Spitz, Douglas R

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive and chemo-resistant sarcomas with poor survival rates. Loss of CDKN2A or P53 following NF1 disruption is a key event in MPNST development. Here, we used CRISPR-Cas9 somatic tumorigenesis in mice to identify transcriptomic and metabolomic features distinguishing CDKN2A - versus P53 -deleted MPNSTs. Convergent, multiomic analyses revealed that CDKN2A -deleted MPNSTs are especially dependent on the pentose phosphate pathway (PPP) and NADPH metabolism for growth and viability. Disruption of glucose-6-phosphate dehydrogenase (G6PD), the PPP rate-limiting enzyme, slowed CDKN2A -deleted MPNST growth and sensitized MPNSTs to standard-of-care chemotherapy. Knockdown of the redox-regulated transcription factor NRF2 slowed MPNST growth and decreased G6PD transcription. Analysis of patient MPNSTs identified a NRF2 gene signature correlating with tumor transformation. Furthermore, G6PD and NRF2 expression in PanCancer TCGA samples correlates with patient survival. This work identifies NRF2-PPP dependency as a targetable vulnerability in these difficult-to-treat MPNSTs, particularly in the NF1/CDKN2A -deleted majority.

Abstract Purpose: Pharmacologic ascorbate (P-AscH−) is hypothesized to be an iron (Fe)-dependent tumor-specific adjuvant to chemoradiation in treating glioblastoma (GBM). This study determined the efficacy of combining P-AscH− with radiation and temozolomide in a phase II clinical trial while simultaneously investigating a mechanism-based, noninvasive biomarker in T2* mapping to predict GBM response to P-AscH− in humans. Patients and Methods: The single-arm phase II clinical trial (NCT02344355) enrolled 55 subjects, with analysis performed 12 months following the completion of treatment. Overall survival (OS) and progression-free survival (PFS) were estimated with the Kaplan–Meier method and compared across patient subgroups with log-rank tests. Forty-nine of 55 subjects were evaluated using T2*-based MRI to assess its utility as an Fe-dependent biomarker. Results: Median OS was estimated to be 19.6 months [90% confidence interval (CI), 15.7–26.5 months], a statistically significant increase compared with historic control patients (14.6 months). Subjects with initial T2* relaxation < 50 ms were associated with a significant increase in PFS compared with T2*-high subjects (11.2 months vs. 5.7 months, P < 0.05) and a trend toward increased OS (26.5 months vs. 17.5 months). These results were validated in preclinical in vitro and in vivo model systems. Conclusions: P-AscH− combined with temozolomide and radiotherapy has the potential to significantly enhance GBM survival. T2*-based MRI assessment of tumor iron content is a prognostic biomarker for GBM clinical outcomes. See related commentary by Nabavizadeh and Bagley, p. 255