Biological relevance of human papillomaviruses in vulvar cancer

Abstract

The carcinogenic role of high-risk human papillomavirus (HR-HPV) types in the increasing subset of vulvar intraepithelial neoplasia and vulvar cancer in young women has been established. However, the actual number of vulvar cancer cases attributed to HPV is still imprecisely defined. In an attempt to provide a more precise definition of HPV-driven vulvar cancer, we performed HPV-type-specific E6*I mRNA analyses available for 20 HR-/possible HR (pHR)-HPV types, on tissue samples from 447 cases of vulvar cancer. HPV DNA genotyping was performed using SPF10-LiPA assay due to its high sensitivity in formalin-fixed paraffin-embedded tissues. Data on p16 expression was available for comparative analysis via kappa statistics. The use of highly sensitive assays covering the detection of HPV mRNA in a broad spectrum of mucosal HPV types resulted in the detection of viral transcripts in 87% of HPV DNA+ vulvar cancers. Overall concordance between HPV mRNA+ and p16 upregulation (strong, diffuse immunostaining in >25% of tumor cells) was 92% (K=0.625, 95% confidence interval (CI)=0.531-0.719). Among these cases, 83% were concordant pairs of HPV mRNA+ and p16+ and 9% were concordant pairs of HPV mRNA- and p16-. Our data confirm the biological role of HR-/pHR-HPV types in the great majority of HPV DNA+ vulvar cancers, resulting in an HPV-attributable fraction of at least 21% worldwide. Most HPV DNA+ vulvar cancers were associated with HPV16 (85%), but a causative role for other, less frequently occurring mucosal HPV types (HPV26, 66, 67, 68, 70 and 73) was also confirmed at the mRNA level for the first time. These findings should be taken into consideration for future screening options as HPV-associated vulvar preneoplastic lesions have increased in incidence in younger women and require different treatment than vulvar lesions that develop from rare autoimmune-related mechanisms in older women.

"Histological characteristics of HPV‐associated and ‐independent squamous cell carcinomas of the vulva: A study of 1,594 cases”

“…The main strength of our study is that it includes a very high number of VSCC, and in all the cases, a detailed histological review and thorough molecular analysis including HPV DNA, mRNA and p16 were performed. The correlation of all the data allowed the study to obtain more accurate evidence of HPV involvement in the large series of tumors …”

“…All tumors were stained with p16 monoclonal antibody using the CINtec Histology Kit (clone E6H4; Roche‐Mtm‐Laboratories, Heidelberg, Germany) . Only cases showing positivity in >25% of tumor cells with strong and diffuse block staining of the basal layer were considered as positive (p16 INK4a upregulation) …”

“…The mRNA extraction and mRNA detection from tissue ribbons were performed as previously described . For each case, HPV type‐specific E6*I mRNA RT‐PCR assays were performed for the HPV type(s) previously determined by genotyping and for a cellular ubiquitin C gene as a control for tissue quality.…”

“…Recently, the combination of two markers has been proposed as a reliable tool to provide robust results in terms of HPV status . In this strategy, tumors positive for HPV DNA and p16 would be indisputably HPV‐associated, whereas tumors negative for the two biomarkers would be classified as unquestionably HPV‐independent.…”

Insertional oncogenesis by HPV70 revealed by multiple genomic analyses in a clinically HPV‐negative cervical cancer

“…Population screening for HPV is based on demanding sensitivity and specificity criteria that balance clinical benefit with increased morbidity risk, emotional duress, and monetary costs of additional follow‐up screening of individuals who test positive. While the limitations of screening tests for detection of HPV types that cause tumors of infrequent or unknown incidence have long been recognized, and broadly based HPV analyses of tumors have suggested roles for non‐hrHPVs in oncogenesis in a minority of tumors broader HPV type screening would create substantial burdens . Nonetheless, it is important to be aware that screening based solely on hrHPV detection may miss a small fraction of at risk individuals such as the patient described here, where the L1 gene PCR target may be deleted or may lack sufficient sequence homology for recognition.…”