US scientists have found human saliva carries markers of breast cancer and have opened the door to the possibility that one day your doctor, or even your dentist, could do a simple saliva test for the disease.
The discovery is reported in a paper published in the 10th January issue of the journal Cancer Investigation and was the work of researchers at the The University of Texas Health Science Center at Houston.
The paper describes how the appearance of breast cancer changes the mix of proteins secreted by the salivary glands. A person with breast cancer secretes a different profile of proteins compared to a person without, claim the researchers.
Professor of diagnostic sciences at The University of Texas Health Science Center Dental Branch, Dr Charles Streckfus, who is an expert on human saliva and molecular epidemiology, led the study. When addressing the question of who could administer a saliva test for cancer, he said:
“Why not the dentist?”
“Most folks, especially women and children, visit the dental office way more often than they ever see the physician. Saliva is a non-invasive, quicker way for detection,” explained Streckfus.
The researchers compared the saliva from three pooled samples, each taken from 10 patients. One sample was from patients who had benign breast tumours, another from patients who had malignant breast tumours (ductal carcinoma in situ, DCIS), and the third was a control sample from healthy patients with neither condition.
The researchers looked for differential expressions of proteins in the samples using isotope tagging. They compared the two tumour groups to the healthy control groups.
Streckfus and colleagues found about 130 proteins altogether. 49 of them were differently expressed between the healthy control pool and the two tumour pools.
They also found unique proteins for a benign type of tumour called fibroadenoma, the most common type of benign breast tumour. This is a unique finding, said Streckfus, “as it targets both the benign and malignant tumor, which could potentially reduce the number of false positives and false negatives associated with current cancer diagnostics”.
Streckfus and colleagues concluded that:
“The study suggests that saliva is a fluid suffused with solubilized by-products of oncogenic expression and that these proteins may be modulated secondary to DCIS. Additionally, there may be salivary protein profiles that are unique to both DCIS and fibroadenoma tumors.”
The research is now being applied to a technology called “lab on a chip”, which basically opens up the possibility that one day, a dental practice or other health care facility, will be able to carry out a diagnostic test that detects the presence of cancer before the tumour forms.
President of the University of Texas (UT) Health Science Center at Houston, Dr James T. Willerson said:
“The unique collaborative opportunities at the UT Health Science Center at Houston, the University of Texas M.D. Anderson Cancer Center and the Texas Medical Center fostered this study and made these remarkable findings possible.”
“A major strength of UT-Houston is putting together outstanding scientists in an environment of collaboration and cooperation,” added Willerson, who also said how proud he was of this latest research by Streckfus and his team.
Co-researcher William P.Dubinsky said saliva could be the key to many medical secrets:
“Saliva is a complex mixture of proteins. We go through a process that compares different samples by chemically labeling them in such a way that we can not only identify the protein, but determine how much of it is in each sample,” explained Dubinsky.
“This allows us to compare the levels of 150-200 different proteins in cancerous versus non-cancerous specimens to identify possible markers for disease,” he added.
According to the Susan G. Komen for the Cure Foundation, an estimated 10 million women worldwide will die from breast cancer in the next 25 years if no cure is found, emphasizing the urgency and importance of early detection.
Screening for breast cancer currently involves use of ultrasound, mammograms, biopsies, and blood tests. The researchers in this study hope that one day that list will include salivary diagnostics.
Dean of the UT Dental Branch at Houston, Dr Catherine M. Flaitz said that:
“Dentistry has entered an exciting new era. On every front, our researchers are exploring links between oral health and the overall health of patients, often with astonishing findings. We’re working to bring those discoveries out of the lab and into the real world of dentists’ and physicians’ offices.”
“Breast Cancer Related Proteins Are Present in Saliva and Are Modulated Secondary to Ductal Carcinoma In Situ of the Breast.”
Charles F. Streckfus; Otilia Mayorga-Wark; Daniel Arreola; Cynthia Edwards; Lenora Bigler; William P. Dubinsky.
Cancer Investigation Published online on 10 January 2008.
Sources: journal abstract, University of Texas at Houston press release.
Written by: Catharine Paddock