Novel SOX10 indel mutations drive schwannomas through impaired transactivation of myelination gene programs

BACKGROUND

Schwannomas are common peripheral nerve sheath tumors that can cause severe morbidity given their stereotypic intracranial and paraspinal locations. Similar to many solid tumors, schwannomas and other nerve sheath tumors are primarily thought to arise due to aberrant hyperactivation of the RAS growth factor signaling pathway. Here, we sought to further define the molecular pathogenesis of schwannomas.

METHODS

We performed comprehensive genomic profiling on a cohort of 96 human schwannomas, as well as DNA methylation profiling on a subset. Functional studies including RNA sequencing, chromatin immunoprecipitation-DNA sequencing, electrophoretic mobility shift assay, and luciferase reporter assays were performed in a fetal glial cell model following transduction with wildtype and tumor-derived mutant isoforms of SOX10.

RESULTS

We identified that nearly one-third of sporadic schwannomas lack alterations in known nerve sheath tumor genes and instead harbor novel recurrent in-frame insertion/deletion mutations in SOX10, which encodes a transcription factor responsible for controlling Schwann cell differentiation and myelination. SOX10 indel mutations were highly enriched in schwannomas arising from nonvestibular cranial nerves (eg facial, trigeminal, vagus) and were absent from vestibular nerve schwannomas driven by NF2 mutation. Functional studies revealed these SOX10 indel mutations have retained DNA binding capacity but impaired transactivation of glial differentiation and myelination gene programs.

CONCLUSIONS

We thus speculate that SOX10 indel mutations drive a unique subtype of schwannomas by impeding proper differentiation of immature Schwann cells.

Trans-aTTom: Breast Cancer Index for prediction of endocrine benefit and late distant recurrence (DR) in patients with HR+ breast cancer treated in the adjuvant tamoxifen—To offer more? (aTTom) trial

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Background: The aTTom study is a prospective phase III trial that randomized 6953 HR+ women to stop or continue tamoxifen (TAM) for 5 more years after completing at least 4 years of prior TAM. Results at 9 years of median follow-up demonstrated fewer breast cancer recurrences (21% vs 25%; RR= 0.86 [95% CI 0.77-0.96]; P = 0.006) and reduced breast cancer mortality (13% vs 15%; HR= 0.91 [95% CI 0.80-1.04]; P = 0.18) but increased incidence of endometrial cancer with longer TAM use (P < 0.0001). The Breast Cancer Index (BCI) is a gene expression–based signature that stratifies patients based on the risk of overall (0-10y) and late (post-5y) DR and predicted the likelihood of benefit from extended endocrine therapy in MA.17. This Translational aTTom (Trans-aTTom) study is a large-scale validation of the predictive ability of BCI for extended endocrine therapy (EET) benefit. Methods: Patients treated in the aTTom trial with available primary tumor tissue were eligible for this multi-institutional prospective-retrospective study. Primary and secondary endpoints were recurrence-free interval (RFI) and disease-free interval (DFI), respectively. Statistical significance level for RFI was set at 0.0336 as per statistical plan. Kaplan-Meier and Cox proportional hazards regression analysis with time-varying coefficients were used to test the predictive activity of BCI by HoxB13/IL17BR (H/I) status (High vs Low). Likelihood ratio test based on Cox regression was used to evaluate treatment by biomarker interaction. Results: 2637 tumors were centrally assessed for ER, PR and HER2 status leading to 1822 HR+ patients analyzed (1018 N0, 583 N+). Initial results from patients with N+ disease at 12 years of median follow-up showed 287 (49%) were classified as H/I-High and 296 (51%) were classified as H/I-Low. H/I High patients showed a statistically significant benefit of 9.8% in RFI with 10y vs 5y of TAM (HR=0.35 [95% CI 0.15-0.85]; P=0.027), whereas H/I Low patients showed no benefit (-0.2% RFI; HR=1.07 [95% CI 0.69-1.65]; P=0.77). A statistically significant interaction between continuous BCI and treatment was demonstrated (P = 0.02). Conclusions: These data provide further validation and establish level 1B evidence for BCI as a predictive biomarker for preferential benefit from EET in HR+ breast cancer.

Prevalence of Intervillous Thrombi Is Increased in Placentas from Pregnancies Complicated by Diabetes

Intervillous thrombus (IVT) is a placental pathology of unclear cause. One possible cause is that IVT protects against fetomaternal transfusion due to trophoblastic disruption. A role for hyperglycemia in trophoblast apoptosis has been suggested. We sought to determine whether placentas from pregnancies complicated by diabetes had an increased incidence of IVT. Medical records of 206 patients with type 1 diabetes (n = 39), type 2 diabetes (n = 37), and gestational diabetes (GDM, n = 130) at the Massachusetts General Hospital were identified. Placental pathology reports were reviewed to determine prevalence of IVT. Gestational and maternal age-matched controls were selected from the pathology archives consisting of placentas examined only for the indication of group B streptococcus screen positivity; controls were confirmed euglycemic and reviewed for IVT. Fisher exact test was used for statistical analysis. An increased incidence of IVT was present in all diabetics (type 1, type 2, and GDM; 32 of 206; 15.5%; P = 0.04) and GDM exclusively (22 of 130; 16.9%; P = 0.03) versus controls (7 of 99; 7.1%). IVT were also increased in patients with type 1 diabetes (4 of 39; 10.3%) and type 2 diabetes (6 of 37; 16.2%) compared to controls (7 of 99; 7.1%), but the results did not attain statistical significance (P = 0.73 and 0.19, respectively). The incidence of IVT was increased in the placentas of patients with diabetes as a group (type 1, type 2, and GDM), and in patients with GDM in particular. This is the first report of an association between diabetes and an increased incidence of placental IVT.