HPV DNA alone poor biomarker for HPV-driven oropharyngeal cancers

Issue: October 25, 2012

Data from two recent studies of head and neck cancers associated with HPV indicated that HPV DNA alone was an insufficient diagnostic tool and prognostic factor.

Oropharyngeal squamous cell carcinomas (OPSCC) that are associated with HPV infection are linked to more favorable outcomes than those not associated with HPV. However, uncertainty remains surrounding the biomarkers that drive HPV-associated disease, according to Dana Holzinger, PhD, of the division of genome modifications and carcinogenesis at the German Cancer Research Center in Heidelberg, Germany, and colleagues.

In the first study, the researchers analyzed 199 fresh-frozen OPSCC specimens for a variety of potential markers for HPV infection, including:

HPV DNA;
Viral load;
RNA expression patterns typical for cervical carcinomas (CxCaRNA⁺);
HPV-targeted tumor suppressor protein p16^INK4a.

Forty-nine percent of the specimens evaluated contained DNA for HPV16, which is linked to cancer.

However, researchers observed a high viral load in only 16% of specimens, and CxCaRNA⁺ was observed in 20%. Seventy-eight percent of CxCaRNA⁺ tumors demonstrated overexpression of p16^INK4a. Overexpression of p16^INK4a also occurred in 14% of HPV-negative tumors, according to study findings.

Results of a multivariate analysis in which HPV negativity was the reference group indicated that CxCaRNA⁺ was the biomarker associated with the lowest mortality risk (HR=0.28; 95% CI, 0.13-0.61) for oropharyngeal cancer. High viral load conferred an HR of 0.28 (95% CI, 0.14-0.73) for death of oropharyngeal cancer.

The researchers found a weaker inverse association between HPV-positive and p16^INK4a high OPSCC (HR=0.55; 95% CI, 0.29-1.08).

“We showed that high viral load and a cancer-specific pattern of viral gene expression are most suited to identify patients with HPV-driven tumors among patients with oropharyngeal cancer,” Holzinger said in a press release. “Viral expression pattern is a completely new marker in this field and viral load has hardly been analyzed before.”

In the second study, researchers investigated polymerase chain reaction (PCR)-based and serologic HPV assays, as well as p16 immunohistochemistry, as links to survival in those with squamous cell carcinoma of the head and neck.

The analysis included 488 patients. Immunohistochemical detection of p16 expression was conducted in 233 of those patients, and PCR-based methods to assess the presence of HPV16 DNA were used in 179 tumors.

Seropositivity for E6 and E7 proteins was significantly associated with improvements in all-cause survival among patients with oropharyngeal disease, (HR_E6/E7+=0.1; 95% CI, 0.02-0.3).

The researchers observed no improvement in OS in the presence of HPV16 DNA (HR_DNA=0.9, 95% CI, 0.3-2.9) or p16 immunostaining (HR_p16=0.3; 95% CI, 0.1-1.1).

The combination of HPV-positive DNA and E6 or E7 serology was associated with improved OS in oropharyngeal cancer (HR_DNA+/E6/E7+=0.1; 95% CI, 0.02-1.0). Patients with E6/E7 seronegativity who also had evidence of HPV in tumor DNA did not experience improved survival outcomes (HR_DNA+/E6-/E7-=3.4; 95% CI, 0.6-18.1).

Patients with p16 staining and E6 or E7 seropositivity experienced longer OS (HR_p16+/E6/E7+=0.1; 95% CI, 0.02-0.4). However, in patients with p16 positivity and E6/E7 negativity, all-cause death was significantly increased (HR_p16+/E6-/E7-=3.1; 95% CI, 1.2-7.7).

“A stronger association of HPV presence with prognosis (assessed by all-cause survival) is observed when ‘HPV-associated’ SCCHN is defined using tumor status (HPV DNA status or P16) and HPV E6/E7 serology in combination rather using tumor HPV status alone,” the researchers concluded.

“Assessment of HPV DNA using polymerase chain reaction methods as a biomarker in individual head and neck cancers is a poor predictor of outcome and is also poorly associated with antibody response indicative of exposure and/or infection by HPV,” researcher Karl T. Kelsey, MD, professor in the departments of epidemiology, and pathology and laboratory medicine at Brown University in Providence, R.I., said in a press release. “We may not be diagnosing these tumors as accurately and precisely as we need to for adjusting treatments.”

Holzinger added: “Once standardized assays for these markers — applicable in routine clinical laboratories — are established, they will allow precise identification of patients with oropharyngeal cancer with or without HPV-driven cancers and, thus, will influence prognosis and potentially treatment decisions.”

For more information:

Holzinger D. Cancer Res. 2012;doi:10.1158/0008-5472.CAN-11-3934.
Liang C. Cancer Res. 2012;doi:10.1158/0008-5472.CAN-11-3277.