Evidence of association of human papillomavirus with prognosis worsening in glioblastoma multiforme

Abstract

Background: Glioblastoma multiforme (GBM) is the most malignant brain tumor in adults, but its etiology still remains unknown. Recently, a role of viruses such as cytomegalovirus and JC virus in gliomagenesis has been suggested. Since human papillomavirus (HPV) is considered the most common oncogenic virus in humans, we evaluated its occurrence in GBM samples.

Material and methods: Fifty-two formalin-fixed paraffin-embedded primary glioblastoma specimens were retrospectively analyzed. The presence of HPV genome on tumor DNA was assessed by MY/GP nested PCR. Confirmation of HPV detection was obtained by chromogenic in situ hybridization (CISH) and immunohistochemistry (IHC) with an antibody directed against the L1 capsidic protein. Finally, univariate and multivariate proportional-hazards models were used to compare the risk of death among HPV-positive and HPV-negative patients.

Results: Strikingly, viral DNA was detected after PCR in 12 cases (23%). HPV16 genome was present in 25% infected samples, whereas the remaining samples tested positive for HPV6. CISH confirmed positivity in all infected samples for which enough material was available. Moreover, IHC positivity suggested that production of viral proteins from HPV genome is an ongoing process in GBM cancer cells. Finally an association between HPV infection and a worse prognosis was found in patients upon age stratification with a univariate analysis (HR, 2.10; 95% CI, 1.00-4.44; log-rank P = .045).

Conclusions: HPV infection status may be considered an independent prognostic factor in GBM patients and suggests that prevention may be considered, should HPV be recognized as a causative agent in gliomagenesis.

Keywords: HPV; glioblastoma multiforme; prognosis.

Fig. 1.

(A) Pairwise alignment between the HPV L1 protein sequence and the query obtained translating the nucleotide sequence detected by PCR (see methods). (B) Chromogenic in situ hybridization of a HPV-positive case (left panel) and a HPV-negative control (right panel); the arrow indicates the nucleus of an endothelial cell showing positivity. (C) Immunohistochemistry staining for L1 capsidic protein. The left panel shows a positive case that displays a classical nuclear positivity to L1 compared to the negative control (right panel). (D) Kaplan–Meier estimates of the survival among GBM patients under study according to HPV status. Patients with HPV-positive tumors have a worse median overall survival than patients with HPV negative tumors (median overall survival 7.3 vs. 11 months; log-rank test P = .19). (E) Kaplan–Meier estimates of the survival among GBM patients according to HPV status within the subset of patients older than 50 (log-rank P = .045, median overall survival = 7.3 vs. 11). (F) Summary of the clinical characteristics of HPV-positive and HPV-negative patient subgroups. P values were calculated with t-test or Fisher's exact test.