The genetic alterations that define primary central nervous system lymphoma (PCNSL) are incompletely elucidated, and the genomic evolution from diagnosis to relapse is poorly understood. We performed whole-exome sequencing (WES) on 36 PCNSL patients and targeted MYD88 sequencing on a validation cohort of 27 PCNSL patients. We also performed WES and phylogenetic analysis of 3 matched newly diagnosed and relapsed tumor specimens and 1 synchronous intracranial and extracranial relapse. Immunohistochemistry (IHC) for programmed death-1 ligand (PD-L1) was performed on 43 patient specimens. Combined WES and targeted sequencing identified MYD88 mutation in 67% (42 of 63) of patients, CDKN2Abiallelic loss in 44% (16 of 36), and CD79b mutation in 61% (22 of 36). Copy-number analysis demonstrated frequent regions of copy loss (ie, CDKN2A), with few areas of amplification. CD79b mutations were associated with improved progression-free and overall survival. We did not identify amplification at the PD-1/PD-L1 loci. IHC for PD-L1 revealed membranous expression in 30% (13 of 43) of specimens. Phylogenetic analysis of paired primary and relapsed specimens identified MYD88mutation and CDKN2A loss as early clonal events. PCNSL is characterized by frequent mutations within the B-cell receptor and NF-κB pathways. The lack of PD-L1 amplifications, along with membranous PD-L1 expression in 30% of our cohort, suggests that PD-1/PD-L1 inhibitors may be useful in a subset of PCNSL. WES of PCNSL provides insight into the genomic landscape and evolution of this rare lymphoma subtype and potentially informs more rational treatment decisions.

Nayyar N1,2, White MD3,4, Gill CM1, Lastrapes M1,2,5, Bertalan M1, Kaplan A1, D’Andrea MR1, Bihun I1, Kaneb A1, Dietrich J1,3,4, Ferry JA6, Martinez-Lage M3,6, Giobbie-Hurder A5, Borger DR1,3, Rodriguez FJ7, Frosch MP3,6, Batchelor E1, Hoang K1, Kuter B1, Fortin S1, Holdhoff M7, Cahill DP1,3,4,8, Carter S2,5,9, Brastianos PK1,2,3,4, Batchelor TT1,3,4.
Blood Adv. 2019 Feb 12;3(3):375-383. doi: 10.1182/bloodadvances.2018027672.

Alvarez-Breckenridge C, Giobbie-Hurder A, Gill CM, Bertalan M, Stocking J, Kaplan A, Nayyar N, Lawrence DP, Flaherty KT, Shih HA, Oh K, Batchelor TT, Cahill DP, Sullivan R, Brastianos P.
Oncologist. 2019 Feb 22. pii: theoncologist.2018-0306. doi: 10.1634/theoncologist.2018-0306. [Epub ahead of print]

Purpose: Previous studies have shown that the PI3K/Akt/mTOR-pathway is activated in up to 70% of breast cancer brain metastases, but there are no approved agents for affected patients. GDC-0084 is a brain penetrant, dual PI3K/mTOR-inhibitor that has shown promising activity in a preclinical model of glioblastoma. The aim of this study was to analyze the efficacy of PI3K/mTOR blockade in breast cancer brain metastases models. Experimental Design: The efficacy of GDC-0084 was evaluated in PIK3CA-mutant and PIK3CA-wildtype breast cancer cell lines and the isogenic pairs of PIK3CA-wildtype and -mutant (H1047R/+) MCF10A cells in vitro. In vitro studies included cell viability and apoptosis assays, cell cycle analysis and Western blots. In vivo, the effect of GDC-0084 was investigated in breast cancer brain metastasis xenograft mouse models and assessed by bioluminescent imaging and immunohistochemistry. Results: In vitro, GDC-0084 considerably decreased cell viability, induced apoptosis and inhibited phosphorylation of Akt and p70 S6 kinase in a dose-dependent manner in PIK3CA-mutant breast cancer brain metastatic cell lines. In contrast, GDC-0084 led only to growth inhibition in PIK3CA-wildtype cell lines in vitro. In vivo, treatment with GDC-0084 markedly inhibited the growth of PIK3CA-mutant, with accompanying signaling changes, and not PIK3CA-wildtype brain tumors. Conclusions: The results of this study suggest that the brain-penetrant PI3K/mTOR-targeting GDC-0084 is a promising treatment option for breast cancer brain metastases with dysregulated PI3K/mTOR signaling pathway conferred by activating PIK3CA mutations. A national clinical trial is planned to further investigate the role of this compound in patients with brain metastases.

Ippen FM, Alvarez-Breckenridge CA, Kuter BM, Fink AL, Bihun IV, Lastrapes M, Penson T, Schmidt SP, Wojtkiewicz GR, Ning J, Subramanian M, Giobbie-Hurder A, Martinez-Lage M, Carter SL, Cahill DP, Wakimoto H, Brastianos PK.
Clin Cancer Res. 2019 Feb 22. pii: clincanres.3049.2018. doi: 10.1158/1078-0432.CCR-18-3049. [Epub ahead of print]

Meningiomas located in the skull base are surgically challenging. Recent genomic research has identified oncogenic SMOand AKT1 mutations in a small subset of meningiomas. METHODS The authors performed targeted sequencing in a large cohort of patients with anterior skull base meningiomas (n = 62) to better define the frequency of SMO and AKT1mutations in these tumors. RESULTS The authors found SMO mutations in 7 of 62 (11%) and AKT1 mutations in 12 of 62 (19%) of their cohort. Of the 7 meningiomas with SMO mutations, 6 (86%) occurred in the olfactory groove. Meningiomas with an SMO mutation presented with significantly larger tumor volume (70.6 ± 36.3 cm³) compared with AKT1-mutated (18.2 ± 26.8 cm³) and wild-type (22.7 ± 23.9 cm³) meningiomas, respectively. CONCLUSIONS Combined, these data demonstrate clinically actionable mutations in 30% of anterior skullbasemeningiomas and suggest an association between SMO mutation status and tumor volume. Genotyping of SMO and AKT1 is likely to be high yield in anterior skull base meningiomas with available surgical tissue.

Glioneuronal tumors constitute a histologically diverse group of primary central nervous system neoplasms that are typically slowgrowing and managed conservatively. Genetic alterations associated with glioneuronal tumors include BRAF mutations and oncogenic fusions. To further characterize this group of tumors, we collected a cohort of 26 glioneuronal tumors and performed indepth genomic analysis. We identified mutations in BRAF (34%) and oncogenic fusions (30%), consistent with previously published reports. In addition, we discovered novel oncogenic fusions involving members of the NTRK gene family in a subset of our cohort. One-patient with BCAN exon 13 fused to NTRK1 exon 11 initially underwent a subtotal resection for a 4th ventricular glioneuronal tumor but ultimately required additional therapy due to progressive, symptomatic disease. Given the patient’s targetable fusion, the patient was enrolled on a clinical trial with entrectinib, a pan-Trk, ROS1, and ALK (anaplastic lymphoma kinase) inhibitor. The patient was treated for 11 months and during this time volumetric analysis of the lesion demonstrated a maximum reduction of 60% in the contrast-enhancing tumor compared to his pre-treatment magnetic resonance imaging study. The radiologic response was associated with resolution of his clinical symptoms and was maintained for 11 months on treatment. This report of a BCAN-NTRK1 fusion in glioneuronal tumors highlights its clinical importance as a novel, targetable alteration.

Craniopharyngiomas are rare intracranial neoplasms that pose clinical challenges due to their location adjacent to vital structures. The authors have previously shown high mutation rates of BRAF V600E in papillary craniopharyngioma and of CTNNB1 in adamantinomatous craniopharyngioma. These activating driver mutations are potential therapeutic targets, and the authors have recently reported a significant response to BRAF/MEK inhibition in a patient with multiply recurrent PCP. As these targetable mutations warrant prospective research, the authors will be conducting a national National Cancer Institute-sponsored multicenter clinical trial to investigate BRAF/MEK inhibition in the treatment of craniopharyngioma. In this new eraof genomic discovery, the treatment paradigm of craniopharyngioma is likely to change.

The blood-brain barrier (BBB) is modified to a blood-tumor barrier (BTB) as a brain metastasisdevelops from breast or other cancers. We (i) quantified the permeability of experimental brainmetastases, (ii) determined the composition of the BTB, and (iii) identified which elements of the BTB distinguished metastases of lower permeability from those with higher permeability.

Melanoma is the third most common systemic cancer that leads to brain metastases. The annual incidence of melanoma has increased over time, with brain metastases developing in 40% to 50% of patients with advanced melanoma. Traditional management of melanoma-related brain metastases has focused on symptom control as a result of the significant neurologic morbidity associated with the disease. Median overall survival for these patients, if untreated, is approximately 3 months. As with other brain metastases, a multidisciplinary treatment approach that includes surgery and radiation therapy is typically used, with historically little role for systemic, cytotoxic therapy. During the past decade, advancement within the field of genomics has led to the identification of melanoma-specific mutations, namely, v-Raf murine sarcoma viral oncogene homolog B and neuroblastoma RAS viral oncogene homolog, as well as to the development of agents that target these driver mutations. In addition, the advent of immunotherapies, specifically, agents that target cytotoxic T-lymphocyte antigen-4, anti–programmed death-1, and programmed death ligand-1, has increased the potential therapeutic options available to patients with both systemic and brain disease. With these advances, early trials have demonstrated improved overall survival in patients with brain metastases who receive these therapies either as single agents or as part of multimodality treatment regimens.

Papillary craniopharyngioma (PCP) is an intracranial tumor that results in high levels of morbidity.We recently demonstrated that the vast majority of these tumors harbor the oncogenic BRAF V600E mutation. The pathologic diagnosis of PCP can now be confirmed using mutation specific immunohistochemistry and targeted genetic testing. Treatment with targeted agents is now also a possibility in select situations. We recently reported a patient with a multiply recurrent PCP in whom targeting both BRAF and MEK resulted in a dramatic therapeutic response with a marked anti-tumor immune response. This work shows that activation of the MAPK pathway is the likely principal oncogenic driver of these tumors.We will now investigate the efficacy of this approach in a multicenter phase II clinical trial. Post-treatment resection samples will be monitored for the emergence of resistance mechanisms. Further advances in the non-invasive diagnosis of PCP by radiologic criteria and by cell-free DNA testing could someday allow neo-adjuvant therapy for this disease in select patient populations.

Meningiomas are the most common primary intracranial tumor in adults. Identification of SMO and AKT1 mutations in meningiomas has raised the possibility of targeted therapies for some patients. The frequency of such mutations in clinical cohorts and the presence of other actionable mutations in meningiomas are important to define.