Investigation of EZH2 pathways for novel epigenetic treatment strategies in oropharyngeal cancer

Methyltransferase-independent function of enhancer of zeste homologue 2 maintains tumorigenicity induced by human oncogenic papillomavirus and polyomavirus

Merkel cell polyomavirus (MCV) and high-risk human papillomavirus (HPV) are human tumor viruses that cause Merkel cell carcinoma (MCC) and oropharyngeal squamous cell carcinoma (OSCC), respectively. HPV E7 and MCV large T (LT) oncoproteins target the retinoblastoma tumor suppressor protein (pRb) through the conserved LxCxE motif. We identified enhancer of zeste homolog 2 (EZH2) as a common host oncoprotein activated by both viral oncoproteins through the pRb binding motif. EZH2 is a catalytic subunit of the polycomb 2 (PRC2) complex that trimethylates histone H3 at lysine 27 (H3K27me3). In MCC tissues EZH2 was highly expressed, irrespective of MCV status. Loss-of-function studies revealed that viral HPV E6/E7 and T antigen expression are required for Ezh2 mRNA expression and that EZH2 is essential for HPV(+)OSCC and MCV(+)MCC cell growth. Furthermore, EZH2 protein degraders reduced cell viability efficiently and rapidly in HPV(+)OSCC and MCV(+)MCC cells, whereas EZH2 histone methyltransferase inhibitors did not affect cell proliferation or viability within the same treatment period. These results suggest that a methyltransferase-independent function of EZH2 contributes to tumorigenesis downstream of two viral oncoproteins, and that direct targeting of EZH2 protein expression could be a promising strategy for the inhibition of tumor growth in HPV(+)OSCC and MCV(+)MCC patients.

Epigenetic and Transcriptomic Regulation Landscape in HPV+ Cancers: Biological and Clinical Implications

Human Papillomavirus (HPV) is an oncogenic virus that causes the highest number of viral-associated cancer cases and deaths worldwide, with more than 690,000 new cases per year and 342,000 deaths only for cervical cancer (CC). Although the incidence and mortality rates for CC are declining in countries where screening and vaccination programs have been implemented, other types of cancer in which HPV is involved, such as oropharyngeal cancer, are increasing, particularly in men. Mutational and transcriptional profiles of various HPV-associated neoplasms have been described, and accumulated evidence has shown the oncogenic capacity of E6, E7, and E5 genes of high-risk HPV. Interestingly, transcriptomic analysis has revealed that although a vast majority of the human genome is transcribed into RNAs, only 2% of transcripts are translated into proteins. The remaining transcripts lacking protein-coding potential are called non-coding RNAs. In addition to the transfer and ribosomal RNAs, there are regulatory non-coding RNAs classified according to size and structure in long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and small RNAs; such as microRNAs (miRNAs), piwi-associated RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and endogenous short-interfering RNAs. Recent evidence has shown that lncRNAs, miRNAs, and circRNAs are aberrantly expressed under pathological conditions such as cancer. In addition, those transcripts are dysregulated in HPV-related neoplasms, and their expression correlates with tumor progression, metastasis, poor prognosis, and recurrence. Nuclear lncRNAs are epigenetic regulators involved in controlling gene expression at the transcriptional level through chromatin modification and remodeling. Moreover, disruption of the expression profiles of those lncRNAs affects multiple biological processes such as cell proliferation, apoptosis, and migration. This review highlights the epigenetic alterations induced by HPV, from infection to neoplastic transformation. We condense the epigenetic role of non-coding RNA alterations and their potential as biomarkers in transformation's early stages and clinical applications. We also summarize the molecular mechanisms of action of nuclear lncRNAs to understand better their role in the epigenetic control of gene expression and how they can drive the malignant phenotype of HPV-related neoplasia. Finally, we review several chemical and epigenetic therapy options to prevent and treat HPV-associated neoplasms.

High Risk-Human Papillomavirus in HNSCC: Present and Future Challenges for Epigenetic Therapies

Head and Neck Squamous Cell Carcinoma (HNSCC) is a highly heterogeneous group of tumors characterized by an incidence of 650,000 new cases and 350,000 deaths per year worldwide and a male to female ratio of 3:1. The main risk factors are alcohol and tobacco consumption and Human Papillomavirus (HPV) infections. HNSCC cases are divided into two subgroups, the HPV-negative (HPV−) and the HPV-positive (HPV+) which have different clinicopathological and molecular profiles. However, patients are still treated with the same therapeutic regimens. It is thus of utmost importance to characterize the molecular mechanisms underlying these differences to find new biomarkers and novel therapeutic targets towards personalized therapies. Epigenetic alterations are a hallmark of cancer and can be exploited as both promising biomarkers and potential new targets. E6 and E7 HPV oncoviral proteins besides targeting p53 and pRb, impair the expression and the activity of several epigenetic regulators. While alterations in DNA methylation patterns have been well described in HPV+ and HPV− HNSCC, accurate histone post-translational modifications (hPTMs) characterization is still missing. Herein, we aim to provide an updated overview on the impact of HPV on the hPTMs landscape in HNSCC. Moreover, we will also discuss the sex and gender bias in HNSCC and how the epigenetic machinery could be involved in this process, and the importance of taking into account sex and/or gender also in this field.

Histone modifiers at the crossroads of oncolytic and oncogenic viruses

Cancer is a disease caused by loss of regulatory processes that control cell cycle, resulting in increased proliferation. The loss of control can deregulate both tumor suppressors and oncogenes. Apart from cell intrinsic gene mutations and environmental factors, infection by cancer-causing viruses also induces changes that lead to malignant transformation. This can be caused by both expression of oncogenic viral proteins and also by changes in cellular genes and proteins that affect the epigenome. Thus, these epigenetic modifiers are good therapeutic targets, and several epigenetic inhibitors are approved for the treatment of different cancers. In addition to small molecule drugs, biological therapies such as antibodies and viral therapies are also increasingly being used to treat cancer. An HSV-1 derived oncolytic virus is currently approved by the US FDA and the European Medicines Agency. Similarly, an adenovirus-based therapeutic is approved for use in China for some cancer types. Since viruses can affect cellular epigenetics, the interaction of epigenome-targeting drugs with oncogenic and oncolytic viruses is a highly significant area of investigation. Here we will review the current knowledge about the impact of using epigenetic drugs in tumors positive for oncogenic viruses or as therapeutic combinations with oncolytic viruses.

ZNF750 exerted its Antitumor Action in Oral Squamous Cell Carcinoma by regulating E2F2

Cell cycle activator E2F transcription factor 2 (E2F2) play a key role in tumor development and metastasis. Previous RNA sequence analysis (GSE134835) revealed E2F2 was significantly reduced by Zinc-finger protein 750 (ZNF750) in oral squamous cell carcinoma (OSCC). This study was aimed to determine the involvement of E2F2 in antitumor action of ZNF750. The nude mouse xenograft model was established by subcutaneously injection of stable cell line CAL-27^oeZNF750 or CAL-27^shZNF750. Xenograft tumor volume and tumor weight was measured. The expression of E2F2, transcriptional repressors such as enhancer of zeste 2 (Ezh2), PHD finger protein 19 (PHF19), and the genes related to cell proliferation or metastasis was studied in vivo or in vitro. Luciferase assay was performed to investigate regulation effect of ZNF750 on E2F2 luciferase activity. The involvement of E2F2 in the antitumor action of ZNF750 was studied by cotransduced ZNF750 with E2F2 lentivirus. The tumor growth and metastasis was repressed by ZNF750 manifested by reduced tumor size, tumor weight and the genes related to cell proliferation and metastasis. However, all of these were reversed by knockdown of the ZNF750 gene. Furthermore, E2F2 luciferase activity was inhibited by ZNF750. E2F2 partly blocked the antitumor action of ZNF750 manifested by increased self-renewal, invasion, migration, elevated Ezh2 and MMP13 protein expression in ZNF750 + E2F2 groups. However, silenced E2F2 further enhanced the antitumor action of ZNF750. ZNF750 depressed E2F2 activity and played a critical role in regulating transcriptional repressors for inhibiting the OSCC growth and metastasis in OSCC.

Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis

Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.

Vulvar Squamous Cell Carcinoma: Comprehensive Genomic Profiling of HPV+ Versus HPV- Forms Reveals Distinct Sets of Potentially Actionable Molecular Targets

PURPOSE

Vulvar squamous cell carcinoma (vSCC) encompasses two predominant variants: one associated with detectable high-risk strains of human papillomavirus (hrHPV) and a second form often occurring in the context of chronic dermatitis in postmenopausal women. Genomic assessment of a large-scale cohort of patients with aggressive vSCC may identify distinct mutational signatures.

MATERIALS AND METHODS

Tumor samples from a total of 280 patients with vSCC underwent hybridization capture with analysis of up to 406 cancer-related genes. Human papillomavirus (HPV) sequences were detected by de novo assembly of nonhuman sequencing reads and aligned to the RefSeq database. Immunohistochemistry for programmed death-ligand 1 (PD-L1) was assessed.

RESULTS

One hundred two of 280 vSCCs (36%) contained hrHPV sequences, predominantly HPV 16 (88%). The HPV-positive (HPV+) group was significantly younger (median age, 59 v 64 years; P = .001). Compared with HPV-negative (HPV–) vSCCs, HPV+ tumors showed more frequent pathogenic alterations in PIK3CA (31% v 16%; P = .004), PTEN (14% v 2%; P < .0001), EP300 (14% v 1%; P < .0001), STK11 (14% v 1%; P < .0001), AR (5% v 0%; P = .006), and FBXW7 (10% v 3%; P = .03). In contrast, HPV– vSCCs showed more alterations in TP53 (83% v 6%; P < .0001), TERTp (71% v 9%; P < .0001), CDKN2A (55% v 2%; P < .0001), CCND1 amplification (22% v 2%; P < .0001), FAT1 (25% v 4%; P < .0001), NOTCH1 (19% v 6%; P = .002), and EGFR amplification (11% v 0%; P < .0001), as well as a higher rate of 9p24.1 (PDL1/PDL2) amplification (5% v 1%) and PD-L1 immunohistochemistry high-positive tumor staining (33% v 9%; P = .04).

CONCLUSION

Comprehensive molecular profiles of vSCC vary considerably with hrHPV status and may inform patient selection into clinical trials. Sixty-one percent of HPV+ vSCCs had a pathogenic alteration in the PI3K/mTOR pathway, whereas HPV– vSCCs showed alterations in TP53, TERTp, CDKN2A, CCND1, and EGFR, and biomarkers associated with responsiveness to immunotherapy.

Epigenetic Modulators as Potential Multi-targeted Drugs Against Hedgehog Pathway for Treatment of Cancer

The Sonic hedgehog signalling is known to play a crucial role in regulating embryonic development, cancer stem cell maintenance and tissue patterning. Dysregulated hedgehog signalling has been reported to affect tumorigenesis and drug response in various human malignancies. Epigenetic therapy relying on DNA methyltransferase and Histone deacetylase inhibitors are being proposed as potential drug candidates considering their efficiency in preventing development of cancer progenitor cells, killing drug resistant cells and also dictating "on/off" switch of tumor suppressor genes and oncogenes. In this docking approach, epigenetic modulators were virtually screened for their efficiency in inhibiting key regulators of SHH pathway viz., sonic hedgehog, Smoothened and Gli using polypharmacological approach. The control drugs and epigenetic modulators were docked with PDB protein structures using AutoDock vina and further checked for their drug-likeness properties. Further molecular dynamics simulation using VMD and NAMD, and MMP/GBSA energy calculation were employed for verifying the stability and entropy of the ligand-receptor complex. EPZ-6438 and GSK 343 (EZH2 inhibitors), CHR 3996 and Mocetinostat (HDAC inhibitors), GSK 126 (HKMT inhibitor) and UNC 1215 (L3MBTL3 antagonist) exhibited multiple-targeted approach in modulating HH signalling. This is the first study to report these epigenetic drugs as potential multi-targeted hedgehog pathway inhibitors. Thus, epigenetic polypharmacology approach can be explored as a better alternative to challenges of acute long term toxicity and drug resistance occurring due to traditional single targeted chemotherapy in the future.

Long-term survival and swallowing outcomes in advanced stage oropharyngeal squamous cell carcinomas

BACKGROUND

There is a paucity of studies reporting long-term survival outcomes for HPV/p16 positive oropharyngeal squamous cell carcinoma (OPSCC). This study aims to compare long-term outcomes of advanced stage p16 positive and negative OPSCCs, treated by surgical and non-surgical modalities.

METHODS

OPSCC patients from 1998 to 2012 were identified through a prospectively collected cancer registry. P16 immunohistochemistry was used as a surrogate marker for HPV-OPSCC. Overall survival (OS) and aspiration free survival (AFS) comparisons were made between patients treated with chemoradiation (CRT) versus primary surgery and radiation/chemoradiation (S+RT/CRT) at 5, 10 and 15 years post-treatment.

RESULTS

A total of 319 patients were included. P16 positive patients and non-smokers had significantly higher long-term (5, 10 and 15-year) OS. Smokers and p16 negative patients treated with S+RT/CRT had improved long-term OS compared to patients who received CRT. Smokers and p16 negative patients had lower long-term AFS. Multivariate analysis showed improved OS was associated with p16 positivity (HR 0.42, 0.28-0.61) and surgery (HR 0.47, 0.32-0.69), whereas lower OS was associated with ECOG ≥ 2 (HR 2.46, 1.61-3.77), smoking (HR 2.37, 1.41-3.99) and higher stage (HR 1.68, 1.05-2.68).

CONCLUSIONS

In smokers and p16-negative OPSCC patients, primary surgery may be associated with improved long-term survival and dysphagia-related outcomes.

EZH2 Inhibition Ameliorates Transverse Aortic Constriction-Induced Pulmonary Arterial Hypertension in Mice

Background

EPZ005687 is a selective inhibiter of methyltransferase EZH2. In this article, we investigated the protective role and mechanism of EPZ005687 in transverse aortic constriction-induced pulmonary arterial hypertension in mice.

Methods

We assigned 15 (6–8 weeks old) male balb/c mice to 3 groups randomly: Sham control + DMSO group, TAC + DMSO group, and TAC + EPZ005687 group (10 mg kg⁻¹, once a week for 4 weeks). On day 28 following TAC operation, the right ventricular systolic blood pressure (RVSBP) was measured, and lung tissues were collected for laboratory examinations (DHE, Western blot, real-time PCR, and ChIP).

Results

Murine PAH model was successfully created by TAC operation as evidenced by increased RVSBP and hypertrophic right ventricle. Compared with the sham control, TAC-induced PAH markedly upregulated the expression of EZH2 and ROS deposition in lungs in PAH mice. The inhibiter of methyltransferase EZH2, EPZ005687 significantly inhibits the development of TAC-induced PAH in an EZH2-SOD1-ROS dependent manner.

Conclusion

Our data identified that EZH2 serves a fundamental role in TAC-induced PAH, and administration of EPZ005687 might represent a novel therapeutic target for the treatment of TAC-induced PAH.

Novel insights into epigenetic drivers of oropharyngeal squamous cell carcinoma: role of HPV and lifestyle factors

In the last years, the explosion of high throughput sequencing technologies has enabled epigenome-wide analyses, allowing a more comprehensive overview of the oropharyngeal squamous cell carcinoma (OPSCC) epigenetic landscape. In this setting, the cellular pathways contributing to the neoplastic phenotype, including cell cycle regulation, cell signaling, DNA repair, and apoptosis have been demonstrated to be potential targets of epigenetic alterations in OPSCC. Of note, it has becoming increasingly clear that HPV infection and OPSCC lifestyle risk factors differently drive the epigenetic machinery in cancer cells. Epigenetic changes, including DNA methylation, histone modifications, and non-coding RNA expression, can be used as powerful and reliable tools for early diagnosis of OPSCC patients and improve prognostication. Since epigenetic changes are dynamic and reversible, epigenetic enzymes may also represent suitable targets for the development of more effective OPSCC therapeutic strategies. Thus, this review will focus on the main known epigenetic modifications that can occur in OPSCC and their exploitation as potential biomarkers and therapeutic targets. Furthermore, we will address epigenetic alterations to OPSCC risk factors, with a particular focus on HPV infection, tobacco exposure, and heavy alcohol consumption.

Efficacy of EZH2 inhibitory drugs in human papillomavirus-positive and human papillomavirus-negative oropharyngeal squamous cell carcinomas

Background

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer worldwide with rates of HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) dramatically increasing. The overexpression of enhancer of zeste homolog 2 (EZH2), a histone methyltransferase responsible for the trimethylation at lysine 27 of histone 3 (H3K27me3), is associated with a poor clinical prognosis and aggressive HPV-positive phenotypes.

Methods

We utilized three EZH2 pathway inhibitors, GSK-343, DZNeP, and EPZ-5687, and tested their efficacy in two HPV-positive and two HPV-negative OPSCC cell lines.

Results

Treatment with GSK-343 decreased H3K27me3 in all cell lines and treatment with DZNeP decreased H3K27me3 in only HPV-negative cell lines as determined by Western blot. Cells treated with EPZ-5687 displayed no appreciable change in H3K27me3. Epigenetic effect on gene expression was measured via ddPCR utilizing 11 target probes. Cells treated with DZNeP showed the most dramatic expressional changes, with decreased EGFR in HPV-positive cell lines and an overall increase in proliferation markers in HPV-negative cell lines. GSK-343-treated cells displayed moderate expressional changes, with CCND1 increased in HPV-positive cell lines and decreased TP53 in HPV-negative SCC-1. EPZ-5687-treated cell lines displayed few expressional changes overall. Only DZNeP-treated cells displayed anti-proliferative characteristics shown in wound-healing assays.

Conclusions

Our findings suggest that EZH2 inhibitors are a viable therapeutic option for the role of epigenetic effect, potentially sensitizing tumors to current chemotherapies or limiting cell differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0390-y) contains supplementary material, which is available to authorized users.

Morphoproteomics, E6/E7 in-situ hybridization, and biomedical analytics define the etiopathogenesis of HPV-associated oropharyngeal carcinoma and provide targeted therapeutic options

BACKGROUND

Human papillomavirus (HPV) has been identified as an etiopathogenetic factor in oropharyngeal squamous cell carcinoma. The HPV E6 and E7 oncogenes are instrumental in promoting proliferation and blocking differentiation leading to tumorigenesis. Although surgical intervention can remove such tumors, the potential for an etiologic field effect with recurrent disease is real. A downstream effector of E7 oncoprotein, enhancer of zeste homolog 2 (EZH2), is known to promote proliferation and to pose a block in differentiation and in turn, could lead to HPV-induced malignant transformation. However, the EZH2 pathway is amenable to low toxicity therapies designed to promote differentiation to a more benign state and prevent recurrent disease by inhibiting the incorporation of HPV into the genome. This is the first study using clinical specimens to demonstrate EZH2 protein expression in oropharyngeal carcinoma (OPC).

METHODS

The study included eight patients with oropharyngeal carcinoma, confirmed p16INK4a- positive by immunohistochemistry (IHC). The tissue expression of E6/E7 messenger RNA (mRNA) was measured by RNAscope® in-situ hybridization technology. Expression of EZH2, Ki-67, and mitotic indices were assessed by morphoproteomic analysis. Biomedical analytics expanded the results with data from Ingenuity Pathway Analysis (IPA) and KEGG databases to construct a molecular network pathway for further insights.

RESULTS

Expression of E6 and E7 oncogenes in p16INK4a- positive oropharyngeal carcinoma was confirmed. EZH2 and its correlates, including elevated proliferation index (Ki-67) and mitotic progression were also present. Biomedical analytics validated the relationship between HPV- E6 and E7 and the expression of the EZH2 pathway.

CONCLUSION

There is morphoproteomic and mRNA evidence of the association of p16INK4a-HPV infection with the E6 and E7 oncogenes and the expression of EZH2, Ki-67 and mitotic progression in oropharyngeal carcinoma. The molecular network biology was confirmed by biomedical analytics as consistent with published literature. This is significant because the biology lends itself to targeted therapeutic options using metformin, curcumin, celecoxib and sulforaphane as therapeutic strategies to prevent progression or recurrence of disease.

Transoral robotic surgery with radial forearm free flap reconstruction: case control analysis

Background

The resection of large oropharyngeal tumors traditionally involves a lip-splitting mandibulotomy for adequate margin visualization and free flap reconstruction of the surgical defect. Transoral robotic surgery (TORS) has emerged as a technique that can resect large and complex oropharyngeal tumors, avoiding a lip-splitting approach. The aim of this study is to compare the lip-splitting mandibulotomy approach versus TORS for the management of advanced stage oropharyngeal carcinomas.

Methods

Prospectively collected data from 18 patients with advanced stage oropharyngeal squamous cell carcinoma (OPSCC) who received TORS with radial forearm free flap reconstruction (RFFF) was compared to a matched cohort of 39 patients who received a lip-splitting mandibulotomy and RFFF. Patients were matched for stage, p16 positivity, smoking, age and gender. Length of hospital stay (LOHS), tracheostomy decanulation time, operative time, surgical margin status, and post-operative complications were compared between groups.

Results

Patients who received TORS with RFFF had a significantly lower mean LOHS, compared to patients who were treated by lip-splitting mandibulotomy and RFFF (14.4 vs 19.7 days, p = 0.03). No significant differences were seen between groups in terms of operative time, tracheostomy decannulation time, margin positivity and post-operative complications.

Conclusion

TORS with radial forearm free flap reconstruction is a safe, effective and cost-saving alternative to the lip-splitting mandibulotomy approach for the treatment of advanced stage OPSCC.

Epigenetics of oropharyngeal squamous cell carcinoma: opportunities for novel chemotherapeutic targets

Epigenetic modifications are heritable changes in gene expression that do not directly alter DNA sequence. These modifications include DNA methylation, histone post-translational modifications, small and non-coding RNAs. Alterations in epigenetic profiles cause deregulation of fundamental gene expression pathways associated with carcinogenesis. The role of epigenetics in oropharyngeal squamous cell carcinoma (OPSCC) has recently been recognized, with implications for novel biomarkers, molecular diagnostics and chemotherapeutics. In this review, important epigenetic pathways in human papillomavirus (HPV) positive and negative OPSCC are summarized, as well as the potential clinical utility of this knowledge.This material has never been published and is not currently under evaluation in any other peer-reviewed publication.

Ultrasensitive detection of oncogenic human papillomavirus in oropharyngeal tissue swabs

BACKGROUND

The incidence of oropharyngeal squamous cell carcinoma (OPSCC) caused by oncogenic human papillomavirus (HPV) is rising worldwide. HPV-OPSCC is commonly diagnosed by RT-qPCR of HPV E6 and E7 oncoproteins or by p16 immunohistochemistry (IHC). Droplet digital PCR (ddPCR) has been recently reported as an ultra-sensitive and highly precise method of nucleic acid quantification for biomarker analysis. To validate the use of a minimally invasive assay for detection of oncogenic HPV based on oropharyngeal swabs using ddPCR. Secondary objectives were to compare the accuracy of ddPCR swabs to fresh tissue p16 IHC and RT-qPCR, and to compare the cost of ddPCR with p16 IHC.

METHODS

We prospectively included patients with p16⁺ oral cavity/oropharyngeal cancer (OC/OPSCC), and two control groups: p16^- OC/OPSCC patients, and healthy controls undergoing tonsillectomy. All underwent an oropharyngeal swab with ddPCR for quantitative detection of E6 and E7 mRNA. Surgical specimens had p16 IHC performed. Agreement between ddPCR and p16 IHC was determined for patients with p16 positive and negative OC/OPSCC as well as for healthy control patients. The sensitivity and specificity of ddPCR of oropharyngeal swabs were calculated against p16 IHC for OPSCC.

RESULTS

122 patients were included: 36 patients with p16⁺OPSCC, 16 patients with p16^-OPSCC, 4 patients with p16⁺OCSCC, 41 patients with p16^-OCSCC, and 25 healthy controls. The sensitivity and specificity of ddPCR of oropharyngeal swabs against p16 IHC were 92 and 98% respectively, using 20-50 times less RNA than that required for conventional RT-qPCR. Overall agreement between ddPCR of tissue swabs and p16 of tumor tissue was high at ĸ = 0.826 [0.662-0.989].

CONCLUSION

Oropharyngeal swabs analyzed by ddPCR is a quantitative, rapid, and effective method for minimally invasive oncogenic HPV detection. This assay represents the most sensitive and accurate mode of HPV detection in OPSCC without a tissue biopsy in the available literature.