Clinicopathologic Features of Osteosarcoma in Patients With Rothmund-Thomson Syndrome

RECQL4-related Rothmund-Thomson syndrome: A case series and literature review

Rothmund-Thomson syndrome (RTS) is a multisystemic tumour-predisposing genodermatosis caused by biallelic pathogenic alterations in the ANAPC1 gene or RECQL4 gene. Herein we describe the clinical and genetic findings in three individuals with molecularly substantiated RECQL4-related RTS. Based on the disease course of two patients with osteosarcoma, we highlight the critical importance of early diagnosis.

Bone sarcomas and cancer predisposition syndromes

Bone sarcomas, constituting less than 1% of malignant neoplasms across all age groups, are rare tumours possibly associated with genetic susceptibility syndromes. This review aims to provide recommendations for the detection of cancer predisposition syndromes associated with bone sarcomas and managing affected patients. Recommendations were formulated by a multidisciplinary working and reviewing group from GROUPOS and SFCE oncogenetic's group, including geneticists, oncologists, and radiologists. For various bone sarcomas including osteosarcomas, chondrosarcomas and Ewing sarcomas, we delineate tumour presentation, management strategies, and follow-up within the context of cancer predisposition syndromes. The inherited predisposition syndrome, associated with germline TP53 variants, known as the Li-Fraumeni syndrome, is the most frequent implicated in osteosarcoma cases. Other cancer predisposition syndromes, such as RB1, RECQ or CDKN2A disorders in osteosarcomas and Ollier and Maffucci diseases in chondrosarcomas, are also recognized. Additionally, we discuss rarer cancer predisposition syndromes associated with bone sarcomas and suggest tailored treatment approaches in some cancer predisposition syndromes to mitigate severe toxicities or secondary oncological events. Furthermore, we emphasize the role of identification somatic molecular variations in identifying constitutional germline variants and describe national and international screening programs, reference networks and molecular tumour boards available for collegial and collaborative management discussion. This comprehensive review provides insights into the intricate interplay between genetic predisposition, tumour biology, and therapeutic interventions in bone sarcoma patients with cancer predisposition syndrome.

Update on Recommendations for Cancer Screening and Surveillance in Children with Genomic Instability Disorders

Genomic instability disorders are characterized by DNA or chromosomal instability, resulting in various clinical manifestations, including developmental anomalies, immunodeficiency, and increased risk of developing cancers beginning in childhood. Many of these genomic instability disorders also present with exquisite sensitivity to anticancer treatments such as ionizing radiation and chemotherapy, which may further increase the risk of second cancers. In July 2023, the American Association for Cancer Research held the second Childhood Cancer Predisposition Workshop, where multidisciplinary international experts discussed, reviewed, and updated recommendations for children with cancer predisposition syndromes. This article discusses childhood cancer risks and surveillance recommendations for the group of genomic instability disorders with predominantly recessive inheritance, including the DNA repair disorders ataxia telangiectasia, Nijmegen breakage syndrome, Fanconi anemia, xeroderma pigmentosum, Bloom syndrome, and Rothmund-Thomson syndrome, as well as the telomere biology disorders and mosaic variegated aneuploidy. Recognition of children with genomic instability disorders is important in order to make the proper diagnosis, enable genetic counseling, and inform cancer screening, cancer risk reduction, and choice of anticancer therapy.

Rothmund-Thomson syndrome investigated by two nationwide surveys in Japan

BACKGROUND

Rothmund-Thomson syndrome (RTS) is an autosomal recessive genetic disorder characterized by poikiloderma of the face, small stature, sparse scalp hair, juvenile cataract, radial aplasia, and predisposition to cancers. Due to the rarity of RTS, the situation of patients with RTS in Japan has not been elucidated.

METHODS

In 2010 and 2020, following the results of a primary questionnaire survey, a secondary questionnaire survey on RTS was conducted nationwide to investigate the number of RTS cases and their associated skin lesions, bone lesions, other clinical features, and quality of life in Japan.

RESULTS

In 2010 and 2020, 10 and eight patients with RTS were recruited, respectively. Skin lesions such as poikiloderma, erythema, pigmentation, and abnormal scalp hair were observed in almost all cases. Bone lesions were observed in four cases in the 2010 and 2020 surveys, respectively. Two cases had mutations in the RECQL4 gene in the 2020 survey.

CONCLUSIONS

Two nationwide surveys have shown the actual situation of patients with RTS in Japan. Cutaneous and bone manifestations are important for the diagnosis of RTS. However, many patients have no RECQL4 mutations. The novel causative gene of RTS should be further elucidated.

Patient-derived iPSCs link elevated mitochondrial respiratory complex I function to osteosarcoma in Rothmund-Thomson syndrome

Rothmund-Thomson syndrome (RTS) is an autosomal recessive genetic disorder characterized by poikiloderma, small stature, skeletal anomalies, sparse brows/lashes, cataracts, and predisposition to cancer. Type 2 RTS patients with biallelic RECQL4 pathogenic variants have multiple skeletal anomalies and a significantly increased incidence of osteosarcoma. Here, we generated RTS patient-derived induced pluripotent stem cells (iPSCs) to dissect the pathological signaling leading to RTS patient-associated osteosarcoma. RTS iPSC-derived osteoblasts showed defective osteogenic differentiation and gain of in vitro tumorigenic ability. Transcriptome analysis of RTS osteoblasts validated decreased bone morphogenesis while revealing aberrantly upregulated mitochondrial respiratory complex I gene expression. RTS osteoblast metabolic assays demonstrated elevated mitochondrial respiratory complex I function, increased oxidative phosphorylation (OXPHOS), and increased ATP production. Inhibition of mitochondrial respiratory complex I activity by IACS-010759 selectively suppressed cellular respiration and cell proliferation of RTS osteoblasts. Furthermore, systems analysis of IACS-010759-induced changes in RTS osteoblasts revealed that chemical inhibition of mitochondrial respiratory complex I impaired cell proliferation, induced senescence, and decreased MAPK signaling and cell cycle associated genes, but increased H19 and ribosomal protein genes. In summary, our study suggests that mitochondrial respiratory complex I is a potential therapeutic target for RTS-associated osteosarcoma and provides future insights for clinical treatment strategies.

Anti-cancer properties of quercetin in osteosarcoma

Osteosarcoma is a primary bone tumor. Although it is a rare disease in general, it is the most common primary bone tumor among children. Despite the significant advances made in the field of osteosarcoma treatment, the outcomes of this disease are still unfavorable. Besides, there is still no targeted therapy for osteosarcoma that can be used in clinical settings. Quercetin is a member of the phytochemical family which is used for different diseases including cardiovascular diseases, diabetes, and cancer. Its anti-cancer effects are examined in many types of cancer including breast, colon, lung, prostate, and pancreatic cancers and have shown promising results. Herein, the studies dealing with the antitumor roles of quercetin in osteosarcoma are reviewed in this article. We take a look into quercetin's ability to affect proliferation, apoptosis, invasion, and chemo-resistance of the osteosarcoma cells through regulating protein expression and signaling pathways.

Novel pathogenic variants in the RECQL4 gene causing Rothmund-Thomson syndrome in three Chinese patients

Rothmund-Thomson syndrome (RTS) is a rare autosomal-recessive disorder characterized by poikiloderma, short stature, sparse hair, skeletal abnormalities, and cancer predisposition. Mutations in ANAPC1 or RECQL4 have been identified to underlie RTS. Either Sanger sequencing or next-generation sequencing (NGS) was performed for three Chinese RTS patients. Copy number variants were called by the eXome-Hidden Markov Model using read-depth data of NGS, and the putative heterozygous deletion was confirmed by PCR with multiple primers. The breakpoints were identified by Sanger sequencing. All patients presented with characteristic features of poikiloderma, short stature, and sparse hair, eyelashes, and eyebrows. In addition, patient 1 had intellectual disability and speech delay, and patient 2 developed osteosarcoma when she was 13 years old. Biallelic RECQL4 variants were identified in all three patients. Five of the six variants were novel, including c.119-1G>A, c.2886-1G>A, c.2290C>T (p.Gln764*), and c.3552dupG (p.Arg1185Glufs*42), and a gross deletion encompassing exons 6 to 10. Our study expands the genetic and clinical spectrums of RTS. Furthermore, we reported the first heterozygous gross deletion in RECQL4.

Second Osteosarcoma in a 16-Year-old Woman Diagnosed With Rothmund-Thomson Syndrome

Rothmund-Thomson syndrome (RTS) is an autosomal recessive disorder associated with an increased predisposition to osteosarcoma (OS) when it is caused by concrete mutations in the RECQL4 gene. Most OSs arise sporadically, but it can also be the first manifestation of a cancer predisposition syndrome as Rothmund Thompson. The early onset, multifocality and metachronism, and a family history of the disease, may suggest a tumor predisposition syndrome. We present the case of a patient with a polymalformative syndrome, who, at 6 years of age, was diagnosed with OS in the right femur. This led to the diagnosis of a RTS type 2. She was cured and surveillance showed no sign of disease. Ten years later, the patient developed a second OS in the contralateral femur. Fortunately, she is in complete remission again after treatment. We describe our patient treatment and recommend a possible screening-surveillance for RTS type II patients.

Rothmund-Thomson Syndrome-Like RECQL4 Truncating Mutations Cause a Haploinsufficient Low-Bone-Mass Phenotype in Mice

Rothmund-Thomson syndrome (RTS) is an autosomal recessive disorder characterized by defects in the skeletal system, such as bone hypoplasia, short stature, low bone mass, and an increased incidence of osteosarcoma. RTS type 2 patients have germ line compound biallelic protein-truncating mutations of RECQL4. As existing murine models employ Recql4 null alleles, we have attempted to more accurately model RTS by generating mice with patient-mimicking truncating Recql4 mutations. Truncating mutations impaired the stability and subcellular localization of RECQL4 and resulted in homozygous embryonic lethality and a haploinsufficient low-bone mass phenotype. Combination of a truncating mutation with a conditional Recql4 null allele demonstrated that the skeletal defects were intrinsic to the osteoblast lineage. However, the truncating mutations did not promote tumorigenesis. We utilized murine Recql4 null cells to assess the impact of human RECQL4 mutations using an in vitro complementation assay. While some mutations created unstable protein products, others altered subcellular localization of the protein. Interestingly, the severity of the phenotypes correlated with the extent of protein truncation. Collectively, our results reveal that truncating RECQL4 mutations in mice lead to an osteoporosis-like phenotype through defects in early osteoblast progenitors and identify RECQL4 gene dosage as a novel regulator of bone mass.

Somatic and germline analysis of a familial Rothmund-Thomson syndrome in two siblings with osteosarcoma

Rothmund–Thomson syndrome (RTS) is characterized by a rash that begins in the first few months of life and eventually develops into poikiloderma. Associated symptoms are alterations in the teeth, sparse hair, thin eyebrows, lack of eyelashes, low stature, bone abnormalities, hematological illnesses, gastrointestinal disease, malnutrition, cataracts, and predisposition to cancer, principally to bone tumors and skin cancer. Diagnostic certitude is provided by a genetic study involving detection of pathogenic variants of the RECQL4 gene. We hereby present a familiar case of RTS in two siblings from a Portuguese family, both diagnosed with osteosarcoma. Genomic analysis (203 genes) of both tumors as well as germline analysis of the RECQL4 gene, thus confirming the syndrome in the family, have been performed. The relevance of clinical recognition of the hallmarks of the disease and thus early diagnosis with early intervention is highlighted.

Chitosan applications in studying and managing osteosarcoma

Osteosarcoma has a high prevalence among children and adolescents. Common treatments of this disease are not promising enough. Molecular processes involved in the pathogenesis of osteosarcoma are not fully understood. Besides, the remnants of tumor cells after surgery can cause bone destruction and recurrence of the disease. Thus, there is a need to develop novel drugs or enhancing the currently-used drugs as well as identifying bone-repairing methods. Chitosan is a natural compound produced by the deacetylation of chitin. Research has shown that chitosan can be used in various fields due to its beneficial effects, such as biodegradability and biocompatibility. Regarding cancer, chitosan exerts several anti-tumor activities. Moreover, it can be used in diagnostic techniques, drug delivery systems, and cell culture methods. Herein, we aim to discuss the potential roles of chitosan in studying and treating osteosarcoma. We review the literature on chitosan's applications as a drug delivery system and how it can be combined with other substances to improve its ability of local drug delivery. We take a look into the studies concerning the possible benefits of chitosan in the field of bone tissue engineering and 3D culturing. Furthermore, anti-cancer activities of different compounds of chitosan are reviewed.

Fusion genes as biomarkers in pediatric cancers: A review of the current state and applicability in diagnostics and personalized therapy

The incidence of pediatric cancers is rising steadily across the world, along with the challenges in understanding the molecular mechanisms and devising effective therapeutic strategies. Pediatric cancers are presented with diverse molecular characteristics and more distinct subtypes when compared to adult cancers. Recent studies on the genomic landscape of pediatric cancers using next-generation sequencing (NGS) approaches have redefined this field by providing better subtype characterization and novel actionable targets. Since early identification and personalized treatment strategies influence therapeutic outcomes, survival, and quality of life in pediatric cancer patients, the quest for actionable biomarkers is of great value in this field. Fusion genes that are prevalent and recurrent in several pediatric cancers are ideally suited in this context due to their disease-specific occurrence. In this review, we explore the current status of fusion genes in pediatric cancer subtypes and their use as biomarkers for diagnosis and personalized therapy. We discuss the technological advancements made in recent years in NGS sequencing and their impact on fusion detection algorithms that have revolutionized this field. Finally, we also discuss the advantages of pairing liquid biopsy protocols for fusion detection and their eventual use in diagnosis and treatment monitoring.

Epidemiology and Risk Factors of Osteosarcoma

Osteosarcoma is a rare tumor diagnosed at any age; however younger age is a common risk factor. In addition, multiple factors are believed to contribute to higher rates of osteosarcoma, particularly race and gender. Although diagnosed worldwide, osteosarcoma is found to be more prevalent in Africa with high numbers of cases reported in Nigeria, Uganda, and Sudan. Additionally, higher rates are detected in African Americans, suggesting a genetic predisposition linked to race. This review focuses on identifying high risk factors of osteosarcoma with an emphasis on sarcoma epidemiology and risk factors in African countries.

RECQ DNA Helicases and Osteosarcoma

The RECQ family of DNA helicases is a conserved group of enzymes that plays an important role in maintaining genomic stability. Humans possess five RECQ helicase genes, and mutations in three of them - BLM, WRN, and RECQL4 - are associated with the genetic disorders Bloom syndrome, Werner syndrome, and Rothmund-Thomson syndrome (RTS), respectively. These syndromes share overlapping clinical features, and importantly they are all associated with an increased risk of cancer. Patients with RTS have the highest specific risk of developing osteosarcoma compared to all other cancer predisposition syndromes; therefore, RTS serves as a relevant model to study the pathogenesis and molecular genetics of osteosarcoma. The "tumor suppressor" function of the RECQ helicases continues to be an area of active investigation. This chapter will focus primarily on the known cellular functions of RECQL4 and how these may relate to tumorigenesis, as well as ongoing efforts to understand RECQL4's functions in vivo using animal models. Understanding the RECQ pathways will provide insight into avenues for novel cancer therapies in the future.

Human RECQL4 represses the RAD52-mediated single-strand annealing pathway after ionizing radiation or cisplatin treatment

Ionizing radiation (IR) and cisplatin are frequently used cancer treatments, although the mechanisms of error-prone DNA repair-mediated genomic instability after anticancer treatment are not fully clarified yet. RECQL4 mutations mainly in the C-terminal region of the RECQL4 gene lead to the cancer-predisposing Rothmund-Thomson syndrome, but the function of RECQL4ΔC (C-terminus deleted) in error-prone DNA repair remains unclear. We established several RECQL4ΔC cell lines and found that RECQL4ΔC cancer cells, but not RECQL4ΔC nontumorigenic cells, exhibited IR/cisplatin hypersensitivity. Notably, RECQL4ΔC cancer cells presented increased RPA2/RAD52 foci after cancer treatments. RECQL4ΔC HCT116 cells exhibited increased error-prone single-strand annealing (SSA) activity and decreased alternative end-joining activities, suggesting that RECQL4 regulates the DNA repair pathway choice at double-strand breaks. RAD52 depletion by siRNA or RAD52 inhibitors (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside [AICAR], (-)-epigallocatechin [EGC]) or a RAD52-phenylalanine 79 aptamer significantly restrained the growth of RAD52-upregulated RECQL4ΔC HCT116 cells in vitro and in mouse xenografts. Remarkably, compared to single-agent cisplatin or EGC treatment, cisplatin followed by low-concentration EGC had a significant suppressive effect on RECQL4ΔC HCT116 cell growth in vivo. Together, the regimens targeting the RAD52-mediated SSA pathway after anticancer treatment may be applicable for cancer patients with RECQL4 gene mutations.

Telomeropathies: Etiology, diagnosis, treatment and follow-up. Ethical and legal considerations

Telomeropathies involve a wide variety of infrequent genetic diseases caused by mutations in the telomerase maintenance mechanism or the DNA damage response (DDR) system. They are considered a family of rare diseases that often share causes, molecular mechanisms and symptoms. Generally, these diseases are not diagnosed until the symptoms are advanced, diminishing the survival time of patients. Although several related syndromes may still be unrecognized this work describes those that are known, highlighting that because they are rare diseases, physicians should be trained in their early diagnosis. The etiology and diagnosis are discussed for each telomeropathy and the treatments when available, along with a new classification of this group of diseases. Ethical and legal issues related to this group of diseases are also considered.

Does ATRX germline variation predispose to osteosarcoma? Three additional cases of osteosarcoma in two ATR-X syndrome patients

Osteosarcoma is the most common malignant bone tumor in adolescents and young adults. Most osteosarcomas are sporadic but the risk of osteosarcoma is also increased by germline variants in TP53, RB1 and RECQL4 genes. ATRX germline variations are responsible for the rare genetic disorder X-linked alpha-thalassemia mental retardation (ATR-X) syndrome characterized by severe developmental delay and alpha-thalassemia but no obvious increased risk of cancer. Here we report two children with ATR-X syndrome who developed osteosarcoma. Notably, one of the children developed two osteosarcomas separated by 10 years. Those two cases raise the possibility that ATRX germline variant could be associated with an increased risk of osteosarcoma.

Fluorescent In Situ Hybridization for TP53 in the Diagnosis of Pediatric Osteogenic Sarcoma

Osteogenic sarcoma (OS) is the most common malignant bone tumor in children and adolescents. Despite advances in molecular genetic characterization of pediatric and adult tumors, the diagnosis of OS still depends almost entirely on light microscopy. The lack of consistent genetic changes in OS has greatly hindered the development of any diagnostic molecular test. Recently, whole-genome sequencing has shown that ~50% of cases of OS have a translocation involving the TP53 gene with breakpoints confined to the first intron. We developed a 2 color break-apart fluorescent in situ hybridization (FISH) probe for intron 1 of TP53 and applied it to an archived series to assess its diagnostic utility. The study group included 37 cases of OS (including osteoblastic, chondroblastic, and fibroblastic), as well as 53 cases of non-OS pediatric sarcomas (including Ewing sarcoma, rhabdomyosarcoma, undifferentiated small cell sarcoma, CCNB3-BCOR sarcoma, CIC-DUX sarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumor) and 27 cases of benign bone lesions (including osteoblastoma, chondromyxoid fibroma, fibrous dysplasia, and fibro-osseous dysplasia). A rearranged signal was found in 20/37 cases (54%) of OS and in none of the other sarcomas or benign bone lesions, giving the FISH test 100% specificity for a diagnosis of OS. p53 immunostaining was generally not predictive of the results obtained by FISH and could not substitute for this test. This FISH probe offers a simple and specific genetic test to aid in the diagnosis of OS, despite the genetic complexity of this tumor.

Rothmund-Thomson syndrome (RTS) with osteosarcoma due to RECQL4 mutation

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder with clinical features consisting of poikiloderma, skeletal abnormalities, sparse hair, absent or scanty eyelashes and eyebrows and short stature. Patients with RTS due to genetic mutations of RECQL4 genes carry a high risk of developing osteosarcoma during childhood. Because of this, early genetic diagnosis is important. Here, we describe a 14-year-old white boy who developed an erythematous rash on both cheeks before the age of 3 months and was noted to have absent eyelashes and scanty eyebrows. He was found to have compound heterozygous mutations of the RECQL4 gene alleles at the age of 6 months and was diagnosed to have RTS type II. He subsequently developed osteosarcoma at age 10 which was successfully treated, and currently he has been tumour free for over 3 years.

Circulating biomarkers in osteosarcoma: new translational tools for diagnosis and treatment

Osteosarcoma (OS) is a rare primary malignant bone tumour arising from primitive bone-forming mesenchymal cells, with high incidence in children and young adults, accounting for approximately 60% of all malignant bone tumours. Currently, long-term disease-free survival can be achieved by surgical treatment plus chemotherapy in approximately 60% of patients with localized extremity disease, and in 20-30% of patients with metastatic lung or bone disease. Diagnosis of primary lesions and recurrences is achieved by using radiological investigations and standard tissue biopsy, the latter being costly, painful and hardly repeatable for patients. Therefore, despite some recent advances, novel biomarkers for OS diagnosis, prediction of response to therapy, disease progression and chemoresistance, are urgently needed. Biological fluids such as blood represent a rich source of non-invasive cancer biomarkers, which allow to understand what is really happening inside the tumour, either at diagnosis or during disease progression. In this regard, liquid biopsy potentially represents an alternative and non-invasive method to detect tumour onset, progression and response to therapy. In this review, we will summarize the state of the art in this novel area, illustrating recent studies on OS. Although the data reported in literature seem preliminary, liquid biopsy represents a promising tool with the potential to be rapidly translated in the clinical practice.

Tumor Syndromes That Include Bone Tumors: An Update

Tumor syndromes, including bone neoplasias, are genetic predisposing conditions characterized by the development of a pattern of malignancies within a family at an early age of onset. Occurrence of bilateral, multifocal, or metachronous neoplasias and specific histopathologic findings suggest a genetic predisposition syndrome. Additional clinical features not related to the neoplasia can be a hallmark of specific genetic syndromes. Mostly, those diseases have an autosomal dominant pattern of inheritance with variable percentage of penetrance. Some syndromic disorders with an increased tumor risk may show an autosomal recessive transmission or are related to somatic mosaicism. Many genetic tumor syndromes are known. This update is specifically focused on syndromes predisposing to osteosarcoma and chondrosarcoma.

Recommendations for Childhood Cancer Screening and Surveillance in DNA Repair Disorders

DNA repair syndromes are heterogeneous disorders caused by pathogenic variants in genes encoding proteins key in DNA replication and/or the cellular response to DNA damage. The majority of these syndromes are inherited in an autosomal-recessive manner, but autosomal-dominant and X-linked recessive disorders also exist. The clinical features of patients with DNA repair syndromes are highly varied and dependent on the underlying genetic cause. Notably, all patients have elevated risks of syndrome-associated cancers, and many of these cancers present in childhood. Although it is clear that the risk of cancer is increased, there are limited data defining the true incidence of cancer and almost no evidence-based approaches to cancer surveillance in patients with DNA repair disorders. This article is the product of the October 2016 AACR Childhood Cancer Predisposition Workshop, which brought together experts from around the world to discuss and develop cancer surveillance guidelines for children with cancer-prone disorders. Herein, we focus on the more common of the rare DNA repair disorders: ataxia telangiectasia, Bloom syndrome, Fanconi anemia, dyskeratosis congenita, Nijmegen breakage syndrome, Rothmund-Thomson syndrome, and Xeroderma pigmentosum. Dedicated syndrome registries and a combination of basic science and clinical research have led to important insights into the underlying biology of these disorders. Given the rarity of these disorders, it is recommended that centralized centers of excellence be involved directly or through consultation in caring for patients with heritable DNA repair syndromes. Clin Cancer Res; 23(11); e23-e31. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Understanding photodermatoses associated with defective DNA repair: Syndromes with cancer predisposition

Hereditary photodermatoses are a spectrum of rare photosensitive disorders that are often caused by genetic deficiency or malfunction of various components of the DNA repair pathway. This results clinically in extreme photosensitivity, with many syndromes exhibiting an increased risk of cutaneous malignancies. This review will focus specifically on the syndromes with malignant potential, including xeroderma pigmentosum, Bloom syndrome, and Rothmund-Thomson syndrome. The typical phenotypic findings of each disorder will be examined and contrasted, including noncutaneous identifiers to aid in diagnosis. The management of these patients will also be discussed. At this time, the mainstay of therapy remains strict photoprotection; however, genetic therapies are under investigation.

Inherited mutations in DNA repair genes and cancer risk

Although most cancer cases are due to somatic mutations, up to 10% of cases are attributable to germline mutations. This inherited cancer predisposition is mostly due to the loss of function of suppressor genes rather than the activation of oncogenes. Defects in DNA repair genes are the genetic events most commonly involved in hereditary cancers. The implementation of high-throughput sequencing in diagnostic testing has uncovered new predisposition genes. Furthermore, for some tumor types these sequencing techniques have also unveiled a prevalence of germline mutations significantly higher than previous estimations. The clinical implications of many of these repair defects are yet to be defined. Further studies will need to be conducted to establish the most appropriated management of unaffected carriers that are likely to grow in numbers. On the contrary, the presence of DNA repair defects provides a unique opportunity for the development of treatments that take advantage of a tumor feature. In this review article, we summarize not only the most common syndromes linked to DNA repair defects but also less known entities. We address the underlying genetics and the clinical implications of each DNA repair defect as well as the current recommendations for cancer surveillance.

Epidemiology and Etiology of Sarcomas

Sarcomas are rare malignancies of mesenchymal origin and are broadly divided into soft tissue sarcomas and bone sarcomas. The etiology of these tumors is largely unknown, and most sarcomas are sporadic. A small subset of sarcomas is associated with certain genetic syndromes and environmental factors. Ionizing radiation is the strongest environmental factor linked to sarcoma development.

Aging in Rothmund-Thomson syndrome and related RECQL4 genetic disorders

Rothmund-Thomson Syndrome (RTS) is a rare autosomal recessive disease which manifests several clinical features of accelerated aging. These findings include atrophic skin and pigment changes, alopecia, osteopenia, cataracts, and an increased incidence of cancer for patients carrying RECQL4 germline mutations. Mutations in RECQL4 are responsible for the majority of cases of RTS. RECQL4 belongs to RECQ DNA helicase family which has been shown to participate in many aspects of DNA metabolism. In the past several years, accumulated evidence indicates that RECQL4 is important not only in cancer development but also in the aging process. In this review, based on recent research data, we summarize the common aging findings in RTS patients and propose possible mechanisms to explain the aging features in these patients.

Osteosarcoma Overview

Osteosarcoma (OS) is the most common primary malignancy of bone and patients with metastatic disease or recurrences continue to have very poor outcomes. Unfortunately, little prognostic improvement has been generated from the last 20 years of research and a new perspective is warranted. OS is extremely heterogeneous in both its origins and manifestations. Although multiple associations have been made between the development of osteosarcoma and race, gender, age, various genomic alterations, and exposure situations among others, the etiology remains unclear and controversial. Noninvasive diagnostic methods include serum markers like alkaline phosphatase and a growing variety of imaging techniques including X-ray, computed tomography, magnetic resonance imaging, and positron emission as well as combinations thereof. Still, biopsy and microscopic examination are required to confirm the diagnosis and carry additional prognostic implications such as subtype classification and histological response to neoadjuvant chemotherapy. The current standard of care combines surgical and chemotherapeutic techniques, with a multitude of experimental biologics and small molecules currently in development and some in clinical trial phases. In this review, in addition to summarizing the current understanding of OS etiology, diagnostic methods, and the current standard of care, our group describes various experimental therapeutics and provides evidence to encourage a potential paradigm shift toward the introduction of immunomodulation, which may offer a more comprehensive approach to battling cancer pleomorphism.

Transcriptional Profiling Identifies the Signaling Axes of IGF and Transforming Growth Factor-b as Involved in the Pathogenesis of Osteosarcoma

BACKGROUND

Osteosarcoma is the most common primary bone tumor in adolescents associated with skeletal development. The molecular pathogenesis of osteosarcoma has not been completely determined, although many molecular alterations have been found in human osteosarcomas and cell lines.

QUESTIONS/PURPOSES

We questioned whether (1) we could identify gene expression in osteosarcoma specimens that differs from normal osteoblasts and mesenchymal stem cells and (2) this would provide clues to the molecular pathogenesis of osteosarcoma?

METHODS

The whole-genome transcriptional profiles of osteosarcomas, including two primary biopsy specimens, two cell lines, two xenografts derived from patient specimens, and one from normal osteoblasts and from mesenchymal stem cells, respectively, were quantitatively measured using serial analysis of gene expression. A statistical enrichment was performed, which selects the common genes altered in each of the osteosarcomas compared with each of the normal counterparts independently.

RESULTS

Sixty (92%) of 65 total genes that were at least twofold downregulated in osteosarcoma compared with osteoblasts and mesenchymal stem cells, could be classified in four categories: (1) seven genes in the insulin–like growth factor (IGF) signaling axis, including three of the IGF-binding proteins (IGFBP) and three of the IGFBPrelated proteins (IGFBPrP); (2) eight genes in the transforming growth factor-b (TGF-b)/bone morphogenetic protein (BMP) signaling cascade; (3) 39 genes encoding cytoskeleton and extracellular matrix proteins that are regulated by TGF-b/BMPs; and (4) six genes involved in cell cycle regulation, including tumor suppressors TP63 and p21.

CONCLUSIONS

Based on these transcriptional profiles, a coordinated theme of clustered gene deregulation in osteosarcoma has emerged. Cell proliferation driven by the IGF axes during bone growth is unrestrained owing to downregulation of IGFBPs and cell cycle regulators. Tumor cells may be maintained in an undifferentiated state secondary to impaired TGF-b/BMP signaling. This wellpreserved pattern suggests that the alterations in the signaling axes of IGF-1 and TGF-b, in concert with cell cycle regulators, may be an important pathogenic basis of osteosarcoma. CLINIC RELEVANCE: This study provides a possible molecular basis of pathogenesis of osteosarcoma. This may help to develop new therapeutic targets and strategy for this disease. Preclinical and subsequently clinical testing of inhibitors of the IGF-1 and TGF pathways would be warranted.

The Childhood Solid Tumor Network: A new resource for the developmental biology and oncology research communities

Significant advances have been made over the past 25 years in our understanding of the most common adult solid tumors such as breast, colon, lung and prostate cancer. Much less is known about childhood solid tumors because they are rare and because they originate in developing organs during fetal development, childhood and adolescence. It can be very difficult to study the cellular origins of pediatric solid tumors in developing organs characterized by rapid proliferative expansion, growth factor signaling, developmental angiogenesis, programmed cell death, tissue reorganization and cell migration. Not only has the etiology of pediatric cancer remained elusive because of their developmental origins, but it also makes it more difficult to treat. Molecular targeted therapeutics that alter developmental pathway signaling may have devastating effects on normal organ development. Therefore, basic research focused on the mechanisms of development provides an essential foundation for pediatric solid tumor translational research. In this article, we describe new resources available for the developmental biology and oncology research communities. In a companion paper, we present the detailed characterization of an orthotopic xenograft of a pediatric solid tumor derived from sympathoadrenal lineage during development.

Chondroblastic osteosarcoma

The purpose of this paper is to report a case of chondroblastic osteosarcoma in the region of the maxilla, with 5 months of evolution. The term osteosarcoma refers to a heterogeneous group of malignancies with bone formation or mesenchymal tissue with histopathological evidence of osteogenic differentiation. The pattern of chondroblastic osteosarcoma represents 25% of all reported cases of this neoplasm. Its histopathological diagnosis is based on the predominance of a chondroid matrix formed in the midst of neoplastic cells. A woman patient, 27-year old, melanoderm, presented on extraoral exam with facial asymmetry caused by the a swelling in the premaxillary region with upper lip protrusion. Intraoral exam showed a maxillary tumefaction with involvement of the vestibular and palatine regions. The computerized tomography (CT) analysis exhibited a radiolucent mass with dispersed areas of radiopacity, with poorly defined and indistinct peripheral edges. The patient was subjected to incisional biopsy and histopathological examination showed the presence of a malignant neoplasm of mesenchymal origin characterized by the presence of irregular bone trabeculae dispersed among mildly atypical chondroblastic cells. The World Health Organization (WHO) recognizes several variants that differ in location, clinical behavior and degree of cellular atypia. The conventional or classical osteosarcoma is the most frequent variant, which develops within the medullary bone. This report illustrates the rapid evolution of one of the histological variants of osteosarcoma.

Osteosarcoma in patients with Rothmund-Thomson syndrome

BACKGROUND

Rothmund-Thomson syndrome (RTS) is associated with an increased risk of osteosarcoma, but information about affected patients is limited.

PROCEDURE

Seven patients with osteosarcoma, treated in the Cooperative Osteosarcoma Study Group-trials, had a diagnosis of RTS. Their patient-, tumor- and treatment-related variables and outcome were reviewed retrospectively.

RESULTS

Median age at diagnosis of osteosarcoma was 13 years (range 7-16), five were female, two male. Tumor involved proximal tibia (n = 4), distal tibia (n = 1), distal fibula (n = 1) and proximal ulna (n = 1). Three patients had metastatic disease at diagnosis. All patients received surgery and chemotherapy. Four of seven patients required dose modifications and three of them terminated treatment prematurely. Complete resection of the primary tumor was achieved in all individuals. Two of three affected patients failed to achieve surgical clearance of their primary metastases and died. The third patient relapsed with multiple metastases and died. Two of four patients with localized disease were alive in first complete remission, a third patient in second complete remission after recurrence and a fourth patient died of acute leukemia, while still in first complete remission of osteosarcoma.

CONCLUSIONS

Patients with RTS and osteosarcoma may be cured of their cancer with appropriate multimodal therapy. They should be treated like other osteosarcoma patients but preexisting disorders, needs for special support and development of toxicities have to be considered.

Recurrent somatic structural variations contribute to tumorigenesis in pediatric osteosarcoma

Pediatric osteosarcoma is characterized by multiple somatic chromosomal lesions, including structural variations (SVs) and copy number alterations (CNAs). To define the landscape of somatic mutations in pediatric osteosarcoma, we performed whole-genome sequencing of DNA from 20 osteosarcoma tumor samples and matched normal tissue in a discovery cohort, as well as 14 samples in a validation cohort. Single-nucleotide variations (SNVs) exhibited a pattern of localized hypermutation called kataegis in 50% of the tumors. We identified p53 pathway lesions in all tumors in the discovery cohort, nine of which were translocations in the first intron of the TP53 gene. Beyond TP53, the RB1, ATRX, and DLG2 genes showed recurrent somatic alterations in 29%-53% of the tumors. These data highlight the power of whole-genome sequencing for identifying recurrent somatic alterations in cancer genomes that may be missed using other methods.

RECQ DNA helicases and osteosarcoma

The RECQ family of DNA helicases is a conserved group of enzymes that are important for maintaining genomic integrity. In humans, there are five RECQ helicase genes, and mutations in three of them-BLM, WRN, and RECQL4-are associated with the genetic disorders Bloom syndrome, Werner syndrome, and Rothmund-Thomson syndrome (RTS), respectively. Importantly all three diseases are cancer predisposition syndromes. Patients with RTS are highly and uniquely susceptible to developing osteosarcoma; thus, RTS provides a good model to study the pathogenesis of osteosarcoma. The "tumor suppressor" role of RECQL4 and the other RECQ helicases is an area of active investigation. This chapter reviews what is currently known about the cellular functions of RECQL4 and how these may relate to tumorigenesis, as well as ongoing efforts to understand RECQL4's functions in vivo using animal models. Understanding the RECQ pathways may provide insight into avenues for novel cancer therapies in the future.

Therapy-related myelodysplasia in a patient with Rothmund-Thomson syndrome

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder of which approximately 300 cases have been reported in the literature. Patients with RTS often present early in life with skeletal and dental abnormalities, short stature, juvenile cataracts, and a characteristic poikilodermal rash. They are at increased risk for the development of osteosarcoma that usually presents by the second decade of life. The genetic defects underlying RTS are truncating mutations in RECQL4, a gene involved with chromosomal stability. Several cases of primary hematological malignancies have been reported in RTS, but it is unclear whether patients with RTS are at higher risk to develop either primary or secondary hematological malignancies. We report a patient with RTS who presented to our clinic at the age of 7, subsequently developed multifocal and recurrent osteosarcoma that was followed by the development of a myelodysplastic syndrome with subsequent progression to acute myeloid leukemia.

Advances in sarcoma genomics and new therapeutic targets

Increasingly, human mesenchymal malignancies are being classified by the abnormalities that drive their pathogenesis. Although many of these aberrations are highly prevalent within particular sarcoma subtypes, few are currently targeted therapeutically. Indeed, most subtypes of sarcoma are still treated with traditional therapeutic modalities, and in many cases sarcomas are resistant to adjuvant therapies. In this Review, we discuss the core molecular determinants of sarcomagenesis and emphasize the emerging genomic and functional genetic approaches that, coupled with novel therapeutic strategies, have the potential to transform the care of patients with sarcoma.

Modeling human osteosarcoma in the mouse: From bedside to bench

Osteosarcoma (OS) is the most common primary tumour of bone, occurring predominantly in the second decade of life. High-dose cytotoxic chemotherapy and surgical resection have improved prognosis, with long-term survival for patients with localized (non-metastatic) disease approaching 70%. At presentation approximately 20% of patients have metastases and almost all patients with recurrent OS have metastatic disease and cure rates for patients with metastatic or recurrent disease remain poor (<20% survival). Over the past 20 years, considerable progress has been made in the understanding of OS pathogenesis, yet these insights have not translated into substantial therapeutic advances and clinical outcomes. Further progress is essential in order to develop molecularly based therapies that target both primary lesions as well as metastatic disease. The increasing sophistication with which gene expression can be modulated in the mouse, both positively and negatively in addition to temporally, has allowed for the recent generation of more faithful OS models than have previously been available. These murine OS models can recapitulate all aspects of the disease process, from initiation and establishment to invasion and dissemination to distant sites. The development and utilisation of murine models that faithfully recapitulate human osteosarcoma, complementing existing approaches using human and canine disease, holds significant promise in furthering our understanding of the genetic basis of the disease and, more critically, in advancing pre-clinical studies aimed at the rational development and trialing of new therapeutic approaches.

Multiple malignant diseases in a patient with Rothmund-Thomson syndrome with RECQL4 mutations: Case report and literature review

RECQL4 mutations cause genetic instability and increase the risk of malignant disease. We report on a patient with compound heterozygosity for two novel RECQL4 mutations: mutation c.1919_1924delTCACAG, p.L640_A642delinsP in exon 12 of the RECQL4 gene and mutation c.1704+1G>A in intron 10 of the RECQL4 gene. He subsequently developed large cell anaplastic T cell lymphoma at the age of 9 years, diffuse large cell B lymphoma and osteosarcoma when he was 14 years old, and finally acute lymphatic leukemia when he was 21 years old. The most remarkable clinical features are young age, spontaneous remission of diffuse large cell lymphoma, and severe CNS and skin toxicity of cytotoxic treatment.

Osteosarcoma in children 5 years of age or younger at initial diagnosis

BACKGROUND

Since osteosarcoma is extremely rare in children < or =5 years of age, we sought to investigate if tumor characteristics, treatment strategies, and outcomes differ compared to older patients.

PROCEDURE

Patients <20 years of age with high-grade osteosarcoma reported to national SEER database from 1973 to 2006 were separated into two groups based on age at diagnosis: < or =5 years (n = 49) and 6-19 years (n = 1,687). Patient, tumor, and treatment characteristics were compared using Fisher exact tests. Overall survival was estimated by Kaplan-Meier methods and compared using log-rank tests and Cox models.

RESULTS

Patients < or =5 years had higher proportions of osteosarcoma arising from the upper limb compared to older patients (24.5% vs. 11.2%; P = 0.006). These very young patients had a significantly higher proportion of telangiectatic histology (10.2% vs. 2.9%; P = 0.017). Sex, metastatic status, race, or ethnicity did not differ by age. A higher proportion of very young patients was treated with amputation (55.2% vs. 27.3%; P = 0.002). Five-year overall survival was inferior for patients with localized osteosarcoma 5 years of age or younger compared to older children (51.9% vs. 67.3%; P = 0.03). After controlling for metastatic status, year of diagnosis, and tumor site, the hazard ratio for death in very young patients was 1.6 (95% confidence interval 1.02-2.36; P = 0.04) compared to older patients.

CONCLUSIONS

Tumor characteristics, treatment, and outcomes differ among children < or =5 years of age compared to older pediatric patients. These differences may reflect differences in tumor biology.

Rothmund-Thomson syndrome

Rothmund-Thomson syndrome (RTS) is a genodermatosis presenting with a characteristic facial rash (poikiloderma) associated with short stature, sparse scalp hair, sparse or absent eyelashes and/or eyebrows, juvenile cataracts, skeletal abnormalities, radial ray defects, premature aging and a predisposition to cancer. The prevalence is unknown but around 300 cases have been reported in the literature so far. The diagnostic hallmark is facial erythema, which spreads to the extremities but spares the trunk, and which manifests itself within the first year and then develops into poikiloderma. Two clinical subforms of RTS have been defined: RTSI characterised by poikiloderma, ectodermal dysplasia and juvenile cataracts, and RTSII characterised by poikiloderma, congenital bone defects and an increased risk of osteosarcoma in childhood and skin cancer later in life. The skeletal abnormalities may be overt (frontal bossing, saddle nose and congenital radial ray defects), and/or subtle (visible only by radiographic analysis). Gastrointestinal, respiratory and haematological signs have been reported in a few patients. RTS is transmitted in an autosomal recessive manner and is genetically heterogeneous: RTSII is caused by homozygous or compound heterozygous mutations in the RECQL4 helicase gene (detected in 60-65% of RTS patients), whereas the aetiology in RTSI remains unknown. Diagnosis is based on clinical findings (primarily on the age of onset, spreading and appearance of the poikiloderma) and molecular analysis for RECQL4 mutations. Missense mutations are rare, while frameshift, nonsense mutations and splice-site mutations prevail. A fully informative test requires transcript analysis not to overlook intronic deletions causing missplicing. The diagnosis of RTS should be considered in all patients with osteosarcoma, particularly if associated with skin changes. The differential diagnosis should include other causes of childhood poikiloderma (including dyskeratosis congenita, Kindler syndrome and Poikiloderma with Neutropaenia), other rare genodermatoses with prominent telangiectasias (including Bloom syndrome, Werner syndrome and Ataxia-telangiectasia) and the allelic disorders, RAPADILINO syndrome and Baller-Gerold syndrome, which also share some clinical features. A few mutations recur in all three RECQL4 diseases. Genetic counselling should be provided for RTS patients and their families, together with a recommendation for cancer surveillance for all patients with RTSII. Patients should be managed by a multidisciplinary team and offered long term follow-up. Treatment includes the use of pulsed dye laser photocoagulation to improve the telangiectatic component of the rash, surgical removal of the cataracts and standard treatment for individuals who develop cancer. Although some clinical signs suggest precocious aging, life expectancy is not impaired in RTS patients if they do not develop cancer. Outcomes in patients with osteosarcoma are similar in RTS and non-RTS patients, with a five-year survival rate of 60-70%. The sensitivity of RTS cells to genotoxic agents exploiting cells with a known RECQL4 status is being elucidated and is aimed at optimizing the chemotherapeutic regimen for osteosarcoma.

Prognostic factors and outcomes for osteosarcoma: an international collaboration

We aimed to evaluate the prognostic significance of traditional clinical predictors in osteosarcoma through an international collaboration of 10 teams of investigators (2680 patients) who participated. In multivariate models the mortality risk increased with older age, presence of metastatic disease at diagnosis, development of local recurrence when the patient was first seen, use of amputation instead of limb salvage/wide resection, employment of unusual treatments, use of chemotherapeutic regimens other than anthracycline and platinum and use of methotrexate. It was also influenced by the site of the tumour. The risk of metastasis increased when metastatic disease was present at the time the patient was first seen and also increased with use of amputation or unusual treatment combinations or chemotherapy regimens not including anthracycline and platinum. Local recurrence risk was higher in older patients, in those who had local recurrence when first seen and when no anthracycline and platinum were used in chemotherapy. Results were similar when limited to patients seen after 1990 and treated with surgery plus combination chemotherapy. This large-scale international collaboration identifies strong predictors of major clinical outcomes in osteosarcoma.

The etiology of osteosarcoma

Studies to determine the etiology of osteosarcoma involve epidemiologic and environmental factors and genetic impairments. Factors related to patient characteristics include age, gender, ethnicity, growth and height, genetic and familial factors, and preexisting bone abnormalities. Rapidly proliferating cells may be particularly susceptible to oncogenic agents and mitotic errors which lead to neoplastic transformation. Genetic aberrations that accompany osteosarcoma have received increasing recognition as an important factor in its etiology. Osteosarcoma tumor cells exhibit karyotypes with a high degree of complexity which has made it difficult to determine whether any recurrent chromosomal aberrations characterize osteosarcoma. Although extremely rare, osteosarcoma has occasionally been observed in several members of the same family. No other clinical abnormalities in the proband or the affected members were reported. Pathologic examination of the tumors revealed no unusual features. Genetic testing was not available in most of these reports. The patients generally responded to conventional therapy. A genetic predisposition to osteosarcoma is found in patients with hereditary retinoblastoma, characterized by mutation of the retinoblastoma gene RB1 on chromosome 13q14. The Rothmund-Thomson syndrome is an autosomal recessive disorder with a heterogeneous clinical profile. Patients may have a few or multiple clinical features including skin rash, small stature, skeletal dysplasias, sparse or absent scalp hair, eyebrows or eyelashes, juvenile cataracts, and gastrointestinal disturbance including chronic emesis and diarrhea; its molecular basis is the mutation in the RECQL4 gene in a subset of cases. The Li-Fraumeni syndrome is an autosomal dominant disorder characterized by a high risk of developing osteosarcoma and has been found in up to 3% of children with osteosarcoma. It is associated with a germline mutation of the p53, a suppressor gene. The following three criteria must be met for a diagnosis of Li-Fraumeni syndrome: (1) A proband diagnosed with sarcoma when younger than 45 years; (2) A first-degree relative with any cancer diagnosed when younger than 45 years; (3) Another first- or second-degree relative of the same genetic lineage with any cancer diagnosed when younger than 45 years or sarcoma diagnosed at any age. A second recessive p53 oncogene on chromosome 17p13.1 may also play a role in the development and progression of osteosarcoma. Osteosarcoma has also been associated with solitary or multiple osteochondroma, solitary enchondroma or enchondromatosis (Ollier's disease), multiple hereditary exostoses, fibrous dysplasia, chronic osteomyelitis, sites of bone infarcts, sites of metallic prostheses and sites of prior internal fixation. Ionizing radiation is a well-documented etiologic factor. Osteosarcoma has also been associated with the use of intravenous radium and Thorotrast. Exposure to alkylating agents may also contribute to its development ,and it is apparently independent of the administration of radiotherapy.

Você conhece esta síndrome?

A síndrome de Rothmund-Thomson é distúrbio autossômico recessivo de expressividade variável associado a mutações do gene RecQL4. Caracteriza-se por poiquilodermia, alopecia, defeitos de crescimento e desenvolvimento, catarata juvenil, alterações dentárias e esqueléticas e predisposição ao câncer cutâneo e ao osteossarcoma. Relata-se caso de paciente de 29 anos de idade com lesões cutâneas desde a infância, catarata bilateral antes dos 20 anos e carcinoma espinocelular aos 26 anos de idade.

Radiographic abnormalities in Rothmund-Thomson syndrome and genotype-phenotype correlation with RECQL4 mutation status

OBJECTIVE

The purpose of this study was to summarize the radiographic skeletal findings in patients with Rothmund-Thomson syndrome (RTS) and to determine whether there is an association between the presence of skeletal abnormalities and the mutational status of the RECQL4 gene.

SUBJECTS AND METHODS

Twenty-eight subjects with RTS underwent skeletal surveys and RECQL4 DNA mutation testing. Radiographs were reviewed by two radiologists. RECQL4 mutation testing by DNA sequencing of the gene was performed by a diagnostic laboratory. Genotype-phenotype analysis by Fisher's exact test was performed to investigate whether there was a correlation between mutation status and skeletal abnormalities.

RESULTS

Twenty-one (75%) of the subjects had at least one significant skeletal abnormality, the more common being abnormal metaphyseal trabeculation, brachymesophalangy, thumb aplasia or hypoplasia, osteopenia, dislocation of the radial head, radial aplasia or hypoplasia, and patellar ossification defects. Three subjects had a history of destructive bone lesion (osteosarcoma). Genotype-phenotype analysis showed a significant correlation between RECQL4 mutational status and the presence of skeletal abnormalities (p < 0.0001).

CONCLUSION

Skeletal abnormalities are frequent in persons with RTS. Many of these abnormalities are not clinically apparent but are detectable on radiographs. The presence of skeletal abnormalities correlates with RECQL4 mutation status, which has been found to correlate with risk of osteosarcoma. Skeletal surveys aid in both diagnosis and management of RTS.

Sensitivity of RECQL4-deficient fibroblasts from Rothmund-Thomson syndrome patients to genotoxic agents

RECQ helicase protein-like 4 (RECQL4) is a member of the human RECQ family of DNA helicases. Two-thirds of patients with Rothmund-Thomson syndrome (RTS) carry biallelic inactivating mutations in the RECQL4 gene. RTS is an autosomal recessive disorder characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts, and an increased risk of cancer. Mutations in two other RECQ helicases, BLM and WRN, are responsible for the cancer predisposition conditions Bloom and Werner syndromes, respectively. Previous studies have shown that BLM and WRN-deficient cells demonstrate increased sensitivity to hydroxyurea (HU), camptothecin (CPT), and 4-nitroquinoline 1-oxide (4NQO). Little is known about the sensitivity of RECQL4-deficient cells to these and other genotoxic agents. The purpose of this study was to determine if RTS cells display any distinct cellular phenotypes in response to DNA damaging agents or replication blocks that could provide insight into the molecular function of the RECQL4 protein. Our results show that primary fibroblasts from RTS patients carrying two deleterious RECQL4 mutations, compared to wild type (WT) fibroblasts, have increased sensitivity to HU, CPT, and doxorubicin (DOX), modest sensitivity to other DNA damaging agents including ultraviolet (UV) irradiation, ionizing radiation (IR), and cisplatin (CDDP), and relative resistance to 4NQO. The RECQ family of DNA helicases has been implicated in the regulation of DNA replication, recombination, and repair. Because HU, CPT, and DOX exert their effects primarily during S phase, these results support a greater role for the RECQL4 protein in DNA replication as opposed to repair of exogenous damage.