Germline duplication of chromosome 2p and neuroblastoma

Multifaceted Roles of ALK Family Receptors and Augmentor Ligands in Health and Disease: A Comprehensive Review

This review commemorates the 10-year anniversary of the discovery of physiological ligands Augα (Augmentor α; ALKAL2; Fam150b) and Augβ (Augmentor β; ALKAL1; Fam150a) for anaplastic lymphoma kinase (ALK) and leukocyte tyrosine kinase (LTK), previously considered orphan receptors. This manuscript provides an in-depth review of the biophysical and cellular properties of ALK family receptors and their roles in cancer, metabolism, pain, ophthalmology, pigmentation, central nervous system (CNS) function, and reproduction. ALK and LTK receptors are implicated in the development of numerous cancers, and targeted inhibition of their signaling pathways can offer therapeutic benefits. Additionally, ALK family receptors are involved in regulating body weight and metabolism, modulating pain signaling, and contributing to eye development and pigmentation. In the CNS, these receptors play a role in synapse modulation, neurogenesis, and various psychiatric pathologies. Lastly, ALK expression is linked to reproductive functions, with potential implications for patients undergoing ALK inhibitor therapy. Further research is needed to better understand the complex interactions of ALK family receptors and Aug ligands and to repurpose targeted therapy for a wide range of human diseases.

Chromosome Imbalances in Neuroblastoma-Recent Molecular Insight into Chromosome 1p-deletion, 2p-gain, and 11q-deletion Identifies New Friends and Foes for the Future

Simple Summary

Neuroblastoma is a pediatric cancer that arises in the sympathetic nervous system. High-risk neuroblastoma is clinically challenging and identification of novel therapies, particularly those that offer a reduction in morbidity for these patients, is a high priority. Combining genetic analyses with investigation of molecular mechanisms, while considering recent advances in our understanding of key developmental events, provides avenues for future treatment. Here we review and highlight several recently published articles that address novel molecular mechanisms arising from chromosome 1p, 2p, and 11q aberrations, which likely contribute to high-risk neuroblastoma, and discusses their potential impact on treatment options.

Abstract

Neuroblastoma is the most common extracranial solid pediatric tumor, with around 15% childhood cancer-related mortality. High-risk neuroblastomas exhibit a range of genetic, morphological, and clinical heterogeneities, which add complexity to diagnosis and treatment with existing modalities. Identification of novel therapies is a high priority in high-risk neuroblastoma, and the combination of genetic analysis with increased mechanistic understanding—including identification of key signaling and developmental events—provides optimism for the future. This focused review highlights several recent findings concerning chromosomes 1p, 2p, and 11q, which link genetic aberrations with aberrant molecular signaling output. These novel molecular insights contribute important knowledge towards more effective treatment strategies for neuroblastoma.

Analysis of ALK, MYCN, and the ALK ligand ALKAL2 (FAM150B/AUGα) in neuroblastoma patient samples with chromosome arm 2p rearrangements

Gain of chromosome arm 2p is a previously described entity in neuroblastoma (NB). This genomic address is home to two important oncogenes in NB-MYCN and anaplastic lymphoma kinase (ALK). MYCN amplification is a critical prognostic factor coupled with poor prognosis in NB. Mutation of the ALK receptor tyrosine kinase has been described in both somatic and familial NB. Here, ALK activation occurs in the context of the full-length receptor, exemplified by activating point mutations in NB. ALK overexpression and activation, in the absence of genetic mutation has also been described in NB. In addition, the recently identified ALK ligand ALKAL2 (previously described as FAM150B and AUGα) is also found on the distal portion of 2p, at 2p25. Here we analyze 356 NB tumor samples and discuss observations indicating that gain of 2p has implications for the development of NB. Finally, we put forward the hypothesis that the effect of 2p gain may result from a combination of MYCN, ALK, and the ALK ligand ALKAL2.

On the significance of germline cytogenetic rearrangements at MYCN locus in neuroblastoma

Background

MYCN oncogene amplification is the most important prognostic factor in neuroblastoma. 25% neuroblastoma tumors have somatic amplifications at this locus but little is known about its constitutional aberrations and their potential role in carcinogenesis. Here, we have performed an array-CGH and qPCR characterization of two patients with constitutional partial 2p trisomy including MYCN genomic region.

Results

One of the patients had congenital neuroblastoma and showed presence of minute areas of gains and losses within the common fragile site FRA2C at 2p24 encompassing MYCN. The link between 2p24 germline rearrangements and neuroblastoma development was reassessed by reviewing similar cases in the literature.

Conclusions

It appears that constitutional rearrangements involving chromosome 2p24 may play role in NB development.

Congenital neuroblastoma in a patient with partial trisomy of 2p

We report the fourth example of a patient with germline partial trisomy of 2p21-pter and congenital neuroblastoma. The male infant had a dysmorphic facial expression and presented with congenital heart disease, supernumerary nipples, hypospadias, shawl scrotum, hemilateral persistent hyperplastic primary vitreous, and neuroblastoma. His germline karyotype of 46,XY,der(8)t(2;8)(p21;p23.2) was inherited from a maternal-balanced translocation, which indicates that the proto-oncogene MYCN region of 2p24.3 is tripicated in germline cells. A cytogenetic study of the biopsied tumor cells did not show MYCN amplification, but the DNA index was 2.4 and histologic fluorescent in situ hybridization analysis indicated somatic mutation with near-pentaploidy of the tumor cells. This could be an alternative mechanism of MYCN activation in the process of the tumorigenesis of neuroblastoma.

Unrelated patients with a rearrangement of chromosome 2 causing duplication of 2p23 and deletion of 2q37

We describe two unrelated patients who each have a similar chromosome 2 with duplication of 2p23 to pter, and deletion of 2q37 to qter. In one, the abnormality was derived from his mother with a pericentric inversion. Both individuals have frontal bossing; abnormally formed, low set and posteriorly rotated ears; redundant nuchal skin; inversion of the nipple(s); fleshy fingertips with prominent pads; a sacral dimple; significant developmental delay/mental retardation; and G-tube dependency. Most of these features are present in previously described individuals with either duplication of the 2p terminus or deletion of the 2q terminus. This report is the first that documents postnatal viability of individuals with concurrent duplication of 2p and deletion of 2q, and also generation of this imbalance through rearrangement of a maternally inherited pericentrically inverted 2. This report should be considered in the reproductive counseling of individuals with pericentric inversions of chromosome 2.

Abnormal constitutional karyotypes in patients with neuroblastoma: a report of four new cases and review of 47 others in the literature

Anomalies of constitutional karyotype, which have led to the discovery of oncogenes and tumor-suppressor genes in embryonal tumors such as retinoblastoma and Wilms tumor, have, until recently, rarely been reported until recently in neuroblastoma. We present four new cases of neuroblastoma associated with (a) a mosaicism for monosomy 22; (b) an 11q interstitial deletion; (c) a pericentric inversion of chromosome 9 at band 9p21; and (d) a Robertsonian translocation t(13;14). These anomalies and 47 others in the literature are worthy of interest, because some are recurrent, involving the same chromosome regions (1p36, 2p23, 3q, 11q23, and 15q), and some anomalies are situated on chromosome regions known to contain genes involved in neuroblastoma development (1p, 2p, 9p, 11q, 16q, and 17q). Chromosome regions 3q and 15q, observed several times, may also contain genes significant for neuroblastoma onset or development. Furthermore, the lack of neuroblastoma in patients with Down syndrome and Klinefelter or triple-X syndromes, together with a probable excess of neuroblastoma in patients with Turner syndrome, suggests that genes of importance for neuroblastoma may map to chromosomes X and 21. A search for genes implicated in neuroblastoma biology should use these data.

MYCN gain and MYCN amplification in a stage 4S neuroblastoma

Stage 4S neuroblastoma is a disease associated with spontaneous regression and good survival. We present a patient whose evolution has shown the variety and complexity of this disease in infants. Biologic factors, such as ploidy, MYCN copy number, loss of 1p36, and other chromosomal gains and losses were determined. A complex pattern of genetic abnormalities, such as near-diploidy, MYCN gain (2-4 copies per haploid genome) and imbalance/deletion of 1p36 was seen in the diagnostic sample. An extensive disseminated disease after a latent period of 26 months was associated with a special genetic evolution, such a tetraploidy, MYCN amplification (2:100-500 copies), 1p36 deletion, and gain of 17q. Our results provide evidence that either the primary tumor was heterogeneous in terms of gene amplification or that amplification was acquired later on as a transition from MYCN gain. We suggest that near-di-/tetraploid 4S tumors with MYCN gain and/or deletion 1p could be progressing 4S tumors.

Genetic parameters of neuroblastomas

Neuroblastoma is a malignant childhood tumor of migrating neuroectodermal cells derived from the neural crest and destined for the adrenal medulla and the sympathetic nervous system. The biological behavior of neuroblastomas is extremely variable and in some respects unique. Neuroblastomas tend to regress spontaneously in a portion of infants or to differentiate into a benign ganglioneuroma in some older patients. Unfortunately, in the majority of patients neuroblastoma is metastatic at the time of diagnosis, and it usually undergoes rapid progression with a fatal outcome. The mechanisms leading to this diverse clinical behavior of neuroblastomas are largely unclear. From the analysis of tumors at the cytogenetic and molecular level non-random genetic changes have been identified, including ploidy changes, amplification of the oncogene MYCN, deletions of chromosome 1p, gains of chromosome arm 17q, and deletions of 11q as well as of other genomic regions that allow tumors to be classified into subsets with distinct biological features and clinical behavior. MYCN status is widely accepted for therapy stratification. Additional genetic parameters are currently under investigation to refine risk assessment, but so far the molecular monitoring tools for prediction of therapy response and disease outcome are still incomplete. This should lead to more risk-adapted therapies according to the clinical-genetic parameters by which individual tumors are characterized. This review aims at discussing the role of genomic changes in neuroblastomas of diverse biological and clinical types.

Neuroblastoma in a dysmorphic girl with a partial duplication of 2p caused by an unbalanced translocation

A 1-year-old female child with multiple dysmorphic features including microcephaly, hypertelorism, a short philtrum, low set ears, a narrow high arched palate, micrognathia and growth retardation was found to have a de novo chromosome abnormality including a partial duplication of the short arm of chromosome 2 and a partial deletion of the long arm of chromosome 17. The clinical features of the case shared many similarities to previous reports of trisomy 2p. Three years later, ecchymotic spots appeared around the left ocular region. Further clinical and pathological examination confirmed the diagnosis of a neuroblastoma. This is the first case of an unbalanced translocation, 46, XX, der (17), t (2; 17) (p23; q25), showing the development of a neuroblastoma in addition to the dysmorphic features. We suggest that trisomy 2p including the N-myc proto-oncogene may have predisposed the patient to the development of a neuroblastoma.

Neuroblastoma tumour genetics: clinical and biological aspects

Neuroblastoma tumour cells show complex combinations of acquired genetic aberrations, including ploidy changes, deletions of chromosome arms 1p and 11q, amplification of the MYCN oncogene, and-most frequently-gains of chromosome arm 17q. Despite intensive investigation, the fundamental role of these features in neuroblastoma initiation and progression remains to be understood. Nonetheless, great progress has been made in relating tumour genetic abnormalities to tumour behaviour and to clinical outcome; indeed, neuroblastoma provides a paradigm for the clinical importance of tumour genetic abnormalities. Knowledge of MYCN status is increasingly being used in treatment decisions for individual children, and the clinical value of 1p and 17q data as adjuncts or refinements in risk stratification is under active investigation. Reliable detection of these molecular cytogenetic features should be regarded as mandatory for all new cases at presentation.

Constitutional balanced chromosomal rearrangements and neoplasm in children

A predisposition to tumor development is currently associated with some, but not all, constitutional chromosomal abnormalities. In a series of 578 children, in which conventional cytogenetic investigation was performed on material from various benign and malignant tumors, four boys and one girl were also found to have constitutional balanced chromosomal rearrangements. The figure of 5 in 578 is notable because the reported incidence of balanced rearrangements in newborns is approximately 1 in 450. Thereby suggesting that some, if not all, children with balanced constitutional chromosomal rearrangements have an increased predisposition for neoplasms developing.

Trisomy 2p syndrome: a fetus with anencephaly and postaxial polydactyly

We report on a male fetus with partial trisomy 2p21-2pter and monosomy 15q26-15qter due to t(2,15)(p21;q26). This fetus had a typical trisomy 2p phenotype including minor facial anomalies, musculoskeletal defects and two unusual findings: polydactyly and anencephaly. The observation of anencephaly adds support to the theory that genetic material mapping to chromosome band 2p24 is involved in neural tube development. In addition, we propose that a gene on 2p23 may play a role in the morphogenetic patterning of hands and feet.