Potential Breakthrough in Detecting Cancers Caused by the Oncogenic HPV16

Human papilloma virus (HPV)-induced cancers remain a global health burden, with an estimated seven billion unprotected people at risk and about 400,000 deaths annually. While the overall trend continues upwards, the exponential rise in oropharyngeal squamous cell carcinoma (OPSCC) is particularly concerning[i]^,[ii], with survival rates still low compared to many other cancers. 

In the past, cancer of the oropharynx was largely associated with the use of alcohol or tobacco (defined as HPV negative) but this is now more likely to be linked to HPV. There are more than 120 different HPV strains with the most aggressive subtype, HPV16, responsible for over 90% [iii] of all HPV-related head and neck tumors, and for over half of all cases of cervical cancer. In the US, the number of HPV16-induced OPSCC cases has already overtaken those of cervical cancer.

In most cases, the infection disappears by itself, but the longer HPV16 persists in the lower cell layers of the mucous membrane, the higher the risk of pre-cancerous cell growth.  While HPV infection does not indicate cancer, scientists have suspected for some time that if antibodies were to develop, there may be a link to cancer. Being able to detect them early enough would have a major impact on patient outcomes.

New Biomarker able to Detect Head & Neck Cancers

Previously, no simple, blood-based assay has been available to detect HPV cancer or differentiate an HPV infection from actual HPV-induced malignancy. Evidence from two recent clinical studies changes this, indicating that a breakthrough is on the horizon.  In different cohorts, the studies evaluated the performance of a novel, blood-based biomarker with the potential to detect HPV16-induced cancer, and predict its course, from just a pinprick of blood[iv] ,[v]. The new biomarker also appears to differentiate between HPV positive and HPV negative cancers^v.

The test is based on the immune response to the HPV L1 gene, previously overlooked because it was believed that it was not expressed by an HPV-induced tumor. However, the two-part, pan-European study published in EbioMedicine describes an immunostaining protocol with which it is possible to visualise L1 expression in tumor tissue. It shows that L1 is indeed expressed in HPV-induced OPSCC (other tumor sites were not tested).

Lead investigator Dr. Thomas Weiland, based at the Graz Medical University, Austria, explained: “This is the first time that we have been able to show a link between raised levels of this specific antibody and HPV cancers, indicating the course of disease. This might raise the potential of being able to detect disease recurrence much earlier than current clinical practice.”

The new HPV16 subtype-specific serological assay was recently developed by Abviris and is based on an HPV16, L1-specific proprietary monoclonal antibody.

Studies Confirm Rising Antibody Levels Indicate Cancer

The Weiland study was conducted in two sections across six clinical centers and investigated a total of 1,500 samples, including samples from patients with carcinomas of the head and neck, oral cavity carcinomas, anal carcinomas as well as a healthy control group. It demonstrated a sensitivity of 90-95% for anal and oropharyngeal cancers and a specificity of 99.3%, performance characteristics that are diagnostically significant compared to existing methods for early detection of HPV-induced cancers.

The retrospective study of patients with anal cancer was able to show that high antibody levels indicating anal cancer would have been detected more than six months (293 days) before the tumor had actually been picked up. The second part, a prospective study of OPSCC patients monitored them for two years after treatment, confirming the test’s ability to predict cancer.

The development of blood-based assays to detect clinically relevant HPV-induced disease was previously hampered for a variety of reasons. For a start, it was generally believed that there was no evidence that serum antibodies against L1 were able to discriminate between cancer and simply HPV infection.

Early Evidence of L1 Tumor Expression

The HPV genome contains nine genes (E1-E7, as well as L1 and L2), with most studies focusing on E6 and E7. The common view was that tumor cells did not produce L1.  However, there was clear, early evidence to support L1 expression in tumors.  It was simply not investigated further until now. This can be seen in several studies published over 10 years ago, for instance, one showing that immune cells programmed to kill L1-positive cells were also able to destroy tumor cells - indirectly demonstrating that tumors do express L1 [vi], [vii], [viii].

Abviris has been able to develop its HPV16 subtype-specific serological assay able to overcome specificity concerns. Further, it is easy to use and can be run as a lateral flow rapid test, with a hands-on time of less than five minutes and results are delivered within 20 minutes, all at the point-of-care.

Most people acquire HPV at some point in their lives. The fact that the new test shows a very low rate of positive results among the general population supports the view that it is not picking up transient, subclinical HPV infection but HPV-induced cancer and pre-cancer (which arises only in very few of those infected with HPV).

Improving Tumor Characterization

For those who are diagnosed with a tumor, the correct classification as HPV-induced or non-HPV-induced has wide-ranging consequences for staging, treatment and prognosis – with a financial impact on pathology and clinical budgets.

This is reflected in the most recent edition of the TNM staging guidelines issued by the American Joint Committee on Cancer and the Union for International Cancer Control which recommends stratification of OPSCC by HPV status. 

Currently, there are no methods specifically approved for HPV-detection in head and neck cancers and there is an ongoing debate over which diagnostic tools are the most appropriate. Guidelines recommend staining of tumor tissue for p16, a cellular protein which can be upregulated as a result of HPV activity. However, numerous studies increasingly indicate the limitations of relying on p16 immunochemistry alone as a surrogate marker for indicating HPV status, as some examples of p16 upregulation may be caused by factors other than HPV.  While HPV DNA detection is highly sensitive, it only confirms infection and is not specific enough to determine the causal agent of the disease.

The second of the new studies (Blatt et al.) specifically compared the performance of the new serological marker with the currently available methods for determining whether a tumor is HPV-induced ^v. It found limitations to the p16 method in terms of specificity, showing how p16 staining was found in some tumors that were actually HPV-negative.  In contrast, Blatt reported that the antibody test had an accuracy of 100% in identifying those tumors that were positive for both p16 and HPV16.

Impact on Patient Outcomes

With more than 90% sensitivity, the Abviris antibody test has already enabled scientists in the two separate studies to show that high levels of HPV antibodies in blood do reflect malignancy, indicating the diagnostic potential of the new, CE-marked biomarker test compared to current detection methods. 

But Abviris recognizes that these are early findings and more investigations are required. That is why the protocol for the Weiland et al. findings will now form the basis of a separate and much larger study across multiple hospital sites, with the aim of delivering conclusive evidence of the accuracy of the antibody test in identifying HPV-induced cancers. This expanded clinical study will also look at its ability to monitor the efficacy of treatment first reported by Weiland. 

Improving the early detection of HPV-induced cancers by means of an easy to use, non-invasive test clearly has implications for patients, who currently risk late diagnosis and poor outcomes for these hard to detect cancers. This is going to be especially important when the cancer site is hard to access, or where the source of the primary cancer is unknown or unidentifiable, such as very early metastasis.  

Need to Expand Repertoire of Diagnostic Tools

The remarkable success of cervical cancer screening is primarily due to the fact that the squamous columnar junction is exactly known, limited in size and easy to access. In contrast, approximately 70% of HPV- induced OPSCCs are typically detected only as T3 or T4 late-stage tumors, reducing survival chances. It is almost impossible to gather and examine cells if the cancer is in the crypts of the tonsil, where most HPV- induced OPSCCs are located.  New strategies for earlier detection are urgently needed to overcome the limitations of current methods[ix].

Taken together, the new studies indicate that there is now an additional weapon in the battle against rising levels of HPV-induced cancers – the Abviris antibody test. It is anticipated that the new biomarker test will expand the repertoire of tools available to disease management and clinical professionals, saving resources and reducing costs while improving the outcomes for patients. 

Abviris is actively seeking collaborations with diagnostic partners and investing in additional clinical studies to garner even more evidence of the efficacy of its new biomarker. The potential is wide-reaching, not only in the early detection of the initial HPV cancer and as a more effective way of differentiating between HPV- positive and HPV-negative cases - but also in post-treatment monitoring. 

 

About the Author: 

Dr. Anna Huber is the Head of Medical Affairs at Abviris GmbH