Coupling and regulation mechanisms of the flavin-dependent halogenase PyrH observed by infrared difference spectroscopy.

Flavin-dependent halogenases are central enzymes in the production of halogenated secondary metabolites in various organisms and they constitute highly promising biocatalysts for regioselective halogenation. The mechanism of these monooxygenases includes formation of hypohalous acid from a reaction of fully reduced flavin with oxygen and halide. The hypohalous acid then diffuses via a tunnel to the substrate-binding site for halogenation of tryptophan and other substrates. Oxidized flavin needs to be reduced for regeneration of the enzyme, which can be performed in vitro by a photoreduction with blue light. Here, we employed this photoreduction to study characteristic structural changes associated with the transition from oxidized to fully reduced flavin in PyrH from Streptomyces rugosporus as a model for tryptophan-5-halogenases. The effect of the presence of bromide and chloride or the absence of any halides on the UV-vis spectrum of the enzyme demonstrated a halide-dependent structure of the flavin-binding pocket. Light-induced FTIR difference spectroscopy was applied and the signals assigned by selective isotope labeling of the protein moiety. The identified structural changes in α-helix and ß-sheet elements were strongly dependent on the presence of bromide, chloride, the substrate tryptophan, and the product 5-chloro-tryptophan, respectively. We identified a clear allosteric coupling in solution at ambient conditions between cofactor-binding site and substrate-binding site that is active in both directions, despite their separation by a tunnel. We suggest that this coupling constitutes a fine-tuned mechanism for the promotion of the enzymatic reaction of flavin-dependent halogenases in dependence of halide and substrate availability.

Diagnostic accuracy of HPV16 early antigen serology for HPV-driven oropharyngeal cancer is independent of age and sex.

A growing proportion of head and neck cancer (HNC), especially oropharyngeal cancer (OPC), is caused by human papillomavirus (HPV). There are several markers for HPV-driven HNC, one being HPV early antigen serology. We aimed to investigate the diagnostic accuracy of HPV serology and its performance across patient characteristics. Data from the VOYAGER consortium was used, which comprises five studies on HNC from North America and Europe. Diagnostic accuracy, that is, sensitivity, specificity, Cohen's kappa and correctly classified proportions of HPV16 E6 serology, was assessed for OPC and other HNC using p16INK4a immunohistochemistry (p16), HPV in situ hybridization (ISH) and HPV PCR as reference methods. Stratified analyses were performed for variables including age, sex, smoking and alcohol use, to test the robustness of diagnostic accuracy. A risk-factor analysis based on serology was conducted, comparing HPV-driven to non-HPV-driven OPC. Overall, HPV serology had a sensitivity of 86.8% (95% CI 85.1-88.3) and specificity of 91.2% (95% CI 88.6-93.4) for HPV-driven OPC using p16 as a reference method. In stratified analyses, diagnostic accuracy remained consistent across sex and different age groups. Sensitivity was lower for heavy smokers (77.7%), OPC without lymph node involvement (74.4%) and the ARCAGE study (66.7%), while specificity decreased for cases with <10 pack-years (72.1%). The risk-factor model included study, year of diagnosis, age, sex, BMI, alcohol use, pack-years, TNM-T and TNM-N stage. HPV serology is a robust biomarker for HPV-driven OPC, and its diagnostic accuracy is independent of age and sex. Future research is suggested on the influence of smoking on HPV antibody levels.

Human papillomavirus-driven head and neck cancers in Japan during 2008-2009 and 2018-2019: The BROADEN study.

There is limited understanding of epidemiology and time trends of human papilloma virus (HPV)-driven head and neck cancers (HNC) in Japan, especially outside of the oropharynx. To assess HPV-driven HNC, a non-interventional study (BROADEN) of HNC patients diagnosed in 2008-2009 and 2018-2019 was conducted in Japan. Adult patients with oropharyngeal, nasopharyngeal, laryngeal, hypopharyngeal or oral cavity cancers were included in this study. HPV was centrally tested using p16INK4a immunohistochemistry, HPV-DNA PCR and HPV E6*I mRNA. HPV attributability required positivity in at least two tests (p16INK4a immunohistochemistry, HPV-DNA PCR, HPV E6*I mRNA) in the oropharynx, and HPV-DNA and HPV E6*I mRNA positivity for non-oropharynx sites. Nineteen hospitals included a total of 1108 patients, of whom 981 had valid samples. Men accounted for 82% of HNC diagnoses. Patients in the earlier cohort were younger and included a higher percentage of smokers. There was an increasing trend of HPV-driven oropharyngeal cancer over the last decade, from 44.2% to 51.7%. HPV attribution in nasopharyngeal cancers was 3.2% in 2008-2009 and 7.5% in 2018-2019; and 4.4% and 0% for larynx respectively. In total, 95.2% of HPV-driven HNC were attributed to HPV genotypes included in the 9-valent HPV vaccine being HPV16 the most prominent genotype. These results suggest that an epidemiologic shift is happening in Japan, with a decrease in smoking and alcohol use and an increase in HPV-driven HNC. The increasing trend of HPV-driven HNC in Japan highlights the need for preventive strategies to mitigate the rise of HPV-driven HNC.

Unraveling most abundant mutational signatures in head and neck cancer.

Genomic alterations are a driving force in the multistep process of head and neck cancer (HNC) and result from the interaction of exogenous environmental exposures and endogenous cellular processes. Each of these processes leaves a characteristic pattern of mutations on the tumor genome providing the unique opportunity to decipher specific signatures of mutational processes operative during HNC pathogenesis and to address their prognostic value. Computational analysis of whole exome sequencing data of the HIPO-HNC (Heidelberg Center for Personalized Oncology-head and neck cancer) (n = 83) and TCGA-HNSC (The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma) (n = 506) cohorts revealed five common mutational signatures (Catalogue of Somatic Mutations in Cancer [COSMIC] Signatures 1, 2, 3, 13 and 16) and demonstrated their significant association with etiological risk factors (tobacco, alcohol and HPV16). Unsupervised hierarchical clustering identified four clusters (A, B, C1 and C2) of which Subcluster C2 was enriched for cases with a higher frequency of signature 16 mutations. Tumors of Subcluster C2 had significantly lower p16INK4A expression accompanied by homozygous CDKN2A deletion in almost one half of cases. Survival analysis revealed an unfavorable prognosis for patients with tumors characterized by a higher mutation burden attributed to signature 16 as well as cases in Subcluster C2. Finally, a LASSO-Cox regression model was applied to prioritize clinically relevant signatures and to establish a prognostic risk score for head and neck squamous cell carcinoma patients. In conclusion, our study provides a proof of concept that computational analysis of somatic mutational signatures is not only a powerful tool to decipher environmental and intrinsic processes in the pathogenesis of HNC, but could also pave the way to establish reliable prognostic patterns.

Survival advantage in patients with human papillomavirus-driven oropharyngeal cancer and variation by demographic characteristics and serologic response: Findings from Head and Neck 5000.

BACKGROUND: Patients with human papillomavirus (HPV)-driven oropharyngeal cancer (OPC) experience better survival than those with HPV-negative OPC. It is unclear whether this benefit varies by demographic characteristics and serologic response. METHODS: Records from 1411 patients with OPC who had HPV serology data were analyzed. HPV status was based on HPV type 16 (HPV16) E6 serology. Participants were followed for a median of 5.9 years, and Cox proportional hazards models were used to estimate hazard ratios (HRs). The association between HPV status and overall survival was analyzed by age group, sex, smoking status, tumor site, HPV antibody levels, and HPV antibody pattern. Models were adjusted for age, sex, smoking status, and comorbidity. RESULTS: For the overall association between HPV status and survival, the fully adjusted HR was 0.43 (95% CI, 0.33-0.56). The HR was 0.19 (95% CI, 0.10-0.35) for participants aged ≤54 years, 0.38 (95% CI, 0.25-0.56) for those aged 55 to 64 years, and 0.73 (95% CI, 0.47-1.13) for those aged ≥65 years (P for interaction = .023). There was no clear evidence for an interaction by sex, smoking status, or tumor site. Survival did not differ according to E6 antibody levels in those who were seropositive. All seropositivity patterns were associated with increased survival compared with a pattern of seronegativity for all antibodies. Patients who are positive for E1, E2, E6, and E7 may experience better survival. CONCLUSIONS: HPV status confers a survival advantage across all groups. This survival advantage is more marked for younger patients. The HPV antibody pattern, but not the antibody level, may also affect survival.

Site-by-site tracking of signal transduction in an azidophenylalanine-labeled bacteriophytochrome with step-scan FTIR spectroscopy.

Signal propagation in photosensory proteins is a complex and multidimensional event. Unraveling such mechanisms site-specifically in real time is an eligible but a challenging goal. Here, we elucidate the site-specific events in a red-light sensing phytochrome using the unnatural amino acid azidophenylalanine, vibrationally distinguishable from all other protein signals. In canonical phytochromes, signal transduction starts with isomerization of an excited bilin chromophore, initiating a multitude of processes in the photosensory unit of the protein, which eventually control the biochemical activity of the output domain, nanometers away from the chromophore. By implementing the label in prime protein locations and running two-color step-scan FTIR spectroscopy on the Deinococcus radiodurans bacteriophytochrome, we track the signal propagation at three specific sites in the photosensory unit. We show that a structurally switchable hairpin extension, a so-called tongue region, responds to the photoconversion already in microseconds and finalizes its structural changes concomitant with the chromophore, in milliseconds. In contrast, kinetics from the other two label positions indicate that the site-specific changes deviate from the chromophore actions, even though the labels locate in the chromophore vicinity. Several other sites for labeling resulted in impaired photoswitching, low structural stability, or no changes in the difference spectrum, which provides additional information on the inner dynamics of the photosensory unit. Our work enlightens the multidimensionality of the structural changes of proteins under action. The study also shows that the signaling mechanism of phytochromes is accessible in a time-resolved and site-specific approach by azido probes and demonstrates challenges in using these labels.

Epstein-Barr virus and human papillomavirus serum antibodies define the viral status of nasopharyngeal carcinoma in a low endemic country.

Epstein-Barr virus (EBV) causes nasopharyngeal carcinoma (NPC) in endemic regions, where almost every tumor is EBV-positive. In Western populations, NPC is rare, and human papillomavirus infection (HPV) has been suggested as another viral cause. We validated multiplex serology with molecular tumor markers, to define EBV-positive, HPV-positive and EBV-/HPV-negative NPCs in the United Kingdom, and analyzed survival differences between those groups. Sera from NPC cases (n = 98) and age- and sex-matched controls (n = 142) from the Head and Neck 5000 clinical cohort study were analyzed. IgA and IgG serum antibodies against 13 EBV antigens were measured and compared with EBER in situ hybridization (EBER-ISH) data of 41 NPC tumors (29 EBER-ISH positive, 12 negative). IgG antibodies to EBV LF2 correctly diagnosed EBV-positive NPCs in 28 of 29 cases, while all EBER-ISH negative NPCs were seronegative to LF2 IgG (specificity = 100%, sensitivity = 97%). HPV early antigen serology was compared to HPV molecular markers (p16 expression, HPV DNA and RNA) available for 41 NPCs (13 positive, 28 negative). Serology matched molecular HPV markers in all but one case (specificity = 100%, sensitivity = 92%). EBV and HPV infections were mutually exclusive. Overall, 67% of the analyzed NPCs were defined as EBV-positive, 18% as HPV-positive and 14% as EBV/HPV-negative. There was no statistical evidence of a difference in survival between the three groups. These data provide evidence that both, EBV-positive and HPV-positive NPCs are present in a low incidence country, and that EBV and HPV serum antibodies correlate with the viral status of the tumor.

Quantitative criticism of literary relationships.

Authors often convey meaning by referring to or imitating prior works of literature, a process that creates complex networks of literary relationships ("intertextuality") and contributes to cultural evolution. In this paper, we use techniques from stylometry and machine learning to address subjective literary critical questions about Latin literature, a corpus marked by an extraordinary concentration of intertextuality. Our work, which we term "quantitative criticism," focuses on case studies involving two influential Roman authors, the playwright Seneca and the historian Livy. We find that four plays related to but distinct from Seneca's main writings are differentiated from the rest of the corpus by subtle but important stylistic features. We offer literary interpretations of the significance of these anomalies, providing quantitative data in support of hypotheses about the use of unusual formal features and the interplay between sound and meaning. The second part of the paper describes a machine-learning approach to the identification and analysis of citational material that Livy loosely appropriated from earlier sources. We extend our approach to map the stylistic topography of Latin prose, identifying the writings of Caesar and his near-contemporary Livy as an inflection point in the development of Latin prose style. In total, our results reflect the integration of computational and humanistic methods to investigate a diverse range of literary questions.

Patterns of antibody responses to nonviral cancer antigens in head and neck squamous cell carcinoma patients differ by human papillomavirus status.

There have been hints that nonviral cancer antigens are differentially expressed in human papillomavirus (HPV)-positive and HPV-negative head and neck squamous cell carcinoma (HNSCC). Antibody responses (AR) to cancer antigens may be used to indirectly determine cancer antigen expression in the tumor using a noninvasive and tissue-saving liquid biopsy. Here, we set out to characterize AR to a panel of nonviral cancer antigens in HPV-positive and HPV-negative HNSCC patients. A fluorescent microbead multiplex serology to 29 cancer antigens (16 cancer-testis antigens, 5 cancer-retina antigens and 8 oncogenes) and 29 HPV-antigens was performed in 382 HNSCC patients from five independent cohorts (153 HPV-positive and 209 HPV-negative). AR to any of the cancer antigens were found in 272/382 patients (72%). The ten most frequent AR were CT47, cTAGE5a, c-myc, LAGE-1, MAGE-A1, -A3, -A4, NY-ESO-1, SpanX-a1 and p53. AR to MAGE-A3, MAGE-A9 and p53 were found at significantly different prevalences by HPV status. An analysis of AR mean fluorescent intensity values uncovered remarkably different AR clusters by HPV status. To identify optimal antigen selections covering a maximum of patients with ≤10 AR, multiobjective optimization revealed distinct antigen selections by HPV status. We identified that AR to nonviral antigens differ by HPV status indicating differential antigen expression. Multiplex serology may be used to characterize antigen expression using serum or plasma as a tissue-sparing liquid biopsy. Cancer antigen panels should address the distinct antigen repertoire of HPV-positive and HPV-negative HNSCC.

Somatic mutations and promotor methylation of the ryanodine receptor 2 is a common event in the pathogenesis of head and neck cancer.

Genomic sequencing projects unraveled the mutational landscape of head and neck squamous cell carcinoma (HNSCC) and provided a comprehensive catalog of somatic mutations. However, the limited number of significant cancer-related genes obtained so far only partially explains the biological complexity of HNSCC and hampers the development of novel diagnostic biomarkers and therapeutic targets. We pursued a multiscale omics approach based on whole-exome sequencing, global DNA methylation and gene expression profiling data derived from tumor samples of the HIPO-HNC cohort (n = 87), and confirmed new findings with datasets from The Cancer Genome Atlas (TCGA). Promoter methylation was confirmed by MassARRAY analysis and protein expression was assessed by immunohistochemistry and immunofluorescence staining. We discovered a set of cancer-related genes with frequent somatic mutations and high frequency of promoter methylation. This included the ryanodine receptor 2 (RYR2), which showed variable promoter methylation and expression in both tumor samples and cell lines. Immunohistochemical staining of tissue sections unraveled a gradual loss of RYR2 expression from normal mucosa via dysplastic lesion to invasive cancer and indicated that reduced RYR2 expression in adjacent tissue and precancerous lesions might serve as risk factor for unfavorable prognosis and upcoming malignant conversion. In summary, our data indicate that impaired RYR2 function by either somatic mutation or epigenetic silencing is a common event in HNSCC pathogenesis. Detection of RYR2 expression and/or promoter methylation might enable risk assessment for malignant conversion of dysplastic lesions.

Following local light-induced structure changes and dynamics of the photoreceptor PYP with the thiocyanate IR label.

Photoactive Yellow Protein (PYP) is a bacterial blue light receptor that enters a photocycle after excitation. The intermediate states are formed on time scales ranging from femtoseconds up to hundreds of milliseconds, after which the signaling state with a lifetime of about 1 s is reached. To investigate structural changes and dynamics, we incorporated the SCN IR label at distinct positions of the photoreceptor via cysteine mutation and cyanylation. FT-IR measurements of the SCN label at different sites of the well-established dark state structure of PYP characterized the spectral response of the label to differences in the environment. Under constant blue light irradiation, we observed the formation of the signaling state with significant changes of wavenumber and lineshape of the SCN bands. Thereby we deduced light-induced structural changes in the local environment of the labels. These results were supported by molecular dynamics simulations on PYP providing the solvent accessible surface area (SASA) at the different positions. To follow protein dynamics via the SCN label during the photocycle, we performed step-scan FT-IR measurements with a time resolution of 10 µs. Global analysis yielded similar time constants of τ1 = 70 µs, τ2 = 640 µs, and τ3 > 20 ms for the wild type and τ1 = 36 µs, τ2 = 530 µs, and τ3 > 20 ms for the SCN-labeled mutant PYP-A44C*, a mutant which provided a sufficiently large SCN difference signal to measure step-scan FT-IR spectra. In comparison to the protein (amide, E46) and chromophore bands the dynamics of the SCN label show a different behavior. This result indicates that the local kinetics sensed by the label are different from the global protein kinetics.

Plasma membrane/cell wall perturbation activates a novel cell cycle checkpoint during G1 in Saccharomyces cerevisiae.

Cellular wound healing or the repair of plasma membrane/cell wall damage (plasma membrane damage) occurs frequently in nature. Although various cellular perturbations, such as DNA damage, spindle misalignment, and impaired daughter cell formation, are monitored by cell cycle checkpoint mechanisms in budding yeast, whether plasma membrane damage is monitored by any of these checkpoints remains to be addressed. Here, we define the mechanism by which cells sense membrane damage and inhibit DNA replication. We found that the inhibition of DNA replication upon plasma membrane damage requires GSK3/Mck1-dependent degradation of Cdc6, a component of the prereplicative complex. Furthermore, the CDK inhibitor Sic1 is stabilized in response to plasma membrane damage, leading to cell integrity maintenance in parallel with the Mck1-Cdc6 pathway. Cells defective in both Cdc6 degradation and Sic1 stabilization failed to grow in the presence of plasma membrane damage. Taking these data together, we propose that plasma membrane damage triggers G1 arrest via Cdc6 degradation and Sic1 stabilization to promote the cellular wound healing process.

Chromophore-Protein Interplay during the Phytochrome Photocycle Revealed by Step-Scan FTIR Spectroscopy.

Phytochrome proteins regulate many photoresponses of plants and microorganisms. Light absorption causes isomerization of the biliverdin chromophore, which triggers a series of structural changes to activate the signaling domains of the protein. However, the structural changes are elusive, and therefore the molecular mechanism of signal transduction remains poorly understood. Here, we apply two-color step-scan infrared spectroscopy to the bacteriophytochrome from Deinococcus radiodurans. We show by recordings in H2O and D2O that the hydrogen bonds to the biliverdin D-ring carbonyl become disordered in the first intermediate (Lumi-R) forming a dynamic microenvironment, then completely detach in the second intermediate (Meta-R), and finally reform in the signaling state (Pfr). The spectra reveal via isotope labeling that the refolding of the conserved "PHY-tongue" region occurs with the last transition between Meta-R and Pfr. Additional changes in the protein backbone are detected already within microseconds in Lumi-R. Aided by molecular dynamics simulations, we find that a strictly conserved salt bridge between an arginine of the PHY tongue and an aspartate of the chromophore binding domains is broken in Lumi-R and the arginine is recruited to the D-ring C═O. This rationalizes how isomerization of the chromophore is linked to the global structural rearrangement in the sensory receptor. Our findings advance the structural understanding of phytochrome photoactivation.

Antibodies against human papillomaviruses as diagnostic and prognostic biomarker in patients with neck squamous cell carcinoma from unknown primary tumor.

Treatment of patients with neck lymph node metastasis of squamous cell carcinoma (SCC) from unknown primary tumor (NSCCUP) is challenging due to the risk of missing occult tumors or inducing toxicity to unaffected sites. Human papillomavirus (HPV) is a promising biomarker given its causal link to oropharyngeal SCC and superior survival of patients with HPV-driven oropharyngeal SCC and NSCCUP. Identification of HPV-driven NSCCUP could focus diagnostic work-up and treatment on the oropharynx. For the first time, we assessed HPV antibodies and their prognostic value in NSCCUP patients. Antibodies against E6 and E7 (HPV16/18/31/33/35), E1 and E2 (HPV16/18) were assessed in 46 NSCCUP patients in sera collected at diagnosis, and in follow-up sera from five patients. In 28 patients, HPV tumor status was determined using molecular markers (HPV DNA, mRNA and cellular p16INK4a ). Thirteen (28%) NSCCUP patients were HPV-seropositive for HPV16, 18, 31, or 33. Of eleven patients with HPV-driven NSCCUP, ten were HPV-seropositive, while all 17 patients with non-HPV-driven NSCCUP were HPV-seronegative, resulting in 91% sensitivity (95% CI: 59-100%) and 100% specificity (95% CI: 80-100%). HPV antibody levels decreased after curative treatment. Recurrence was associated with increasing levels in an individual case. HPV-seropositive patients had a better overall and progression-free survival with hazard ratios of 0.09 (95% CI: 0.01-0.42) and 0.03 (95% CI: 0.002-0.18), respectively. For the first time, seropositivity to HPV proteins is described in NSCCUP patients, and high sensitivity and specificity for HPV-driven NSCCUP are demonstrated. HPV seropositivity appears to be a reliable diagnostic and prognostic biomarker for patients with HPV-driven NSCCUP.

Time-Resolved Infrared Spectroscopy on Plant Cryptochrome-Relevance of Proton Transfer and ATP Binding for Signaling.

Plant cryptochromes are light receptors in land plants and algae with very diverse functions such as circadian timing and lifecycle progression. The receptor consists of a photolyase homology region (PHR) binding the flavin chromophore and a C-terminal extension (CCT) responsible for signaling. The reputed signaling state, the flavin neutral radical, is formed by a femtosecond electron transfer and microsecond proton transfer to the excited, oxidized flavin. Subsequently, a 500 µs loss of ß-sheet structure ∼25 Å away from flavin was resolved and suggested to be part of the signal conduction to the CCT. Here, we performed time-resolved, step-scan Fourier transform IR spectroscopy on the PHR of the plant cryptochrome pCRY (formerly CPH1) from Chlamydomonas reinhardtii. In a mutant lacking the proton donor aspartic acid 396 only the flavin anion radical is formed, but we observed the loss of ß-sheet structure with a time constant of 1.3 ms, similar to the 500 µs of the wild type. This finding implies that the anion radical may be considered signaling-competent. In the steady state, a variation of external pH up to 8.3 did not have any effect on the difference spectra including the protonated state of Asp396. However, we detected the prominent loss of ß-sheet structure by illumination only in the presence of adenosine triphosphate (ATP). We conclude that the bound ATP stabilizes these light-induced changes in secondary structure to ensure a physiological lifetime compatible with signaling by plant cryptochrome.

Sensitivity and specificity of antibodies against HPV16 E6 and other early proteins for the detection of HPV16-driven oropharyngeal squamous cell carcinoma.

To determine the sensitivity and specificity of HPV16 serology as diagnostic marker for HPV16-driven oropharyngeal squamous cell carcinoma (OPSCC), 214 HNSCC patients from Germany and Italy with fresh-frozen tumor tissues and sera collected before treatment were included in this study. Hundred and twenty cancer cases were from the oropharynx and 94 were from head and neck cancer regions outside the oropharynx (45 oral cavity, 12 hypopharynx and 35 larynx). Serum antibodies to early (E1, E2, E6 and E7) and late (L1) HPV16 proteins were analyzed by multiplex serology and were compared to tumor HPV RNA status as the gold standard. A tumor was defined as HPV-driven in the presence of HPV16 DNA and HPV16 transformation-specific RNA transcript patterns (E6*I, E1∧ E4 and E1C). Of 120 OPSCC, 66 (55%) were HPV16-driven. HPV16 E6 seropositivity was the best predictor of HPV16-driven OPSCC (diagnostic accuracy 97% [95%CI 92-99%], Cohen's kappa 0.93 [95%CI 0.8-1.0]). Of the 66 HPV-driven OPSCC, 63 were HPV16 E6 seropositive, compared to only one (1.8%) among the 54 non-HPV-driven OPSCC, resulting in a sensitivity of 96% (95%CI 88-98) and a specificity of 98% (95%CI 90-100). Of 94 HNSCC outside the oropharynx, six (6%) were HPV16-driven. In these patients, HPV16 E6 seropositivity had lower sensitivity (50%, 95%CI 19-81), but was highly specific (100%, 95%CI 96-100). In conclusion, HPV16 E6 seropositivity appears to be a highly reliable diagnostic marker for HPV16-driven OPSCC with very high sensitivity and specificity, but might be less sensitive for HPV16-driven HNSCC outside the oropharynx.

A yeast GSK-3 kinase Mck1 promotes Cdc6 degradation to inhibit DNA re-replication.

Cdc6p is an essential component of the pre-replicative complex (pre-RC), which binds to DNA replication origins to promote initiation of DNA replication. Only once per cell cycle does DNA replication take place. After initiation, the pre-RC components are disassembled in order to prevent re-replication. It has been shown that the N-terminal region of Cdc6p is targeted for degradation after phosphorylation by Cyclin Dependent Kinase (CDK). Here we show that Mck1p, a yeast homologue of GSK-3 kinase, is also required for Cdc6 degradation through a distinct mechanism. Cdc6 is an unstable protein and is accumulated in the nucleus only during G1 and early S-phase in wild-type cells. In mck1 deletion cells, CDC6p is stabilized and accumulates in the nucleus even in late S phase and mitosis. Overexpression of Mck1p induces rapid Cdc6p degradation in a manner dependent on Threonine-368, a GSK-3 phosphorylation consensus site, and SCF(CDC4). We show evidence that Mck1p-dependent degradation of Cdc6 is required for prevention of DNA re-replication. Loss of Mck1 activity results in synthetic lethality with other pre-RC mutants previously implicated in re-replication control, and these double mutant strains over-replicate DNA within a single cell cycle. These results suggest that a GSK3 family protein plays an unexpected role in preventing DNA over-replication through Cdc6 degradation in Saccharomyces cerevisiae. We propose that both CDK and Mck1 kinases are required for Cdc6 degradation to ensure a tight control of DNA replication.

Quantification of human papillomavirus cell-free DNA from low-volume blood plasma samples by digital PCR.

The incidence rate of human papillomavirus-driven oropharyngeal cancer (HPV-OPC) is increasing in countries with high human development index. HPV cell-free DNA (cfDNA) isolated from 3 to 4 mL blood plasma has been successfully used for therapy surveillance. A highly discussed application of HPV-cfDNA is early detection of HPV-OPC. This requires sensitive and specific cfDNA detection as cfDNA levels can be very low. To study the predictive power of pre-diagnostic HPV-cfDNA, archived samples from epidemiological cohorts with limited plasma volume are an important source. To establish a cfDNA detection workflow for low plasma volumes, we compared cfDNA purification methods [MagNA Pure 96 (MP96) and QIAamp ccfDNA/RNA] and digital PCR systems (Biorad QX200 and QIAGEN QIAcuity One). Final assay validation included 65 low-volume plasma samples from oropharyngeal cancer (OPC) patients with defined HPV status stored for 2-9 years. MP96 yielded a 28% higher cfDNA isolation efficiency in comparison to QIAamp. Both digital PCR systems showed comparable analytical sensitivity (6-17 copies for HPV16 and HPV33), but QIAcuity detected both types in the same assay. In the validation set, the assay had 80% sensitivity (n = 28/35) for HPV16 and HPV33 and a specificity of 97% (n = 29/30). In samples with ≥750 µL plasma, the sensitivity was 85% (n = 17/20), while in samples with <750 µL plasma, it was 73% (n = 11/15). Despite the expected drop in sensitivity with decreased plasma volume, the assay is sensitive and highly specific even in low-volume samples and thus suited for studies exploring HPV-cfDNA as an early HPV-OPC detection marker in low-volume archival material.IMPORTANCEHPV-OPC has a favorable prognosis compared to HPV-negative OPC. However, the majority of tumors is diagnosed after regional spread, thus making intensive treatment necessary. This can cause lasting morbidity with a large impact on quality of life. One potential method to decrease treatment-related morbidity is early detection of the cancer. HPV cfDNA has been successfully used for therapy surveillance and has also been detected in pre-diagnostic samples of HPV-OPC patients. These pre-diagnostic samples are only commonly available from biobanks, which usually only have small volumes of blood plasma available. Hence, we have developed a workflow optimized for small-volume archival samples. With this method, a high sensitivity can be achieved despite sample limitations, making it suitable to conduct further large-scale biobank studies of HPV-cfDNA as a prognostic biomarker for HPV-OPC.

Detection of serum biomarkers of HPV-16 driven oropharynx and oral cavity cancer in Brazil.

BACKGROUND: HPV-16 driven oropharynx/oral cavity squamous cell carcinomas prevalence varies globally. We evaluated the presence of HPV-16 ctDNA and HPV-16 E6 antibodies in samples obtained from participants treated at the Instituto do Cancer do Estado de Sao Paulo, ICESP, and from whom tumoral HPV DNA, HPV-16 E6*I mRNA, and p16INK4a status was also accessed. METHODS: HPV was genotyped by PCR-hybridization. All HPV DNA positive and ∼10 % HPV DNA negative cases underwent p16INK4a immunohistochemistry and E6*I RNA testing using a multiplex bead based protocol. HPV-16 ctDNA and anti-E6 antibodies were assessed by ddPCR (digital droplet PCR) and multiplex serology, respectively. RESULTS: The prevalence of HPV-16 in oropharynx carcinoma (OPC) cases was low (8.7 %) when considering solely HPV-16 DNA detection, and even lower (5.2 %) when taken into consideration the concomitant detection of HPV-16 E6*I RNA and/or p16INK4 (HPV-16 attributable fraction - AF). None of the oral cavity cancer (OCC) cases were detected with HPV-16 DNA. HPV-16 ctDNA was more commonly detected than HPV-16 E6 antibodies (29.8 % versus 10.6 %). Both serum biomarkers attained 100 % sensitivity of detecting HPV-16 AF OPC, however the specificity of the HPV-16 anti-E6 biomarker was higher compared to ctDNA (93.2 % versus 75.0 %). Finally, when both HPV-16 ctDNA and anti-E6 biomarkers were considered together, the sensitivity and specificity for HPV-16 OPC detection was 100 % and about 70 %, respectively, independently of analyzing HPV-16 DNA positive or HPV-16 AF tumors. CONCLUSIONS: Our findings corroborate that serum biomarkers are highly sensitive and specific biomarkers for detection of HPV-associated OPC.