Background

Diffuse gliomas are poorly immunogenic, fatal brain tumors. The basis for insufficient antitumor immunity in diffuse gliomas is unknown. Gain-of-function mutations in isocitrate dehydrogenases (IDH1 and IDH2) promote diffuse glioma formation through epigenetic reprogramming of a number of genes, including immune-related genes. Here, we identify epigenetic dysregulation of natural killer (NK) cell ligand genes as significant contributors to immune escape in glioma.

Methods

We analyzed the database of The Cancer Genome Atlas for immune gene expression patterns in IDH mutant or wild-type gliomas and identified differentially expressed immune genes. NKG2D ligand expression levels and NK cell-mediated lysis were measured in IDH mutant and wild-type patient-derived glioma stem cells and genetically engineered astrocytes. Finally, we assessed the impact of hypomethylating agent 5-aza-2'deoxycytodine (decitabine) as a potential NK cell sensitizing agent in IDH mutant cells.

Results

IDH mutant glioma stemlike cell lines exhibited significantly lower expression of NKG2D ligands compared with IDH wild-type cells. Consistent with these findings, IDH mutant glioma cells and astrocytes are resistant to NK cell-mediated lysis. Decitabine increases NKG2D ligand expression and restores NK-mediated lysis of IDH mutant cells in an NKG2D-dependent manner.

Conclusions

IDH mutant glioma cells acquire resistance to NK cells through epigenetic silencing of NKG2D ligands ULBP1 and ULBP3. Decitabine-mediated hypomethylation restores ULBP1 and ULBP3 expression in IDH mutant glioma cells and may provide a clinically useful method to sensitize IDH mutant gliomas to NK cell-mediated immune surveillance in patients with IDH mutated diffuse gliomas.

OBJECTIVE In children, the repair of skull defects arising from decompressive craniectomy presents a unique set of challenges. Single-center studies have identified different risk factors for the common complications of cranioplasty resorption and infection. The goal of the present study was to determine the risk factors for bone resorption and infection after pediatric cranioplasty. METHODS The authors conducted a multicenter retrospective case study that included all patients who underwent cranioplasty to correct a skull defect arising from a decompressive craniectomy at 13 centers between 2000 and 2011 and were less than 19 years old at the time of cranioplasty. Prior systematic review of the literature along with expert opinion guided the selection of variables to be collected. These included: indication for craniectomy; history of abusive head trauma; method of bone storage; method of bone fixation; use of drains; size of bone graft; presence of other implants, including ventriculoperitoneal (VP) shunt; presence of fluid collections; age at craniectomy; and time between craniectomy and cranioplasty. RESULTS A total of 359 patients met the inclusion criteria. The patients' mean age was 8.4 years, and 51.5% were female. Thirty-eight cases (10.5%) were complicated by infection. In multivariate analysis, presence of a cranial implant (primarily VP shunt) (OR 2.41, 95% CI 1.17-4.98), presence of gastrostomy (OR 2.44, 95% CI 1.03-5.79), and ventilator dependence (OR 8.45, 95% CI 1.10-65.08) were significant risk factors for cranioplasty infection. No other variable was associated with infection. Of the 240 patients who underwent a cranioplasty with bone graft, 21.7% showed bone resorption significant enough to warrant repeat surgical intervention. The most important predictor of cranioplasty bone resorption was age at the time of cranioplasty. For every month of increased age the risk of bone flap resorption decreased by 1% (OR 0.99, 95% CI 0.98-0.99, p < 0.001). Other risk factors for resorption in multivariate models were the use of external ventricular drains and lumbar shunts. CONCLUSIONS This is the largest study of pediatric cranioplasty outcomes performed to date. Analysis included variables found to be significant in previous retrospective reports. Presence of a cranial implant such as VP shunt is the most significant risk factor for cranioplasty infection, whereas younger age at cranioplasty is the dominant risk factor for bone resorption.

INTRODUCTION: Historical reservations regarding stereotactic radiosurgery (SRS) for small-cell lung cancer (SCLC) brain metastases include concerns for short-interval and diffuse central nervous system (CNS) progression, poor prognoses, and increased neurological mortality specific to SCLC histology. We compared SRS outcomes for SCLC and non-small cell lung cancer (NSCLC) where SRS is well established. METHODS: Multicenter first-line SRS outcomes for SCLC and NSCLC from 2000 to 2022 were retrospectively collected (n = 892 SCLC, n = 4785 NSCLC). Data from the prospective Japanese Leksell Gamma Knife Society (JLGK0901) clinical trial of first-line SRS were analyzed as a comparison cohort (n = 98 SCLC, n = 814 NSCLC). Overall survival (OS) and CNS progression were analyzed using Cox proportional hazard and Fine-Gray models, respectively, with multivariable adjustment for cofactors including age, sex, performance status, year, extracranial disease status, and brain metastasis number and volume. Mutation-stratified analyses were performed in propensity score-matched retrospective cohorts of epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) positive NSCLC, mutation-negative NSCLC, and SCLC. RESULTS: OS was superior for patients with NSCLC compared to SCLC in the retrospective dataset (median OS = 10.5 vs 8.6 months; P < .001) and in the JLGK0901 dataset. Hazard estimates for first CNS progression favoring NSCLC were similar in both datasets but reached statistical significance in the retrospective dataset only (multivariable hazard ratio = 0.82, 95% confidence interval = 0.73 to 0.92, P = .001). In the propensity score-matched cohorts, there were continued OS advantages for NSCLC patients (median OS = 23.7 [EGFR and ALK positive NSCLC] vs 13.6 [mutation-negative NSCLC] vs 10.4 months [SCLC], pairwise P values < 0.001), but no statistically significant differences in CNS progression were observed in the matched cohorts. Neurological mortality and number of lesions at CNS progression were similar for NSCLC and SCLC patients. Leptomeningeal progression was increased in patients with NSCLC compared to SCLC in the retrospective dataset only (multivariable hazard ratio = 1.61, 95% confidence interval = 1.14 to 2.26, P = .007). CONCLUSIONS: After SRS, SCLC histology was associated with shorter OS compared to NSCLC. CNS progression occurred earlier in SCLC patients overall but was similar in patients matched on baseline factors. SCLC was not associated with increased neurological mortality, number of lesions at CNS progression, or leptomeningeal progression compared to NSCLC. These findings may better inform clinical expectations and individualized decision making regarding SRS for SCLC patients.