The Fanconi anemia pathway: repairing the link between DNA damage and squamous cell carcinoma

Overview of familial syndromes with increased skin malignancies

The vast majority of skin cancers can be classified into two main types: melanoma and keratinocyte carcinomas. The most common keratinocyte carcinomas include basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Multiple familial syndromes have been identified that can increase the risk of developing SCC, BCC, and/or melanoma. The major syndromes include oculocutaneous albinism for SCC, basal cell nevus syndrome for BCC, familial atypical multiple mole-melanoma syndrome, and hereditary breast and ovarian cancer syndrome for melanoma. In addition, familial syndromes that can predispose individuals to all three major skin cancers include xeroderma pigmentosum and Li-Fraumeni syndrome. This review highlights the epidemiology, risk factors, pathogenesis, and etiology of the major and minor syndromes to better identify and manage these conditions. Current investigational trials in genomic medicine are making their way in revolutionizing the clinical diagnosis of these familial syndromes for earlier preventative measures and improvement of long-term prognosis in these patients.

A Rare MSH2 Variant as a Candidate Marker for Lynch Syndrome II Screening in Tunisia: A Case of Diffuse Gastric Carcinoma

Several syndromic forms of digestive cancers are known to predispose to early-onset gastric tumors such as Hereditary Diffuse Gastric Cancer (HDGC) and Lynch Syndrome (LS). LSII is an extracolonic cancer syndrome characterized by a tumor spectrum including gastric cancer (GC). In the current work, our main aim was to identify the mutational spectrum underlying the genetic predisposition to diffuse gastric tumors occurring in a Tunisian family suspected of both HDGC and LS II syndromes. We selected the index case “JI-021”, which was a woman diagnosed with a Diffuse Gastric Carcinoma and fulfilling the international guidelines for both HDGC and LSII syndromes. For DNA repair, a custom panel targeting 87 candidate genes recovering the four DNA repair pathways was used. Structural bioinformatics analysis was conducted to predict the effect of the revealed variants on the functional properties of the proteins. DNA repair genes panel screening identified two variants: a rare MSH2 c.728G>A classified as a variant with uncertain significance (VUS) and a novel FANCD2 variant c.1879G>T. The structural prediction model of the MSH2 variant and electrostatic potential calculation showed for the first time that MSH2 c.728G>A is likely pathogenic and is involved in the MSH2-MLH1 complex stability. It appears to affect the MSH2-MLH1 complex as well as DNA-complex stability. The c.1879G>T FANCD2 variant was predicted to destabilize the protein structure. Our results showed that the MSH2 p.R243Q variant is likely pathogenic and is involved in the MSH2-MLH1 complex stability, and molecular modeling analysis highlights a putative impact on the binding with MLH1 by disrupting the electrostatic potential, suggesting the revision of its status from VUS to likely pathogenic. This variant seems to be a shared variant in the Mediterranean region. These findings emphasize the importance of testing DNA repair genes for patients diagnosed with diffuse GC with suspicion of LSII and colorectal cancer allowing better clinical surveillance for more personalized medicine.

Head and Neck Cancer Susceptibility and Metabolism in Fanconi Anemia

Fanconi anemia (FA) is a rare inherited, generally autosomal recessive syndrome, but it displays X-linked or dominant negative inheritance for certain genes. FA is characterized by a deficiency in DNA damage repair that results in bone marrow failure, and in an increased risk for various epithelial tumors, most commonly squamous cell carcinomas of the head and neck (HNSCC) and of the esophagus, anogenital tract and skin. Individuals with FA exhibit increased human papilloma virus (HPV) prevalence. Furthermore, a subset of anogenital squamous cell carcinomas (SCCs) in FA harbor HPV sequences and FA-deficient laboratory models reveal molecular crosstalk between HPV and FA proteins. However, a definitive role for HPV in HNSCC development in the FA patient population is unproven. Cellular metabolism plays an integral role in tissue homeostasis, and metabolic deregulation is a known hallmark of cancer progression that supports uncontrolled proliferation, tumor development and metastatic dissemination. The metabolic consequences of FA deficiency in keratinocytes and associated impact on the development of SCC in the FA population is poorly understood. Herein, we review the current literature on the metabolic consequences of FA deficiency and potential effects of resulting metabolic reprogramming on FA cancer phenotypes.

Laryngeal cancers in paediatric and young adult patients: epidemiology, biology and treatment

PURPOSE OF REVIEW

The aim of thi study was to review the recent literature on epidemiology, biology and treatment of laryngeal cancer in paediatric and young adult patients.

RECENT FINDINGS

Epidemiological studies reported that 2-10% of patients with laryngeal cancer are younger than 40-year-old, while the prevalence of laryngeal cancer remains unknown in the paediatric population. The development of laryngeal cancer in young adults is multifactorial and may be linked to common carcinogens (tobacco and alcohol), occupational factors, laryngopharyngeal reflux, immunosuppression, human papillomavirus infection and genetic polymorphism. A substantial number of cohort studies reported a significant lower proportion of drinkers and smokers in young populations with laryngeal cancer, supporting the higher prevalence of chromosomal losses or abnormalities predisposing to cancer in this group. The development of laryngeal cancer in paediatric patients is strongly associated with genetic syndromes with DNA repair abnormalities. The pathological, clinical and survival outcome differences between young and old patient groups vary significantly between studies, depending on epidemiological, genetic features and therapeutic strategies used.

SUMMARY

Paediatric and adult populations with laryngeal cancer present different clinical, pathological and survival outcomes. In the adult population, the patient age at the time of disease development underlies genetic and etiological differences with different mutation patterns between young and old patients, the latter being more frequently individuals with a history of tobacco and alcohol abuse. The differences between age groups regarding stage of cancer at initial presentation, as well as clinical and survival outcomes, are unclear, which may be due to demographic, ethnicity and population genetic differences.

FANCD2 limits acetaldehyde-induced genomic instability during DNA replication in esophageal keratinocytes

Individuals with Fanconi anemia (FA), a rare genetic bone marrow failure syndrome, have an increased risk of young-onset head and neck squamous cell carcinomas (SCCs) and esophageal SCC. The FA DNA repair pathway is activated upon DNA damage induced by acetaldehyde, a chief alcohol metabolite and one of the major carcinogens in humans. However, the molecular basis of acetaldehyde-induced genomic instability in SCCs of the head and neck and of the esophagus in FA remains elusive. Here, we report the effects of acetaldehyde on replication stress response in esophageal epithelial cells (keratinocytes). Acetaldehyde-exposed esophageal keratinocytes displayed accumulation of DNA damage foci consisting of 53BP1 and BRCA1. At physiologically relevant concentrations, acetaldehyde activated the ATR-Chk1 pathway, leading to S- and G2/M-phase delay with accumulation of the FA complementation group D2 protein (FANCD2) at the sites of DNA synthesis, suggesting that acetaldehyde impedes replication fork progression. Consistently, depletion of the replication fork protection protein Timeless led to elevated DNA damage upon acetaldehyde exposure. Furthermore, FANCD2 depletion exacerbated replication abnormalities, elevated DNA damage, and led to apoptotic cell death, indicating that FANCD2 prevents acetaldehyde-induced genomic instability in esophageal keratinocytes. These observations contribute to our understanding of the mechanisms that drive genomic instability in FA patients and alcohol-related carcinogenesis, thereby providing a translational implication in the development of more effective therapies for SCCs.

Post-hematopoietic stem cell transplant squamous cell carcinoma in patients with Fanconi anemia: a dreadful enemy

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) is a curative option for patients with Fanconi anemia (FA) and hematological manifestations but it does not prevent solid tumors, especially squamous cell carcinomas (SCC).

METHODS

Retrospective study in 22 FA patients who had received HSCT and had been followed up beyond 2 years after HSCT.

RESULTS

The median follow-up was 15 years. Six patients developed head-and-neck SCC after transplantation. The cumulative incidence of SCC at 15 and 30 years from the HSCT was 14.2% and 71.2%, respectively. One patient was diagnosed in stage IV and the rest, who were being followed up in cancer screening programs, in stage I. Treatment of SCC consisted of surgery in all patients; radiotherapy and chemotherapy were used in two patients and were poorly tolerated.

CONCLUSION

FA patients have high risk of head-and-neck SCC. Multi-disciplinary programs for early cancer detection are of special relevance in these patients.

Oral Cancer: Genetics and the Role of Precision Medicine

Oral squamous cell carcinoma (OSCC) is one of the leading cancers in the world. OSCC patients are managed with surgery and/or chemoradiation. Prognoses and survival rates are dismal, however, and have not improved for more than 20 years. Recently, the concept of precision medicine was introduced, and the introduction of targeted therapeutics demonstrated promising outcomes. This article reviews the current understanding of initiation, progression, and metastasis of OSCC from both genetic and epigenetic perspectives. In addition, the applications and integration of omics technologies in biomarker discovery and drug development for treating OSCC are reviewed.

Targeted Treatment of Head and Neck (Pre)Cancer: Preclinical Target Identification and Development of Novel Therapeutic Applications

Head and neck squamous cell carcinomas (HNSCC) develop in the mucosal lining of the upper-aerodigestive tract. In carcinogen-induced HNSCC, tumors emerge from premalignant mucosal changes characterized by tumor-associated genetic alterations, also coined as 'fields' that are occasionally visible as leukoplakia or erythroplakia lesions but are mostly invisible. Consequently, HNSCC is generally diagnosed de novo at more advanced stages in about 70% of new diagnosis. Despite intense multimodality treatment protocols, the overall 5-years survival rate is 50-60% for patients with advanced stage of disease and seems to have reached a plateau. Of notable concern is the lack of further improvement in prognosis despite advances in treatment. This can be attributed to the late clinical presentation, failure of advanced HNSCC to respond to treatment, the deficit of effective targeted therapies to eradicate tumors and precancerous changes, and the lack of suitable markers for screening and personalized therapy. The molecular landscape of head and neck cancer has been elucidated in great detail, but the absence of oncogenic mutations hampers the identification of druggable targets for therapy to improve outcome of HNSCC. Currently, functional genomic approaches are being explored to identify potential therapeutic targets. Identification and validation of essential genes for both HNSCC and oral premalignancies, accompanied with biomarkers for therapy response, are being investigated. Attentive diagnosis and targeted therapy of the preceding oral premalignant (preHNSCC) changes may prevent the development of tumors. As classic oncogene addiction through activating mutations is not a realistic concept for treatment of HNSCC, synthetic lethality and collateral lethality need to be exploited, next to immune therapies. In recent studies it was shown that cell cycle regulation and DNA damage response pathways become significantly altered in HNSCC causing replication stress, which is an avenue that deserves further exploitation as an HNSCC vulnerability for treatment. The focus of this review is to summarize the current literature on the preclinical identification of potential druggable targets for therapy of (pre)HNSCC, emerging from the variety of gene knockdown and knockout strategies, and the testing of targeted inhibitors. We will conclude with a future perspective on targeted therapy of HNSCC and premalignant changes.

Canonical and Noncanonical Roles of Fanconi Anemia Proteins: Implications in Cancer Predisposition

Simple Summary

Fanconi anemia (FA) is a genetic disorder that is characterized by bone marrow failure (BMF), developmental abnormalities, and predisposition to cancer. In this review, we present an overview of both canonical (regulation of interstrand cross-links repair, ICLs) and noncanonical roles of FA proteins. We divide noncanonical alternative functions in two types: nuclear (outside ICLs such as FA action in replication stress or DSB repair) and cytosolic (such as in mitochondrial quality control or selective autophagy). We further discuss the involvement of FA genes in the predisposition to develop different types of cancers and we examine current DNA damage response-targeted therapies. Finally, we promote an insightful perspective regarding the clinical implication of the cytosolic noncanonical roles of FA proteins in cancer predisposition, suggesting that these alternative roles could be of critical importance for disease progression.

Abstract

Fanconi anemia (FA) is a clinically and genetically heterogeneous disorder characterized by the variable presence of congenital somatic abnormalities, bone marrow failure (BMF), and a predisposition to develop cancer. Monoallelic germline mutations in at least five genes involved in the FA pathway are associated with the development of sporadic hematological and solid malignancies. The key function of the FA pathway is to orchestrate proteins involved in the repair of interstrand cross-links (ICLs), to prevent genomic instability and replication stress. Recently, many studies have highlighted the importance of FA genes in noncanonical pathways, such as mitochondria homeostasis, inflammation, and virophagy, which act, in some cases, independently of DNA repair processes. Thus, primary defects in DNA repair mechanisms of FA patients are typically exacerbated by an impairment of other cytoprotective pathways that contribute to the multifaceted clinical phenotype of this disease. In this review, we summarize recent advances in the understanding of the pathogenesis of FA, with a focus on the cytosolic noncanonical roles of FA genes, discussing how they may contribute to cancer development, thus suggesting opportunities to envisage novel therapeutic approaches.

Management of Fanconi Anemia patients with head and neck carcinoma: Diagnosis and treatment adaptation

Fanconi anemia (FA) is a rare genetic disease that is mostly transmitted, according to a recessive model with biallelic germline alterations in one of the 22 genes of the FA pathway, or monoallelic alteration of the 23rd FA gene (RAD51). The FA pathway is implicated in interstrand DNA crosslink repair, induces genome stability, and is a potent driver of tumorigenesis. Patients with FA have a 500 to 1000-fold increased risk of developing head and neck squamous cell carcinoma (HNSCC). Patients with FA developing an HNSCC, usually have severe radiation toxicities. In this context, the modalities of radiation therapy should be adapted. Some patients with FA present a milder phenotype, especially in the case of medullary FA gene spontaneous reversion. Therefore, in an unusual context of HNSCC, such as no risk factors or a young age, it may be very useful to search anemia or development abnormalities, that may unravel a yet undiagnosed FA disease. Besides, in some young patients with HNSCC who did not suffer from FA, a monoallelic germline alteration in an FA gene could be combined with a second risk factor such as HPV infection or APOBEC alteration. Although several in vitro studies showed that normal cells with monoallelic FA gene alteration may have a particular radiosensitivity, these observations have not been confirmed in vivo in FA heterozygotes patients. Finally, some somatic activating alterations have also been found in HSNCC tumor samples and could be associated with radioresistance.

Drug Sensitivity Prediction Models Reveal a Link between DNA Repair Defects and Poor Prognosis in HNSCC

Head and neck squamous cell carcinoma (HNSCC) is characterized by the frequent manifestation of DNA crosslink repair defects. We established novel expression-based DNA repair defect markers to determine the clinical impact of such repair defects. Using hypersensitivity to the DNA crosslinking agents, mitomycin C and olaparib, as proxies for functional DNA repair defects in a panel of 25 HNSCC cell lines, we applied machine learning to define gene expression models that predict repair defects. The expression profiles established predicted hypersensitivity to DNA-damaging agents and were associated with mutations in crosslink repair genes, as well as downregulation of DNA damage response and repair genes, in two independent datasets. The prognostic value of the repair defect prediction profiles was assessed in two retrospective cohorts with a total of 180 patients with advanced HPV-negative HNSCC, who were treated with cisplatin-based chemoradiotherapy. DNA repair defects, as predicted by the profiles, were associated with poor outcome in both patient cohorts. The poor prognosis association was particularly strong in normoxic tumor samples and was linked to an increased risk of distant metastasis. In vitro, only crosslink repair-defective HNSCC cell lines are highly migratory and invasive. This phenotype could also be induced in cells by inhibiting rad51 in repair competent and reduced by DNA-PK inhibition. In conclusion, DNA crosslink repair prediction expression profiles reveal a poor prognosis association in HNSCC. SIGNIFICANCE: This study uses innovative machine learning-based approaches to derive models that predict the effect of DNA repair defects on treatment outcome in HNSCC.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/21/5597/F1.large.jpg.

Holding All the Cards-How Fanconi Anemia Proteins Deal with Replication Stress and Preserve Genomic Stability

Fanconi anemia (FA) is a hereditary chromosomal instability disorder often displaying congenital abnormalities and characterized by a predisposition to progressive bone marrow failure (BMF) and cancer. Over the last 25 years since the discovery of the first linkage of genetic mutations to FA, its molecular genetic landscape has expanded tremendously as it became apparent that FA is a disease characterized by a defect in a specific DNA repair pathway responsible for the correction of covalent cross-links between the two complementary strands of the DNA double helix. This pathway has become increasingly complex, with the discovery of now over 20 FA-linked genes implicated in interstrand cross-link (ICL) repair. Moreover, gene products known to be involved in double-strand break (DSB) repair, mismatch repair (MMR), and nucleotide excision repair (NER) play roles in the ICL response and repair of associated DNA damage. While ICL repair is predominantly coupled with DNA replication, it also can occur in non-replicating cells. DNA damage accumulation and hematopoietic stem cell failure are thought to contribute to the increased inflammation and oxidative stress prevalent in FA. Adding to its confounding nature, certain FA gene products are also engaged in the response to replication stress, caused endogenously or by agents other than ICL-inducing drugs. In this review, we discuss the mechanistic aspects of the FA pathway and the molecular defects leading to elevated replication stress believed to underlie the cellular phenotypes and clinical features of FA.

Oral Cancer: Genetics and the Role of Precision Medicine

Oral squamous cell carcinoma (OSCC) is one of the leading cancers in the world. OSCC patients are managed with surgery and/or chemoradiation. Prognoses and survival rates are dismal, however, and have not improved for more than 20 years. Recently, the concept of precision medicine was introduced, and the introduction of targeted therapeutics demonstrated promising outcomes. This article reviews the current understanding of initiation, progression, and metastasis of OSCC from both genetic and epigenetic perspectives. In addition, the applications and integration of omics technologies in biomarker discovery and drug development for treating OSCC are reviewed.

Salivary lactate dehydrogenase (LDH) as a tool for early diagnosis of oral cancer in individuals with Fanconi anemia

Currently one of the greater challenges is the diagnosis and treatment of cancer. Many studies address the genetic and metabolic aspects to support in early diagnosis and increase the survival of individuals at high risk. Individuals with Fanconi anemia can be included in this high risk group because they have a predisposition to develop head and neck cancer. The use of salivary enzymes as biomarkers to detect the changes in oral tissue at the initial phase seems viable, because saliva is easy to obtain, it moisture oral mucosa and cells metabolic compounds can be found on it. Due to the metabolic characteristics of the cancer cell, an increase in Lactate Dehydrogenase (LDH) may indicate a carcinogenesis process. The hypothesis of this study is to use of salivary LDH as a tool in the early diagnosis of oral cancer on a high risk group such as Fanconi anemia's patients.

Molecular mechanisms of the preventable causes of cancer in the United States

Annually, there are 1.6 million new cases of cancer and nearly 600,000 cancer deaths in the United States alone. The public health burden associated with these numbers has motivated enormous research efforts into understanding the root causes of cancer. These efforts have led to the recognition that between 40% and 45% of cancers are associated with preventable risk factors and, importantly, have identified specific molecular mechanisms by which these exposures modify human physiology to induce or promote cancer. The increasingly refined knowledge of these mechanisms, which we summarize here, emphasizes the need for greater efforts toward primary cancer prevention through mitigation of modifiable risk factors. It also suggests exploitable avenues for improved secondary prevention (which includes the development of therapeutics designed for cancer interception and enhanced techniques for noninvasive screening and early detection) based on detailed knowledge of early neoplastic pathobiology. Such efforts would complement the current emphasis on the development of therapeutic approaches to treat established cancers and are likely to result in far greater gains in reducing morbidity and mortality.

Fanconi anemia and homologous recombination gene variants are associated with functional DNA repair defects in vitro and poor outcome in patients with advanced head and neck squamous cell carcinoma

Mutations in Fanconi Anemia or Homologous Recombination (FA/HR) genes can cause DNA repair defects and could therefore impact cancer treatment response and patient outcome. Their functional impact and clinical relevance in head and neck squamous cell carcinoma (HNSCC) is unknown. We therefore questioned whether functional FA/HR defects occurred in HNSCC and whether they are associated with FA/HR variants. We assayed a panel of 29 patient-derived HNSCC cell lines and found that a considerable fraction is hypersensitive to the crosslinker Mitomycin C and PARP inhibitors, a functional measure of FA/HR defects. DNA sequencing showed that these hypersensitivities are associated with the presence of bi-allelic rare germline and somatic FA/HR gene variants. We next questioned whether such variants are associated with prognosis and treatment response in HNSCC patients. DNA sequencing of 77 advanced stage HNSCC tumors revealed a 19% incidence of such variants. Importantly, these variants were associated with a poor prognosis (p = 0.027; HR = 2.6, 1.1–6.0) but favorable response to high cumulative cisplatin dose. We show how an integrated in vitro functional repair and genomic analysis can improve the prognostic value of genetic biomarkers. We conclude that repair defects are marked and frequent in HNSCC and are associated with clinical outcome.

Lipidomic Profiling Links the Fanconi Anemia Pathway to Glycosphingolipid Metabolism in Head and Neck Cancer Cells

Purpose: Mutations in Fanconi anemia (FA) genes are common in sporadic squamous cell carcinoma of the head and neck (HNSCC), and we have previously demonstrated that FA pathway depletion in HNSCC cell lines stimulates invasion. The goal of our studies was to use a systems approach in order to define FA pathway-dependent lipid metabolism and to extract lipid-based signatures and effectors of invasion in FA-deficient cells.Experimental Design: We subjected FA-isogenic HNSCC keratinocyte cell lines to untargeted and targeted lipidomics analyses to discover novel biomarkers and candidate therapeutic targets in FA-deficient cells. Cellular invasion assays were carried out in the presence and absence of N-butyldeoxynojirimycin (NB-DNJ), a biosynthetic inhibitor of the newly identified class of gangliosides, to investigate the requirement of ganglioside upregulation in FA-deficient HNSCC cells.Results: The most notable element of the lipid profiling results was a consistent elevation of glycosphingolipids, and particularly the accumulation of gangliosides. Conversely, repression of this same class of lipids was observed upon genetic correction of FA patient-derived HNSCC cells. Functional studies demonstrate that ganglioside upregulation is required for HNSCC cell invasion driven by FA pathway loss. The motility of nontransformed keratinocytes in response to FA loss displayed a similar dependence, thus supporting early and late roles for the FA pathway in controlling keratinocyte invasion through lipid regulation.Conclusions: Elevation of glycosphingolipids including the ganglioside GM3 in response to FA loss stimulates invasive characteristics of immortalized and transformed keratinocytes. An inhibitor of glycosphingolipid biosynthesis NB-DNJ attenuates invasive characteristics of FA-deficient HNSCC cells. Clin Cancer Res; 24(11); 2700-9. ©2018 AACR.

Beyond interstrand crosslinks repair: contribution of FANCD2 and other Fanconi Anemia proteins to the replication of DNA

Biallelic mutations of FANCD2 and other components of the Fanconi Anemia (FA) pathway cause a disease characterized by bone marrow failure, cancer predisposition and a striking sensitivity to agents that induce crosslinks between the two complementary DNA strands (inter-strand crosslinks-ICL). Such genotoxins were used to characterize the contribution of the FA pathway to the genomic stability of cells, thus unravelling the biological relevance of ICL repair in the context of the disease. Notwithstanding this, whether the defect in ICL repair as the sole trigger for the multiple physiological alterations observed in FA patients is still under investigation. Remarkably, ICL-independent functions of FANCD2 and other components of the FA pathway were recently reported. FANCD2 contributes to the processing of very challenging double strand ends (DSEs: one ended Double Strand Breaks -DSBs- created during DNA replication). Other ICL-independent functions of FANCD2 include prevention of DNA breakage at stalled replication forks and facilitation of chromosome segregation at the end of M phase. The current understanding of replication-associated functions of FANCD2 and its relevance for the survival of genomically stable cells is herein discussed.

The etiologic spectrum of head and neck squamous cell carcinoma in young patients

Head and neck squamous cell carcinoma (HNSCC), accounting for more than 80% in head and neck malignancies, kills thousands of people a year in the world. Despite most of the patients are more than 45, and the occurrences of head and neck cancer shows a decreasing trend; however, horribly, the incidences of the patients under 45 years old is steadily increasing. Hence, it's of vital importance to get more pathogen information about risk factors of HNSCC in children and young adults. This review outlines the etiologic spectrum of HNSCC, especially oral/oropharyngeal squamous cell carcinoma, in patients under 45 years of age.

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.

Risk of Human Papillomavirus Infection in Cancer-Prone Individuals: What We Know

Human papillomavirus (HPV) infections cause a significant proportion of cancers worldwide, predominantly squamous cell carcinomas (SCC) of the mucosas and skin. High-risk HPV types are associated with SCCs of the anogenital and oropharyngeal tract. HPV oncogene activities and the biology of SCCs have been intensely studied in laboratory models and humans. What remains largely unknown are host tissue and immune-related factors that determine an individual's susceptibility to infection and/or carcinogenesis. Such susceptibility factors could serve to identify those at greatest risk and spark individually tailored HPV and SCC prevention efforts. Fanconi anemia (FA) is an inherited DNA repair disorder that is in part characterized by extreme susceptibility to SCCs. An increased prevalence of HPV has been reported in affected individuals, and molecular and functional connections between FA, SCC, and HPV were established in laboratory models. However, the presence of HPV in some human FA tumors is controversial, and the extent of the etiological connections remains to be established. Herein, we discuss cellular, immunological, and phenotypic features of FA, placed into the context of HPV pathogenesis. The goal is to highlight this orphan disease as a unique model system to uncover host genetic and molecular HPV features, as well as SCC susceptibility factors.

ACCIDENTAL DUPLICATION: Beyond interstrand crosslinks repair: Contribution of FANCD2 and other Fanconi Anemia proteins to the replication of DNA

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/ 10.1016/j.mrfmmm.2017.09.006. This duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Profile of pembrolizumab in the treatment of head and neck squamous cell carcinoma: design development and place in therapy

Head and neck squamous cell cancer (HNSCC) is the sixth most common malignancy worldwide, and despite advances in cytotoxic, surgical and radiation techniques, outcomes are still poor in those with both locally advanced and metastatic diseases. The need for development of better therapeutics along with a greater understanding of the relationship between the immune system and malignancies has led to a new therapeutic modality, immune modulators, particularly checkpoint inhibitors in HNSCC. It is now well recognized that HNSCC circumvents crucial pathways utilized by the immune system to escape surveillance. These hijacked pathways include impairing tumor antigen presentation machinery and co-opting checkpoint receptors. This understanding has led to the development of monoclonal antibodies targeting checkpoint receptors and has resulted in promising outcomes in HNSCC. This article describes the mechanisms that HNSCC utilizes to escape immune surveillance, clinical impact of checkpoint inhibitors (with a focus on pembrolizumab), ongoing studies, and future directions.

FANCD2 and DNA Damage

Investigators have dedicated considerable effort to understanding the molecular basis underlying Fanconi Anemia (FA), a rare human genetic disease featuring an extremely high incidence of cancer and many congenital defects. Among those studies, FA group D2 protein (FANCD2) has emerged as the focal point of FA signaling and plays crucial roles in multiple aspects of cellular life, especially in the cellular responses to DNA damage. Here, we discuss the recent and relevant studies to provide an updated review on the roles of FANCD2 in the DNA damage response.

The Salivary Microbiome and Oral Cancer Risk: a Pilot Study in Fanconi Anemia

Fanconi anemia (FA) is a rare genetic disease characterized by chromosomal instability and impaired DNA damage repair. FA patients develop oral squamous cell carcinoma (OSCC) earlier and more frequently than the general population, especially after hematopoietic stem cell transplantation (HSCT). Although evidence of an etiological role of the local microbiome and carcinogenesis has been mounting, no information exists regarding the oral microbiome of FA patients. The aim of this study was to explore the salivary microbiome of 61 FA patients regarding their oral health status and OSCC risk factors. After answering a questionnaire and receiving clinical examination, saliva samples were collected and analyzed using 16S rRNA sequencing of the V3-V4 hypervariable region. The microbial profiles associated with medical and clinical parameters were analyzed using general linear models. Patients were young (mean age, 22 y) and most had received HSCT ( n = 53). The most abundant phyla were Firmicutes [mean relative abundance (SD), 42.1% (10.1%)] and Bacteroidetes [(25.4% (11.4%)]. A history of graft-versus-host disease (GVHD) ( n = 27) was associated with higher proportions of Firmicutes (43.8% × 38.5%, P = 0.05). High levels of gingival bleeding were associated with the genera Prevotella (22.25% × 20%), Streptococcus (19.83% × 17.61%), Porphyromonas (3.63% × 1.42%, P = 0.03), Treponema (1.02% × 0.28%, P = 0.009), Parvimonas (0.28% × 0.07%, P = 0.02) and Dialister (0.27% × 0.10%, P = 0.04). Finally, participants transplanted over 11 y ago showed the highest levels of Streptococcus (18.4%), Haemophilus (12.7%) and Neisseria (6.8%). In conclusion, FA patients that showed poor oral hygiene harbored higher proportions of the genera of bacteria compatible with gingival disease. Specific microbial differences were associated with a history of oral GVHD and a history of oral mucositis.

Multifaceted role of TREX2 in the skin defense against UV-induced skin carcinogenesis

TREX2 is a 3′-DNA exonuclease specifically expressed in keratinocytes. Here, we investigated the relevance and mechanisms of TREX2 in ultraviolet (UV)-induced skin carcinogenesis. TREX2 expression was up-regulated by chronic UV exposure whereas it was de-regulated or lost in human squamous cell carcinomas (SCCs). Moreover, we identified SNPs in the TREX2 gene that were more frequent in patients with head and neck SCCs than in healthy individuals. In mice, TREX2 deficiency led to enhanced susceptibility to UVB-induced skin carcinogenesis which was preceded by aberrant DNA damage removal and degradation as well as reduced inflammation. Specifically, TREX2 loss diminished the up-regulation of IL12 and IFNγ, key cytokines related to DNA repair and antitumor immunity. In UV-treated keratinocytes, TREX2 promoted DNA repair and passage to late apoptotic stages. Notably, TREX2 was recruited to low-density nuclear chromatin and micronuclei, where it interacted with phosphorylated H2AX histone, which is a critical player in both DNA repair and cell death. Altogether, our data provide new insights in the molecular mechanisms of TREX2 activity and establish cell autonomous and non-cell autonomous functions of TREX2 in the UVB-induced skin response.

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.

Defects in the Fanconi Anemia Pathway in Head and Neck Cancer Cells Stimulate Tumor Cell Invasion through DNA-PK and Rac1 Signaling

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) remains a devastating disease, and Fanconi anemia (FA) gene mutations and transcriptional repression are common. Invasive tumor behavior is associated with poor outcome, but relevant pathways triggering invasion are poorly understood. There is a significant need to improve our understanding of genetic pathways and molecular mechanisms driving advanced tumor phenotypes, to develop tailored therapies. Here we sought to investigate the phenotypic and molecular consequences of FA pathway loss in HNSCC cells.

EXPERIMENTAL DESIGN

Using sporadic HNSCC cell lines with and without FA gene knockdown, we sought to characterize the phenotypic and molecular consequences of FA deficiency. FA pathway inactivation was confirmed by the detection of classic hallmarks of FA following exposure to DNA cross-linkers. Cells were subjected to RNA sequencing with qRT-PCR validation, followed by cellular adhesion and invasion assays in the presence and absence of DNA-dependent protein kinase (DNA-PK) and Rac1 inhibitors.

RESULTS

We demonstrate that FA loss in HNSCC cells leads to cytoskeletal reorganization and invasive tumor cell behavior in the absence of proliferative gains. We further demonstrate that cellular invasion following FA loss is mediated, at least in part, through NHEJ-associated DNA-PK and downstream Rac1 GTPase activity.

CONCLUSIONS

These findings demonstrate that FA loss stimulates HNSCC cell motility and invasion, and implicate a targetable DNA-PK/Rac1 signaling axis in advanced tumor phenotypes.

Recent Insights into the Control of Human Papillomavirus (HPV) Genome Stability, Loss, and Degradation

Most human papillomavirus (HPV) antiviral strategies have focused upon inhibiting viral DNA replication, but it is increasingly apparent that viral DNA levels can be chemically controlled by approaches that promote its instability. HPVs and other DNA viruses have a tenuous relationship with their hosts. They must replicate and hide from the DNA damage response (DDR) and innate immune systems, which serve to protect cells from foreign or “non-self” DNA, and yet they draft these same systems to support their life cycles. DNA binding antiviral agents promoting massive viral DNA instability and elimination are reviewed. Mechanistic studies of these agents have identified genetic antiviral enhancers and repressors, antiviral sensitizers, and host cell elements that protect and stabilize HPV genomes. Viral DNA degradation appears to be an important means of controlling HPV DNA levels in some cases, but the underlying mechanisms remain poorly understood. These findings may prove useful not only for understanding viral DNA persistence but only in devising future antiviral strategies.

Involvement of Fanconi anemia genes FANCD2 and FANCF in the molecular basis of drug resistance in leukemia

The Fanconi anemia (FA)‑associated proteins FANCF and FANCD2 are important components of the FA pathway of DNA crosslink repair. FANCF and FANCD2 have been found to be involved in drug‑resistant multiple myeloma, ovarian cancer, non‑small‑cell lung cancer, and head and neck cancer. However, it is unclear whether these two genes participate in adriamycin (ADR)‑resistant leukemia. Therefore, the aim of the current study was to investigate FANCF and FANCD2 expression in drug‑resistant and drug‑sensitive leukemia cells. Western blot analysis revealed enhanced FANCF expression and monoubiquitination of FANCD2 in ADR‑resistant cells. Additionally, it was observed that drug‑resistant cells had reduced DNA damage compared with drug‑sensitive cells. The results of this study indicate that the FA pathway may confer leukemia resistance to ADR via enhanced DNA interstrand crosslink repair.

Genomic landscape of human papillomavirus-associated cancers

Recent next-generation sequencing studies have generated a comprehensive overview of the genomic landscape of human papillomavirus (HPV)-associated cancers. This review summarizes these findings to provide insight into the tumor biology of these cancers and potential therapeutic opportunities for HPV-driven malignancies. In addition to the tumorigenic properties of the HPV oncoproteins, integration of HPV DNA into the host genome is suggested to be a driver of the neoplastic process. Integration may confer a growth and survival advantage via enhanced expression of viral oncoproteins, alteration of critical cellular genes, and changes in global promoter methylation and transcription. Alteration of cellular genes may lead to loss of function of tumor suppressor genes, enhanced oncogene expression, loss of function of DNA repair genes, or other vital cellular functions. Recurrent integrations in RAD51B, NR4A2, and TP63, leading to aberrant forms of these proteins, are observed in both HPV-positive head and neck squamous cell carcinoma (HNSCC) and cervical carcinoma. Additional genomic alterations, independent of integration events, include recurrent PIK3CA mutations (and aberrations in other members of the PI3K pathway), alterations in receptor tyrosine kinases (primarily FGFR2 and FGFR3 in HPV-positive HNSCC, and ERBB2 in cervical squamous cell carcinoma), and genes in pathways related to squamous cell differentiation and immune responses. A number of the alterations identified are potentially targetable, which may lead to advances in the treatment of HPV-associated cancers.

Fanconi anemia: young patients at high risk for squamous cell carcinoma

BACKGROUND

Fanconi anemia is one of the best studied inherited cancer-prone diseases. Greatly improved protocols for hematopoietic stem cell transplantation increasingly save the lives of these young patients. However, in both transplanted and not transplanted patients, the emergence of aggressive squamous cell carcinoma represents a major medical challenge.

CONCLUSIONS

This mini review summarizes current knowledge about the pathogenesis of squamous cell carcinoma (SCC) in the special context of Fanconi anemia.

The Fanconi anemia/BRCA pathway is involved in DNA interstrand cross-link repair of adriamycin-resistant leukemia cells

The Fanconi anemia/BRCA (FA/BRCA) pathway plays a vital role in DNA damage repair induced by DNA cross-linking agents and is closely related to drug response in cancer treatment. Here we demonstrate that the FA/BRCA pathway contributes to acquired drug resistance in adriamycin (ADR)-resistant leukemia cell lines, and disruption of this pathway partially reverses the drug resistance. We observed that ADR-resistant cells have reduced DNA interstrand cross-links (ICL) compared with ADR-sensitive cells. Western blot studies demonstrated enhanced FA protein expression in ADR-resistant cells. Using siRNA to knock down FANCF in K562/R drug-resistant cells showed increases in sensitivity to ADR and ADR-induced DNA damage, and demonstrated a direct relationship between the FA/BRCA pathway and drug sensitivity. Overexpression of FANCF in K562 drug-sensitive cells partially reproduced the drug-resistant phenotype. These results show that the FA/BRCA pathway is involved in acquired ADR resistance of leukemia cells. The FA/BRCA pathway may be a new target to reverse ADR resistance in leukemia treatment.

High-risk human papillomavirus E6 protein promotes reprogramming of Fanconi anemia patient cells through repression of p53 but does not allow for sustained growth of induced pluripotent stem cells

DNA repair plays a crucial role in embryonic and somatic stem cell biology and cell reprogramming. The Fanconi anemia (FA) pathway, which promotes error-free repair of DNA double-strand breaks, is required for somatic cell reprogramming to induced pluripotent stem cells (iPSC). Thus, cells from Fanconi anemia patients, which lack this critical pathway, fail to be reprogrammed to iPSC under standard conditions unless the defective FA gene is complemented. In this study, we utilized the oncogenes of high-risk human papillomavirus 16 (HPV16) to overcome the resistance of FA patient cells to reprogramming. We found that E6, but not E7, recovers FA iPSC colony formation and, furthermore, that p53 inhibition is necessary and sufficient for this activity. The iPSC colonies resulting from each of these approaches stained positive for alkaline phosphatase, NANOG, and Tra-1-60, indicating that they were fully reprogrammed into pluripotent cells. However, FA iPSC were incapable of outgrowth into stable iPSC lines regardless of p53 suppression, whereas their FA-complemented counterparts grew efficiently. Thus, we conclude that the FA pathway is required for the growth of iPSC beyond reprogramming and that p53-independent mechanisms are involved.

IMPORTANCE

A novel approach is described whereby HPV oncogenes are used as tools to uncover DNA repair-related molecular mechanisms affecting somatic cell reprogramming. The findings indicate that p53-dependent mechanisms block FA cells from reprogramming but also uncover a previously unrecognized defect in FA iPSC proliferation independent of p53.

Molecular functions and cellular roles of the ChlR1 (DDX11) helicase defective in the rare cohesinopathy Warsaw breakage syndrome

In 2010, a new recessive cohesinopathy disorder, designated Warsaw breakage syndrome (WABS), was described. The individual with WABS displayed microcephaly, pre- and postnatal growth retardation, and abnormal skin pigmentation. Cytogenetic analysis revealed mitomycin C (MMC)-induced chromosomal breakage; however, an additional sister chromatid cohesion defect was also observed. WABS is genetically linked to bi-allelic mutations in the ChlR1/DDX11 gene which encodes a protein of the conserved family of Iron-Sulfur (Fe-S) cluster DNA helicases. Mutations in the budding yeast ortholog of ChlR1, known as Chl1, were known to cause sister chromatid cohesion defects, indicating a conserved function of the gene. In 2012, three affected siblings were identified with similar symptoms to the original WABS case, and found to have a homozygous mutation in the conserved Fe-S domain of ChlR1, confirming the genetic linkage. Significantly, the clinically relevant mutations perturbed ChlR1 DNA unwinding activity. In addition to its genetic importance in human disease, ChlR1 is implicated in papillomavirus genome maintenance and cancer. Although its precise functions in genome homeostasis are still not well understood, ongoing molecular studies of ChlR1 suggest the helicase plays a critically important role in cellular replication and/or DNA repair.

DNA-damage foci to detect and characterize DNA repair alterations in children treated for pediatric malignancies

Purpose

In children diagnosed with cancer, we evaluated the DNA damage foci approach to identify patients with double-strand break (DSB) repair deficiencies, who may overreact to DNA-damaging radio- and chemotherapy. In one patient with Fanconi anemia (FA) suffering relapsing squamous cell carcinomas of the oral cavity we also characterized the repair defect in biopsies of skin, mucosa and tumor.

Methods and Materials

In children with histologically confirmed tumors or leukemias and healthy control-children DSB repair was investigated by counting γH2AX-, 53BP1- and pATM-foci in blood lymphocytes at defined time points after ex-vivo irradiation. This DSB repair capacity was correlated with treatment-related normal-tissue responses. For the FA patient the defective repair was also characterized in tissue biopsies by analyzing DNA damage response proteins by light and electron microscopy.

Results

Between tumor-children and healthy control-children we observed significant differences in mean DSB repair capacity, suggesting that childhood cancer is based on genetic alterations affecting DNA repair. Only 1 out of 4 patients with grade-4 normal-tissue toxicities revealed an impaired DSB repair capacity. The defective DNA repair in FA patient was verified in irradiated blood lymphocytes as well as in non-irradiated mucosa and skin biopsies leading to an excessive accumulation of heterochromatin-associated DSBs in rapidly cycling cells.

Conclusions

Analyzing human tissues we show that DSB repair alterations predispose to cancer formation at younger ages and affect the susceptibility to normal-tissue toxicities. DNA damage foci analysis of blood and tissue samples allows one to detect and characterize DSB repair deficiencies and enables identification of patients at risk for high-grade toxicities. However, not all treatment-associated normal-tissue toxicities can be explained by DSB repair deficiencies.

The rs7003908 (T>G) polymorphism in the XRCC7 gene and the risk of cancers

The association between the rs7003908 (T>G) polymorphism in the XRCC7 gene and the risk of cancers had been widely studied; however, the results were inconsistent. The objective of the current study was to investigate the association between the rs7003908 polymorphism in the XRCC7 gene and the risk of cancers by meta-analysis. We searched PubMed, EMbase, CNKI and Wanfang databases; the last search was performed on January 10th, 2014. Statistical analysis was performed using the Revman4.2 and STATA10.0 softwares. A total of 3,684 cancer cases and 5,232 controls from 11 case-control studies were included for data analysis. In the dominant model analysis, the results suggested a lack of association between the polymorphism and the risk of cancers: OR 1.01, 95% CI 0.83-1.16, P = 0.70. In the subgroup analysis by ethnicity, no significant association was found either for Asians or Caucasians. In the subgroup analysis by cancer types, significant association was found for prostate cancer, but not for bladder cancer, breast cancer and glioma. In summary, the current meta-analysis confirmed that the rs7003908 polymorphism in the XRCC7 gene might be a risk factor for prostate cancer. In the future, more studies are needed to validate these results.

Deletion of Fanca or Fancd2 dysregulates Treg in mice

Fanconi anemia (FA) is a genetic disorder associated with bone marrow (BM) failure and leukemia. Recent studies demonstrate variable immune defects in FA. However, the cause for FA immunodeficiency is unknown. Here we report that deletion of Fanca or Fancd2 dysregulates the suppressive activity of regulatory T cells (Tregs), shown functionally as exacerbation of graft-vs-host disease (GVHD) in mice. Recipient mice of Fanca(-/-) or Fancd2(-/-) BM chimeras exhibited severe acute GVHD after allogeneic BM transplantation (BMT). T cells from Fanca(-/-) or Fancd2(-/-) mice induced higher GVHD lethality than those from wild-type (WT) littermates. FA Tregs possessed lower proliferative suppression potential compared with WT Tregs, as demonstrated by in vitro proliferation assay and BMT. Analysis of CD25(+)Foxp3(+) Tregs indicated that loss of Fanca or Fancd2 dysregulated Foxp3 target gene expression. Additionally, CD25(+)Foxp3(+) Tregs of Fanca(-/-) or Fancd2(-/-) mice were less efficient in suppressing the production of GVHD-associated inflammatory cytokines. Consistently, aberrant NF-κB activity was observed in infiltrated T cells from FA GVHD mice. Conditional deletion of p65 in FA Tregs decreased GVHD mortality. Our study uncovers an essential role for FA proteins in maintaining Treg homeostasis, possibly explaining, at least in part, the immune deficiency reported in some FA patients.

FANCD2 activates transcription of TAp63 and suppresses tumorigenesis

Fanconi anemia (FA) is a rare genetic disorder characterized by an increased susceptibility to squamous cell cancers. Fifteen FA genes are known, and the encoded proteins cooperate in a common DNA repair pathway. A critical step is the monoubiquitination of the FANCD2 protein, and cells from most FA patients are deficient in this step. How monoubiquitinated FANCD2 suppresses squamous cell cancers is unknown. Here we show that Fancd2-deficient mice are prone to Ras-oncogene-driven skin carcinogenesis, while Usp1-deficient mice, expressing elevated cellular levels of Fancd2-Ub, are resistant to skin tumors. Moreover, Fancd2-Ub activates the transcription of the tumor suppressor TAp63, thereby promoting cellular senescence and blocking skin tumorigenesis. For FA patients, the reduction of FANCD2-Ub and TAp63 protein levels may account for their susceptibility to squamous cell neoplasia. Taken together, Usp1 inhibition may be a useful strategy for upregulating TAp63 and preventing or treating squamous cell cancers in the general non-FA population.