[BRAF V600E mutation and clinicopathologic characteristics in 250 cases of brain tumors associated with epilepsy]

Low-grade epilepsy-associated neuroepithelial tumors: Tumor spectrum and diagnosis based on genetic alterations

Brain tumors can always result in seizures when involving the cortical neurons or their circuits, and they were found to be one of the most common etiologies of intractable focal seizures. The low-grade epilepsy-associated neuroepithelial tumors (LEAT), as a special group of brain tumors associated with seizures, share common clinicopathological features, such as seizure onsets at a young age, a predilection for involving the temporal lobe, and an almost benign course, including a rather slow growth pattern and thus a long-term history of seizures. Ganglioglioma (GG) and dysembryoplastic neuroepithelial tumor (DNET) are the typical representatives of LEATs. Surgical treatments with complete resection of tumors and related epileptogenic zones are deemed the optimal way to achieve postoperative seizure control and lifetime recurrence-free survival in patients with LEATs. Although the term LEAT was originally introduced in 2003, debates on the tumor spectrum and the diagnosis or classification of LEAT entities are still confusing among epileptologists and neuropathologists. In this review, we would further discuss these questions, especially based on the updated classification of central nervous system tumors in the WHO fifth edition and the latest molecular genetic findings of tumor entities in LEAT entities.

Benign Glioma

Benign glioma broadly refers to a heterogeneous group of slow-growing glial tumors with low proliferative rates and a more indolent clinical course. These tumors may also be described as "low-grade" glioma (LGG) and are classified as WHO grade I or II lesions according to the Classification of Tumors of the Central Nervous System (CNS) (Louis et al. in Acta Neuropathol 114:97-109, 2007). Advances in molecular genetics have improved understanding of glioma tumorigenesis, leading to the identification of common mutation profiles with significant treatment and prognostic implications. The most recent WHO 2016 classification system has introduced several notable changes in the way that gliomas are diagnosed, with a new emphasis on molecular features as key factors in differentiation (Wesseling and Capper in Neuropathol Appl Neurobiol 44:139-150, 2018). Benign gliomas have a predilection for younger patients and are among the most frequently diagnosed tumors in children and young adults (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). These tumors can be separated into two clinically distinct subgroups. The first group is of focal, well-circumscribed lesions that notably are not associated with an increased risk of malignant transformation. Primarily diagnosed in pediatric patients, these WHO grade I tumors may be cured with surgical resection alone (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). Recurrence rates are low, and the prognosis for these patients is excellent (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). Diffuse gliomas are WHO grade II lesions with a more infiltrative pattern of growth and high propensity for recurrence. These tumors are primarily diagnosed in young adult patients, and classically present with seizures (Pallud et al. Brain 137:449-462, 2014). The term "benign" is a misnomer in many cases, as the natural history of these tumors is with malignant transformation and recurrence as grade III or grade IV tumors (Jooma et al. in J Neurosurg 14:356-363, 2019). For all LGG, surgery with maximal safe resection is the treatment of choice for both primary and recurrent tumors. The goal of surgery should be for gross total resection (GTR), as complete tumor removal is associated with higher rates of tumor control and seizure freedom. Chemotherapy and radiation therapy (RT), while not typically a component of first-line treatment in most cases, may be employed as adjunctive therapy in high-risk or recurrent tumors and in some select cases. The prognosis of benign gliomas varies widely; non-infiltrative tumor subtypes generally have an excellent prognosis, while diffusely infiltrative tumors, although slow-growing, are eventually fatal (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). This chapter reviews the shared and unique individual features of the benign glioma including diffuse glioma, pilocytic astrocytoma and pilomyxoid astrocytoma (PMA), subependymal giant cell astrocytoma (SEGA), pleomorphic xanthoastrocytoma (PXA), subependymoma (SE), angiocentric glioma (AG), and chordoid glioma (CG). Also discussed is ganglioglioma (GG), a mixed neuronal-glial tumor that represents a notable diagnosis in the differential for other LGG (Wesseling and Capper 2018). Ependymomas of the brain and spinal cord, including major histologic subtypes, are discussed in other chapters.

Clinical Characteristics of BRAF V600E Gene Mutation in Patients of Epilepsy-Associated Brain Tumor: a Meta-analysis

Epilepsy-associated brain tumors (EATs) are usually slow-growing, with seizures as the primary and most dominant symptom. BRAF (v-raf murine sarcoma viral oncogene homolog B1) gene mutations have been found in several subsets of EATs; the V600E mutation is currently believed to contribute to the intrinsic epileptogenicity and tumor growth. However, the relationship between BRAF V600E gene mutation and clinical characteristics in EAT patients is not clear. In this study, we aimed to systematically review the frequency of BRAF V600E gene mutation, as well as the relationship between BRAF V600E gene mutation and clinical characteristics, which may help with the diagnosis and treatment of EATs. Cochrane Library, PubMed, Embase, CNKI, WanFang Data, CQVIP, and SinoMed databases were searched up to October 2020 to identify peer-reviewed human studies on assessing the relationship between BRAF V600E gene mutations and clinical characteristics in EATs. The following data were calculated: the frequency of BRAF V600E mutation and clinical feature comparison between BRAF V600E mutations and wild type in EATs, such as gender, age of seizure onset, duration of epilepsy, location of tumors, and Engel outcome. A total of 12 articles were included in the analysis. Five hundred and nine patients with epilepsy-associated brain tumors were screened for the BRAF V600E gene mutation. Among them, 193 patients had the BRAF V600E mutation (34.06%, 95% CI = 0.25 to 0.43). The subgroup analyses of BRAF V600E mutation showed positive frequency of 44.76% (95% CI = 0.36 to 0.54) in ganglioglioma, 24.75% (95% CI = 0.14 to 0.37) in gysembryoplastic neuroepithelial tumor, 2.15% (95% CI = 0 to 0.19) in angiocentric glioma, and 50.16% (95% CI = 0.33 to 0.68) in pleomorphic xanthoastrocytoma. Compared with the overall frequency, the BRAF V600E positive frequency in ganglioglioma was significantly higher (P = 0.0283). We also found that BRAF V600E gene mutation was significantly associated with age at seizure onset (MD = -2.37; 95% CI = -4.33 to -0.41; P = 0.02). There was no statistical difference between BRAF V600E mutations and wild type in gender, duration of epilepsy, tumor site, and Engel outcome comparison. In conclusion, our updated and comprehensive meta-analysis based on a large number of clinical data demonstrated that BRAF V600E mutation is a specific biomarker and could be a pharmacological target for ganglioglioma patients and an exclusion diagnostic criterion for angiocentric glioma. This meta-analysis suggested the critical role of BRAF V600E mutation in the occurrence and development of EATs. Our findings help to elucidate the progression mechanisms in EATs and develop future therapeutic strategies for EATs.

The Mitochondrial Chaperone TRAP1 as a Candidate Target of Oncotherapy

Tumor necrosis factor receptor-associated protein 1 (TRAP1), a member of the heat shock protein 90 (Hsp90) chaperone family, protects cells against oxidative stress and maintains mitochondrial integrity. To date, numerous studies have focused on understanding the relationship between aberrant TRAP1 expression and tumorigenesis. Mitochondrial TRAP1 is a key regulatory factor involved in metabolic reprogramming in tumor cells that favors the metabolic switch of tumor cells toward the Warburg phenotype. In addition, TRAP1 is involved in dual regulation of the mitochondrial apoptotic pathway and exerts an antiapoptotic effect on tumor cells. Furthermore, TRAP1 is involved in many cellular pathways by disrupting the cell cycle, increasing cell motility, and promoting tumor cell invasion and metastasis. Thus, TRAP1 is a very important therapeutic target, and treatment with TRAP1 inhibitors combined with chemotherapeutic agents may become a new therapeutic strategy for cancer. This review discusses the molecular mechanisms by which TRAP1 regulates tumor progression, considers its role in apoptosis, and summarizes recent advances in the development of selective, targeted TRAP1 and Hsp90 inhibitors.