food through the throat and the stomach.
Remnants of embryogenesis
A similar population of cells has been found to reside in the cervix, Crum said. They are the remnants of a process known as embryogenesis, which is the process of cell division and growth that we all undergo in the process of growing from embryo to foetus.
"There is a population of cells in the cervix that during foetal life disappears and is replaced by another type. We found out that a small number of these cells are actually not lost and they remained there, almost like little sentinels from a prior age," Crum said.
"It appears that that particular group of remaining embryonic cells at the squamo-columnar junction is the population that you must infect, at least in the great majority of cases, to produce the significant cancers and precancers," he added.
"During reproductive life they undergo changes, or metaplasia, when they become other cell types, so they are kind of like stem cells."
Cervical cancer a major killer of women
Knowing the biology of these cells and where they reside could help physicians both clarify which cervical precancers (dysplasias) need treatment and also possibly prevent cancer altogether by destroying the cells in advance.
Further study may shed light on whether similar populations of cells reside in other areas of the body known to be affected by HPV-related cancers, such as the penis, vulva, anus and the throat.
HPV types 16 and 18 are believed to be responsible for about 70% of all cases of cervical cancer in the world, according to the World Health Organization.
While regular screening has drastically cut down on death rates in the West, cervical cancer continues to be a major killer of women in the developing world, and ranks as the third most common cancer among women globally.
The WHO estimates nearly 530,000 women are diagnosed with cervical cancer annually worldwide and 275 000 die from the disease.
(Kerry Sheridan, Sapa, June 2012)