Human papillomavirus (HPV) is responsible for the majority of cervical cancer and a substantial portion of head and neck and anal cancers, but therapy available to date is surgery and non-specific chemotherapy. In most cases, HPV goes away on its own and does not cause any health problems. But when HPV does not go away, it can cause health problems like genital warts and cancer.
A study that teases apart the biological mechanisms by which HPV cause cancer has found what researchers at Georgetown University Medical Center say is a new strategy that might provide targeted treatment for these cancers.
The new study, published in the journal Oncotarget, found that E6, an oncoprotein produced by the virus, interacts with several other molecules in host cells in a manner that ensures infected cells cannot die. If they are immortal and continue to multiply, cancer develops.
Liu and his team have previously found that the HPV E6 oncoprotein interferes with the well-known p53 tumor suppressor to increase telomerase activity that extends the life span of infected cells. A telomerase is a protein that allows a cell to divide indefinitely when it would have stopped after a certain number of divisions.
In this study, researchers found that E6 also interacts with myc, a protein produced by the Myc gene, which controls gene expression in all healthy cells. They concluded that telomerase activity is dependent on E6-myc proteins hooking on to each other.
This means, says Liu, that designing a small molecule that stops E6 from joining up with myc should shut down persistent activation of telomerase. A small molecule could bind to E6 in the same spot that myc would, or bind on to myc in the same spot that E6 would, thus preventing an E6-myc complex.
"This small molecule would not be toxic to all normal cells or, importantly, to master stem cells, because myc would not be affected," says Liu. "It could be a unique treatment, targeted specifically to HPV cancers."
Georgetown researchers are now working on a prototype chemical to interfere with E6/Myc binding.