In Reply: Retention of ATRX and DAXX Expression in Meningiomas

To the Editor: We read with great interest the article "Letter: Retention of ATRX and DAXX Expression In Meningioma" by Fürtjes et al1 published in Neurosurgery. The authors evaluated ATRX expression with immunohistochemistry (IHC) in 101 meningiomas. They report that ATRX expression was maintained in all 101 samples, including World Health Organization (WHO) Grade I, II, and III samples. Others recently performed targeted sequencing of ATRX in a small series of 18 meningiomas and ATRX IHC in 42 meningiomas, finding no confirmed alterations in ATRX.2 Given these findings, we sought to definitively characterize whether ATRX alterations are present in meningiomas. We performed next-generation targeted sequencing of ATRX in a large series of 188 meningiomas. A board-certified neuropathologist (M.F.) reviewed histopathological diagnosis, grade, and purity of each case. Deoxyribonucleic acid (DNA) was extracted from representative formalin-fixed paraffin-embedded (FFPE) tissue using Maxwell FFPE Plus DNA Purification Kit (Promega, Madison, Wisconsin). DNA tissue libraries were generated using the AmpliSeq Oncomine Comprehensive research panel versions 2.0 and 3.0 (ThermoFisher Scientific, Waltham, Massachusetts) as described previously.3 Sequencing data analysis was performed using Torrent Suite (versions 5.6.0. and 5.8.0.) (ThermoFisher Scientific) and Ion Reporter (versions 5.2, 5.6, and 5.8) (ThermoFisher Scientific). Lollipop plots (Figure 1) were created using cBioPortal MutationMapper.4,5 Our cohort included 188 meningiomas and included low and high-grade lesions, as well as samples from primary and recurrent surgeries (Table). We identified ATRX loss-of-function mutations in 6.9% of our cohort (13/188) (Figure 1 and 9). From the 13 samples, there were 17 alterations in ATRX, which included 15 nonsense mutations, 1 missense mutation, and 1 frame-shift insertion.FIGURE 1.: Lollipop plot visualizing protein alterations in ATRX. TABLE. - Clinical Characteristics of Whole Cohort and ATRX Mutated Meningiomas Clinical characteristic Whole cohort (n = 188) ATRX mutated (n = 13) Age Median (interquartile range) 60.9 (49.1, 69.9) 67.6 (47.1, 84.9) Range 20.3–95.7 20.3–89.9 Sex (Female) 114 (60.6) 7 (53.8) WHO grade I 54 (28.7) 3 (23.1) II 118 (62.8) 9 (69.2) III 16 (8.5) 1 (7.7) Occurrence Primary 100 (53.2) 7 (53.8) Recurrent 88 (46.8) 6 (46.2) Data in parenthesis represent percentage in column, unless otherwise indicated. ATRX mutations were seen in 3 low-grade (Grade I) and 10 high-grade (Grade II and III) meningiomas, as well as 6 from recurrent disease. ATRX mutation status did not significantly affect overall survival (Figure 2). Median overall survival for patients with ATRX-mutated meningiomas was 10.9 yr (95% CI: 2.2, NR) compared to 16.8 yr (95% CI: 9.9, 16.8) (P = .7, log-rank).FIGURE 2.: Kaplan–Meier curve for overall survival by ATRX mutation status.Human Telomerase Reserve Transcriptase (TERT) is commonly upregulated in cancer, which supports telomere lengthening.6 In meningiomas, TERT promoter mutations are associated with shorter progression free survival and overall survival in high-grade meningiomas,7 and may be associated with malignant progression.8 In one cohort of 252 meningiomas, TERT promoter mutations were identified in 16 samples (6.4%), resulting in a significant reduction in progression free survival (10.1 mo compared to 179.0 mo).9 A second cohort of 128 meningioma samples identified TERT promoter mutations in 5.5% of samples; the authors similarly report significantly shorter overall survival (53.8 mo compared to 115.6 mo) in meningiomas that harbored TERT promoter mutations.10 Beyond TERT promoter mutations, alterations in ATRX and DAXX lead to telomere lengthening through a mechanism known as alternative lengthening of telomeres, which is telomerase-independent.11,12 Recent evidence confirms that ATRX loss induces telomere DNA replication dysfunction.13 Our data support that ATRX mutations occur as frequently as TERT promoter mutations in meningiomas. While we did not assess TERT promoter status in our samples, future work ought to identify whether ATRX loss occurs in combination with or exclusive from TERT promoter mutations in meningiomas. Since Fürtjes et al1 utilized IHC to evaluate ATRX status, it would be interesting if these samples could undergo targeted sequencing. Targeted sequencing of ATRX in 18 meningioma samples by Juratli et al2 was likely underpowered for such analysis. In summary, we identified ATRX mutations in 6.9% of a large cohort of 188 meningiomas. These data contribute to the emerging understanding of the underlying tumor biology that supports meningioma oncogenesis. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.