A Paradigm Shift in the Management of Cherubism? A Preliminary Report Using Imatinib

Loss-of-function OGFRL1 variants identified in autosomal recessive cherubism families

Cherubism (OMIM 118400) is a rare craniofacial disorder in children characterized by destructive jawbone expansion due to the growth of inflammatory fibrous lesions. Our previous studies have shown that gain-of-function mutations in SH3 domain-binding protein 2 (SH3BP2) are responsible for cherubism and that a knock-in mouse model for cherubism recapitulates the features of cherubism, such as increased osteoclast formation and jawbone destruction. To date, SH3BP2 is the only gene identified to be responsible for cherubism. Since not all patients clinically diagnosed with cherubism had mutations in SH3BP2, we hypothesized that there may be novel cherubism genes and that these genes may play a role in jawbone homeostasis. Here, using whole exome sequencing, we identified homozygous loss-of-function variants in the opioid growth factor receptor like 1 (OGFRL1) gene in 2 independent autosomal recessive cherubism families from Syria and India. The newly identified pathogenic homozygous variants were not reported in any variant databases, suggesting that OGFRL1 is a novel gene responsible for cherubism. Single cell analysis of mouse jawbone tissue revealed that Ogfrl1 is highly expressed in myeloid lineage cells. We generated OGFRL1 knockout mice and mice carrying the Syrian frameshift mutation to understand the in vivo role of OGFRL1. However, neither mouse model recapitulated human cherubism or the phenotypes exhibited by SH3BP2 cherubism mice under physiological and periodontitis conditions. Unlike bone marrow-derived M-CSF-dependent macrophages (BMMs) carrying the SH3BP2 cherubism mutation, BMMs lacking OGFRL1 or carrying the Syrian mutation showed no difference in TNF-ɑ mRNA induction by LPS or TNF-ɑ compared to WT BMMs. Osteoclast formation induced by RANKL was also comparable. These results suggest that the loss-of-function effects of OGFRL1 in humans differ from those in mice and highlight the fact that mice are not always an ideal model for studying rare craniofacial bone disorders.

Thoughts on the Etiology of Cherubism

Cherubism is nowadays classified as an autoimmune disease and was first described in 1933. Although suspected at that time to be the result of defective tooth development, it was primarily classified as a bone disease caused by a mutation in the SH3BP2 gene. Despite a knock-in mouse model, phenotypic signs in the jaw area were not reproducible in this model. The features of classical cherubism can be attributed to a disturbed formation of the dental placode of the second molar. Since 2019, it has become clear that inhibition of the WNT pathway leads to the accumulation of SH3BP2 via tankyrase inhibition. As the dental placode is triggered via WNT (in epithelia) and MSX1 (in mesenchyme), aplasia of the second and third molars occurs due to a block in the WNT pathway. The mesenchymal part, which occurs prior to the body plan regulation of the WNT/MSX1 pathway, remains unaffected and provides the substrate for the giant cell granuloma. Considering macrophage polarization and the role of the extracellular matrix in general, cherubism is situated in the field of tension between autoimmune diseases and cancer. In this sense, we see the cause of cherubism in a WNT-related dysregulation, which can be proven postnatally in the neural crest-related tooth development of the replacement tooth ridge, both genotypically and phenotypically.

Efficacy and Toxicity of Calcitonin Treatment in Children with Cherubism: A Single-Center Cohort Study

Cherubism is a rare autosomal dominant disease characterized by expansile osteolytic jawbone lesions. The effect and safety of off-label calcitonin treatment during the progressive phase of the disease are not well described. In this retrospective study, we present data on the radiological response and adverse effects of subcutaneously administered calcitonin in a cohort of nine cherubism children (three female, six male). Two of the nine patients underwent two separate treatment courses with a significant off-treatment interval in between; therefore, a total of 11 treatment courses with a mean duration of 17.9 months (range <1 to 35, SD 10.8) were studied. To measure the response, the cumulative volume of cherubism lesions was calculated from available three-dimensional imaging. The primary outcome was the change in the volume of lesions during calcitonin treatment and only assessed for the eight treatment courses with a minimal duration of 6 months. A statistically significant reduction in the mean cumulative volume of lesions was seen regardless of treatment duration. Average volume reduction was highest in the first half year of treatment, with a gradual, ongoing reduction thereafter. For the secondary outcome, the change in the cumulative volume of lesions after treatment cessation was assessed for the seven treatment courses with follow-up imaging available. After six of these seven treatment courses, the cumulative volume increased again but remained undoubtedly smaller than the initial volume at the start of therapy. Adverse effects were assessed for all 11 treatment courses and occurred in 73% of them. Most adverse effects were mild and low grade, with the most severe being one grade 3 symptomatic hypocalcemia requiring hospitalization and early treatment termination. Calcitonin treatment seems effective and tolerable in treating actively progressing cherubism in children. However, further research is required to better understand the pharmacological treatment of cherubism, including also other drugs, dosing, and protocols. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Current concepts in targeted therapies for benign tumors of the jaw - A review of the literature

The aim of our study was to review current concepts in targeted therapies for benign tumors of the jaw. Benign odontogenic and maxillofacial bone tumors often require radical surgery, with consequent morbidity that impacts patients' postsurgical quality of life. Currently, targeted therapies and novel nonsurgical therapeutics are being explored for management of non-resectable tumors, with the aim of avoiding surgery or minimizing surgical scope. However, data on clinical applications of targeted therapies for benign tumors of the jaw remain sparse. Therefore, a literature review was conducted, based on the PubMed database, which included in vivo human clinical studies describing clinical application of targeted therapy for benign tumor of the jaw. The review assessed the outcomes of BRAF and MEK inhibitors for treatment of ameloblastoma, RANKL monoclonal antibody for treatment of giant cell tumor, cherubism, aneurysmal bone cyst, and fibrous dysplasia, and tyrosine kinase inhibitor for treatment of odontogenic myxoma and cherubism. Targeted therapies decreased tumor size, slowed down tumor progression, and reduced bone pain. Surgery remains the gold standard, but targeted therapies are promising adjuvant or alternative treatment options for reducing tumor progression and morbidity of tumor surgery.

Surgical management of mandibular cherubism in an adolescent: integration of virtual surgical planning

Cherubism, also known as familial fibrodysplasia of the jaw, is an autosomal dominant disorder with variable penetrance. The disease process is characterised by painless and progressive bilateral enlargement of the maxillofacial skeleton. We present an adolescent female with a family history of cherubism who presented to the Oral and Maxillofacial Surgery clinic with progressive bilateral swelling of the mandible. The diagnosis of cherubism was established through a thorough history which was confirmed with an incisional biopsy. The progressive swelling negatively affected her appearance and psychosocial well-being. The patient opted for surgical intervention after a course of conservative management. Although there is often resolution of these lesions into adulthood, surgical intervention may be considered when managing this condition in adolescence. Integration with virtual surgical planning can aid in obtaining desired postoperative outcomes.

Response of Central Giant Cell Granuloma of the Jaw to Imatinib

Central giant cell granuloma of the jaw (CGCJ) can be locally aggressive and result in facial and dental deformity. A child with CGCJ was treated surgically and with denosumab with a response but life-threatening toxicity. Imatinib, a tyrosine kinase inhibitor, was prescribed based on clinical similarities between CGCJ and cherubism, for which Imatinib has been effective. Within 2 months, a computed tomographic scan showed significant ossification, which increased over the following 8 months. This case suggests that tyrosine kinase inhibitors may be an effective option, and one with limited toxicity, for CGCJ.

Imatinib has minimal effects on inflammatory and osteopenic phenotypes in a murine cherubism model

OBJECTIVE

Cherubism is a genetic disorder characterised by bilateral jawbone deformation. The associated jawbone lesions regress after puberty, whereas severe cases require surgical treatment. Although several drugs have been tested, fundamental treatment strategies for cherubism have not been established. The effectiveness of imatinib has recently been reported; however, its pharmaceutical mechanism remains unclear. In this study, we tested the effects of imatinib using a cherubism mouse model.

METHODS

We used Sh3bp2 P416R cherubism mutant mice, which exhibit systemic organ inflammation and osteopenia. The effects of imatinib were determined using primary bone marrow-derived macrophages. Imatinib was administered intraperitoneally to the mice, and serum tumour necrosis factor-α (TNFα), organ inflammation and bone properties were examined.

RESULTS

The cherubism mutant macrophages produced higher levels of TNFα in response to lipopolysaccharide compared to wild-type macrophages, and imatinib did not significantly suppress TNFα production. Although imatinib suppressed osteoclast formation in vitro, administering it in vivo did not suppress organ inflammation and osteopenia.

CONCLUSION

The in vivo administration of imatinib had a minimal therapeutic impact in cherubism mutant mice. To establish better pharmaceutical interventions, it is necessary to integrate new findings from murine models with clinical data from patients with a definitive diagnosis of cherubism.

Pharmacological management of cherubism: A systematic review

OBJECTIVE

The aim of this systematic review was to determine if there exists an efficacious drug treatment for cherubism, based on published studies.

METHODS

This systematic review included observational case studies reporting pharmacological management of cherubism. We developed specific search strategies for PubMed (including Medline), ScienceDirect, Web of Science. We evaluated the methodological quality of the included studies using criteria from the Joanna Briggs Institute's critical appraisal tools.

RESULTS

Among the 621 studies initially identified by our search script, 14 were selected for inclusion, of which five were classified as having a low risk of bias, four as having an unclear risk, and five a high risk. Overall, 18 cherubism patients were treated. The sample size in each case study ranged from one to three subjects. This review identified three types of drugs used for cherubism management: calcitonin, immunomodulators and anti-resorptive agents. However, the high heterogeneity in case reports and the lack of standardized outcomes precluded a definitive conclusion regarding the efficacy of any treatment for cherubism.

CONCLUSIONS

The present systematic review could not identify an effective treatment for cherubism due to the heterogeneity and limitations of the included studies. However, in response to these shortcomings, we devised a checklist of items that we recommend authors consider in order to standardize the reporting of cherubism cases and specifically when a treatment is given toward identification of an efficacious cherubism therapy.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022351044, identifier CRD42022351044.

Adjuvant Alendronic Acid in the Management of Severe Cherubism: A Case Report and Literature Review

Cherubism is a rare disease of the jaws characterized by bilateral symmetrical painless expansion of the mandible and maxilla. In extreme cases, larger lesions can become exophytic and have profound functional and esthetic implications. Several pharmacologic agents have been trialed in the treatment of cherubism with variable success reported. Bisphosphonates have not been significantly studied in this setting. We present a case where oral alendronic acid was used as an adjuvant treatment after surgical debulking of the maxilla in a 13-year-old boy with a severe case of cherubism.

Cherubism as a systemic skeletal disease: evidence from an aggressive case

Background

Cherubism is a rare autosomal dominant genetic condition caused by mutations in the SH3BP2 gene. This disease is characterized by osteolysis of the jaws, with the bone replaced by soft tissue rich in fibroblasts and multinuclear giant cells. SH3BP2 is a ubiquitous adaptor protein yet the consequences of SH3BP2 mutation have so far been described as impacting only face. Cherubism mouse models have been generated and unlike human patients, the knock-in mice exhibit systemic bone loss together with a systemic inflammation.

Case presentation

In light of these observations, we decided to search for a systemic cherubism phenotype in a 6-year-old girl with an aggressive cherubism. We report here the first case of cherubism with systemic manifestations. Bone densitometry showed low overall bone density (total body Z-score = − 4.6 SD). Several markers of bone remodelling (CTx, BALP, P1NP) as well as inflammation (TNFα and IL-1) were elevated. A causative second-site mutation in other genes known to influence bone density was ruled out by sequencing a panel of such genes.

Conclusions

If this systemic skeletal cherubism phenotype should be confirmed, it would simplify the treatment of severe cherubism patients and allay reservations about applying a systemic treatment such as those recently published (tacrolimus or imatinib) to a disease heretofore believed to be localised to the jaws.

Positive Outcomes of Denosumab Treatment in 2 Patients With Cherubism

Cherubism is a rare autosomal dominant disease whose severity ranges widely, from asymptomatic to life-threatening. Bilateral symmetrical painless expansion of the mandible and maxilla resulting in a typical appearance of the face resembling a cherub, are the highlighted features of the condition. In most cases, cherubism-induced lesions in the jaws appear around the age of 3 years and tend to expand and increase in numbers until puberty. Treatment options for cherubism range from observation to surgical correction and various pharmacologic therapies. Given the excess sensitivity of cherubism osteoclasts to RANKL (receptor activator of nuclear factor κB ligand) and the positive effects of denosumab (XGEVA; Amgen, Thousand Oaks, CA) treatment in patients with giant cell granuloma, we have designed a treatment based on denosumab for 2 cherubism patients that achieves what we consider promising results.

New perspectives on the treatment of skeletal dysplasia

The last few decades have been marked by the identification of numerous genes implicated in genetic disorders, helping in the elucidation of the underlying pathophysiology of these conditions. This has allowed new therapeutic approaches to emerge such as cellular therapy, gene therapy, or pharmacological therapy for various conditions. Skeletal dysplasias are good models to illustrate these scientific advances. Indeed, several therapeutic strategies are currently being investigated in osteogenesis imperfecta; there are ongoing clinical trials based on pharmacological approaches, targeting signaling pathways in achondroplasia and fibrodysplasia ossificans progressiva or the endoplasmic reticulum stress in metaphyseal dysplasia type Schmid or pseudoachondroplasia. Moreover, the treatment of hypophosphatasia or Morquio A disease illustrates the efficacy of enzyme drug replacement. To provide a highly specialized multidisciplinary approach, these treatments are managed by reference centers. The emergence of treatments in skeletal dysplasia provides new perspectives on the prognosis of these severe conditions and may change prenatal counseling in these diseases over the coming years.

Clinical and radiological evaluation of cherubism: A rare case report

Cherubism is a rare, non-neoplastic, genetic disorder, characterized by painless bilateral swelling of the jaws. A 5-year-old girl presented with a painless, bilateral symmetrical swelling of both mandible and maxilla. Intraoral examination revealed malocclusion with displacement of teeth and expansion of the alveolar ridges. There was a bilateral expansion of the jaws. In conclusion, cherubism is a genetic disorder that has non-neoplastic bone lesions that affect the jaws. If there is a functional or esthetic problem, it should be treated surgically. The surgical treatment is usually delayed until after puberty.

Case Report: Safety and Efficacy of Denosumab in Four Children With Noonan Syndrome With Multiple Giant Cell Lesions of the Jaw

Noonan syndrome is a genetic disorder caused by mutations in the RAS/MAPK pathway. Multiple giant cell lesions are a rare sequelae of disruptions in this pathway, termed Noonan-like multiple giant cell lesions (NL/MGCLs). Medical management of these tumors rather than surgical intervention is preferential as the lesions are benign but locally destructive and recurring. This case series describes four male pediatric patients with Noonan syndrome and multiple giant cell lesions of the jaw treated with denosumab, a monoclonal antibody to receptor activator of nuclear factor kappa B ligand (RANKL), which has been approved for the treatment of malignant giant cell tumors in adults but not evaluated for safety or efficacy in children. All four pediatric patients responded clinically and radiographically to the treatment. Adverse events occurred in a predictable pattern and included hypocalcemia and joint pain during the initiation of treatment and symptomatic hypercalcemia after the cessation of treatment. Growth was not significantly impaired in these skeletally immature patients. This case series demonstrates how a weight-adjusted denosumab dose can effectively treat NL/MGCLs and provides laboratory data for consideration of the timing of monitoring for known side effects.