Combined CDK4/6 and ERK1/2 Inhibition Enhances Antitumor Activity in NF1-Associated Plexiform Neurofibroma

PURPOSE

Plexiform neurofibromas (PNF) are peripheral nerve sheath tumors that cause significant morbidity in persons with neurofibromatosis type 1 (NF1), yet treatment options remain limited. To identify novel therapeutic targets for PNF, we applied an integrated multi-omic approach to quantitatively profile kinome enrichment in a mouse model that has predicted therapeutic responses in clinical trials for NF1-associated PNF with high fidelity.

EXPERIMENTAL DESIGN

Utilizing RNA sequencing combined with chemical proteomic profiling of the functionally enriched kinome using multiplexed inhibitor beads coupled with mass spectrometry, we identified molecular signatures predictive of response to CDK4/6 and RAS/MAPK pathway inhibition in PNF. Informed by these results, we evaluated the efficacy of the CDK4/6 inhibitor, abemaciclib, and the ERK1/2 inhibitor, LY3214996, alone and in combination in reducing PNF tumor burden in Nf1flox/flox;PostnCre mice.

RESULTS

Converging signatures of CDK4/6 and RAS/MAPK pathway activation were identified within the transcriptome and kinome that were conserved in both murine and human PNF. We observed robust additivity of the CDK4/6 inhibitor, abemaciclib, in combination with the ERK1/2 inhibitor, LY3214996, in murine and human NF1(Nf1) mutant Schwann cells. Consistent with these findings, the combination of abemaciclib (CDK4/6i) and LY3214996 (ERK1/2i) synergized to suppress molecular signatures of MAPK activation and exhibited enhanced antitumor activity in Nf1flox/flox;PostnCre mice in vivo.

CONCLUSIONS

These findings provide rationale for the clinical translation of CDK4/6 inhibitors alone and in combination with therapies targeting the RAS/MAPK pathway for the treatment of PNF and other peripheral nerve sheath tumors in persons with NF1.

Esthetic subunit approach in massive facial plexiform neurofibroma: a case report

Plexiform neurofibroma is a presentation of neurofibromatosis type 1 (NF1) which can cause great facial deformities. Treatment rarely has a healing effect, so the surgical approach is aimed at improving esthetics and function. It requires a cross-disciplinary approach and typically needs multi-stage surgery. This is the case of a 16-year-old male patient with NF1 presenting with left periorbital and malar facial plexiform neurofibroma with slow-growth intraconal and extraconal invasion. He presented at the plastic surgery consultation for facial soft tissue deformity correction. Removal was performed using an esthetic subunit approach, with canthopexy and orbital cavity reconstruction, resulting in facial region symmetrization. This allowed for remarkable esthetic and functional improvement, facilitating ocular prosthesis adaptation. The subsequent use of selumetinib allowed the lesion to be stabilized.

Recommendations for imaging tumor response in neurofibromatosis clinical trials

OBJECTIVE

Neurofibromatosis (NF)-related benign tumors such as plexiform neurofibromas (PN) and vestibular schwannomas (VS) can cause substantial morbidity. Clinical trials directed at these tumors have become available. Due to differences in disease manifestations and the natural history of NF-related tumors, response criteria used for solid cancers (1-dimensional/RECIST [Response Evaluation Criteria in Solid Tumors] and bidimensional/World Health Organization) have limited applicability. No standardized response criteria for benign NF tumors exist. The goal of the Tumor Measurement Working Group of the REiNS (Response Evaluation in Neurofibromatosis and Schwannomatosis) committee is to propose consensus guidelines for the evaluation of imaging response in clinical trials for NF tumors.

METHODS

Currently used imaging endpoints, designs of NF clinical trials, and knowledge of the natural history of NF-related tumors, in particular PN and VS, were reviewed. Consensus recommendations for response evaluation for future studies were developed based on this review and the expertise of group members.

RESULTS

MRI with volumetric analysis is recommended to sensitively and reproducibly evaluate changes in tumor size in clinical trials. Volumetric analysis requires adherence to specific imaging recommendations. A 20% volume change was chosen to indicate a decrease or increase in tumor size. Use of these criteria in future trials will enable meaningful comparison of results across studies.

CONCLUSIONS

The proposed imaging response evaluation guidelines, along with validated clinical outcome measures, will maximize the ability to identify potentially active agents for patients with NF and benign tumors.

Phase I trial and pharmacokinetic study of sorafenib in children with neurofibromatosis type I and plexiform neurofibromas

BACKGROUND

Sorafenib targets multiple pathways thought to be crucial in growth of plexiform neurofibroma (PN) in children with neurofibromatosis type 1 (NF1). Sorafenib has been tolerated with manageable toxicities in adults and children with refractory cancer. We conducted a separate study in this population. Monitoring long-term toxicities such as effects on growth and obtaining additional pharmacokinetic data were of importance due to the young age and long duration of therapy seen in previous phase I trials in children with NF1.

PROCEDURE

Children ≥3 and ≤18-year-old with NF1 and inoperable PN were eligible. Sorafenib was administered orally twice daily for consecutive 28-day cycles. Maximum tolerated dose (MTD) was determined from toxicities observed during the first three cycles.

RESULTS

Nine children enrolled, median age 8 (6-12) years. At the starting 115 mg/m(2) /dose (n = 5), two experienced dose-limiting grade 3 pain in their PN. At the de-escalated 80 mg/m(2) /dose (n = 4), approximately 40% of the pediatric solid tumor MTD, two had dose-limiting toxicity (grade 3 rash and grade 4 mood alteration), exceeding the MTD. At 80 mg/m(2) /dose, the median AUC(0-12 hours) at steady-state was 39.5 µg hours/ml. Toxicities appeared to correspond with decreases in quality of life (QOL). No tumor shrinkage was observed.

CONCLUSIONS

Children with NF1 and PN did not tolerate sorafenib at doses substantially lower than the MTD in children and adults with malignant solid tumors. Future trials with targeted agents for children with NF1 may require a more conservative starting dose and separate definitions of dose limiting toxicities (DLT) than children with cancer.

[Plexiform neurofibroma of the bladder associated with neurofibromatosis type 1: a case report]

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease with multiple neurofibroma and café-au-lait spots. We report a case of plexiform neurofibroma of the bladder associated with NF1. A 34-year-old female was referred to our hospital for thickness of the bladder wall. Multiple café-au-lait spots and neurofibroma was found on her skin,and she was diagnosed with neurofibromatosis type 1. Ultrasound examination demonstrated bladder wall thickening,and cystoscopy revealed an irregular and erythematous mucosa. Transurethral biopsy of the bladder wall was performed. Histopathological diagnosis was plexiform neurofibroma of the bladder.

Identification of growth hormone receptor in plexiform neurofibromas of patients with neurofibromatosis type 1

OBJECTIVE

The aim of this study was to investigate the presence of growth hormone receptor in plexiform neurofibromas of neurofibromatosis type 1 patients.

INTRODUCTION

The development of multiple neurofibromas is one of the major features of neurofibromatosis type 1. Since neurofibromas commonly grow during periods of hormonal change, especially during puberty and pregnancy, it has been suggested that hormones may influence neurofibromatosis type 1 neurofibromas. A recent study showed that the majority of localized neurofibromas from neurofibromatosis type 1 patients have growth hormone receptor.

METHODS

Growth hormone receptor expression was investigated in 5 plexiform neurofibromas using immunohistochemistry.

RESULTS

Four of the 5 plexiform neurofibromas were immunopositive for growth hormone receptor.

CONCLUSION

This study suggests that growth hormone may influence the development of plexiform neurofibromas in patients with neurofibromatosis type 1.

Clinical relevance of positron emission tomography and magnetic resonance imaging in the progression of internal plexiform neurofibroma in NF1

Neurofibromatosis type 1 (NF1) is a frequent and inherited disease with a predisposition for malignant peripheral nerve sheath tumor (MPNST) development. MPNST are soft tissue sarcomas that arise from peripheral nerves, being one of the most aggressive malignancies in humans with extremely poor prognosis. MPNST frequently arise from a previously undetected plexiform neurofibroma (PNF). The malignant transformation of an internal PNF to an MPNST is difficult to assess and requires advanced imaging techniques like magnetic resonance imaging or positron emission tomography. Despite the high quality of current diagnostics, the changing tumor biology inside a plexiform neurofibroma cannot currently be visualized accurately. We report 4 cases of NF1 patients with PNF who showed imaging findings suspicious for malignant degeneration, but proved to have MPNST in only one case. Three tumors might represent an intermediate type between PNF and MPNST. Ablative surgery and complete histological work-up of specimens is the only way to clarify tumor status, thereby enabling provision of adequate local treatment.

Pigmented plexiform neurofibroma: Distinction from a large congenital melanocytic nevus

The substantial clinical and histologic overlap between neurotized congenital melanocytic nevi and the subset of plexiform neurofibromas with hyperpigmentation and hypertrichosis of the overlying skin (pigmented neurofibroma) has led to considerable confusion in the literature. A dark-brown, hypertrichotic plaque covered much of the right lower aspect of the trunk of a 1-year-old girl with a diffuse and plexiform neurofibroma in the same area, numerous café-au-lait macules, and intertriginous freckling. The latter findings were diagnostic of neurofibromatosis-1, which was further supported by the presence of unidentified bright objects on magnetic resonance imaging of the brain. Histologic examination of the hyperpigmented plaque revealed melanocytic hyperplasia at the dermoepidermal junction and a proliferation of rounded, pigmented melanocytes dispersed individually and in occasional small nests in the papillary dermis and scattered within underlying neurofibromatous tissue. Immunohistochemical staining with A103 (Melan-A/MART-1) and PNL2 confirmed the melanocytic differentiation of the pigmented cells, whereas glial fibrillary acidic protein and Leu-7 were detected only within plexiform areas and slender neuroid spindle cells. This case draws attention to the pigmented neurofibroma as a distinct clinicopathologic entity resulting from proliferation of melanocytes and neurosustentacular cells in the setting of neurofibromatosis-1.

A Novel Approach to the Management of Severe Facial Disfigurement in Neurofibromatosis Type 1

A 12-year-old girl with neurofibromatosis type 1 underwent subtotal anterior exenteration of a blind, unsightly, buphthalmic eye and orbital/eyelid plexiform neurofibroma. Simultaneously, a channeled Medpor orbital implant was positioned to reduce a meningoencephalocele resulting from severe sphenoid wing dysgenesis. Two-stage osseointegration was subsequently performed to permit secure fitting of an orbital prosthesis. This patient's cosmesis and social interaction were improved markedly with this surgical approach for disfiguring ocular, eyelid, and orbital disease due to neurofibromatosis type 1.

[Unilateral facial and cerebral hyperplasia associated with neurofibromatosis type 1. Report of four patients]

INTRODUCTION

Plexiform neurofibroma in any location is one of the commonest complications associated with neurofibromatosis type 1 (NF1). Plexiform neurofibroma of the upper eyelid and orbit is usually associated with ipsilateral hemifacial hyperplasia. We present four patients with NF1 and plexiform neurofibroma of the eyelid and orbit associated with hemifacial hyperplasia, who also showed hyperplasia of the unilateral cerebral hemisphere.

CASE REPORTS

There are four patients, three females and one male, who consulted because of NF1 with plexiform neurofibroma of upper eyelid and hemifacial hyperplasia. Upper eyelid involvement was observed since birth and progressed during the first years of life. The patients showed normal neurological and mental development without motor or cerebellar disorders. Magnetic resonance studies demonstrated the asymmetric hyperplasia of the ipsilateral hemisphere in all four cases and of the cerebellar hemisphere in one case. The degree of hemispheric hyperplasia was related to the size and extension of the plexiform neurofibroma, as well as to the severity of the hemifacial hyperplasia. In our case which had the plexiform neurofibroma extended to the neck and the upper thorax, the hyperplasia not only affected the cerebral hemisphere but also the ipsilateral cerebellar hemisphere. All parts of the hemisphere showed increased size. The cortex of the entire hemisphere showed normal differentiation of the subcortical white matter.

CONCLUSION

NF1 appears to be related with facial and cerebral ipsilateral hemihyperplasia. The relation between the size and extension of the orbital, eyelid and facial plexiform neurofibroma and the degree of asymmetry of the hemispheric hyperplasia suggest that different influences of a still unknown agent, possibly a gene, obviously related to NF1, causes both the intracranial and extracranial abnormalities.

Radiofrequency in the Treatment of Craniofacial Plexiform Neurofibromatosis: A Pilot Study

BACKGROUND

Neurofibromatosis type 1 manifests itself by the development of plexiform neurofibromas, with craniofacial deformities caused by bone alterations and soft-tissue infiltration. The medical treatment of this disease is disappointing, and the surgical management of these deformities calls for aggressive procedures. There is a strong risk of recurrence.

METHODS

A pilot study was performed to test radiofrequency as a minimally invasive method with which to diminish the size of craniofacial neurofibromas either as an adjunct to craniofacial surgery (in cranio-orbital neurofibromas) or to avoid a visible scar in young patients (in infraorbital neurofibromas). Five patients ranging in age from 6 to 18 years were treated by three procedures 2 months apart using radiofrequency performed under local anesthesia or under sedation for the youngest patients.

RESULTS

The tolerance of the treatment was excellent, with no major side effects and no pain in the postoperative course. A diminution of the size of the lesion was noted clinically in four patients and on computed tomography in two patients. A biopsy performed in one case illustrated the effect of the treatment.

CONCLUSIONS

A partial diminution or stabilization of plexiform neurofibromas may be obtained using radiofrequency. This treatment is well tolerated. The best effect can be observed in the early stages of the disease. The optimal dose and frequency of the procedure require further study.

[KID syndrome: a cause of pachydermatoglyphia]

INTRODUCTION

The KID syndrome is a rare ectodermal dysplasia associating erythrokeratodermia, deafness and keratitis. Other disorders such as sensitivity to infections or hypohidrosis may be associated. Pachydermatoglyphia is characterized by diffuse hyperkeratosis in which the dermatoglyphe crests are accentuated in thickness and height.

CASE REPORT

We report the case of a KID syndrome in a young girl, born of non-consanguine parents and without any familial context. The classical elements of this dysplasia were present: erythrokeratoderma with dryness and roughness of the whole tegument, plicatured pachydermia of the knees, facial erythema, grooves around the mouth, hypotrichosis of the lashes and eyebrows, deafness, and ophthalmologic involvement. Involvement of the palms was characterized by the pachydermatoglyphic aspect.

DISCUSSION

In this case report, the palmar keratoderma corresponded to the original description of pachydermatoglyphia and we consider that the KID syndrome should be integrated as a possible etiology of pachydermatoglyphia.

Congenital glaucoma and neurofibromatosis in a monozygotic twin: case report and review of the literature

We describe a dramatic case of an identical twin presenting at birth with unilateral congenital glaucoma. Because of the suspicion of neurofibromatosis 1 a magnetic resonance image of the neural axis was obtained, which revealed a plexiform neurofibroma with spinal cord impingement. Diagnosis of neurofibromatosis 1 was confirmed by 3 months of age with the emergence of café-au-lait spots. This case was compared with all 19 reports published in the English literature of neurofibromatosis 1 associated with congenital glaucoma. Initial presentation, family history, characteristics ofthe clinical syndrome, and outcome of glaucoma in infants with neurofibromatosis 1 and congenital glaucoma were reviewed. A plexiform neurofibroma of the ipsilateral eyelid was present in eight patients and ipsilateral facial hypertrophy occurred in three patients. Café-au-lait spots appeared between the ages of 5 weeks and 8 years; none of the patients were reported to have café-au-lait spots at birth. Newborns with unilateral congenital glaucoma should raise high suspicion for neurofibromatosis 1 and its associated findings, which might need immediate intervention.

NF1 mutations in neurofibromatosis 1 patients with plexiform neurofibromas

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder caused by genetic alterations of the NF1 gene on 17q11.2. About 30% of NF1 patients develop plexiform neurofibromas (PNFs), which often cause severe clinical deficits. To determine whether there is a certain genotype underlying PNFs or subtypes of PNFs, we screened 42 NF1 patients from 41 families with PNFs for mutations in the NF1 gene. In 33 out of the 41 (80%) unrelated patients NF1 mutations were found, 24 are novel while the other 9 have been described in previous studies. The 33 mutations included 23 nonsense and frameshift, six splice and four missense mutations. The tumors in these patients had various sizes and features/growth characteristics. No correlation was found between the type or location of the NF1 mutations and size, location or feature of the PNFs, suggesting that many types of NF1 mutations can lead to development of PNFs.

Management issues in massive pediatric facial plexiform neurofibroma with neurofibromatosis type 1

BACKGROUND

Plexiform neurofibroma is a relatively common but potentially devastating manifestation of neurofibromatosis type 1 (NF1). Surgical management is the mainstay of therapy, but within the head and neck region it is limited by the infiltrating nature of these tumors, inherent operative morbidity, and high rate of regrowth.

METHOD

We describe a case of a 7-year-old girl with neurofibromatosis type 1 and a massive facial plexiform neurofibroma with the aim of emphasizing the treatment and timing issues involved in the management of this difficult problem. A MEDLINE search (1966 through December 2000) was carried out, and pertinent literature on the subject was reviewed.

RESULT

The patient described in this case report was carefully observed for a period of 6 years from diagnosis before surgical excision of the tumor was undertaken with an uneventful recovery.

CONCLUSION

Surgical management remains the mainstay of treatment for these locally invasive tumors, but functional disturbances are almost inevitable in resecting substantial tumors involving the head and neck region. The indication and timing of surgery in pediatric patients therefore needs to be carefully weighed against the physical and psychologic consequences of treatment.

Clinic-based study of plexiform neurofibromas in neurofibromatosis 1

Individuals with neurofibromatosis 1 (NF1) develop both benign and malignant tumors at an increased frequency. One of the most common benign tumors in NF1 is the plexiform neurofibroma. These tumors cause significant morbidity and mortality on account of their propensity to grow and affect adjacent normal tissues. To determine the clinical profile of plexiform neurofibromas in NF1, we conducted a retrospective review of 68 NF1 patients with plexiform neurofibroma. In our series, 44% of tumors were detected by 5 years of age and most were located in the trunk and extremities. Only two patients developed malignant peripheral nerve sheath tumors in their preexisting plexiform neurofibromas. Lastly, we demonstrate that there were no specific clinical features of NF1 associated with the presence of plexiform neurofibroma. These results underscore the importance of careful serial examinations in the evaluation of patients with NF1.

Allelic loss of the NF1 gene in NF1-associated plexiform neurofibromas

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder with a complex variety of clinical symptoms. Genetic alteration of the NF1 gene on 17q11.2 is the disease. Neurofibromas of the peripheral nervous system are one main manifestation. A variant of neurofibroma is the plexiform neurofibroma which can be found in about 30% of NF1-patients, often causing severe clinical symptoms. In this study, we examined 14 such tumors from 10 NF1-patients for allele loss of the NF1 gene (LOH: loss of heterozygosity) using four intragenic polymorphic markers. Loss of heterozygosity was found in eight tumors from five patients, and suspected in one additional tumor from another patient. This finding suggests that loss of the second allele, and thus inactivation of both alleles of the NF1 gene, is associated with the development of plexiform neurofibromas. The 14 plexiform neufibromas were also examined for mutation in the TP53 gene by screening exons 5 through 8 using temperature gradient gel electrophoresis. No mutation was found in any of the tumors.

A prospective 10 year follow up study of patients with neurofibromatosis type 1

OBJECTIVE

To establish the prevalence and incidence of symptoms and complications in children with neurofibromatosis type 1 (NF1) and to assess possible risk factors for the development of complications.

DESIGN

A 10 year prospective multidisciplinary follow up study.

PATIENTS

One hundred and fifty children diagnosed with NF1 according to criteria set by the National Institutes of Health.

RESULTS

In 62 of 150 children (41.3%) complications were present, including 42 (28.0%) children with one complication, 18 (12.0%) with two complications, and two (1.3%) with three complications (mean (SD) duration of follow up 4.9 (3.8) years). Ninety five of the 150 children presented without complications (follow up, 340.8 person-years). The incidence of complications was 2.4/100 person-years in this group. An association was found between behavioural problems and the presence of complications.

CONCLUSION

This is the largest single centre case series of NF1 affected children followed until 18 years of age. Children with NF1, including those initially presenting without complications, should have regular clinical examinations.

Neurofibromatosis types I and II: radiological appearance

The neurocutaneous disorders frequently involve the central nervous system. This, the first in a pair of articles which describe and illustrate the radiological appearances of the central nervous system manifestations of the most common neurocutaneous disorders, looks at neurofibromatosis types I and II.