Overgrowth syndromes and pediatric cancers: how many roads lead to IGF2?

Overgrowth syndromes, diagnosis and management

PURPOSE OF REVIEW

This review will focus on the current knowledge of the diagnosis and management of overgrowth syndromes with specific focus on mosaic conditions and treatment strategies.

RECENT FINDINGS

With the implementation of massively parallel sequencing, the genetic etiology of many classically described overgrowth syndromes have been identified. More recently, the role of mosaic genetic changes has been well described in numerous syndromes. Furthermore, the role of imprinting and methylation, especially of the 11p15 region, has been shown to be instrumental for growth. Perhaps most importantly, many overgrowth syndromes carry an increased risk of neoplasm formation especially in the first 10 years of life and possibly beyond. The systematic approach to the child with overgrowth will aide in timely diagnosis and efficiently align them with appropriate screening strategies. In some cases, precision medical interventions are available to target the perturbed growth signaling pathways.

SUMMARY

The systematic approach to the child with overgrowth aids in the standardization of the diagnostic pathway for these young patients, thereby expediting the diagnostic timeline, enabling rigorous monitoring, and delivering tailored therapeutic interventions.

Non-coding RNAs: The link between maternal malnutrition and offspring metabolism

Early life nutrition is associated with the development and metabolism in later life, which is known as the Developmental Origin of Health and Diseases (DOHaD). Epigenetics have been proposed as an important explanation for this link between early life malnutrition and long-term diseases. Non-coding RNAs (ncRNAs) may play a role in this epigenetic programming. The expression of ncRNAs (such as long non-coding RNA H19, microRNA-122, and circular RNA-SETD2) was significantly altered in specific tissues of offspring exposed to maternal malnutrition. Changes in these downstream targets of ncRNAs lead to abnormal development and metabolism. This review aims to summarize the existing knowledge on ncRNAs linking the maternal nutrition condition and offspring metabolic diseases, such as obesity, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD).

Characterization of tRNA expression profiles in large offspring syndrome

Background

Assisted Reproductive Technologies (ART) use can increase the risk of congenital overgrowth syndromes, such as large offspring syndrome (LOS) in ruminants. Epigenetic variations are known to influence gene expression and differentially methylated regions (DMRs) were previously determined to be associated with LOS in cattle. We observed DMRs overlapping tRNA clusters which could affect tRNA abundance and be associated with tissue specificity or overgrowth. Variations in tRNA expression have been identified in several disease pathways suggesting an important role in the regulation of biological processes. Understanding the role of tRNA expression in cattle offers an opportunity to reveal mechanisms of regulation at the translational level. We analyzed tRNA expression in the skeletal muscle and liver tissues of day 105 artificial insemination-conceived, ART-conceived with a normal body weight, and ART-conceived bovine fetuses with a body weight above the 97^th percentile compared to Control-AI.

Results

Despite the centrality of tRNAs to translation, in silico predictions have revealed dramatic differences in the number of tRNA genes between humans and cattle (597 vs 1,659). Consistent with reports in human, only a fraction of predicted tRNA genes are expressed. We detected the expression of 474 and 487 bovine tRNA genes in the muscle and liver with the remainder being unexpressed. 193 and 198 unique tRNA sequences were expressed in all treatment groups within muscle and liver respectively. In addition, an average of 193 tRNA sequences were expressed within the same treatment group in different tissues. Some tRNA isodecoders were differentially expressed between treatment groups. In the skeletal muscle and liver, we categorized 11 tRNA isoacceptors with undetected expression as well as an isodecoder that was unexpressed in the liver (Ser^GGA). Our results identified variation in the proportion of tRNA gene copies expressed between tissues and differences in the highest contributing tRNA anticodon within an amino acid family due to treatment and tissue type. Out of all amino acid families, roughly half of the most highly expressed tRNA isoacceptors correlated to their most frequent codon in the bovine genome.

Conclusion

Although the number of bovine tRNA genes is nearly triple of that of the tRNA genes in human, there is a shared occurrence of transcriptionally inactive tRNA genes in both species. We detected differential expression of tRNA genes as well as tissue- and treatment- specific tRNA transcripts with unique sequence variations that could modulate translation during protein homeostasis or cellular stress, and give rise to regulatory products targeting genes related to overgrowth in the skeletal muscle and/or tumor development in the liver of LOS individuals. While the absence of certain isodecoders may be relieved by wobble base pairing, missing tRNA species could increase the likelihood of mistranslation or mRNA degradation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08496-7.

TRIM28 variants and Wilms' tumour predisposition

TRIM28 was recently identified as a Wilms' tumour (WT) predisposition gene, with germline pathogenic variants identified in around 1% of isolated and 8% of familial WT cases. TRIM28 variants are associated with epithelial WT, but the presence of other tumour components or anaplasia does not exclude the presence of a germline or somatic TRIM28 variant. In children with WT, TRIM28 acts as a classical tumour suppressor gene, with both alleles generally disrupted in the tumour. Therefore, loss of TRIM28 (KAP1/TIF1beta) protein expression in tumour tissue by immunohistochemistry is an effective strategy to identify patients carrying pathogenic TRIM28 variants. TRIM28 is a ubiquitously expressed corepressor that binds transcription factors in a context‐, species‐, and cell‐type‐specific manner to control the expression of genes and transposable elements during embryogenesis and cellular differentiation. In this review, we describe the inheritance patterns, histopathological and clinical features of TRIM28‐associated WT, as well as potential underlying mechanisms of tumourigenesis during embryonic kidney development. Recognizing germline TRIM28 variants in patients with WT can enable counselling, genetic testing, and potential early detection of WT in other children in the family. A further exploration of TRIM28‐associated WT will help to unravel the diverse and complex mechanisms underlying WT development. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Modeling the developmental origins of pediatric cancer to improve patient outcomes

In the treatment of children and adolescents with cancer, multimodal approaches combining surgery, chemotherapy and radiation can cure most patients, but may cause lifelong health problems in survivors. Current therapies only modestly reflect increased knowledge about the molecular mechanisms of these cancers. Advances in next-generation sequencing have provided unprecedented cataloging of genetic aberrations in tumors, but understanding how these genetic changes drive cellular transformation, and how they can be effectively targeted, will require multidisciplinary collaboration and preclinical models that are truly representative of the in vivo environment. Here, I discuss some of the key challenges in pediatric cancer from my perspective as a physician-scientist, and touch on some promising new approaches that have the potential to transform our understanding of these diseases.

Summary: This Perspective discusses the special features that make it challenging to develop new therapies for pediatric cancers, and the ways in which collaboration centered on improved models can meet these challenges.

Genetic variation associated with childhood and adult stature and risk of MYCN-amplified neuroblastoma

Background

Neuroblastoma is the most common pediatric solid tumor. MYCN‐amplification is an important negative prognostic indicator and inherited genetic contributions to risk are incompletely understood. Genetic determinants of stature increase risk of several adult and childhood cancers, but have not been studied in neuroblastoma despite elevated neuroblastoma incidence in children with congenital overgrowth syndromes.

Methods

We investigated the association between genetic determinants of height and neuroblastoma risk in 1538 neuroblastoma cases, stratified by MYCN‐amplification status, and compared to 3390 European‐ancestry controls using polygenic scores for birth length (five variants), childhood height (six variants), and adult height (413 variants). We further examined the UK Biobank to evaluate the association of known neuroblastoma risk loci and stature.

Results

An increase in the polygenic score for childhood stature, corresponding to a ~0.5 cm increase in pre‐pubertal height, was associated with greater risk of MYCN‐amplified neuroblastoma (OR = 1.14, P = .047). An increase in the polygenic score for adult stature, corresponding to a ~1.7 cm increase in adult height attainment, was associated with decreased risk of MYCN‐amplified neuroblastoma (OR = 0.87, P = .047). These associations persisted in case‐case analyses comparing MYCN‐amplified to MYCN‐unamplified neuroblastoma. No polygenic height scores were associated with MYCN‐unamplified neuroblastoma risk. Previously identified genome‐wide association study hits for neuroblastoma (N = 10) were significantly enriched for association with both childhood (P = 4.0 × 10⁻³) and adult height (P = 8.9 × 10⁻³) in >250 000 UK Biobank study participants.

Conclusions

Genetic propensity to taller childhood height and shorter adult height were associated with MYCN‐amplified neuroblastoma risk, suggesting that biological pathways affecting growth trajectories and pubertal timing may contribute to MYCN‐amplified neuroblastoma etiology.

MiR-155-5p exerts tumor-suppressing functions in Wilms tumor by targeting IGF2 via the PI3K signaling pathway

BACKGROUND

MicroRNA-155-5p (miR-155-5p) has been reported to play an oncogenic role in different human malignancies; however, its role in Wilms tumor (WT) remains unclear.

METHODS

Differentially expressed miRNAs (DE-miRNAs) and mRNAs (DEGs) in WT blood and tissues were identified by using miRNA microarray and RNA-sequencing. Bioinformatics prediction and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to predict the potential functions of DE-miRNAs. DE-miRNAs and DEGs in WT obtained from Gene Expression Omnibus (GEO) and Therapeutically Applicable Research to Generate Effective Treatments (TARGET) were identified by using the "edgeR" package. RT-qPCR was used to explore miR-155-5p and IGF2 expression and their clinical significance in WT specimens. A rhabdoid cell line (G401) and Ewing sarcoma cell line (SK-NEP-1) were used. Immunohistochemical staining, western blotting and dual-luciferase reporter assays were performed to study the mechanisms involved. The CCK-8, flow cytometry, wound healing and transwell assays were performed to identify the effects of miR-155-5p and IGF2 knockdown on cell proliferation, apoptosis, migration and invasion, respectively.

RESULTS

MiR-155-5p was downregulated in both blood and tissues from WT patients who did not receive chemotherapy before surgery but was upregulated in tissues from WT patients who had received chemotherapy before surgery. IGF2, PI3K, AKT and mTOR were found to be upregulated in WT tissues. Additionally, miR-155-5p and IGF2 were significantly correlated with TNM stage and lymphatic metastasis in WT patients. Molecular mechanism exploration indicated that IGF2 was downregulated by miR-155-5p via direct binding to its 3' untranslated region in cell lines. Furthermore, IGF2, PI3K, AKT and mTOR expression was inversely correlated with miR-155-5p expression, and PI3K, AKT and mTOR expression was positively correlated with IGF2 expression in cell culture. Functional studies demonstrated that miR-155-5p upregulation and IGF2 knockdown suppressed cell proliferation, migration and invasion and induced cell apoptosis. Moreover, the tumor-suppressing effects of miR-155-5p in cells were abrogated by miR-155-5p inhibitor treatment.

CONCLUSIONS

Taken together, these findings suggest that miR-155-5p functions as a tumor suppressor in WT through inactivating the PI3K/AKT/mTOR signaling pathway by directly targeting IGF2. Thus, miR-155-5p might be a novel therapeutic target for WT.

Overgrowth Syndromes-Evaluation, Diagnosis, and Management

Abnormally excessive growth results from perturbation of a complex interplay of genetic, epigenetic, and hormonal factors that orchestrate human growth. Overgrowth syndromes generally present with inherent health concerns and, in some instances, an increased risk of tumor predisposition that necessitate prompt diagnosis and appropriate referral. In this review, we introduce some of the more common overgrowth syndromes, along with their molecular mechanisms, diagnostics, and medical complications for improved recognition and management of patients affected with these disorders.

Genetic predisposition to cancer: Surveillance and intervention

Cancer is one of the leading causes of early mortality for children and adolescents. Identifiable genetic cancer predisposition conditions account for a growing proportion of pediatric and adolescent cancer, likely due to increasing knowledge about various predisposition conditions, more widespread cancer genetic counseling, and available diagnostics. Greater awareness, data-driven surgical intervention and clinical surveillance can help facilitate cancer prevention and early detection at cancer stages more amenable to cure. An extensive literature review of published studies and expert opinion with consensus guidelines are reviewed. Specific syndromes where genetics, imaging and surgical intervention are utilized to benefit affected patients and families are presented. In many tumor predisposition syndromes, the underlying genetic diagnosis is made concurrently, or after, malignancy is identified. Improved recognition of underlying predispositions, along with appropriate surgical interventions and imaging surveillance should lead to increased patient survival.