Measuring Anti-HPV Protein Levels to Predict Recurrence of Oropharyngeal Cancer

Human papilloma virus (HPV)-associated cancers are caused by the expression of HPV's E6 and E7 proteins that bind to and inactivate tumor suppressor proteins p53 and retinoblastoma protein (pRB), respectively, leading to malignant transformation of HPV infected cells. The two proteins are highly immunogenic, resulting in readily detected serum antibodies.

Investigators at the University of Michigan (Ann Arbor, USA) carried out a study to determine if serum E6 and E7 antibody levels could potentially serve as a biomarker of recurrence in patients with oropharyngeal squamous cell carcinoma (OPSCC) caused by HPV. To this end they used a glutathione-S-transferase capture ELISA to compare E6/E7 antibody levels in 22 HPV+OPSCC patients who developed recurrence to 30 patients who remained disease-free. The two groups were similar in age, cancer classification, and smoking status. All tumors were linked to HPV.

Results revealed that recurrent patients had significantly higher E6 and E7 serum antibody levels than the non-recurrent patients over the follow-up period. Patients who recurred had a lower clearance of E7 antibody than patients who remained disease free.

"The key is to look at the ratio of E7 antibodies. Every patient had a different baseline level, and the absolute level is not an indication", said first author Dr. Matthew E. Spector, assistant professor of otolaryngology at the University of Michigan. "Most patients recur within the first two years, so the window to catch it is two years after treatment. Everyone's level goes down over time, but some start to go up a little - and those are the ones we have to focus on. If we can monitor someone through blood markers, then instead of a patient coming for a clinic visit every two to three months, they could get blood drawn near home. If there is evidence of high E7, we can tell the patient to come in for more evaluation. It is very patient-specific. Each patient will have different levels, but the question is what happens when you track it over time. If it rises, that suggests recurrence."

The study was published in the November 21, 2016, online edition of the journal Clinical Cancer Research.

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