Liberation of functional p53 by proteasome inhibition in human papilloma virus-positive head and neck squamous cell carcinoma cells promotes apoptosis and cell cycle arrest

Mouse Models for Head and Neck Squamous Cell Carcinoma

The prognosis and survival rate of head and neck squamous cell carcinoma (HNSCC) have remained unchanged for years, and the pathogenesis of HNSCC is still not fully understood, necessitating further research. An ideal animal model that accurately replicates the complex microenvironment of HNSCC is urgently needed. Among all the animal models for preclinical cancer research, tumor-bearing mouse models are the best known and widely used due to their high similarity to humans. Currently, mouse models for HNSCC can be broadly categorized into chemical-induced models, genetically engineered mouse models (GEMMs), and transplanted mouse models, each with its distinct advantages and limitations. In chemical-induced models, the carcinogen spontaneously initiates tumor formation through a multistep process. The resemblance of this model to human carcinogenesis renders it an ideal preclinical platform for studying HNSCC initiation and progression from precancerous lesions. The major drawback is that these models are time-consuming and, like human cancer, unpredictable in terms of timing, location, and number of lesions. GEMMs involve transgenic and knockout mice with gene modifications, leading to malignant transformation within a tumor microenvironment that recapitulates tumorigenesis in vivo, including their interaction with the immune system. However, most HNSCC GEMMs exhibit low tumor incidence and limited prognostic significance when translated to clinical studies. Transplanted mouse models are the most widely used in cancer research due to their consistency, availability, and efficiency. Based on the donor and recipient species matching, transplanted mouse models can be divided into xenografts and syngeneic models. In the latter, transplanted cells and host are from the same strain, making syngeneic models relevant to study functional immune system. In this review, we provide a comprehensive summary of the characteristics, establishment methods, and potential applications of these different HNSCC mouse models, aiming to assist researchers in choosing suitable animal models for their research.

Developments and future prospects of personalized medicine in head and neck squamous cell carcinoma diagnoses and treatments

BACKGROUND

Precision healthcare has entered a new era because of the developments in personalized medicine, especially in the diagnosis and treatment of head and neck squamous cell carcinoma (HNSCC). This paper explores the dynamic landscape of personalized medicine as applied to HNSCC, encompassing both current developments and future prospects.

RECENT FINDINGS

The integration of personalized medicine strategies into HNSCC diagnosis is driven by the utilization of genetic data and biomarkers. Epigenetic biomarkers, which reflect modifications to DNA that can influence gene expression, have emerged as valuable indicators for early detection and risk assessment. Treatment approaches within the personalized medicine framework are equally promising. Immunotherapy, gene silencing, and editing techniques, including RNA interference and CRISPR/Cas9, offer innovative means to modulate gene expression and correct genetic aberrations driving HNSCC. The integration of stem cell research with personalized medicine presents opportunities for tailored regenerative approaches. The synergy between personalized medicine and technological advancements is exemplified by artificial intelligence (AI) and machine learning (ML) applications. These tools empower clinicians to analyze vast datasets, predict patient responses, and optimize treatment strategies with unprecedented accuracy.

CONCLUSION

The developments and prospects of personalized medicine in HNSCC diagnosis and treatment offer a transformative approach to managing this complex malignancy. By harnessing genetic insights, biomarkers, immunotherapy, gene editing, stem cell therapies, and advanced technologies like AI and ML, personalized medicine holds the key to enhancing patient outcomes and ushering in a new era of precision oncology.

PSMD1 as a prognostic marker and potential target in oropharyngeal cancer

BACKGROUND

Despite the diverse genetic mutations in head and neck cancer, the chemotherapy outcome for this cancer has not improved for decades. It is urgent to select prognostic factors and therapeutic targets for oropharyngeal cancer to establish precision medicine. Recent studies have identified PSMD1 as a potential prognostic marker in several cancers. We aimed to assess the prognostic significance of PSMD1 expression in oropharyngeal squamous cell carcinoma (OPSCC) patients using immunohistochemistry.

METHODS

We studied 64 individuals with OPSCC tissue from surgery at Seoul National University Bundang Hospital between April 2008 and August 2017. Immunostaining analysis was conducted on the tissue microarray (TMA) sections (4 μm) for p16 and PSMD1. H-score, which scale from 0 to 300, was calculated from each nucleus, cytoplasm, and cellular expression. Clinicopathological data were compared with Chi-squared test, Fisher's exact test, t-test, and logistic regression. Survival data until 2021 were achieved from national statistical office of Korea. Kaplan-Meier method and cox-regression model were used for disease-specific survival (DSS) analysis.

RESULTS

H-score of 90 in nucleus was appropriate cutoff value for 'High PSMD1 expression' in OPSCC. Tonsil was more frequent location in low PSMD1 group (42/52, 80.8%) than in high PSMD1 group (4/12, 33.3%; P = .002). Early-stage tumor was more frequent in in low PSMD1 group (45/52, 86.5%) than in high PSMD1 group (6/12, 50%; P = .005). HPV was more positive in low PSMD1 group (43/52, 82.7%) than in high PSMD1 group (5/12, 41.7%; P = .016). Patients with PSMD1 high expression showed poorer DSS than in patients with PSMD1 low expression (P = .006 in log rank test). In multivariate analysis, PSMD1 expression, pathologic T staging, and specimen age were found to be associated with DSS (P = .011, P = .025, P = .029, respectively).

CONCLUSIONS

In our study, we established PSMD1 as a negative prognostic factor in oropharyngeal squamous cell carcinoma, indicating its potential as a target for targeted therapy and paving the way for future in vitro studies on drug repositioning.

Advanced Nanomedicine for High-Risk HPV-Driven Head and Neck Cancer

The incidence of high-risk Human Papillomavirus (HR-HPV)-driven head and neck squamous cell carcinoma (HNSCC) is on the rise globally. HR-HPV-driven HNSCC displays molecular and clinical characteristics distinct from HPV-uninvolved cases. Therapeutic strategies for HR-HPV-driven HNSCC are under investigation. HR-HPVs encode the oncogenes E6 and E7, which are essential in tumorigenesis. Meanwhile, involvement of E6 and E7 provides attractive targets for developing new therapeutic regimen. Here we will review some of the recent advancements observed in preclinical studies and clinical trials on HR-HPV-driven HNSCC, focusing on nanotechnology related methods. Materials science innovation leads to great improvement for cancer therapeutics including HNSCC. This article discusses HPV-E6 or -E7- based vaccines, based on plasmid, messenger RNA or peptide, at their current stage of development and testing as well as how nanoparticles can be designed to target and access cancer cells and activate certain immunology pathways besides serving as a delivery vehicle. Nanotechnology was also used for chemotherapy and photothermal treatment. Short interference RNA targeting E6/E7 showed some potential in animal models. Gene editing by CRISPR-CAS9 combined with other treatments has also been assessed. These advancements have the potential to improve the outcome in HR-HPV-driven HNSCC, however breakthroughs are still to be awaited with nanomedicine playing an important role.

Hyperactivating p53 in Human Papillomavirus-Driven Cancers: A Potential Therapeutic Intervention

Despite a vaccine being available, human papillomavirus virus (HPV)-driven cancers remain the ninth most prevalent cancers globally. Current therapies have significant drawbacks and often still lead to poor prognosis and underwhelming survival rates. With gene therapy becoming more available in the clinic, it poses a new front for therapeutic development. A characteristic of HPV-driven cancers is the ability to encode oncoproteins that aberrate normal p53 function without mutating this tumour-suppressor gene. The HPV E6 oncoprotein degrades p53 to allow the HPV-driven carcinogenic process to proceed. This review aimed to investigate the use of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) gene-editing technology and how it may be used to overcome HPV-mediated silencing of p53 by hyper-expressing the p53 promoter. Increasing p53 bioavailability may have promising potential as a therapy and has been a goal in the context of HPV-driven cancers. Clinical trials and proof-of-concept pre-clinical work have shown positive outcomes and tumour death when p53 levels are increased. Despite previous successes of RNA-based medicines, including the knockout of HPV oncogenes, the use of CRISPR activation is yet to be investigated as a promising potential therapy. This short review summarises key developments on attempts that have been made to increase p53 expression in the context of HPV cancer therapy, but leaves open the possibility for other cancers bearing a p53 wild-type gene.

Proteasome inhibition by bortezomib parallels a reduction in head and neck cancer cells growth, and an increase in tumor-infiltrating immune cells

Head and neck cancer (HNC) has frequently an aggressive course for the development of resistance to standard chemotherapy. Thus, the use of innovative therapeutic drugs is being assessed. Bortezomib is a proteasome inhibitor with anticancer effects. In vitro antitumoral activity of Bortezomib was investigated employing human tongue (SCC-15, CAL-27), pharynx (FaDu), salivary gland (A-253) cancer cell lines and a murine cell line (SALTO-5) originated from a salivary gland adenocarcinoma arising in BALB-neuT male mice transgenic for the oncogene neu. Bortezomib inhibited cell proliferation, triggered apoptosis, modulated the expression and activation of pro-survival signaling transduction pathways proteins activated by ErbB receptors and inhibited proteasome activity in vitro. Intraperitoneal administration of Bortezomib delayed tumor growth of SALTO-5 cells transplanted in BALB-neuT mice, protracted mice survival and adjusted tumor microenvironment by increasing tumor-infiltrating immune cells (CD4⁺ and CD8⁺ T cells, B lymphocytes, macrophages, and Natural Killer cells) and by decreasing vessels density. In addition, Bortezomib modified the expression of proteasome structural subunits in transplanted SALTO-5 cells. Our findings further support the use of Bortezomib for the treatment of HNC and reveal its ineffectiveness in counteracting the activation of deregulated specific signaling pathways in HNC cell lines when resistance to proteasome inhibition is developed.

Therapeutic inhibitory RNA in head and neck cancer via functional targeted lipid nanoparticles

Currently there are no specific therapies addressing the distinctive biology of human papillomavirus (HPV)-induced cancer approved for clinical use. Short interfering RNA (siRNA) has much potential for therapeutic manipulation of HPV E6/E7 oncoproteins. Lipid-based nanoparticles (LNPs) can be utilized for systemic transportation and delivery of siRNA at target site. We recently developed a recombinant protein linker that enables uniform conjugation of targeting antibodies to the LNPs. Herein, we demonstrate the therapeutic efficacy of anti-E6/E7 siRNA delivered via targeted LNPs (tLNPs) in a xenograft HPV-positive tumor model. We show that anti-epidermal growth factor receptor (EGFR) antibodies, anchored to the LNPs as targeting moieties, facilitate cargo delivery but also mediate anti-tumor activity. Treatment with siE6 via tLNPs resulted in 50% greater reduction of tumor volume compared to treatment with siControl encapsulated in isoLNPs (coated with isotype control antibodies). We demonstrate superior suppression of HPV oncogenes and higher induction of apoptosis by the tLNPs both in vitro and in vivo. Altogether, the coupling of inhibitory siE6 with anti-EGFR antibodies, that further elicited anti-tumor effects, successfully restricted tumor progression. This system that combines potent siRNA and therapeutically functional tLNPs can be modulated against various cancer models.

NF-Y Subunits Overexpression in HNSCC

Simple Summary

Cancer cells have altered gene expression profiles. This is ultimately elicited by altered structure, expression or binding of transcription factors to regulatory regions of genomes. The CCAAT-binding trimer is a pioneer transcription factor involved in the activation of “cancer” genes. We and others have shown that the regulatory NF-YA subunit is overexpressed in epithelial cancers. Here, we examined large datasets of bulk gene expression profiles, as well as single-cell data, in head and neck squamous cell carcinomas by bioinformatic methods. We partitioned tumors according to molecular subtypes, mutations and positivity for HPV. We came to the conclusion that high levels of the histone-like subunits and the “short” NF-YAs isoform are protective in HPV-positive tumors. On the other hand, high levels of the “long” NF-YAl were found in the recently identified aggressive and metastasis-prone cell population undergoing partial epithelial to mesenchymal transition, p-EMT.

Abstract

NF-Y is the CCAAT-binding trimer formed by the histone fold domain (HFD), NF-YB/NF-YC and NF-YA. The CCAAT box is generally prevalent in promoters of “cancer” genes. We reported the overexpression of NF-YA in BRCA, LUAD and LUSC, and of all subunits in HCC. Altered splicing of NF-YA was found in breast and lung cancer. We analyzed RNA-seq datasets of TCGA and cell lines of head and neck squamous cell carcinomas (HNSCC). We partitioned all TCGA data into four subtypes, deconvoluted single-cell RNA-seq of tumors and derived survival curves. The CCAAT box was enriched in the promoters of overexpressed genes. The “short” NF-YAs was overexpressed in all subtypes and the “long” NF-YAl in Mesenchymal. The HFD subunits are overexpressed, except Basal (NF-YB) and Atypical (NF-YC); NF-YAl is increased in p53 mutated tumors. In HPV-positive tumors, high levels of NF-YAs, p16 and ΔNp63 correlate with better prognosis. Deconvolution of single cell RNA-seq (scRNA-seq) found a correlation of NF-YAl with Cancer Associated Fibroblasts (CAFs) and p-EMT cells, a population endowed with metastatic potential. We conclude that overexpression of HFD subunits and NF-YAs is protective in HPV-positive tumors; expression of NF-YAl is largely confined to mutp53 tumors and malignant p-EMT cells.

Ethanol Extracts of Solanum lyratum Thunb Regulate Ovarian Cancer Cell Proliferation, Apoptosis, and Epithelial-to-Mesenchymal Transition (EMT) via the ROS-Mediated p53 Pathway

Ovarian cancer is a type of common gynecological tumors with high incidence and poor survival. The anticancer effects of the traditional Chinese medicine Solanum lyratum Thunb (SLT) have been intensively investigated in various cancers but in ovarian cancer is rare. The current study is aimed at investigating the effect of SLT on ovarian cancer cells. Lactate dehydrogenase (LDH) and MTT assays indicated that SLT concentrations of 0.25 and 0.5 μg/mL were not cytotoxic and had significant inhibitory effects on the cell viabilities of A2780 and SKOV3 cells, hence were used for subsequent experiments. Flow cytometric and western blot analysis revealed that SLT effectively suppressed ovarian cancer cell proliferation via inducing cell cycle arrest and increasing apoptosis. Cell cycle and apoptosis-related protein expressions were also regulated in SLT-treated cells. Moreover, DCFH-DA and western blot assays demonstrated that SLT enhanced ROS accumulation and subsequently activated the p53 signaling pathway. However, SLT-regulated ovarian cancer cell proliferation, apoptosis, migration, invasion, and EMT were significantly reversed by an ROS inhibitor (NAC, N-acetyl-L-cysteine). Furthermore, A2780 and SKOV3 cells cocultured with M0 macrophages showed that SLT activated the polarization of M0 macrophages to M1 macrophages and inhibited the polarization to M2 macrophages, with the increased percentage of CD86+ cells and decreased percentage of CD206+ cells were detected. In summary, this study illustrated the anticancer effects of SLT on ovarian cancer cells, suggesting that SLT may have the potential to provide basic evidence for the discovery of antiovarian cancer agents.

p53 Is Regulated in a Biphasic Manner in Hypoxic Human Papillomavirus Type 16 (HPV16)-Positive Cervical Cancer Cells

Although the effect of hypoxia on p53 in human papillomavirus (HPV)-positive cancer cells has been studied for decades, the impact of p53 regulation on downstream targets and cellular adaptation processes during different periods under hypoxia remains elusive. Here, we show that, despite continuous repression of HPV16 E6/E7 oncogenes, p53 did not instantly recover but instead showed a biphasic regulation marked by further depletion within 24 h followed by an increase at 72 h. Of note, during E6/E7 oncogene suppression, lysosomal degradation antagonizes p53 reconstitution. Consequently, the transcription of p53 responsive genes associated with senescence (e.g., PML and YPEL3) cannot be upregulated. In contrast, downstream genes involved in autophagy (e.g., DRAM1 and BNIP3) were activated, allowing the evasion of senescence under hypoxic conditions. Hence, dynamic regulation of p53 along with its downstream network of responsive genes favors cellular adaptation and enhances cell survival, although the expression of the viral E6/E7-oncogenes as drivers for proliferation remained inhibited under hypoxia.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

A novel small-molecule inhibitor of the human papillomavirus E6-p53 interaction that reactivates p53 function and blocks cancer cells growth

Despite prophylactic vaccination campaigns, human papillomavirus (HPV)-induced cancers still represent a major medical issue for global population, thus specific anti-HPV drugs are needed. Since the ability of HPV E6 oncoprotein to promote p53 degradation is linked to tumor progression, E6 has been proposed as an ideal target for cancer treatment. Using the crystal structure of the E6/E6AP/p53 complex, we performed an in silico screening of small-molecule libraries against a highly conserved alpha-helix in the N-terminal domain of E6 involved in the E6-p53 interaction. We discovered a compound able to inhibit the E6-mediated degradation of p53 through disruption of E6-p53 binding both in vitro and in cells. This compound could restore p53 intracellular levels and transcriptional activity, reduce the viability and proliferation of HPV-positive cancer cells, and block 3D cervospheres formation. Mechanistic studies revealed that the compound anti-tumor activity mainly relies on induction of cell cycle arrest and senescence. Our data demonstrate that the disruption of the direct E6-p53 interaction can be obtained with a small-molecule compound leading to specific antitumoral activity in HPV-positive cancer cells and thus represents a new approach for anti-HPV drug development.

In HPV-Positive HNSCC Cells, Functional Restoration of the p53/p21 Pathway by Proteasome Inhibitor Bortezomib Does Not Affect Radio- or Chemosensitivity

Human papillomavirus (HPV) associated squamous cell carcinomas of the head and neck region (HPV+ HNSCCs) harbor diverging biological features as compared to classical noxa-induced (HPV−) HNSCC. One striking difference between subtypes is that the tumor suppressor gene TP53 is usually not mutated in HPV+ HNSCCs. However, p53 is inhibited by viral oncoprotein E6, leading to premature proteasomal degradation. We asked whether bortezomib (BZM), a clinically approved inhibitor of the proteasome, can functionally restore p53 and investigated in how far this will result in an enhanced radio- or chemosensitivity of HPV+ HNSCC cell lines. For all four HPV+ cell lines tested, BZM led to functional restoration of p53 and transactivation of downstream protein p21. In HPV+ cells, BZM also restored the radiation-induced p53/p21 transactivation. Consistently, in HPV+ cells, a restored G1 arrest as well as enhanced apoptosis were seen when BZM was given prior to irradiation (IR) or cisplatin (CDDP). BZM alone reduced the clonogenic survival of both HPV− and HPV+ cells. However, if BZM was combined with IR or CDDP, BZM did not significantly enhance radio- or chemosensitivity of HPV+ or HPV− HNSCC cell lines.

Curcumin-Mediated Degradation of S-Phase Kinase Protein 2 Induces Cytotoxic Effects in Human Papillomavirus-Positive and Negative Squamous Carcinoma Cells

S-phase kinase-associated protein2 (Skp2), a proto-oncoprotein, plays an important role in development and progression of human malignancies. Skp2 is frequently overexpressed in many human malignancies. It targets cell cycle progression through ubiquitin mediated degradation of G1-checkpoint CDK inhibitors-p21 (CDKN1A) and p27 (CDKN1B). We investigated the role of Skp2 and its ubiquitin-proteasome pathway in head and neck squamous cell carcinoma (HNSCC) using a panel of cell lines with and without human papillomavirus (HPV+, HPV-). Treatment of HNSCC cell lines with curcumin, a natural compound isolated from rhizomes of the plant Curcuma longa, or transfection of small interfering RNA of Skp2, causes down-regulation of Skp2 with concomitant accumulation of p21 and p27 in HPV+, HPV- cells. Furthermore curcumin inhibits cell viability and induces apoptosis in a dose-dependent manner. Treatment of HPV+ and HPV- cells with curcumin induced apoptosis via mitochondrial pathway and activation of caspases. In addition, treatment of HPV+ and HPV- cell lines with curcumin down-regulated the expression of XIAP, cIAP1, and cIAP2. Interestingly, co-treatment of HNSCC cells with curcumin and cisplatin potentiated inhibition of cell viability and apoptotic effects. Altogether, these data suggest an important function for curcumin, acting as a suppressor of oncoprotein Skp2 in squamous cell carcinoma cells in both HPV+ and HPV- cells; raise the possibility that this agent may have a future therapeutic role in squamous cell carcinoma.

Positioning of proteasome inhibitors in therapy of solid malignancies

Targeting of the protein degradation pathway, in particular, the ubiquitin-proteasome system, has emerged as an attractive novel cancer chemotherapeutic modality. Although proteasome inhibitors have been most successfully applied in the treatment of hematological malignancies, they also received continuing interest for the treatment of solid tumors. In this review, we summarize the current positioning of proteasome inhibitors in the treatment of common solid malignancies (e.g., lung, colon, pancreas, breast, and head and neck cancer), addressing topics of their mechanism(s) of action, predictive factors and molecular mechanisms of resistance.

Synthetic siRNA targeting human papillomavirus 16 E6: a perspective on in vitro nanotherapeutic approaches

High-risk human papillomaviruses infect skin and mucosa, causing approximately 5% of cancers worldwide. In the search for targeted nanotherapeutic approaches, siRNAs against the viral E6 transcript have been molecules of interest but have not yet seen successful translation into the clinic. By reviewing the past approximately 15 years of in vitro literature, we identify the need for siRNA validation protocols which concurrently evaluate ranges of key treatment parameters as well as characterize downstream process restoration in a methodical, quantitative manner and demonstrate their implementation using our own data. We also reflect on the future need for more appropriate cell culture models to represent patient lesions as well as the application of personalized approaches to identify optimal treatment strategies.

3q26-29 Amplification in head and neck squamous cell carcinoma: a review of established and prospective oncogenes

Head and neck squamous cell carcinoma (HNSCC) is significantly underrepresented in worldwide cancer research, yet survival rates for the disease have remained static for over 50 years. Distant metastasis is often present at the time of diagnosis, and is the primary cause of death in cancer patients. In the absence of routine effective targeted therapies, the standard of care treatment remains chemoradiation in combination with (often disfiguring) surgery. A defining characteristic of HNSCC is the amplification of a region of chromosome 3 (3q26-29), which is consistently associated with poorer patient outcome. This review provides an overview of the role the 3q26-29 region plays in HNSCC, in terms of both known and as yet undiscovered processes, which may have potential clinical relevance.

DNA-based immunotherapy for HPV-associated head and neck cancer

Squamous cell carcinoma of the head and neck (SCCHN) accounts for 3% of all cancers. Most patients present with locally advanced disease, where multimodality therapies are used with curative intent. Despite favorable early local treatment results, about one third of the patients will eventually develop metastatic disease. Immunotherapy offers a novel therapeutic strategy beyond cytotoxic chemotherapy, with initial approvals in melanoma and non-small-cell lung cancer. HPV-associated SCCHN is a distinct subset, with unique epidemiology and treatment outcomes. Both subsets of SCCHN (HPV-related or not) are particularly favorable for immunotherapy, as immune evasion and dysregulation have been shown to play a key role in the initiation and progression of disease. This review focuses on the latest developments in immunotherapy in SCCHN, with a particular focus on DNA-based approaches including vaccine and adoptive cellular therapies.

Infectious Agents Associated with Head and Neck Carcinomas

In addition to traditional risk factors such as smoking habits and alcohol consumption, certain microbes also play an important role in the generation of head and neck carcinomas. Infection with high-risk human papillomavirus types is strongly associated with the development of oropharyngeal carcinoma, and Epstein-Barr virus appears to be indispensable for the development of non-keratinizing squamous cell carcinoma of the nasopharynx. Other viruses including torque teno virus and hepatitis C virus may act as co-carcinogens, increasing the risk of malignant transformation. A shift in the composition of the oral microbiome was associated with the development of oral squamous cell carcinoma, although the causal or casual role of oral bacteria remains to be clarified. Conversion of ethanol to acetaldehyde, a mutagenic compound, by members of the oral microflora as well as by fungi including Candida albicans and others is a potential mechanism that may increase oral cancer risk. In addition, distinct Candida spp. also produce NBMA (N-nitrosobenzylmethylamine), a potent carcinogen. Inflammatory processes elicited by microbes may also facilitate tumorigenesis in the head and neck region.

TRIP12 as a mediator of human papillomavirus/p16-related radiation enhancement effects

Patients with human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) have better responses to radiotherapy and higher overall survival rates than do patients with HPV-negative HNSCC, but the mechanisms underlying this phenomenon are unknown. p16 is used as a surrogate marker for HPV infection. Our goal was to examine the role of p16 in HPV-related favorable treatment outcomes and to investigate the mechanisms by which p16 may regulate radiosensitivity. HNSCC cells and xenografts (HPV/p16-positive and -negative) were used. p16-overexpressing and small hairpin RNA-knockdown cells were generated, and the effect of p16 on radiosensitivity was determined by clonogenic cell survival and tumor growth delay assays. DNA double-strand breaks (DSBs) were assessed by immunofluorescence analysis of 53BP1 foci; DSB levels were determined by neutral comet assay; western blotting was used to evaluate protein changes; changes in protein half-life were tested with a cycloheximide assay; gene expression was examined by real-time polymerase chain reaction; and data from The Cancer Genome Atlas HNSCC project were analyzed. p16 overexpression led to downregulation of TRIP12, which in turn led to increased RNF168 levels, repressed DNA damage repair (DDR), increased 53BP1 foci and enhanced radioresponsiveness. Inhibition of TRIP12 expression further led to radiosensitization, and overexpression of TRIP12 was associated with poor survival in patients with HPV-positive HNSCC. These findings reveal that p16 participates in radiosensitization through influencing DDR and support the rationale of blocking TRIP12 to improve radiotherapy outcomes.

A Small Molecule Inhibitor Selectively Induces Apoptosis in Cells Transformed by High Risk Human Papilloma Viruses

A phenotypic high-throughput cell culture screen was performed to identify compounds that prevented proliferation of the human Papilloma virus type 16 (HPV-16) transformed cell line Ca Ski. A series of quinoxaline compounds exemplified by Compound 1 was identified. Testing against a panel of cell lines demonstrated that Compound 1 selectively inhibited replication of all HPV-16, HPV-18, and HPV-31 transformed cell lines tested with 50% Inhibitory Concentration (IC₅₀) values of 2 to 8 μM relative to IC₅₀ values of 28 to 73 μM in HPV-negative cell lines. Treatment with Compound 1 resulted in a cascade of multiple apoptotic events, including selective activation of effector caspases 3 and 7, fragmentation of cellular DNA, and PARP (poly(ADP-ribose) polymerase) cleavage in HPV-positive cells relative to HPV-negative cells. Unregulated proliferation of HPV transformed cells is dependent on the viral oncogenes, E6 and E7. Treatment with Compound 1 resulted in a decrease in HPV E7 protein in Ca Ski cells. However, the timing of this reduction relative to other effects of compound treatment suggests that this was a consequence, rather than a cause, of the apoptotic cascade. Likewise, compound treatment resulted in no obvious effects on the E6- and E7- mediated down regulation of p53 and Rb, or their downstream effectors, p21 or PCNA. Further investigation of apoptotic signals induced by Compound 1 revealed cleavage of Caspase-8 in HPV-positive cells as early as 2 hours post-treatment, suggesting the compound initiates apoptosis through the extrinsic, death receptor-mediated, pathway of cell death. These studies provide proof of concept that cells transformed by oncogenic Papillomaviruses can be selectively induced to undergo apoptosis by compound treatment.

Increased sensitivity of HPV-positive head and neck cancer cell lines to x-irradiation ± Cisplatin due to decreased expression of E6 and E7 oncoproteins and enhanced apoptosis

Squamous cell carcinoma of the head and neck region (HNSCC), which is related to an infection with human papilloma virus (HPV), responds better to simultaneous radio-chemotherapy with Cisplatin based regimens than HPV-negative tumors. The underlying molecular mechanisms for this clinical observation are not fully understood. Therefore, the response of four HPV-positive (HPV+) (UM-SCC-47, UM-SCC-104, 93-VU-147T, UPCI:SCC152) and four HPV-negative (HPV-) (UD-SCC-1, UM-SCC-6, UM-SCC-11b, UT-SCC-33) HNSCC cell lines to x-irradiation ± Cisplatin incubation in terms of clonogenic survival, cell cycle progression, protein expression (cyclin A2, cyclin E2, E6, E7, p53) and induction of apoptosis, was investigated. HPV+ cells were more radio- and chemosensitive and were more effectively sensitized to x-irradiation by simultaneous Cisplatin incubation than HPV- cell lines. HPV+ cell lines revealed an increased and prolonged G2/M arrest after irradiation, whereas Cisplatin induced a blockage of cells in S phase. In comparison to irradiation only, addition of Cisplatin significantly enhanced apoptosis especially in HPV+ cell lines. While irradiation alone increased the amount of HPV E6 and E7 proteins, both were down-regulated by Cisplatin incubation either alone or in combination with x-rays, which however did not increase the expression of endogenous p53. Our results demonstrate that cell cycle deregulation together with downregulation of HPV E6 and E7 proteins facilitating apoptosis after Cisplatin incubation promote the enhanced sensitivity of HPV+ HNSCC cells to simultaneous radio-chemotherapy. Combined effects of irradiation and Cisplatin appear to be relevant in mediating the enhanced therapeutic response of HPV-related HNSCC and are indicative of the benefit of combined modality approaches in future treatment optimization strategies.

Anti-proliferative effects of polyphenols from pomegranate rind (Punica granatum L.) on EJ bladder cancer cells via regulation of p53/miR-34a axis

miRNAs and their validated miRNA targets appear as novel effectors in biological activities of plant polyphenols; however, limited information is available on miR-34a mediated cytotoxicity of pomegranate rind polyphenols in cancer cell lines. For this purpose, cell viability assay, Realtime quantitative PCR for mRNA quantification, western blot for essential protein expression, p53 silencing by shRNA and miR-34a knockdown were performed in the present study. EJ cell treatment with 100 µg (GAE)/mL PRE for 48 h evoked poor cell viability and caspase-dependent pro-apoptosis appearance. PRE also elevated p53 protein and triggered miR-34a expression. The c-Myc and CD44 were confirmed as direct targets of miR-34a in EJ cell apoptosis induced by PRE. Our results provide sufficient evidence that polyphenols in PRE can be potential molecular clusters to suppress bladder cancer cell EJ proliferation via p53/miR-34a axis.

Bortezomib sensitises TRAIL-resistant HPV-positive head and neck cancer cells to TRAIL through a caspase-dependent, E6-independent mechanism

Human papillomavirus (HPV) is causative for a new and increasing form of head and neck squamous cell carcinomas (HNSCCs). Although localised HPV-positive cancers have a favourable response to radio-chemotherapy (RT/CT), the impact of HPV in advanced or metastatic HNSCC remains to be defined and targeted therapeutics need to be tested for cancers resistant to RT/CT. To this end, we investigated the sensitivity of HPV-positive and -negative HNSCC cell lines to TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), which induces tumour cell-specific apoptosis in various cancer types. A clear correlation was observed between HPV positivity and resistance to TRAIL compared with HPV-negative head and neck cancer cell lines. All TRAIL-resistant HPV-positive cell lines tested were sensitised to TRAIL-induced cell death by treatment with bortezomib, a clinically approved proteasome inhibitor. Bortezomib-mediated sensitisation to TRAIL was associated with enhanced activation of caspase-8, -9 and -3, elevated membrane expression levels of TRAIL-R2, cytochrome c release and G2/M arrest. Knockdown of caspase-8 significantly blocked cell death induced by the combination therapy, whereas the BH3-only protein Bid was not required for induction of apoptosis. XIAP depletion increased the sensitivity of both HPV-positive and -negative cells to TRAIL alone or in combination with bortezomib. In contrast, restoration of p53 following E6 knockdown in HPV-positive cells had no effect on their sensitivity to either single or combination therapy, suggesting a p53-independent pathway for the observed response. In summary, bortezomib-mediated proteasome inhibition sensitises previously resistant HPV-positive HNSCC cells to TRAIL-induced cell death through a mechanism involving both the extrinsic and intrinsic pathways of apoptosis. The cooperative effect of these two targeted anticancer agents therefore represents a promising treatment strategy for RT/CT-resistant HPV-associated head and neck cancers.

Wild-type p53 reactivation by small-molecule Minnelide™ in human papillomavirus (HPV)-positive head and neck squamous cell carcinoma

OBJECTIVES

The incidence of high-risk human papillomavirus (HR-HPV) head and neck squamous cell carcinoma (HNSCC) continues to increase, particularly oropharyngeal squamous cell carcinoma (OPSCC) cases. The inactivation of the p53 tumor suppressor gene promotes a chain of molecular events, including cell cycle progression and apoptosis resistance. Reactivation of wild-type p53 function is an intriguing therapeutic strategy. The aim of this study was to investigate whether a novel compound derived from diterpene triepoxide (Minnelide™) can reactivate wild-type p53 function in HPV-positive HNSCC.

MATERIALS AND METHODS

For all of our in vitro experiments, we used 2 HPV-positive HNSCC cell lines, University of Michigan squamous cell carcinoma (UM-SCC) 47 and 93-VU-147, and 2 HPV-positive human cervical cancer cell lines, SiHa and CaSki. Cells were treated with different concentrations of triptolide and analyzed for p53 activation. Mice bearing UM-SCC 47 subcutaneous xenografts and HPV-positive patient-derived tumor xenografts were treated with Minnelide and evaluated for tumor growth and p53 activation.

RESULTS

In HPV-positive HNSCC, Minnelide reactivated p53 by suppressing E6 oncoprotein. Activation of apoptosis followed, both in vitro and in vivo. In 2 preclinical HNSCC animal models (a subcutaneous xenograft model and a patient-derived tumor xenograft model), Minnelide reactivated p53 function and significantly decreased tumor progression and tumor volume.

CONCLUSION

Triptolide and Minnelide caused cell death in vitro and in vivo in HPV-positive HNSCC by reactivating wild-type p53 and thus inducing apoptosis. In addition, in 2 HPV-positive HNSCC animal models, Minnelide decreased tumor progression and induced apoptosis.

Carfilzomib and oprozomib synergize with histone deacetylase inhibitors in head and neck squamous cell carcinoma models of acquired resistance to proteasome inhibitors

Acquired resistance to proteasome inhibitors represents a considerable impediment to their effective clinical application. Carfilzomib and its orally bioavailable structural analog oprozomib are second-generation, highly-selective, proteasome inhibitors. However, the mechanisms of acquired resistance to carfilzomib and oprozomib are incompletely understood, and effective strategies for overcoming this resistance are needed. Here, we developed models of acquired resistance to carfilzomib in two head and neck squamous cell carcinoma cell lines, UMSCC-1 and Cal33, through gradual exposure to increasing drug concentrations. The resistant lines R-UMSCC-1 and R-Cal33 demonstrated 205- and 64-fold resistance, respectively, relative to the parental lines. Similarly, a high level of cross-resistance to oprozomib, as well as paclitaxel, was observed, whereas only moderate resistance to bortezomib (8- to 29-fold), and low level resistance to cisplatin (1.5- to 5-fold) was seen. Synergistic induction of apoptosis signaling and cell death, and inhibition of colony formation followed co-treatment of acquired resistance models with carfilzomib and the histone deacetylase inhibitor (HDACi) vorinostat. Synergism was also seen with other combinations, including oprozomib plus vorinostat, or carfilzomib plus the HDACi entinostat. Synergism was accompanied by upregulation of proapoptotic Bik, and suppression of Bik attenuated the synergy. The acquired resistance models also exhibited elevated levels of MDR-1/P-gp. Inhibition of MDR-1/P-gp with reversin 121 partially overcame carfilzomib resistance in R-UMSCC-1 and R-Cal33 cells. Collectively, these studies indicate that combining carfilzomib or oprozomib with HDAC or MDR-1/P-gp inhibitors may be a useful strategy for overcoming acquired resistance to these proteasome inhibitors.

Drugging the p53 pathway: understanding the route to clinical efficacy

The tumour suppressor p53 is the most frequently mutated gene in human cancer, with more than half of all human tumours carrying mutations in this particular gene. Intense efforts to develop drugs that could activate or restore the p53 pathway have now reached clinical trials. The first clinical results with inhibitors of MDM2, a negative regulator of p53, have shown efficacy but hint at on-target toxicities. Here, we describe the current state of the development of p53 pathway modulators and new pathway targets that have emerged. The challenge of targeting protein-protein interactions and a fragile mutant transcription factor has stimulated many exciting new approaches to drug discovery.

Caspase-8 mutations in head and neck cancer confer resistance to death receptor-mediated apoptosis and enhance migration, invasion, and tumor growth

Little is known regarding molecular markers in head and neck squamous cell carcinoma (HNSCC) that predict responsiveness to different therapeutic regimens or predict HNSCC progression. Mutations in procaspase-8 occur in 9% of HNSCC primary tumors, but the functional consequences of these mutations are poorly understood. In this study, we examined the impact of four, representative, HNSCC-associated procaspase-8 mutations on activation of the extrinsic apoptosis pathway, as well as cellular migration and invasion, and in vivo tumor growth. All four mutant proteins acted to potently inhibit activation of apoptosis following treatment with TRAIL or agonistic anti-Fas. In contrast to wild-type procaspase-8, the mutant proteins were not recruited to FADD following treatment with TRAIL or anti-Fas, but may be constitutively bound by FADD. Three of the four procaspase-8 mutants promoted enhanced cellular migration and invasion through matrigel, relative to that seen with the wild-type procaspase-8 protein. Procaspase-8 mutation also stimulated the growth of HNSCC xenograft tumors. These findings indicate that HNSCC-associated procaspase-8 mutations inhibit activation of the extrinsic apoptosis pathway and are likely to represent markers for resistance to therapeutic regimens incorporating death receptor activators. Moreover, procaspase-8 mutations may serve as markers of HNSCC tumor progression, as exemplified by enhanced migration, invasion, and tumor growth.

Single-agent obatoclax (GX15-070) potently induces apoptosis and pro-survival autophagy in head and neck squamous cell carcinoma cells

OBJECTIVES

More than half of head and neck squamous cell carcinoma (HNSCC) patients are initially treated with curative intent, but will relapse over the course of their disease and have poor prognosis with a median survival of approximately 6months. Novel therapeutic approaches are in desperate need for this patient population. The anti-apoptotic BCL-2 family proteins such as BCL-2, BCL-XL, and MCL-1 are involved in oncogenesis and chemoresistance and are overexpressed in HNSCC. Obatoclax is a small-molecule antagonist of the BH3-binding groove of anti-apoptotic BCL-2 family. We evaluated the activity of obatoclax against 4 HNSCC cell lines (UMSCC-1, Cal33, 1483, UMSCC-22A).

METHODS

Cell viability was determined by MTT assay, cell cycle status by propidium iodide staining, and apoptosis by Annexin-V staining and immunoblotting. Autophagy was assessed by immunofluorescence and immunoblotting.

RESULTS

All four HNSCC cell lines were highly sensitive to single-agent obatoclax with IC50's ranging from 46 to 177nM. Obatoclax induced apoptosis in all four HNSCC cell lines as evidenced by increases in sub-G1 DNA content, Annexin-V staining, and PARP cleavage. In addition, obatoclax induced autophagy in all 4 cell lines, and the addition of the autophagy inhibitor chloroquine enhanced obatoclax cytotoxicity.

CONCLUSION

Our findings demonstrate potent monotherapeutic activity of obatoclax against HNSCC cells, and enhancement of this activity in the presence of chloroquine. This preclinical study suggests that obatoclax might have therapeutic value in the treatment of HNSCC, either alone or in combination with inhibitors of autophagy.

Pathways enrichment analysis for differentially expressed genes in squamous lung cancer

Squamous lung cancer (SQLC) is a common type of lung cancer, but its oncogenesis mechanism is not so clear. The aim of this study was to screen the potential pathways changed in SQLC and elucidate the mechanism of it. Published microarray data of GSE3268 series was downloaded from Gene Expression Omnibus (GEO). Significance analysis of microarrays was performed using software R, and differentially expressed genes (DEGs) were harvested. The functions and pathways of DEGs were mapped in Gene Otology and KEGG pathway database, respectively. A total of 2961 genes were filtered as DEGs between normal and SQLC cells. Cell cycle and metabolism were the mainly changed functions of SQLC cells. Meanwhile genes such as MCM, RFC, FEN1, and POLD may induce SQLC through DNA replication pathway, and genes such as PTTG1, CCNB1, CDC6, and PCNA may be involved in SQLC through cell cycle pathway. It is demonstrated that pathway analysis is useful in the identification of target genes in SQLC.