Concomitant variants in NF1, LZTR1 and GNAZ genes probably contribute to the aggressiveness of plexiform neurofibroma and warrant treatment with MEK inhibitor

Superimposed Mosaicism in the Form of Extremely Extended Segmental Plexiform Neurofibroma Caused by a Novel Pathogenic Variant in the NF1 Gene

Plexiform neurofibromas occurring in approximately 20-50% of all neurofibromatosis type-1 (NF1) cases are histologically benign tumors, but they can be fatal due to compression of vital structures or transformation to malignant sarcomas or malignant peripheral nerve sheath tumors. All sizeable plexiform neurofibromas are thought to result from an early second mutation giving rise to a loss of heterozygosity of the NF1 gene. In this unusual case, a 12-year-old girl presented with a rapidly growing, extremely extensive plexiform neurofibroma with segmental distribution over the entire right arm, extending to the right chest wall and mediastinum, superimposed on classic cutaneous lesions of NF1. After several surgical interventions, the patient was efficiently treated with an oral selective MEK inhibitor, selumetinib, which resulted in a rapid reduction of the tumor volume. Molecular analysis of the NF1 gene revealed a c.2326-2 A>G splice-site mutation in the clinically unaffected skin, peripheral blood sample, and plexiform neurofibroma, which explains the general clinical symptoms. Furthermore, a novel likely pathogenic variant, c.4933dupC (p.Leu1645Profs*7), has been identified exclusively in the girl's plexiform neurofibromas. This second-hit mutation can explain the extremely extensive segmental involvement.

LZTR1 Mutation Mediates Oncogenesis through Stabilization of EGFR and AXL

LZTR1 is the substrate-specific adaptor of a CUL3-dependent ubiquitin ligase frequently mutated in sporadic and syndromic cancer. We combined biochemical and genetic studies to identify LZTR1 substrates and interrogated their tumor-driving function in the context of LZTR1 loss-of-function mutations. Unbiased screens converged on EGFR and AXL receptor tyrosine kinases as LZTR1 interactors targeted for ubiquitin-dependent degradation in the lysosome. Pathogenic cancer-associated mutations of LZTR1 failed to promote EGFR and AXL degradation, resulting in dysregulated growth factor signaling. Conditional inactivation of Lztr1 and Cdkn2a in the mouse nervous system caused tumors in the peripheral nervous system including schwannoma-like tumors, thus recapitulating aspects of schwannomatosis, the prototype tumor predisposition syndrome sustained by LZTR1 germline mutations. Lztr1- and Cdkn2a-deleted tumors aberrantly accumulated EGFR and AXL and exhibited specific vulnerability to EGFR and AXL coinhibition. These findings explain tumorigenesis by LZTR1 inactivation and offer therapeutic opportunities to patients with LZTR1-mutant cancer.

SIGNIFICANCE

EGFR and AXL are substrates of LZTR1-CUL3 ubiquitin ligase. The frequent somatic and germline mutations of LZTR1 in human cancer cause EGFR and AXL accumulation and deregulated signaling. LZTR1-mutant tumors show vulnerability to concurrent inhibition of EGFR and AXL, thus providing precision targeting to patients affected by LZTR1-mutant cancer. This article is highlighted in the In This Issue feature, p. 517.

Mapping the Landscape of Neurofibromatosis: A Bibliometric Evaluation Highlighting Our Current Understanding, Emerging Therapies, and Global Research Trends

BACKGROUND

The literature on neurofibromatosis (NF) has never been systematically assessed using bibliometric analytic methodologies. We quantitatively analyzed the major trends and scientific output regarding NF, highlighting potential avenues for research.

METHODS

An Elsevier's Scopus database search was performed for all indexed studies related to NF from 1898 to 2021. Validated bibliometric parameters were analyzed using productivity, citation, and keyword analysis, including text mining, content analysis, and collaboration network mapping from inception to date on R 4.1.2.

RESULTS

Our search yielded 15,024 documents. Annual scientific production has grown at a compounded rate of 5.86%, with the largest occurring in 2021 (n = 626). Journals with the most publications on NF include the Journal of Medical Genetics (n = 117) and Neurology (n = 113). The topmost cited author was Gutmann DH (n = 295). The United States had the most international collaboration (n = 435; multiple country publications). Identification of citation classics revealed a shift in recent decades towards understanding genetic and molecular pathways of NF tumorigenesis. Macro-level and micro-level text mining revealed the top 20 genetic and molecular pathways, and syndromes, associated with NF.

CONCLUSIONS

Our study exemplifies a quantitative method for understanding the historical and current state of academic efforts regarding NF. There has been a shift of treatment strategies towards targeting specific pathways involved in tumorigenesis. We highlight the top 20 genetic and molecular pathways in the literature as well as the top 20 associated syndromes. This data is encouraging as increased research in molecular targeted therapies aimed at NF pathogenesis may allow advances in disease control.