Downregulation of Fanconi anemia genes in sporadic head and neck squamous cell carcinoma

The cGAS/STING/IFN-1 Response in Squamous Head and Neck Cancer Cells after Genotoxic Challenges and Abrogation of the ATR-Chk1 and Fanconi Anemia Axis

Locally advanced head and neck squamous cell carcinomas (HNSCC) are often refractory to platinum-based radiochemotherapy and new immuno-oncological strategies. To stimulate immunogenic antitumor responses in HNSCC patients, we investigated the cGAS/STING/IFN-1 signaling pathway after genotoxic treatments and concomitant abrogation of the DNA damage response (DDR). For this purpose, FaDu and UM-SCC1 cells were exposed to X-rays or cisplatin and treated with an ATR or Chk1 inhibitor, or by Fanconi anemia gene A knockout (FANCA ko). We assessed clonogenic survival, cell cycle regulation, micronuclei, free cytosolic double-stranded DNA, and the protein expression and activity of the cGAS/STING/IFN-1 pathway and related players. Cell survival, regulation of G2/M arrest, and formation of rupture-prone cGAS-positive micronuclei after genotoxic treatments were most affected by ATR inhibition and FANCA ko. In UM-SCC-1 cells only, 8 Gy X-rays promoted IFN-1 expression unaltered by abrogation of the DDR or concomitant increased TREX1 expression. At a higher dose of 20 Gy, this effect was observed only for concurrent Chk1- or ATR-inhibition. FANCA ko or cisplatin treatment was ineffective in this regard. Our observations open new perspectives for the enhancement of cGAS/STING/IFN-1-mediated antitumor immune response in HNSCC by hypofractionated or stereotactic radiotherapy concepts in multimodal settings with immuno-oncological strategies.

Genomic signature of Fanconi anaemia DNA repair pathway deficiency in cancer

Fanconi anaemia (FA), a model syndrome of genome instability, is caused by a deficiency in DNA interstrand crosslink repair resulting in chromosome breakage^1-3. The FA repair pathway protects against endogenous and exogenous carcinogenic aldehydes^4-7. Individuals with FA are hundreds to thousands fold more likely to develop head and neck (HNSCC), oesophageal and anogenital squamous cell carcinomas⁸ (SCCs). Molecular studies of SCCs from individuals with FA (FA SCCs) are limited, and it is unclear how FA SCCs relate to sporadic HNSCCs primarily driven by tobacco and alcohol exposure or infection with human papillomavirus⁹ (HPV). Here, by sequencing genomes and exomes of FA SCCs, we demonstrate that the primary genomic signature of FA repair deficiency is the presence of high numbers of structural variants. Structural variants are enriched for small deletions, unbalanced translocations and fold-back inversions, and are often connected, thereby forming complex rearrangements. They arise in the context of TP53 loss, but not in the context of HPV infection, and lead to somatic copy-number alterations of HNSCC driver genes. We further show that FA pathway deficiency may lead to epithelial-to-mesenchymal transition and enhanced keratinocyte-intrinsic inflammatory signalling, which would contribute to the aggressive nature of FA SCCs. We propose that the genomic instability in sporadic HPV-negative HNSCC may arise as a result of the FA repair pathway being overwhelmed by DNA interstrand crosslink damage caused by alcohol and tobacco-derived aldehydes, making FA SCC a powerful model to study tumorigenesis resulting from DNA-crosslinking damage.

[Association of CDH1, FANCB and APC Gene Polymorphisms with Lung Cancer Susceptibility in Chinese Population]

BACKGROUND

Lung cancer is the main cause of cancer-related death globally. Single nucleotide polymorphism (SNP) is one of the important factors leading to the occurrence of lung cancer, but its mechanism has not been elucidated. This study intends to investigate the relationship between SNPs of CDH1, FANCB, APC genes and lung cancer genetic susceptibility.

METHODS

The case-control study design was used. We collected blood samples from 270 lung cancer cases in the Department of Lung Cancer Surgery, Tianjin Medical University General Hospital, as well as blood samples from 445 healthy volunteers as controls, and extracted genomic DNA for genotyping using the Taqman® SNP genotyping kit. The distribution of three SNP loci of CDH1 gene rs201141645, FANCB gene rs754552650 and APC gene rs149353082 in Chinese population was analyzed. Chi-square test and Logistic regression were used to analyze the relationship between different genotypes and the risk of lung cancer.

RESULTS

The distribution frequencies of AA, A/G and GG genotypes at rs754552650 of FANCB gene in the control group were 27.2%, 52.6% and 20.2%, respectively. The distribution frequencies of AA and A/G genotypes were 93.7% and 6.3% in the case group, respectively, and no GG genotype was detected. The A/G genotype of the rs754552650 locus of the FANCB gene was significantly different between the case group and the control group. Compared with the carriers of AA genotype, the individuals with FANCB rs754552650 A/G genotype had a lower risk of lung cancer (OR=0.035, 95%CI: 0.020-0.062, P<0.001). CDH1 gene rs201141645 A/C and CC genotypes only existed in the control group. In addition, only 1 sample was found to have APC rs149353082 genotype in the case group.

CONCLUSIONS

In the Chinese population, the lung cancer risk of the individuals with FANCB rs754552650 A/G genotype was significantly decreased.

Association of variations in the Fanconi anemia complementation group and prognosis in Non-small cell lung cancer patients with Platinum-based chemotherapy

PURPOSE

To explore the associations between FANC (FANCA, FANCC, FANCE, FANCF, and FANCJ) single nucleotide polymorphisms (SNPs) and prognosis of non-small cell lung cancer (NSCLC) patients with platinum-based chemotherapy.

METHODS

According to the inclusion criteria, we selected 395 DNA samples from NSCLC patients for genotyping and combined with clinical data for Cox regression analysis and stratification analyses to assess relationships between overall survival (OS) and progression free survival (PFS) with SNPs genotypes.

RESULTS

The results revealed that patients with FANCE rs6907678 TT genotype have a longer OS than TC and CC genotype (Additive model: P = 0.004, HR = 1.696, 95% CI = 1.186-2.425). In stratification analyses, Longer PFS is found in female, age ≤ 55 years old and non-smoking patients with FANCE rs6907678 TT genotype, and patients with TT genotypes were significantly had longer OS in male, age ＞55 years old, non-smoking, squamous cell carcinoma and stage IV stratification.

CONCLUSION

Our data demonstrates that patients with FANCE rs6907678 TT genotype are contributed to better prognosis. FANCE rs6907678 may be used as a clinical biomarker for predicting the prognosis of NSCLC patients with platinum-based chemotherapy.

Comprehensive analysis of the autophagy-dependent ferroptosis-related gene FANCD2 in lung adenocarcinoma

BACKGROUND

The development of lung adenocarcinoma (LUAD) involves the interactions between cell proliferation and death. Autophagy-dependent ferroptosis, a distinctive cell death process, was implicated in a multitude of diseases, whereas no research revealing the relationship between autophagy-dependent ferroptosis and LUAD pathogenesis was reported. Thus, the primary objective was to explore the role and potential function of the autophagy-dependent ferroptosis-related genes in LUAD.

METHODS

Clinical information and transcriptome profiling of patients with LUAD were retrieved and downloaded from open-source databases. Autophagy-dependent ferroptosis-related genes were screened by published articles. The critical gene was identified as the intersection between the differentially expressed genes and prognosis-related genes. Patients were divided into high- and low-risk groups using the expression level of the critical gene. The validity of the key gene prognosis model was verified by survival analysis. The correlation between the clinical characteristics of LUAD and the expression level of the key gene was analyzed to explore the clinical significance and prognosis value. And the roles of the key gene in response to chemotherapy, immune microenvironment, and tumor mutation burden were predicted. The validation of key gene expression levels was further performed by quantitative real-time PCR and immunohistochemistry staining.

RESULTS

FANCD2, an essential autophagy-dependent ferroptosis-related gene by searching database, was confirmed as an independent prognostic factor for LUAD occurrence. The high expression level of FANCD2 was associated with an advantaged TNM stage, a less chemotherapy sensitivity, a low ImmuneScore, which indicated a deactivation status in an immune microenvironment, a high tumor mutation burden, and poor survival for LUAD patients. Pathway enrichment analysis showed that FANCD2 responded to oxidative stress and neutrophil-mediated immunity. Quantitative real-time PCR and immunohistochemistry staining showed that the expression level of FANCD2 is higher in LUAD patients than in normal tissue samples, which was in accordance with the database report.

CONCLUSION

FANCD2, an essential gene related to autophagy-dependent ferroptosis, could work as a biomarker, predicting the survival, chemotherapy sensitivity, tumor immunity, and mutation burden of LUAD. Researching autophagy-dependent ferroptosis and targeting the FANCD2 may offer a new perspective for treating and improving prognosis in LUAD.

Age-specific oncogenic pathways in head and neck squamous cell carcinoma - are elderly a different subcategory?

BACKGROUND

In recent clinical practice, an increasing number of elderly patients suffering from head and neck squamous cell carcinoma (HNSCC) of unknown pathophysiology is observed. The majority of HNSCC patients can roughly be divided into three subcategories. First, a small group of young patients who present with variants of genomic aberrations and inheritable diseases like Fanconi anaemia. Second, an increasing population of HPV-related HNSCCs that are regarded as genomic stable tumours with a more favourable prognosis. Though HPV-related tumours used to be more common among younger males, a notable rise in the elderly population is observed. The third subcategory, that of HPV-negative tumours, has been shown to be more heterogeneous with involvement of a variety of oncogenic pathways related to lifestyle factors like smoking and alcohol consumption, often seen in middle-aged males. Some of these pathways could be related to age, such as TP53 alterations, EGFR activation, apoptotic pathway alterations and field cancerization.

CONCLUSIONS

In this narrative review, we provide an overview of established and newly discovered age-specific pathophysiological mechanisms underlying HNSCC. We propose a fourth subcategory of patients with a suspected different pathophysiology: elderly (HPV-negative) HNSCC patients without a history of tobacco and alcohol consumption. In this subcategory, carcinogenesis seems to be a multi-step process based on genomic instability, immunosenescence, cell cycle disruption and telomere shortening. To conclude, we discuss suggestions for future research to fill the knowledge gap about age-dependent HNSCC carcinogenesis.

Cell senescence and malignant transformation in the inherited bone marrow failure syndromes: Overlapping pathophysiology with therapeutic implications

Fanconi anemia, telomeropathies and ribosomopathies are members of the inherited bone marrow failure syndromes, rare genetic disorders that lead to failure of hematopoiesis, developmental abnormalities, and cancer predisposition. While each disorder is caused by different genetic defects in seemingly disparate processes of DNA repair, telomere maintenance, or ribosome biogenesis, they appear to lead to a common pathway characterized by premature senescence of hematopoietic stem cells. Here we review the experimental data on senescence and inflammation underlying marrow failure and malignant transformation. We conclude with a critical assessment of current and future therapies targeting these pathways in inherited bone marrow failure syndromes patients.

Type 2 diabetes mellitus promotes the proliferation, metastasis, and suppresses the apoptosis in oral squamous cell carcinoma

BACKGROUND

Our previous study revealed that patients with oral squamous cell carcinoma and concomitant type 2 diabetes mellitus presented a lower 5-year survival rate. Hyperglycemia has been increasingly recognized as a risk factor for more advanced disease and poorer prognosis in patients with oral squamous cell carcinoma. However, its role remains unclear.

METHODS

The expressions of BRIP1, Ki67, E-cadherin, and cleaved caspase-3 were detected by immunohistochemistry in oral squamous cell carcinoma tissues with or without type 2 diabetes mellitus. Cell counting kit-8 assay and wound healing assay were used to determine the proliferative and migratory ability of oral squamous cell carcinoma cells cultured with or without high glucose in vitro. Flow cytometry was applied to distinguish the role of high glucose on the cell cycle and apoptosis rates.

RESULTS

The expression level of Ki67 was elevated while BRIP1, E-cadherin, and cleaved caspase-3 were downregulated in patients with oral squamous cell carcinoma coexisting with diabetes. The cell proliferation and migration in oral squamous cell carcinoma cell lines were significantly enhanced by high glucose. Flow cytometric analysis suggested that high glucose predisposed cancer cells to stay at S/G₂ phase and to exhibit lower apoptosis rates.

CONCLUSION

Our results implicated that type 2 diabetes mellitus may play a crucial role in the development and progression of oral squamous cell carcinoma through hyperglycemia, affecting cancer cell proliferation, migration, and apoptosis. This finding might provide a new direction for the prevention and treatment of oral squamous cell carcinoma.

Molecular Tumor Subtypes of HPV-Positive Head and Neck Cancers: Biological Characteristics and Implications for Clinical Outcomes

Until recently, research on the molecular signatures of Human papillomavirus (HPV)-associated head and neck cancers mainly focused on their differences with respect to HPV-negative head and neck squamous cell carcinomas (HNSCCs). However, given the continuing high incidence level of HPV-related HNSCC, the time is ripe to characterize the heterogeneity that exists within these cancers. Here, we review research thus far on HPV-positive HNSCC molecular subtypes, and their relationship with clinical characteristics and HPV integration into the host genome. Different omics data including host transcriptomics and epigenomics, as well as HPV characteristics, can provide complementary viewpoints. Keratinization, mesenchymal differentiation, immune signatures, stromal cells and oxidoreductive processes all play important roles.

Comprehensive analysis of macrophage-related multigene signature in the tumor microenvironment of head and neck squamous cancer

Macrophages are among the most abundant cells of the tumor microenvironment in head and neck squamous cancer (HNSC). Although the marker gene sets of macrophages have been found, the mechanism by which they affect macrophages and whether they further predict the clinical outcome is unclear. In this study, a univariate COX analysis and a random forest algorithm were used to construct a prognostic model. Differential expression of the key gene, methylation status, function, and signaling pathways were further analyzed. We cross-analyzed multiple databases to detect the relationship between the most critical gene and the infiltration of multiple immune cells, as well as its impact on the prognosis of pan-cancer. FANCE is recognized as hub gene by different algorithms. It was overexpressed in HNSC, and high expression was predictive of better prognosis. It might promote apoptosis through the Wnt/β-catenin pathway. The expression of FANCE is inversely proportional to the infiltration of CD4 + T cells and their subsets, tumor-associated macrophages (TAMs), M2 macrophages, but positively co-expressed with M1 macrophages. In summary, FANCE was identified as the hub gene from the macrophage marker gene set, and it may improve the prognosis of HNSC patients by inhibiting lymphocytes and tumor-associated macrophages infiltration.

Common fragile sites: protection and repair

Common fragile sites (CFSs) are large chromosomal regions that exhibit breakage on metaphase chromosomes upon replication stress. They become preferentially unstable at the early stage of cancer development and are hotspots for chromosomal rearrangements in cancers. Increasing evidence has highlighted the complexity underlying the instability of CFSs, and a combination of multiple mechanisms is believed to cause CFS fragility. We will review recent advancements in our understanding of the molecular mechanisms underlying the maintenance of CFS stability and the relevance of CFSs to cancer-associated genome instability. We will emphasize the contribution of the structure-prone AT-rich sequences to CFS instability, which is in line with the recent genome-wide study showing that structure-forming repeat sequences are principal sites of replication stress.

Replication Stress Response Links RAD52 to Protecting Common Fragile Sites

Rad52 in yeast is a key player in homologous recombination (HR), but mammalian RAD52 is dispensable for HR as shown by the lack of a strong HR phenotype in RAD52-deficient cells and in RAD52 knockout mice. RAD52 function in mammalian cells first emerged with the discovery of its important backup role to BRCA (breast cancer genes) in HR. Recent new evidence further demonstrates that RAD52 possesses multiple activities to cope with replication stress. For example, replication stress-induced DNA repair synthesis in mitosis (MiDAS) and oncogene overexpression-induced DNA replication are dependent on RAD52. RAD52 becomes essential in HR to repair DSBs containing secondary structures, which often arise at collapsed replication forks. RAD52 is also implicated in break-induced replication (BIR) and is found to inhibit excessive fork reversal at stalled replication forks. These various functions of RAD52 to deal with replication stress have been linked to the protection of genome stability at common fragile sites, which are often associated with the DNA breakpoints in cancer. Therefore, RAD52 has important recombination roles under special stress conditions in mammalian cells, and presents as a promising anti-cancer therapy target.

Exome sequencing of oral leukoplakia and oral squamous cell carcinoma implicates DNA damage repair gene defects in malignant transformation

OBJECTIVES

To map the genomic pathways of patients with oral leukoplakia (OLK) which transformed to cancer (progressive) and those which did not (non-progressive), and to compare their exomic profiles.

MATERIALS AND METHODS

Whole exome sequencing was performed on 42 sequential samples from five progressive and eight non-progressive patients. Association of genomic variant frequencies with progression or lesion severity were analysed by non-parametric tests (Kruskal-Wallis and Mann-Whitney-Wilcoxon) and multivariate sparse partial least squares discriminant analysis (sPLS-DA). Enrichment analysis was used to characterise the effect of mutations upon biological pathways. Confirmatory studies used qPCR and immunohistochemistry.

RESULTS

Using sPLS-DA, the variant frequency of a small number of genes could be used to classify the samples based on lesion severity or progressive status. Enrichment analysis showed that DNA damage repair gene related pathways were highly impacted in lesions which progressed to cancer. Multivariate analysis of a set of 148 DNA damage repair genes could be used to classify progressive lesions using mutation frequency. BRCA1, BRCA2 and other double strand break (DSB) repair Fanconi anaemia (FA)/BRCA pathway genes were prominent contributors to this classification.

CONCLUSION

Patients with progressive and non-progressive OLK can be differentiated using the frequency of exomic variants, particularly in DNA damage repair pathway genes. To our knowledge, this is the first report of FA/BRCA (DSB) pathway involvement in malignant transformation of OLK to oral squamous cell carcinoma (OSCC).

ERCC1/XPF Is Important for Repair of DNA Double-Strand Breaks Containing Secondary Structures

The structure-specific endonuclease ERCC1/XPF plays an important role in nucleotide excision repair and interstrand cross-link repair. In this study, we identified new functions of ERCC1/XPF in DNA double-strand break (DSB) repair. We found that the conserved function of ERCC1/XPF to remove non-homologous sequences at DSBs is a rate-limiting step for homologous recombination in mammalian cells, and more importantly, we uncovered an indispensable role of ERCC1/XPF in repair of DSBs containing DNA secondary structures, including the structure-prone AT-rich DNA sequences derived from common fragile sites and G-quadruplexes (G4s). We also demonstrated a synthetic lethal interaction of XPF with DNA translocase FANCM that is involved in removing DNA secondary structures. Furthermore, inactivation of XPF sensitizes FANCM-deficient cells to G4-interacting compounds. These results suggest an important function of ERCC1/XPF in protecting DNA secondary structures and provide a rationale for targeted treatment of FANCM-deficient tumors through inhibition of XPF.

The concerted roles of FANCM and Rad52 in the protection of common fragile sites

Common fragile sites (CFSs) are prone to chromosomal breakage and are hotspots for chromosomal rearrangements in cancer cells. We uncovered a novel function of Fanconi anemia (FA) protein FANCM in the protection of CFSs that is independent of the FA core complex and the FANCI–FANCD2 complex. FANCM, along with its binding partners FAAP24 and MHF1/2, is recruited to CFS-derived structure-prone AT-rich sequences, where it suppresses DNA double-strand break (DSB) formation and mitotic recombination in a manner dependent on FANCM translocase activity. Interestingly, we also identified an indispensable function of Rad52 in the repair of DSBs at CFS-derived AT-rich sequences, despite its nonessential function in general homologous recombination (HR) in mammalian cells. Suppression of Rad52 expression in combination with FANCM knockout drastically reduces cell and tumor growth, suggesting a synthetic lethality interaction between these two genes, which offers a potential targeted treatment strategy for FANCM-deficient tumors with Rad52 inhibition.

Fanconi anemia core proteins have been linked to common fragile site stability. Here the authors shed light into the role of FANCM in common fragile site protection by suppressing double-strand break formation and mitotic recombination.

Development of a Human Leukocyte Antigen Score to Predict Progression-Free Survival in Head and Neck Squamous Cell Carcinoma Patients

Background

In personalized medicine and treatment stratification of head and neck squamous cell carcinoma (HNSCC), the heterogeneous genetic background of patients is not considered. Human leukocyte antigen (HLA) alleles and HLA haplotypes (HLA traits) are linked to development of HNSCC and affect progression-free survival (PFS) of HNSCC patients but most head and neck oncologists are not familiar with HLA typing. Hence, we developed an HLA-score abstracting from complexity of HLA-typing results to facilitate potential use of HLA-associated hazard ratios (HR) for prognostic stratification.

Methods

The HR for PFS of 8 HLA traits shown to be independent predictors (Pi) of PFS in a test cohort (TC) of 90 HNSCC patients were used to build the HLA-score based on the natural logarithm (ln) of the Pi-associated HR. Crude ln-transformed HR of the eight Pi, alleles B*13 (2), B*35 (1), B*51 (2), DQB1*06 (1), homozygous Cw (1), homozygous DRB4 (2), and haplotypes A*01/B*08 (−6) and B*08/C*07 (4), were summed up to yield the individual patient’s HLA-score. Receiver operating characteristic (ROC) and Kaplan–Meier curves were used to proof the suitability of the HLA-score as prognostic marker for PFS. An independent validation cohort (iVC) of 32 patients treated in the larynx-organ preservation trial DeLOS-II was utilized for validation.

Results

The individual HLA-scores (range −2 to 6) in TC classified HNSCC patients regarding PFS. ROC analysis (area under the curve = 0.750, 95% CI 0.665–0.836; P = 0.0000034) demonstrated an optimum cutoff for the HLA-score at 0.5 (97.9% sensitivity, 34.7% specificity), and 70/90 patients in TC with HLA-score > 0 had significant reduced PFS (P = 0.001). Applying the same classifier (HLA-score > 0) confirmed these findings in the iVC revealing reduced PFS of 25/32 patients (P = 0.040).

Conclusion

HLA traits constitute critical Pi. Considering the HLA-score may potentially facilitate the use of genetic information from HLA typing for prognostic stratification, e.g., within clinical trials.

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.

Fanconi anaemia and cancer: an intricate relationship

Fanconi anaemia (FA) is a genetic disorder that is characterized by bone marrow failure (BMF), developmental abnormalities and predisposition to cancer. Together with other proteins involved in DNA repair processes and cell division, the FA proteins maintain genome homeostasis, and germline mutation of any one of the genes that encode FA proteins causes FA. Monoallelic inactivation of some FA genes, such as FA complementation group D1 (FANCD1; also known as the breast and ovarian cancer susceptibility gene BRCA2), leads to adult-onset cancer predisposition but does not cause FA, and somatic mutations in FA genes occur in cancers in the general population. Carcinogenesis resulting from a dysregulated FA pathway is multifaceted, as FA proteins monitor multiple complementary genome-surveillance checkpoints throughout interphase, where monoubiquitylation of the FANCD2-FANCI heterodimer by the FA core complex promotes recruitment of DNA repair effectors to chromatin lesions to resolve DNA damage and mitosis. In this Review, we discuss how the FA pathway safeguards genome integrity throughout the cell cycle and show how studies of FA have revealed opportunities to develop rational therapeutics for this genetic disease and for malignancies that acquire somatic mutations within the FA pathway.

HLA traits linked to development of head and neck squamous cell carcinoma affect the progression-free survival of patients

BACKGROUND

Personalized medicine and treatment stratification of patients with head and neck squamous cell carcinoma (HNSCC) today mostly ignore genetic heterogeneity in HNSCC but especially the patient's genetic background. We hypothesized that particular human leukocyte antigen (HLA) class I (HLA-A, B, Cw) and II proteins (DR, DQ) confer susceptibility for and influence development of HNSCC and may be prognostic factors for progression-free survival (PFS).

METHODS

90 consecutive HNSCC patients of the prospective observational cohort study LIFE treated between 08/2010 and 05/2011 at the University Leipzig underwent low resolution typing of HLA-A, B, Cw, DR, and DQ. Antigen and haplotype frequencies were compared to those in German blood donors. Effects on PFS were analyzed using Kaplan-Meier curves and Cox models.

RESULTS

HNSCC patients had overall altered HLA-B frequencies (P<0.05); frequencies of B∗44 were lower, those of B∗13, B∗52, and B∗57 increased (P<0.05). Almost all other antigen frequencies showed no deviation. Homozygous HLA-Cw and DRB4 were frequent and associated with reduced PFS (P<0.05). Altered haplotype frequencies were common and particular haplotypes accompanied by differing PFS. B∗13/Cw∗06 carriers had poorest outcome (P=0.011). However, multivariate Cox proportional hazard models revealed 3 clinical covariates (localization oropharynx, loco-regional metastasis, and T4 category), HPV16-DNA positivity, and 10 HLA traits as independent predictors for PFS.

CONCLUSIONS

The relevance of the genetic background of HNSCC patients calls for future research to clarify the role of HLA traits in HNSCC and if PFS depends on HLA.

Loss of heterozygosity in FANCG, FANCF and BRIP1 from head and neck squamous cell carcinoma of the oral cavity

Recent advances have been made in the understanding of Fanconi anemia (FA), a hereditary disease that increases the risk for head and neck squamous cell carcinomas (HNSCC) by 500- to 700-fold. FA patients harbour germline mutations in genes of cellular DNA repair pathways that are assumed to facilitate the accumulation of mutations during HNSCC development. Mutations in these FA genes may also contribute to HNSCC in general. In the present study, we analysed three FA genes; FANCF, FANCG and BRIP1, that are involved in the repair of DNA inter strand cross-links, in HNSCC and their potential role for patient survival. We measured loss of heterozygosity (LOH) mutations at eight microsatellite loci flanking three FA genes in 54 HNSCC of the oral cavity and corresponding blood samples. Survival analyses were carried out using mutational data and clinical variables. LOH was present in 17% (FANCF region), 41% (FANCG region) and 11% (BRIP1 region) of the patients. Kaplan-Meier survival curves and log-rank tests indicated strong clinical predictors (lymph node stages with decreased survival: p=2.69e-12; surgery with improved survival: p=0.0005). LOH in the FANCF region showed a weaker association with decreased overall survival (p=0.006), which however, did not hold in multivariate analyses. LOH may predominantly indicate copy number gains in FANCF and losses in FANCG and BRIP1. Integration of copy number data and gene expression proved difficult as the available sample sets did not overlap. In conclusion, LOH in FA genes appears to be a common feature of HNSCC development seen here in 57% of patients and other mutation types may increase this mutation frequency. We suggest larger patient cohorts would be needed to test the observed association of LOH in FANCF and patient survival comprehensively.

Genomic amplification of Fanconi anemia complementation group A (FancA) in head and neck squamous cell carcinoma (HNSCC): Cellular mechanisms of radioresistance and clinical relevance

Radio (chemo) therapy is a crucial treatment modality for head and neck squamous cell carcinoma (HNSCC), but relapse is frequent, and the underlying mechanisms remain largely elusive. Therefore, novel biomarkers are urgently needed. Previously, we identified gains on 16q23-24 to be associated with amplification of the Fanconi anemia A (FancA) gene and to correlate with reduced progression-free survival after radiotherapy. Here, we analyzed the effects of FancA on radiation sensitivity in vitro, characterized the underlying mechanisms, and evaluated their clinical relevance. Silencing of FancA expression in HNSCC cell lines with genomic gains on 16q23-24 resulted in significantly impaired clonogenic survival upon irradiation. Conversely, overexpression of FancA in immortalized keratinocytes conferred increased survival accompanied by improved DNA repair, reduced accumulation of chromosomal translocations, but no hyperactivation of the FA/BRCA-pathway. Downregulation of interferon signaling as identified by microarray analyses, enforced irradiation-induced senescence, and elevated production of the senescence-associated secretory phenotype (SASP) appeared to be candidate mechanisms contributing to FancA-mediated radioresistance. Data of the TCGA HNSCC cohort confirmed the association of gains on 16q24.3 with FancA overexpression and impaired overall survival. Importantly, transcriptomic alterations similar to those observed upon FancA overexpression in vitro strengthened the clinical relevance. Overall, FancA amplification and overexpression appear to be crucial for radiotherapeutic failure in HNSCC.

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.

Coregulation of FANCA and BRCA1 in human cells

Fanconi anemia (FA) is a genetically heterogeneous syndrome associated with increased cancer predisposition. The underlying genes govern the FA pathway which functions to protect the genome during the S-phase of the cell cycle. While upregulation of FA genes has been linked to chemotherapy resistance, little is known about their regulation in response to proliferative stimuli. The purpose of this study was to examine how FA genes are regulated, especially in relation to the cell cycle, in order to reveal their possible participation in biochemical networks. Expression of 14 FA genes was monitored in two human cell-cycle models and in two RB1/E2F pathway-associated primary cancers, retinoblastoma and basal breast cancer. In silico studies were performed to further evaluate coregulation and identify connected networks and diseases. Only FANCA was consistently induced over 2-fold; FANCF failed to exhibit any regulatory fluctuations. Two tools exploiting public data sets indicated coregulation of FANCA with BRCA1. Upregulation of FANCA and BRCA1 correlated with upregulation of E2F3. Genes coregulated with both FANCA and BRCA1 were enriched for MeSH-Term id(s) genomic instability, microcephaly, and Bloom syndrome, and enriched for the cellular component centrosome. The regulation of FA genes appears highly divergent. In RB1-linked tumors, upregulation of FA network genes was associated with reduced expression of FANCF. FANCA and BRCA1 may jointly act in a subnetwork - supporting vital function(s) at the subcellular level (centrosome) as well as at the level of embryonic development (mechanisms controlling head circumference).

Comprehensive analysis of HPV16 integration in OSCC reveals no significant impact of physical status on viral oncogene and virally disrupted human gene expression

Infection with high-risk human papillomavirus (HPV) type 16 is an independent risk factor for the development of oropharyngeal squamous cell carcinomas (OSCC). However, it is unclear whether viral integration is an essential hallmark in the carcinogenic process of OSCC and whether HPV integration correlates with the level of viral gene transcription and influences the expression of disrupted host genes. We analyzed 75 patients with OSCC. HPV16-positivity was proven by p16(INK4A) immunohistochemistry, PCR and FISH. Viral integration was examined using DIPS- as well as APOT-PCR. Viral E2, E6 and E7 gene expression levels were quantified by quantitative reverse transcriptase (RT-q)PCR. Expression levels of 7 human genes disrupted by the virus were extracted from mRNA expression profiling data of 32 OSCCs. Viral copy numbers were assessed by qPCR in 73 tumors. We identified 37 HPV16-human fusion products indicating viral integration in 29 (39%) OSCC. In the remaining tumors (61%) only episome-derived PCR products were detected. When comparing OSCC with or without an integration-derived fusion product, we did not find significant differences in the mean RNA expression of viral genes E2, E6 and E7 or the viral copy numbers per cell, nor did the RNA expression of the HPV-disrupted genes differ from either group of OSCC. In conclusion, our data do not support the hypothesis that integration affects the levels of viral and/or HPV-disrupted human gene transcripts. Thus constitutive, rather than a high level, of expression of oncogene transcripts appears to be required in HPV-related OSCC.

RAD51C--a new human cancer susceptibility gene for sporadic squamous cell carcinoma of the head and neck (HNSCC)

INTRODUCTION

Head and neck squamous cell carcinomas (HNSSCs) are one of the leading causes of cancer-associated death worldwide. Although certain behavioral risk factors are well recognized as tumor promoting, there is very little known about the presence of predisposing germline mutations in HNSCC patients.

METHODS

In this study, we analyzed 121 individuals with HNSCCs collected at our institution for germline alterations in the newly identified cancer susceptibility gene RAD51C.

RESULTS

Sequencing of all exons and the adjacent introns revealed five distinct heterozygous sequence deviations in RAD51C in seven patients (5.8%). A female patient without any other risk factors carried a germline mutation that disrupted the canonical splice acceptor site of exon 5 (c.706-2A>G).

CONCLUSIONS

As there are only a few publications in the literature identifying germline mutations in head and neck cancer patients, our results provide the first indication that paralogs of RAD51, recently described as mutated in breast and ovarian cancer patients, might also be candidates for genetic risk factors in sporadic squamous cell carcinomas of the head and neck.

Genome stability pathways in head and neck cancers

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.

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

Fanconi anemia (FA) is a rare inherited recessive disease caused by mutations in one of fifteen genes known to encode FA pathway components. In response to DNA damage, nuclear FA proteins associate into high molecular weight complexes through a cascade of post-translational modifications and physical interactions, followed by the repair of damaged DNA. Hematopoietic cells are particularly sensitive to the loss of these interactions, and bone marrow failure occurs almost universally in FA patients. FA as a disease is further characterized by cancer susceptibility, which highlights the importance of the FA pathway in tumor suppression, and will be the focus of this review. Acute myeloid leukemia is the most common cancer type, often subsequent to bone marrow failure. However, FA patients are also at an extreme risk of squamous cell carcinoma (SCC) of the head and neck and gynecological tract, with an even greater incidence in those individuals who have received a bone marrow transplant and recovered from hematopoietic disease. FA tumor suppression in hematopoietic versus epithelial compartments could be mechanistically similar or distinct. Definition of compartment specific FA activities is now critical to assess the effects of today's bone marrow failure treatments on tomorrow's solid tumor development. It is our hope that current therapies can then be optimized to decrease the risk of malignant transformation in both hematopoietic and epithelial cells. Here we review our current understanding of the mechanisms of action of the Fanconi anemia pathway as it contributes to stress responses, DNA repair and squamous cell carcinoma susceptibility.

Components of a Fanconi-like pathway control Pso2-independent DNA interstrand crosslink repair in yeast

Fanconi anemia (FA) is a devastating genetic disease, associated with genomic instability and defects in DNA interstrand cross-link (ICL) repair. The FA repair pathway is not thought to be conserved in budding yeast, and although the yeast Mph1 helicase is a putative homolog of human FANCM, yeast cells disrupted for MPH1 are not sensitive to ICLs. Here, we reveal a key role for Mph1 in ICL repair when the Pso2 exonuclease is inactivated. We find that the yeast FANCM ortholog Mph1 physically and functionally interacts with Mgm101, a protein previously implicated in mitochondrial DNA repair, and the MutSα mismatch repair factor (Msh2-Msh6). Co-disruption of MPH1, MGM101, MSH6, or MSH2 with PSO2 produces a lesion-specific increase in ICL sensitivity, the elevation of ICL-induced chromosomal rearrangements, and persistence of ICL-associated DNA double-strand breaks. We find that Mph1-Mgm101-MutSα directs the ICL-induced recruitment of Exo1 to chromatin, and we propose that Exo1 is an alternative 5′-3′ exonuclease utilised for ICL repair in the absence of Pso2. Moreover, ICL-induced Rad51 chromatin loading is delayed when both Pso2 and components of the Mph1-Mgm101-MutSα and Exo1 pathway are inactivated, demonstrating that the homologous recombination stages of ICL repair are inhibited. Finally, the FANCJ- and FANCP-related factors Chl1 and Slx4, respectively, are also components of the genetic pathway controlled by Mph1-Mgm101-MutSα. Together this suggests that a prototypical FA–related ICL repair pathway operates in budding yeast, which acts redundantly with the pathway controlled by Pso2, and is required for the targeting of Exo1 to chromatin to execute ICL repair.

Individuals with Fanconi anemia (FA) suffer from bone marrow failure and from elevated rates of haematological and solid malignancy. Moreover, FA patients exhibit extreme sensitivity to DNA interstrand cross-links (ICLs), but not other forms of DNA damage. Despite recent progress in identifying and characterising FA factors, little is known about the mechanistic basis of the ICL repair defect in FA. The identification and characterisation of FA–like pathways in simple model eukaryotes, amenable to genetic dissection, would clearly accelerate progress. Here, we have identified an ICL repair pathway in budding yeast that has significant similarities to the FA pathway and that acts in parallel to an established pathway controlled by the Pso2 exonuclease. We have discovered that a key component of this pathway, the FANCM-like helicase, Mph1, interacts and collaborates with a mismatch repair factor (MutSα) and a novel nuclear DNA repair factor Mgm101 to control ICL repair. We also found that a central role of these factors is to recruit Exonuclease 1 (Exo1) to ICL-damaged chromatin, and propose that this factor acts redundantly with Pso2 to execute the exonucleolytic processing of ICLs. Our findings reveal new mechanistic insights into the control of ICL repair by FA–like proteins in an important model organism.

Association of FANCC and PTCH1 with the development of early dysplastic lesions of the head and neck

BACKGROUND

Alteration of chromosome 9q22.3 region is an early and frequent event in head and neck squamous cell carcinoma (HNSCC). The aim of this study was to understand the association of candidate tumor suppressor genes PHF2, FANCC, PTCH1, and XPA located in this region in the development of HNSCC.

METHODS

The alterations (deletion, promoter methylation, mutation, expression) of these genes were analyzed in 65 dysplastic head and neck lesions and 84 primary HNSCC samples. Clinicopathologic correlations were made with alterations of the genes.

RESULTS

Overall alterations (deletion, promoter methylation) of FANCC and PTCH1 were high in mild dysplasia and comparable in subsequent stages of tumor progression. However, PHF2 alteration was low in mild dysplasia, but increased in moderate and severe dysplasias. Alterations (deletion, promoter methylation) of FANCC and PTCH1 showed association with each other. Two novel mutations in GLI binding sites of PTCH1 promoter and a novel microsatellite marker hmPTCH1 with four alleles at immediate upstream of the gene were identified. In a case-control study, the (CGG)7 allele of hmPTCH1 was found to be susceptible for HNSCC development. Concordance was seen in the expression (RNA, protein) of these genes with their molecular alterations.

CONCLUSIONS

Alterations of FANCC and PTCH1 could be used as molecular marker for early diagnosis and prognosis of HNSCC.

Establishment and Molecular Cytogenetic Characterization of a Cell Culture Model of Head and Neck Squamous Cell Carcinoma (HNSCC)

Cytogenetic analysis of head and neck squamous cell carcinoma (HNSCC) established several biomarkers that have been correlated to clinical parameters during the past years. Adequate cell culture model systems are required for functional studies investigating those potential prognostic markers in HNSCC. We have used a cell line, CAL 33, for the establishment of a cell culture model in order to perform functional analyses of interesting candidate genes and proteins. The cell line was cytogenetically characterized using array CGH, spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). As a starting point for the investigation of genetic markers predicting radiosensitivity in tumor cells, irradiation experiments were carried out and radiation responses of CAL 33 have been determined. Radiosensitivity of CAL 33 cells was intermediate when compared to published data on tumor cell lines.

Redox-dependent Brca1 transcriptional regulation by an NADH-sensor CtBP1

C-terminal binding protein 1 (CtBP1) is a transcriptional co-repressor and metabolic sensory protein, which often represses tumor suppressor genes. Hence, we sought to determine if CtBP1 affects expression of the tumor suppressor Brca1 in head and neck tissue, as downregulation of Brca1 begins at the early stages of head and neck squamous cell carcinomas (HNSCCs). We found that CtBP1 represses Brca1 transcription by binding to the E2F4 site of the Brca1 promoter. Additionally, the recruitment of CtBP1 to the Brca1 promoter is redox-dependent, that is, increased at high NADH levels in hypoxic conditions. Further, immunostaining using a human HNSCC tissue array revealed that nuclear CtBP1 staining began to accumulate in hyperplasic lesions and HNSCCs, this staining correlated with Brca1 downregulation in these lesions. Pharmacological disruption of CtBP1 binding to Brca1 promoter by the antioxidant Tempol, which reduces NADH levels, relieved CtBP1-mediated repression of Brca1, leading to increased DNA repair in HNSCC cells. As tumor cells are generally hypoxic with increased NADH levels, the dynamic control of Brca1 by a 'metabolic switch' found in this study not only provides an important link between tumor metabolism and tumor suppressor expression but also suggests a potential chemo preventative or therapeutic strategy for HNSCC by blocking NADH-dependent CtBP1 activity at early stages of HNSCC carcinogenesis.

TGFβ signaling in head and neck squamous cell carcinoma

Transforming growth factor beta (TGFβ) is a key regulator of epithelial cell proliferation, immune function and angiogenesis. Because TGFβ signaling maintains epithelial homeostasis, dysregulated TGFβ signaling is common in many malignancies, including head and neck squamous cell carcinoma (HNSCC). Defective TGFβ signaling in epithelial cells causes hyperproliferation, reduced apoptosis and increased genomic instability, and the compensatory increase in TGFβ production by tumor epithelial cells with TGFβ signaling defects further promotes tumor growth and metastases by increasing angiogenesis and inflammation in tumor stromal cells. Here, we review the mouse models that we used to study TGFβ signaling in HNSCC.

Fanconi anemia pathway heterogeneity revealed by cisplatin and oxaliplatin treatments

Genetic or epigenetic inactivation of the pathway formed by the Fanconi Anemia (FA) proteins occurs in several cancer types, including head and neck squamous cell carcinomas (HNSCC), rendering the affected tumors potentially hypersensitive to DNA crosslinking agents. However, the cytotoxicity of other commonly used cancer therapeutics in cells with FA pathway defects remains to be defined. Here, we focused on the effects of cisplatin and oxaliplatin in a panel of HNSCC and fibroblast cell lines. We found that FANCC- and FANCD2-mutant cells were unexpectedly more sensitive to platinum drugs than FANCA-mutant cells, and mono-ubiquitination of FANCD2, which is mediated by the FANCA and FANCC containing FA core complex was not required for platinum resistance. Interestingly, platinum hypersensitivity could be dissociated from mitomycin C hypersensitivity suggesting different underlying mechanisms. FANCD2 or RAD51 subnuclear foci were not useful as biomarkers of platinum hypersensitivity of FANCC/FANCD2-mutant cells. Our data add to an emerging body of evidence indicating that the FA pathway is not linear and that several protein subcomplexes with different functions exist. It will be important to establish biomarkers that can predict the sensitivity of tumors with specific FA defects to chemotherapeutic agents.

Smad4 loss in mice causes spontaneous head and neck cancer with increased genomic instability and inflammation

Smad4 is a central mediator of TGF-beta signaling, and its expression is downregulated or lost at the malignant stage in several cancer types. In this study, we found that Smad4 was frequently downregulated not only in human head and neck squamous cell carcinoma (HNSCC) malignant lesions, but also in grossly normal adjacent buccal mucosa. To gain insight into the importance of this observation, we generated mice in which Smad4 was deleted in head and neck epithelia (referred to herein as HN-Smad4-/- mice) and found that they developed spontaneous HNSCC. Interestingly, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited increased genomic instability, which correlated with downregulated expression and function of genes encoding proteins in the Fanconi anemia/Brca (Fanc/Brca) DNA repair pathway linked to HNSCC susceptibility in humans. Consistent with this, further analysis revealed a correlation between downregulation of Smad4 protein and downregulation of the Brca1 and Rad51 proteins in human HNSCC. In addition to the above changes in tumor epithelia, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited severe inflammation, which was associated with increased expression of TGF-beta1 and activated Smad3. We present what we believe to be the first single gene-knockout model for HNSCC, in which both HNSCC formation and invasion occurred as a result of Smad4 deletion. Our results reveal an intriguing connection between Smad4 and the Fanc/Brca pathway and highlight the impact of epithelial Smad4 loss on inflammation.

Alterations in candidate genes PHF2, FANCC, PTCH1 and XPA at chromosomal 9q22.3 region: pathological significance in early- and late-onset breast carcinoma

Introduction

Younger women with breast carcinoma (BC) exhibits more aggressive pathologic features compared to older women; young age could be an independent predictor of adverse prognosis. To find any existing differences in the molecular pathogenesis of BC in both younger and older women, alterations at chromosomal (chr.) 9q22.32-22.33 region were studied owing to its association in wide variety of tumors. Present work focuses on comparative analysis of alterations of four candidate genes; PHF2, FANCC, PTCH1 and XPA located within 4.4 Mb region of the afore-said locus in two age groups of BC, as well as the interrelation and prognostic significance of alterations of these genes.

Methods

Deletion analysis of PHF2, FANCC, PTCH1 and XPA were examined in a subset of 47 early-onset (group-A: ≤ 40 years) and 59 late-onset (group-B: > 40 years) breast carcinomas using both microsatellite and exonic markers. Methylation Sensitive Restriction analysis (MSRA) was done to check for promoter methylation. Quantitative real-time polymerase chain reaction (Q-PCR) and immunohistochemisty (IHC) was done in some genes to see their relative mRNA and protein expressions respectively. Clinico-pathological correlation of different parameters as well as patient survival was calculated using different statistical softwares like EpiInfo 6.04b, SPSS 10.0 etc.

Results

Either age group exhibited high frequency of overall alterations in PHF2, FANCC and PTCH1 compared to XPA. Samples with alteration (deletion/methylation) in these genes showed reduced level of mRNA expression as seen by Q-PCR. Immunohistochemical analysis of FANCC and PTCH1 also supported this observation. Poor patient survival was noted in both age groups having alterations in FANCC. Similar result was also seen with PTCH1 and XPA alterations in group-A and PHF2 alterations in group-B. This reflected their roles as prognostic tools in the respective groups in which they were altered.

Conclusion

Overall alterations of PHF2, FANCC and PTCH1 were comparatively higher than XPA. Differential association of alterations in FANCC and PTCH1 with that of PHF2, XPA and two breast cancer susceptibility genes (BRCA1/BRCA2) in the two age groups suggests differences in their molecular pathogenesis and dysregulation of multiple DNA repair pathways as well as hedgehog dependent stem cell renewal pathway.

A novel breast cancer-associated BRIP1 (FANCJ/BACH1) germ-line mutation impairs protein stability and function

PURPOSE

BRCA1-interacting protein 1 (BRIP1; FANCJ/BACH1), which encodes a DNA helicase that interacts with BRCA1, has been suggested to be a low-penetrance breast cancer predisposing gene. We aimed to assess whether BRIP1 mutations contribute to breast cancer susceptibility in our population and, if so, to investigate the effect of such mutation(s) on BRIP1 function.

EXPERIMENTAL DESIGN

A series of 49 breast/ovarian cancer families, devoid of a BRCA1/BRCA2 mutation, were screened for BRIP1 mutations. Functional analyses, including coimmunoprecipitation and stability assays, were employed to further characterize a previously unreported variant.

RESULTS

Five sequence alterations were identified, of which four had been already described. Herein, we report a novel BRIP1 germ-line mutation identified in a woman with early-onset breast cancer. The mutation consists of a 4-nucleotide deletion (c.2992-2995delAAGA) in BRIP1 exon 20 that causes a shift in the reading frame, disrupts the BRCA1-binding domain of BRIP1, and creates a premature stop codon. Functional analysis of the recombinant mutant protein in transfected cells showed that the truncation interferes with the stability of the protein and with its ability to interact with BRCA1. Loss of the wild-type BRIP1 allele with retention of the mutated one was observed in the patient's breast tumor tissue.

CONCLUSIONS

These results, by showing that the newly identified BRIP1 c.2992-2995delAAGA mutation is associated with instability and functional impairment of the encoded protein, provide further evidence of a breast cancer-related role for BRIP1.

Coordinate regulation of Fanconi anemia gene expression occurs through the Rb/E2F pathway

Fanconi anemia (FA) is a genome instability syndrome that is characterized by progressive bone marrow failure and a high risk of cancer. FA patients are particularly susceptible to leukemia as well as squamous cell carcinomas (SCCs) of the head and neck, anogenital region and skin. Thirteen complementation groups and the corresponding FA genes have been identified, and their protein products assemble into nuclear core complexes during DNA-damage responses. Much progress has been made in our understanding of post-translational FA protein modifications and physical interactions. By contrast, little is known about the control of protein availability at the level of transcription. We report here that multiple FA proteins were downregulated during the proliferative arrest of primary human keratinocytes and HeLa cells, and that the observed regulation was at a transcriptional level. Proliferative stimuli such as expression of HPV16 E7 as well as E2F1 overexpression in primary cells resulted in coordinate FA upregulation. To define the underlying mechanism, we examined the endogenous FANCD2 promoter, and detected regulated binding of members of the E2F/Rb family in chromatin immunoprecipitation assays. Finally, a 1 kb promoter fragment was sufficient to confer E2F/Rb regulation in reporter assays. Taken together, our data demonstrate FA gene co-regulation in synchrony with the cell cycle and suggest that deregulated expression of individual FA genes-in addition to FA gene mutation-may promote FA-related human cancer.

Genetic and environmental factors in head and neck cancer genesis

Head and neck squamous cell carcinoma (HNSCC) include squamous cell carcinomas of the oral cavity, pharynx, and larynx. Epidemiologic data suggest that the etiology and pathogenesis of HNSCC are influenced by environmental and lifestyle-related factors, such as tobacco use, ethanol consumption, papilloma virus infection, dietary factors and exposure to toxic substances. DNA repair systems and carcinogen-metabolizing enzymes can increase the risk for HNSCC but no definite causal mechanism has been demonstrated. There are several well-characterized entities that are associated with risk and prognosis of head and neck cancer, including Lynch-II syndrome, Bloom syndrome, Fanconi's anemia, xeroderma pigmentosum, ataxia telangiectasia, and Li-Fraumeni syndrome. This review aims to present the current status in our understanding of HNSCC and highlight controversies relating to the role of several factors in the genesis of the cancer.