Modifying effect of MDM4 variants on risk of HPV16-associated squamous cell carcinoma of oropharynx

MDM4: What do we know about the association between its polymorphisms and cancer?

MDM4 is an important p53-negative regulator, consequently, it is involved in cell proliferation, DNA repair, and apoptosis regulation. MDM4 overexpression and amplification are described to lead to cancer formation, metastasis, and poor disease prognosis. Several MDM4 SNPs are in non-coding regions, and some affect the MDM4 regulation by disrupting the micro RNA binding site in 3'UTR (untranslated region). Here, we gathered several association studies with different MDM4 SNPs and populations to understand the relationship between its SNPs and solid tumor risk. Many studies failed to replicate their results regarding different populations, cancer types, and risk genotypes, leading to conflicting conclusions. We suggested that distinct haplotype patterns in different populations might affect the association between MDM4 SNPs and cancer risk. Thus, we propose to investigate some linkage SNPs in specific haplotypes to provide informative MDM4 markers for association studies with cancer.

MDM4 polymorphisms associated with the risk but not the prognosis of esophageal cancer in Cixian high-incidence region from northern China

AIM

The mouse double minute 4 (MDM4) may contribute to tumorgenesis by inhibiting p53 tumor suppressor activity. This study was designed to investigate whether MDM4 polymorphisms could affect susceptibility to esophageal squamous cell carcinoma (ESCC) and the survival of ESCC patients in a population from Cixian high-incidence region of northern China, which has not been explored.

METHODS

MDM4 rs1380576 and rs4245739 were genotyped by polymerase chain reaction-ligase detection reaction (PCR-LDR) in 568 ESCC patients and 578 controls.

RESULTS

Compared to rs1380576 C/C genotype, C/G genotype was associated with decreased risk of ESCC (odds ratio [OR] = 0.761, 95% confidence interval [CI] = 0.595-0.973). Compared to rs4245739 A/A genotype, A/C or C/C genotype was related to increased susceptibility to ESCC (OR = 1.551, 95% CI = 1.001-2.402). Individuals with GC haplotype had significantly higher risk of ESCC than those with CA or GA haplotype (OR = 1.598, 95% CI = 1.048-2.438). Neither rs1380576 nor rs4245739 influenced the survival of ESCC patients.

CONCLUSION

rs1380576 and rs4245739 may be used to predict susceptibility to ESCC for population in Cixian high-incidence region.

Five MDM4 gene polymorphisms on cancer risk: An updated systematic review and meta-analysis

PURPOSE

The study aims to provide a comprehensive account of the association of five MDM4 gene polymorphisms (rs1380576, rs1563828, rs10900598, rs11801299, and rs4245739) with susceptibility to cancer.

METHODS

A literature search for eligible candidate gene studies published before 27 February 2021 was conducted in PubMed, Medline and Web of Science. The following combinations of main keywords were used: (MDM4 OR MDMX OR HDMX OR mouse double minute 4 homolog) AND (polymorphism OR mutation OR variation OR SNP OR genotype) AND (cancer OR tumor OR neoplasm OR malignancy OR carcinoma OR adenocarcinoma). Potential sources of heterogeneity were sought out via meta-regression, subgroup and sensitivity analysis.

RESULTS

Overall, a total of 15 articles with 21,365 cases and 29,280 controls for five polymorphisms of the MDM4 gene were enrolled. In the stratified analysis of rs1380576, we found that Asians might have less susceptibility to cancer. We found that rs4245739 was correlated with a decreased risk of cancer for Asians and breast cancer susceptibility. However, for other polymorphisms, the results showed no significant association with cancer risk.

CONCLUSION

MDM4 rs1380576 polymorphism is negatively associated with the risk of cancer in the Asian population. MDM4 rs4245739 polymorphism is inversely associated with cancer risk for Asians and breast cancer susceptibility.

Genome-wide association meta-analysis identifies pleiotropic risk loci for aerodigestive squamous cell cancers

Squamous cell carcinomas (SqCC) of the aerodigestive tract have similar etiological risk factors. Although genetic risk variants for individual cancers have been identified, an agnostic, genome-wide search for shared genetic susceptibility has not been performed. To identify novel and pleotropic SqCC risk variants, we performed a meta-analysis of GWAS data on lung SqCC (LuSqCC), oro/pharyngeal SqCC (OSqCC), laryngeal SqCC (LaSqCC) and esophageal SqCC (ESqCC) cancers, totaling 13,887 cases and 61,961 controls of European ancestry. We identified one novel genome-wide significant (Pmeta<5x10-8) aerodigestive SqCC susceptibility loci in the 2q33.1 region (rs56321285, TMEM273). Additionally, three previously unknown loci reached suggestive significance (Pmeta<5x10-7): 1q32.1 (rs12133735, near MDM4), 5q31.2 (rs13181561, TMEM173) and 19p13.11 (rs61494113, ABHD8). Multiple previously identified loci for aerodigestive SqCC also showed evidence of pleiotropy in at least another SqCC site, these include: 4q23 (ADH1B), 6p21.33 (STK19), 6p21.32 (HLA-DQB1), 9p21.33 (CDKN2B-AS1) and 13q13.1(BRCA2). Gene-based association and gene set enrichment identified a set of 48 SqCC-related genes rel to DNA damage and epigenetic regulation pathways. Our study highlights the importance of cross-cancer analyses to identify pleiotropic risk loci of histology-related cancers arising at distinct anatomical sites.

Combined Effect of HPV and Several Gene SNPs in Laryngeal Cancer

Background and objectives: Laryngeal squamous cell carcinoma (LSCC) is one of the most common head and neck tumors. The molecular mechanism of LSCC remains unclear. The aim of this study was to evaluate the prevalence of Human papillomavirus (HPV) and single nucleotide polymorphisms (SNPs) of TP53, MDM2, MDM4, MTHFR, CASP8, and CCR5 genes in LSCC, and to assess their correlations with patient survival. Materials and Methods: 49 LSCC patients were enrolled in this study. PCR and qRT-PCR were used to detect, identify, and quantify HPV. SNPs were genotyped using PCR and PCR-RFLP. Results: By analyzing the interactions of the SNPs of the genes with clinical parameters, the majority of patients with lymph node status (N1,2) were identified as carriers of MDM2T/G, CASP8ins/del, CCR5wt/wt SNP. Cluster analysis showed that patients with MDM2T/T SNP survive longer than patients identified as CASP8ins/ins, MTHFRC/C, and MDM4A/A variant carriers; meanwhile, LSCC patients with MDM2T/T polymorphic variant had the best survival. Multivariate analysis showed that HPV-positive patients without metastasis in regional lymph nodes (N0) and harboring CASP8ins/del variant had the best survival. Meanwhile, HPV-negative patients with identified metastasis in lymph nodes (N1 and N2) and CASP8ins/del variant had poor survival. Conclusions: This finding suggests patients survival prognosis and tumor behavior are different according HPV status, SNP variants, and clinical characteristics of the LSCC.

A genetic variant within MDM4 3'UTR miRNA binding site is associated with HPV16-positive tumors and survival of oropharyngeal cancer

As mouse double minute 4 (MDM4) and HPV16 E6 oncoproteins play important roles in inhibition of p53 activity, a functional polymorphism (rs4245739) in the 3' untranslated regions of MDM4 targeted by microRNA-191 may alter its expression level or functional efficiency, thus affecting tumor status and survival in human papillomavirus (HPV)-positive squamous cell carcinoma of oropharynx (SCCOP). A total of 564 incident SCCOP patients with definitive radiotherapy were included for determination of tumor HPV16 status and genotypes of the polymorphism. Univariate and multivariable Cox models were performed to assess the associations between the polymorphism and outcomes. We found that MDM4 rs4245739 had statistically significant associations with tumor HPV-positivity and survival of SCCOP patients. Patients with AC/CC variant genotypes of MDM4 rs4245739 were approximately 3-fold more likely to be HPV16-positive tumors among SCCOP patients compared with common homozygous AA genotype (adjusted odds ratio = 3.2, 95% confidence interval = 1.9-5.5). Moreover, patients with MDM4 rs4245739 AC/CC variant genotypes had significantly better overall, disease-specific, and disease-free survival compared with those with the corresponding common homozygous AA genotype (all log-rank = P < .05); and these genotypes were significantly associated with an approximately three to four times reduced risk of overall death, death owing to disease, and recurrence after multivariable adjustment. Finally, the significant effects of MDM4 rs4245739 polymorphism on survival were found among HPV16-positive SCCOP patients only after the stratified analyses by tumor HPV status. We concluded that MDM4 rs4245739 polymorphism is significantly associated with tumor HPV status and survival of SCCOP, especially in HPV16-positive SCCOP patients treated with definitive radiotherapy; nevertheless, prospective larger studies are warranted.

The long and the short of it: the MDM4 tail so far

The mouse double minute 4 (MDM4) is emerging from the shadow of its more famous relative MDM2 and is starting to steal the limelight, largely due to its therapeutic possibilities. MDM4 is a vital regulator of the tumor suppressor p53. It restricts p53 transcriptional activity and also, at least in development, facilitates MDM2's E3 ligase activity toward p53. These functions of MDM4 are critical for normal cell function and a proper response to stress. Their importance for proper cell maintenance and proliferation identifies them as a risk for deregulation associated with the uncontrolled growth of cancer. MDM4 tails are vital for its function, where its N-terminus transactivation domain engages p53 and its C-terminus RING domain binds to MDM2. In this review, we highlight recently identified cellular functions of MDM4 and survey emerging therapies directed to correcting its dysregulation in disease.

Comprehensive Analysis of Long Noncoding RNAs and Messenger RNAs Expression Profiles in Patients with Marjolin Ulcer

Background

Marjolin ulcer (MU) is an aggressive cutaneous malignancy. Typically, MU occurs over a period of time in post-burn and/or post-traumatic lesions and scars. However, the pathogenesis of scar carcinogenesis and MU development remains to be elucidated. The present study aimed to investigate the long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression profiling in MU, which could provide new information on the potential molecular mechanisms of MU development.

Material/Methods

The lncRNA microarray analysis was conducted in normal skin, scar, and MU tissue, and quantitative real-time PCR experiment was carried out to validate the reliability of the microarray data. Furthermore, a series of integrative bioinformatic approaches were applied to decipher the function of differentially expressed lncRNAs.

Results

A total of 7130 lncRNAs and 9867 mRNAs were differentially expressed among normal skin, scar, and MU tissues. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated that these aberrantly expressed transcripts were mainly involved in cell cycle, immune response, and the p53 signaling pathway. Series Test of Cluster analysis indicated certain dysregulated lncRNAs were expressed with a gradually increasing or decreasing trend and might participated in malignant transformation of scar tissue postburn. Co-expression analysis showed 5 selected lncRNAs might regulate cell proliferation through the p53 signaling pathway. Finally, the competing endogenous RNA (ceRNA) network indicated that lncRNA uc001oou.3 might be implicated in ceRNA mechanism during MU development.

Conclusions

Taken together, our study implied the aberrant expression of lncRNAs may play an important role in the pathogenesis and development of MU, and the exact mechanism warrants further investigation.

Comprehensive review of genetic factors contributing to head and neck squamous cell carcinoma development in low-risk, nontraditional patients

BACKGROUND

The past 2 decades have seen an increased incidence of head and neck squamous cell carcinoma (HNSCC) in a nontraditional, low-risk patient population (ie, ≤45 years of age, no substance use history), owing to a combination of human papillomavirus (HPV) infection and individual genetic variation.

METHODS

Articles positing genetic variants as contributing factors in HNSCC incidence in low-risk, nontraditional patients were identified using a PubMed search, reviewed in detail, and concisely summarized herein.

RESULTS

Recent data suggest that common polymorphisms in DNA repair enzymes, cell-cycle control proteins, apoptotic pathway members, and Fanconi anemia-associated genes likely modulate susceptibility to HNSCC development in low-risk, nontraditional patients.

CONCLUSION

At present, there is a lack of robust, comprehensive data on genetic drivers of oncogenesis in low-risk patients and a clear need for further research on genetic alterations underlying the rising incidence of HNSCC in low-risk, nontraditional patients.

The associations between MDM4 gene polymorphisms and cancer risk

Considerable studies have investigated the associations between MDM4 gene polymorphisms and cancer risk recently, but with contradictory results. The aim of this meta-analysis was to evaluate the associations between MDM4 gene polymorphisms and cancer risk. Relevant studies were identified by a systematic search of PubMed, Embase, and CNKI databases. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were used to describe the strength of the associations. Fifty-six studies published in 11 publications involving 18,910 cases and 51,609 controls were included in this meta-analysis. Five MDM4 gene polymorphisms were evaluated: rs4245739, rs1563828, rs11801299, rs10900598, and rs1380576. Our analyses suggested that the rs4245739 polymorphism was significantly associated with overall cancer risk. Furthermore, stratification analyses of ethnicity indicated that rs4245739 decreased the risk of cancer among the Asian population, and stratification analyses of smoking status indicated that rs4245739 decreased the risk of cancer among nonsmokers. However, stratification analyses of cancer type and sex suggested that rs4245739 was not related to cancer risk. There were no associations of rs1563828, rs11801299, rs10900598, or rs1380576 with overall cancer risk. In conclusion, our analyses indicated that rs4245739 polymorphism in the MDM4 gene may play an important role in the etiology of cancer.

Mouse double minute 4 variants modify susceptibility to risk of recurrence in patients with squamous cell carcinoma of the oropharynx

Given the crucial role of Mouse double minute 4 (MDM4) oncoprotein in p53 pathway, single nucleotide polymorphisms (SNPs) could serve as such biomarkers for prediction of SCCOP recurrence. Thus, we investigated associations between three tagging putatively functional variants of MDM4, two in the 3' untranslated region of 3' UTR [rs11801299 (NC_000001.10:g.204529084G>A) and rs10900598(NC_000001.10:g.204525568G>T)] and one in intron 1 [rs1380576(NC_000001.10:g.204488278G>C)], and recurrence risk of SCCOP in 1,008 incident patients. A log-rank test and multivariable Cox models were used to assess associations. Patients with MDM4-rs10900598 GT/TT had a worse disease-free survival (DFS) compared with corresponding GG genotype, while those with rs11801299 AG/AA genotypes had a lower recurrence risk than the cases with rs11801299 GG genotype (both log-rank, P < 0.001). Multivariable analysis showed that significantly different recurrence risk were found among patients with MDM4-rs10900598 GT/TT and rs11801299 AG/AA variant genotypes (HR, 2.0, 95% CI, 1.4-2.9 and HR, 0.4, 95% CI, 0.3-0.6, respectively) compared with their corresponding common homozygous genotypes. Furthermore, after combining the risk genotypes of the three SNPs, patients among low-risk group had a significantly lower risk of SCCOP recurrence than those in high-risk group (HR, 0.2, 95% CI, 0.1-0.3). The risk for both individual SNPs or combined risk genotypes was restricted to HPV-positive SCCOP patients. Our findings suggest that the MDM4 polymorphisms may, individually or in combination, confer an independent risk of SCCOP recurrence, particularly in HPV-positive SCCOP patients. However, larger studies are needed to validate our findings.

MDM4 genetic variants predict HPV16-positive tumors of patients with squamous cell carcinoma of the oropharynx

The increasing incidence of squamous cell carcinoma of the oropharynx (SCCOP) is majorly attributed to the human papillomavirus (HPV) infection. Both HPV and MDM4 play a critical role in inhibition of p53 activity, thus affecting HPV tumor status of SCCOP. Three polymorphisms in MDM4 were genotyped from blood genomic DNA samples and HPV16 status in tumor specimens was examined. Odds ratio (OR) and 95% confidence intervals (CIs) in univariate and multivariable logistic regression models were calculated for the associations between these polymorphisms and HPV16 status. Three MDM4 variant genotypes were significantly associated with HPV16 tumor status among SCCOP patients compared with the common homozygous genotypes (OR, 0.6; 95% CI, 0.4–1.0 for rs10900598; OR, 1.6, 95% CI; 1.1–2.4 for rs1380576; and OR, 1.8, 95% CI, 1.1–2.9 for rs11801299; respectively). When we combined all risk genotypes of the 3 polymorphisms, the patients carrying 1-3 MDM4 risk genotypes were approximately 2.5 time as likely to have an HPV16-positive tumor than those with no risk genotypes (OR, 2.5, 95% CI, 1.6–3.9). Additionally, modifying effect of MDM4 risk genotypes was more pronounced among non-Hispanic white, never-smokers, and never-drinkers. Potential functional polymorphisms in MDM4 may serve as biomarkers for predicting tumor HPV16 status among SCCOP patients, particularly in non-Hispanic white, never-smokers and never-drinkers. However, validation of these results in larger studies is needed.

A PRISMA-compliant meta-analysis of MDM4 genetic variants and cancer susceptibility

Molecular epidemiological research suggests that mouse double minute 4 (MDM4) polymorphisms may be associated with cancer susceptibility, but results remain controversial. To derive a more precise evaluation, we performed a PRISMA compliant meta-analysis focused on five single nucleotide polymorphisms (rs11801299, rs1380576, rs10900598, rs1563828, and rs4245739) of MDM4. Overall, 23 studies involving 22,218 cases and 55,033 controls were analyzed. The results showed that rs4245739 was significantly associated with a decreased cancer risk in the allelic (C vs. A: odds ratio [OR] = 0.848, 95% confidence interval [CI] = 0.765-0.941, P = 0.002), heterozygous (AC vs. AA: OR = 0.831, 95% CI = 0.735-0.939, P = 0.003), and dominant (AC+CC vs. A: OR = 0.823, 95% CI = 0.727-0.932, P = 0.002) models. The association was more prominent in Asians. No significant association was found using any genetic model for the rs11801299, rs1380576, rs10900598, and rs1563828 SNPs. These results indicate that the rs4245739 polymorphism may contribute to a decreased cancer susceptibility and support the hypothesis that genetic variants in the MDM4 genes act as important modifiers of cancer risk.

MDM4 rs4245739 A > C polymorphism correlates with reduced overall cancer risk in a meta-analysis of 69477 subjects

Mouse double minute 4 (MDM4) is a p53-interacting oncoprotein that plays an important role in the p53 tumor suppressor pathway. The common rs4245739 A > C polymorphism creates a miR-191 binding site in the MDM4 gene transcript. Numerous studies have investigated the association between this MDM4 polymorphism and cancer risk, but have failed to reach a definitive conclusion. To address this issue, we conducted a meta-analysis by selecting eligible studies from MEDLINE, EMBASE, and Chinese Biomedical databases. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations. We also performed genotype-based mRNA expression analysis using data from 270 individuals retrieved from public datasets. A total of 15 studies with 19796 cases and 49681 controls were included in the final meta-analysis. The pooled results revealed that the MDM4 rs4245739C allele is associated with a decreased cancer risk in the heterozygous (AC vs. AA: OR = 0.82, 95% CI = 0.73-0.93), dominant (AC/CC vs. AA: OR = 0.82, 95% CI = 0.72-0.93), and allele contrast models (C vs. A: OR = 0.84, 95% CI = 0.76-0.94). The association was more prominent in Asians and population-based studies. We also found that the rs4245739C allele was associated with decreased MDM4 mRNA expression, especially for Caucasians. Thus the MDM4 rs4245739 A > C polymorphism appears to be associated with decreased cancer risk. These findings would be strengthened by new studies with larger sample sizes and encompassing additional ethnicities.

Human papillomavirus and host genetic polymorphisms in carcinogenesis: a systematic review and meta-analysis

BACKGROUND

As the role of human papillomavirus (HPV) in carcinogenesis continues to rise, the role of genetic factors that modify this risk have become increasingly important. In this study, we reviewed the literature for associations between polymorphisms and HPV in carcinogenesis.

OBJECTIVE

To identify any associations of genetic polymorphisms with oncogenic HPV in carcinogenesis and to evaluate the methodology used.

STUDY DESIGN

Systematic literature review of HPV, genetic polymorphisms, and cancer risk. Odds ratios (OR), interaction terms, and p-values were tabulated. Meta-analyses and measures of heterogeneity were estimated using RevMan 5.1.

RESULTS

The cervix was the most frequently studied cancer site followed by the head and neck. Overall risk of cancer (cancer vs. control) was the most common comparison, whereas reports of initiation (pre-cancer vs. control) and progression (cancer vs. pre-cancer) were rare. Case-series and joint-effect of HPV and genotype on risk was evaluated frequently, but the independent effect of either risk factor alone was rarely provided. P53-Arg72Pro was the most commonly studied polymorphism studied. No consistent interaction was detected by meta-analysis in the HPV(+) [OR 0.98 (0.55-1.76)] or the HPV(-) [OR 1.10 (0.76-1.60)] subsets in head and neck cancer risk. Polymorphisms in genes known to encode proteins that physically interact with HPV were infrequently studied.

CONCLUSION

No consistent polymorphism-HPV interactions were observed. Study design, choice of candidate polymorphisms/genes, and a focus on overall risk rather than any specific portions of the carcinogenic pathway may have contributed to lack of significant findings.

Human papillomavirus and diseases of the upper airway: head and neck cancer and respiratory papillomatosis

Human papillomavirus (HPV) infection is causally associated with benign and malignant diseases of the upper airway, including respiratory papillomatosis and oropharyngeal cancer. Low-risk HPV types 6 and 11 are the predominant cause of papillomatosis, whereas only HPV16 definitively satisfies both molecular and epidemiological causal criteria as a carcinogenic or high-risk type in the upper airway. HPV16 E6/E7 mRNA expression and integration are observed predominantly among oropharyngeal cancers, and experimental models have shown E6/E7 expression to be necessary for the initiation and maintenance of the malignant phenotype of these cancers. From an epidemiological perspective, a strong and consistent association between markers of HPV16 exposure and oropharyngeal cancer has been demonstrated in numerous case-control studies. HPV-positive oropharyngeal cancers have also been shown to be distinct from HPV-negative head and neck squamous cell cancers with regard to risk-factor profiles, molecular genetic alterations, population-level incidence trends over time, and prognosis. Tumor HPV status (as determined by certain HPV16 in situ hybridization assays or certain p16 immunohistochemistry assays) is the strongest determinant of survival for patients with local-regionally advanced oropharyngeal cancer: patients with HPV-positive cancer have at least a 50% improvement in overall survival at 5 years, which is equivalent to an approximate 30% difference in absolute survival. Thus, HPV status determination is now part of the routine diagnostic evaluation for prognostication. Preliminary evidence indicates that a small proportion of head and neck cancers may be caused by additional HPV types (e.g., 18, 31, 33, 35) and that HPV-caused cancers may rarely arise from non-oropharyngeal sites (e.g., the oral cavity, nasopharynx, and larynx). Whether or not HPV vaccination has the potential to prevent oral HPV infections that lead to cancer or papillomatosis in the upper airway is currently unknown, as is the potential for secondary prevention with HPV detection. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012.

Combined p53-related genetic variants together with HPV infection increase oral cancer risk

To explore the role of polymorphisms of p53-related genes in etiology of oral cancer, we investigated joint effects of seven putatively functional polymorphisms of p53 (codon 72 Arg/Pro), p73 (4/14 GC/AT), murine double minute 2 gene (MDM2; A2164G and T2580G) and MDM4 (rs11801299 G > A, rs10900598 G > T and rs1380576 C > G) on risk of human papillomavirus (HPV)16-associated oral cancer in a case-control study with 325 cases and 335 cancer-free controls. We found that HPV16 seropositivity alone was associated with an increased risk of oral cancer [adjusted odds ratio (OR), 3.1; 95% confidence interval (CI), 2.1-4.6]. After combining genotypes of seven polymorphisms and using the low-risk group (0-3 combined risk genotypes) and HPV16 seronegativity as the reference group, the medium-risk (4 combined risk genotypes) and high-risk groups (5-7 combined risk genotypes) and HPV16 seronegativity were associated with only an OR of 1.6 (95% CI, 1.1-2.5) and 1.2 (95% CI, 0.7-1.9) for oral cancer risk, respectively, whereas the low-risk, medium-risk and high-risk groups and HPV16 seropositivity were significantly associated with a higher OR of 2.1 (95% CI, 1.2-3.6), 4.0 (95% CI, 1.8-9.1) and 19.1 (95% CI, 5.7-64.2), respectively. Notably, such effect modification by these combined risk genotypes was particularly pronounced in young subjects (aged < 50 years), never smokers and patients with oropharyngeal cancer. Taken together, these findings suggest that the combined risk genotypes of p53-related genes may modify risk of HPV16-associated oral cancer, especially in young patients, never-smokers and patients with oropharyngeal cancer. Larger studies are needed to validate our findings.