Saliva test offers easier detection of mouth and throat cancer

An international team of researchers has revealed that a novel non-invasive technique can successfully detect human papilloma virus-16 — the strain associated with oropharyngeal cancer — in saliva samples.

Cancers that occur in the back of the mouth and upper throat are often not diagnosed until they become advanced, partly because their location makes them difficult to see during routine clinical exams. Researchers writing in The Journal of Molecular Diagnostics have now described how a non-invasive method known as acoustofluidics can analyse saliva for the presence of human papilloma virus (HPV)-16 — the pathogenic strain associated with oropharyngeal cancers (OPCs).

“OPC has an approximate incidence of 115,000 cases per year worldwide and is one of the fastest-rising cancers in Western countries due to increasing HPV-related incidence, especially in younger patients,” said co-lead investigator Dr Tony Jun Huang, Duke University. “It is paramount that surveillance methods are developed to improve early detection and outcomes.”

Exosomes are tiny microvesicles originating within cells that are secreted into body fluids. They are believed to play a role in intercellular communication and their numbers are elevated in association with several types of cancers. In acoustofluidics — a fusion of acoustics and microfluidics — fluid samples are analysed using a tiny acoustofluidic chip developed to isolate salivary exosomes by removing unwanted particles based on size, leaving exosome-rich concentrated samples that make it easier to detect tumour-specific biomarkers.

Investigators analysed saliva samples from 10 patients diagnosed with HPV-OPC using traditional methods. They found that the technique identified the tumour biomarker HPV-16 DNA in 80% of confirmed cases when coupled with droplet digit PCR. Since this method is independent of sample variability that arises due to changes in saliva viscosity and collection methods used, it may prove ideal for use in clinical settings.

“The successful detection of HPV from salivary exosomes isolated by our acoustofluidic platform offers distinct advantages, including early detection, risk assessment and screening,” Dr Huang said.

Dr Huang highlighted some of the technique’s features, including automated and fast exosome isolation (less than 5 min of processing time compared to approximately 8 h of processing time using benchmark technologies). Analyses can be performed at relatively low cost and at points of care. Unlike traditional biopsy, it is suitable for repeated and continuous monitoring of tumour progression and treatment. This technique may also help physicians predict which patients will respond well to radiation therapy or achieve longer progression-free survival.

“With these features, the acoustofluidic technology has the potential to significantly exceed current industry standards, address unmet needs in the field, help expedite exosome-related biomedical research and aid in the discovery of new exosomal biomarkers,” Dr Huang said. The technology could also be used to analyse other biofluids such as blood, urine and plasma, the researchers said.

“The saliva exosome liquid biopsy is an effective early detection and risk assessment approach for OPC,” added co-lead investigator Professor David TW Wong from the University of California, Los Angeles. “The acoustofluidic separation technique provides a fast, biocompatible, high-yield, high-purity, label-free method for exosome isolation from saliva.”

Image caption: Acoustofluidic exosome isolation chip for salivary exosome isolation. The microfluidic channel is shown by red dye solution and the coin demonstrates the size of the chip. Two pairs of gold interdigital transducers are deposited along the channel, which separates particles according to size.

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